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World J Gastrointest Oncol. Jan 15, 2014; 6(1): 11-21
Published online Jan 15, 2014. doi: 10.4251/wjgo.v6.i1.11
Antidepressant fluoxetine and its potential against colon tumors
Helga Stopper, Vinicius Kannen, Department of Toxicology, University of Wuerzburg, D-97078 Wurzburg, Germany
Sergio Britto Garcia, Department of Pathology, Medical School of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP 14040-902, Brazil
Ana Maria Waaga-Gasser, Department of Surgery I, Molecular Oncology and Immunology, University of Wuerzburg, D-97078 Wuerzburg, Germany
Supported by German Academic Exchange Service (DAAD), National Council for Scientific and Technological Development (CNPQ); and Foundation for Research Support of the State of São Paulo (FAPESP)
Author contributions: Stoppe H, Garcia SB, and Waaga-Gasser AM contributed with unpublished data and discussions; Kannen V conceived and wrote this manuscript.
Correspondence to: Vinicius Kannen, PhD, Department of Toxicology, University of Wuerzburg, Versbacher Strasse 9, D-97078 Wuerzburg, Germany. vinicius.cardoso@uni-wuerzburg.de
Telephone: +49-931-86133 Fax: +49-931-86133
Received: September 20, 2013
Revised: November 9, 2013
Accepted: December 9, 2013
Published online: January 15, 2014

Abstract

Colon cancer is one of the most common tumors worldwide, with increasing incidence in developing countries. Patients treated with fluoxetine (FLX) have a reduced incidence of colon cancer, although there still remains great controversy about the nature of its effects. Here we explore the latest achievements related to FLX treatment and colon cancer. Moreover, we discuss new ideas about the mechanisms of the effects of FLX treatment in colon cancer. This leads to the hypothesis of FLX arresting colon tumor cells at the at G1 cell-cycle phase through a control of the tumor-related energy generation machinery. We believe that the potential of FLX to act against tumor metabolism warrants further investigation.

Key Words: Fluoxetine, Colon cancer, Cancer therapy, Tumor metabolism

Core tip: It is currently thought that aerobic glycolysis is key for understanding cell survival in the hostile tumor microenvironment. Then, the antidepressant fluoxetine (FLX) has been shown to reduce colon tumor growth in animals and colon cancer incidence in humans. Here, we explore new perspectives of FLX reducing the development of colon tumors through a blockage in tumor metabolism. This perspective review is based on our current unpublished experimental dataset which shows FLX as a potential co-chemotherapeutic agent for colon cancer therapy.



INTRODUCTION

Colon cancer is one of the most common human malignancies worldwide and much effort has been applied to understand its development. The discovery of new therapeutical strategies or potential co-therapeutical agents against it might reduce the suffering of millions of people. A growing body of evidence suggests that the use of fluoxetine (FLX), an antidepressant belonging to the selective serotonin reuptake inhibitors (SSRIs), may be related to a reduced colon cancer incidence. However, its activity is not completely understood and potential new mechanisms are unknown to date.

Here, we discuss our recent published and unpublished data regarding the activity of FLX against colon cancer. This review takes a fresh view of the material, mainly of how FLX acts to block malignant metabolism, reducing colon tumors.

COLON CANCER

The American Cancer Society estimates the number of new cases and expected deaths for cancer in the United States every year[1]. About 1.5 million cases and 569490 deaths of cancer were expected in 2010. This ranked colon cancer as the third most common cancer in the United States, with almost 50000 deaths per year[1,2]. In this year, it is expected that more than 143460 patients will be newly diagnosed with colon cancer in the United States[3]. Although survival has increased during the 5 years after diagnosis[2], a 60% increase for newly diagnosed cancer cases is projected for developing countries until 2030[4]. This highlights colon cancer as one of the major human malignancies worldwide and a great challenge for cancer therapy[5-7].

Adenoma-adenocarcinoma sequence model

The adenoma-adenocarcinoma sequence model is the most well-known and accepted hypothesis for the development of colon cancer[8]. It is thought that a sequence of mutations of the epithelial stem cell niche induces the development of colon tumors through different stages, such as initiation, promotion and progression[8]. Initiation is known as an irreversible step, where mutations in one or two gatekeeper genes occur in a single cryptal stem cell. This will then disrupt cell proliferation, leading to the expansion of malignant clones, a process termed promotion[9,10]. Mutations are thought to derive from cell exposure to carcinogenic compounds which directly attack the DNA or lead to increased oxidative stress (OS) with the generation of reactive oxygen species (ROS), which would then attack the DNA basis inducing mutations[11,12]. Clever’s research group has elegantly generated Lgr5-EGFP-IRES-creERT2/Apcflox/flox mice, which have a stem cell-specific knockin reporter for tamoxifen-inducible loss of the adenomatous polyposis coli (APC) sequence, and found that this genetic deletion in epithelial stem cells leads to their transformation within days, which was due to β-catenin accumulation[13]. This further supports the idea that a monoclonal propagation of acquired stem cell mutations occurs during the initial steps of colon carcinogenesis[9]. The manifestation of mutations in colon epithelia seems to be closely related to hyperproliferation[13-15]. In fact, mutations in the APC gene sequence at cryptal stem cell niches activate hyperproliferation due to an increase in β-catenin transcriptional activity which blocks p53 activity[15-17].

Subepithelial cells and their role in carcinogenesis

The cancer-enhancing activity of the microenvironment has been a matter of discussion since recent reports showed that disrupting key genetic sequences in stromal cells abrogates epithelial homeostasis, which then induces tumors[18-20]. An elegant report has specifically shown that epithelial tumors have arisen in forestomach after disrupting the transforming growth factor-β (TGF-β) signaling within the subepithelial compartment[21]. Previous studies had already shown that the subepithelial TGF-β signaling has tumor promoting potential on epithelial cells, due to its control over proliferation[22,23]. Nevertheless, under inflammatory conditions, subepithelial cells seem to be able to transform epithelial progenitor cells towards malignancy[20]. These ideas have actually been applied to colon carcinogenesis, confirming the malignant participation of subepithelial cells in the development and manifestation of colon tumors[20,24,25].

TUMOR METABOLISM

Hyperproliferation enables the clonal expansion of mutated cells, which further drives tumor growth[14,15,17,26-29]. For this, tumor cells require: high and fast adenosine-5’-ATP generation; a tightened maintenance of the cell redox status to overcome the stressful tumor microenvironment; and enhanced biosynthesis of macromolecules. Basically, tumor cells shift their energy generation machinery from oxidative phosphorylation to an aerobic-glycolytic metabolism[30,31]. This allows tumor cells to keep a high ATP generation and at the same time to avoid the negative feedback regulation from overusing glycolysis, which would otherwise activate metabolic and cell-cycle inhibitors, such as p53[30]. This was extensively discussed by Cairns et al[31]. Specifically, glycolysis-related mechanisms enhance the synthesis of nucleotides and DNA repair[30,31]. However, high proliferation enlarges the distance between cells and microvessels, which reduces the oxygen and nutrient supplies to the cells and creates a hypoxic microenvironment. While hypoxia generally promotes the expression of growth factors, inducing neovascularization, hypoxic areas in tumors may persist due to the chaotic and malformed structures of tumoral vessels and microvessels[14,32-34].

Moreover, hypoxic tumor cells are known to use glycolysis in order to increase energy generation (Figure 1). This requires an over-activation of glucose transporters (i.e., GLUT1), lactate transporters (i.e., MCT4) and lactate dehydrogenase A (LDH-A) through the hypoxia-inducible factor 1 (HIF-1) transcriptional activity. By inhibiting the degradation of HIF-1, a transcription factor which upregulates the glycolysis-related molecular activities, tumor cells increase the conversion of pyruvate to lactate[32,35]. Because tumor cells would then suffer from the hypoxia-induced and glycolysis-related acidosis, they alkalinize their intracellular pH (ipH) on their way to survival and proliferation. This is achieved via hyperactivation of HIF-1 activity, which enhances the hydration of carbon dioxide to bicarbonate by the catalytic activity of carbonic anhydrase IX and XII enzymes and promotes the activity of MCT-4 to extrude lactate and H+ ions, both supporting an ipH alkalinization[32,36]. Overall, tumor cells undergo deep metabolic changes on their way to survival in the stressful tumoral microenvironment[31].

Figure 1
Figure 1 Main metabolic interactions lead to formation of the aerobic glycolytic metabolism in colon tumor cells. The increased biosynthetic activity of cancer cells, as related to the activation of the aerobic glycolytic metabolism or “Warburg effect”, is based on the activation of glucose and lactate transporters supplying tumor cells not only with vast amounts of energy (glucose), but further reducing blockage-associated mechanisms due to glycolysis over usage. It seems that the lactate overproduction is compensated by the hyperactivation of lactate transporters allowing a rapid transport of this molecule across the plasma membrane together with H+ atoms, which results in an intracellular alkalinization. This event hyperpolarizes the mitochondrial membrane potential (ΔΨm) and induces a higher uptake of NADH by the first and succinate by the second mitochondrial complexes enhancing the oxidative mitochondrial phosphorylation (Krebs cycle). All together, this means that tumor cells are prone to produce higher energy amounts (ATP) than found in a normal tissue. ROS: Reactive oxygen species; CO2: Carbon dioxide; ipH: intracellular pH. NADH: Nicotinamide adenine dinucleotide phosphate-oxidase.
ANTIDEPRESSANT FLX MODULATES OXIDATIVE STRESS

FLX was first reported by a research group from the Eli Lilly Company in 1974 as a SSRI[37]. In 1978, the United States Food and Drug Administration approved FLX for the treatment of patients with depression, anxiety and insomnia; this medication became known worldwide as Prozac[38,39]. This antidepressant exhibits higher safety and fewer side effects than other groups of antidepressants[38-41]. FLX was characterized as a lipophilic weak base, which when administered orally experiences a direct contact with epithelial cells in the intestines. In these epithelial cells, it induces an increase in serotonin (5-HT) levels by blocking L-monoamine oxidase and serotonin reuptake transporters[41-43].

On the other hand, FLX has been shown to interfere with the OS machinery in experimental models and humans[44-55]. Treatment with FLX was found to reduce malondialdehyde (MDA) and carbonyl levels in stressed rats, whilst it enhanced superoxide dismutase (SOD), catalase, glutathione S-transferase, glutathione reductase and glutathione contents[45,46]. Similar findings were reported by another research group[48]. Then, this compound showed neuroprotective effects, decreasing the translocation of p67 protein and ROS generation (by suppressing the activation of nicotinamide adenine dinucleotide phosphate-oxidase oxidase and inducible nitric oxide synthase) in rats exposed to lipopolysaccharide[47]. In depressive patients, FLX was found to decrease serum MDA, SOD and ascorbic acid levels[44].

FLX AND TUMORS

Tutton and Barkla first revealed the anticancer potential of FLX against colon tumors[56]. However, in 1992, Brandes and colleagues reported a 40% increase of the numbers of mammary fibrosarcomas among mice treated with FLX for 5 d, which was followed by findings of a 95% enhancement in breast cancer incidence after 15 wk[57]. Opposite to that, Volpe et al[58] showed that treating human and murine breast tumor cell lines with FLX in vitro did not stimulate tumor cell proliferation, DNA synthesis or colony formation. Jia et al[59] reported that FLX did not enhance the growth of pancreatic tumors. Moreover, this treatment was further found to reduce lymphoma growth, modulating the T-cell-mediated immunity reaction through a 5-HT-dependent activity[40].

In patients, FLX treatment was reported to reduce the risk of colon cancer to almost 50%[60]. Chubak et al[61] also observed that FLX reduced the risk of colon cancer in humans, while one meta-analysis study suggested that FLX does not act on colon cancer[62]. Studies with animal models support the idea of FLX reducing colon cancer incidence in different animal models, such as carcinogen induced preneoplastic lesions and tumors in rats and mice, and xenograft tumors in immunosuppressed rats[38,63-65]. These studies have mainly been focused on the antiproliferative effects of FLX treatment in colon tumorigenesis[38,63-65]. In cell culture models, FLX was reported to not only inhibit multidrug resistance and increase the intracellular doxorubicin concentration[66], but also to induce a further nuclear distribution of this chemotherapeutic drug[67].

FLX reduces preneoplastic lesions acting on colonic microenvironment

We have reported that FLX treatment counteracted the carcinogen-induced dysplasia in two different experimental colon cancer models[64,65]. Our first report revealed FLX as a chemopreventive compound against colonic dysplasia since treatment with FLX was started before the treatment with the carcinogen[65]. We then reported that FLX could also reduce pre-existent colon preneoplastic lesions[64]. Our findings suggested that FLX takes the carcinogen-induced preneoplastic changes under control by reducing epithelial proliferation[38,56,60,61,64,65].

Besides the fact that FLX treatment reduced dysplasia and preneoplastic angiogenesis, decreasing the epithelial and subepithelial proliferation[64,65], our unpublished dataset further suggests that by suppressing the NF-κB nuclear activity, through increased expression of cytoplasmic NF-κB-inhibitor IκB-α and IκB-β proteins, FLX reduced c-Myc expression and then stromal proliferation (Figures 2 and 3). As we will discuss next, FLX treatment seems to take preneoplastic angiogenesis under control by reducing the proliferation of subepithelial cells (Figure 4). Indeed, NF-κB-transcriptional activity was reported to induce the transformation of subepithelial cells from normal to reactive phenotypes, enhancing the expression of pro-inflammatory molecules and periendothelial cell numbers[68,69]. Koh et al[38] reported that FLX inhibited NF-κB signaling in colonic epithelial tumor cells. Inhibition of the NF-κB-transcriptional activity actually yields reduced expression of its downstream genes c-Myc and vascular endothelial growth fator, which blocks the proliferation of colon cancer cells[70,71].

Figure 2
Figure 2 Fluoxetine modulates nuclear factor kappa-B nuclear activity among subepithelial colonic cells. For this figure, groups of female C57BL/6 mice (25 g) consisted of control (CTRL) animals or received methylnitronitrosoguanidine (MNNG) treatment [four successive doses of MNNG (5 mg/mL; intrarectal deposits of 100 µL) twice a week for 2 wk], FLX treatment (30 mg/kg per day; intraperitoneal, ip) or MNNG + FLX treatment. FLX treatment was started after 2 wk from the end of MNNG treatment, and continued for the next 4 wk. All mice were euthanized by CO2 exposure at week 8. Individual autopsies were performed and colon tissue samples were fixed in paraformaldehyde buffer (4%; 24 h). All experimental protocols were approved by the Internal Animal Care, Ethical and Use Committee (n° 068/2012). Immunohistochemistry was performed with anti-nuclear factor kappa-light-chain-enhancer of activated B cells [nuclear factor kappa-B (NF-κB), p50; clone C-19], nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor (IκB), alpha (IκB-α; clone N-20), beta (IκB-β; clone H-4). Antibodies were acquired from Santa Cruz Biotechnology (Heidelberg, Germany). A: Representative histological image of a colonic-longitudinal section labeled with anti-NF-κB antibody, picture taken at × 400 magnification and scale bar of 45 μm inserted. A cytoplasmic anti-NF-κB antibody positively cell detected within cryptal area (inset below; × 1000 magnification of the boxed region, middle-left). Nuclear-NF-κB protein detected in stromal cells (inset right-side; × 1000 magnification of the boxed region, middle-right). Graph shows the relative number of nuclear-NF-κB positive cells within colonic subepithelial areas (PCCS; bP < 0.01 vs MNNG without FLX, n = 4; FLX + MNNG, n = 4); B: Relative number of IκB-α positive cells (aP < 0.05 vs MNNG without FLX, n = 4; FLX+MNNG, n = 4); and C: IκB-β positive cells within colon stromal areas (aP < 0.05 vs MNNG without FLX, n = 5; FLX + MNNG, n = 4). FLX: Fluoxetine. PCCS: Pericryptal colonic stroma.
Figure 3
Figure 3 Schematic illustration shows fluoxetine antiproliferative activities in colon tissue. Boxed figure shows the clear division between epithelial and subepithelial colonic areas. Considering that crypts compose the colonic epithelia, it is known that microvessels surround these gland structures. Fluoxetine (chemical structure represented at the center) blocks cell-cycle (blue line and letters) in colonic tissue. We have observed that fluoxetine treatment reduced two proliferative markers, named proliferating cell nuclear antigen (PCNA, red line) and KI67 (green line). These effects of fluoxetine treatment might be related to its enhancement on IκB-α and IκB-β proteins. This could arrest nuclear factor kappa-B (NF-κB) protein in the cytoplasm, reducing its transcriptional activity which, due to its activation over c-Myc transcription factor, would decrease this protein activation and proliferation. We believe that a similar mechanism could take a place in epithelial and subepithelial cells.
Figure 4
Figure 4 Schematic illustration shows fluoxetine anti-angiogenic potential in colon preneoplastic tissue. This means that by reducing proliferation of subepithelial cells, blocking their cell-cycle, fluoxetine would reduce microvessel density. This anti-angiogenic potential was observed in a direct relationship with reduced differentiation-related angiogenesis of subepithelial stem cells. This suggests that fluoxetine would reduce the differentiation of CD133 positive cells into a CD34 phenotype, which would also not differentiate in endothelial cells, as CD31. This sequence of events would mainly be associated with the control of fluoxetine treatment on nuclear factor kappa-B signaling, as reducing proliferation and preneoplastic angiogenesis. PCNA: Proliferating cell nuclear antigen.

The activity of FLX on the colonic preneoplastic microenvironment further includes the question whether this treatment could directly act upon angiogenesis-related cell phenotypes[64,65]. We have demonstrated that the anti-angiogenic potential of FLX could be related to its control over the differentiation and further transition of endothelial cells through different angiogenesis-related stem cell markers in colon preneoplastic lesions (Figure 4)[64]. This idea was abetted by the discovery of a small subset of stromal spindle cells expressing CD133 and CD34 in angiofibromas, which suggests tumors promoting subepithelial resident cells to transit towards endothelial cell phenotypes[72]. Endothelial progenitor cells were then shown to lose, in a process related to high proliferation[73], the expression of CD133 during their differentiation into vascular cells, while the expression of CD34 was increased[74-76]. Considering that CD31-positive cells have been designated as mature endothelial lineage promoting microvessels[77], vascular smooth muscle cells were found to increase the expression of CD31 during their differentiation process, whilst a simultaneous decrease of CD133 and CD34 progenitor markers was previously observed[78,79].

FLX TAKES ENERGY GENERATION UNDER CONTROL TO REDUCE MALIGNANT EXPANSION

Here, we should pull a few points together about malignancy, ROS production and energy generations, as: (1) unbalancing the machinery for energy generation induces ROS production; (2) ROS production is one of the main known events inducing DNA damage and mutation; (3) ROS generation promotes genetic mutations leading to the manifestation of preneoplastic lesions; (4) tumor cells undergo deep metabolic changes to survive and promote malignant expansion; (5) tumors enhance ROS production to promote growth through malignant molecular signaling; and (6) malignant metabolism seems to be the Achilles’ heel in tumors. These few remarks give us the notion that metabolism, or energy generation, is a key for malignant transformation, tumor manifestation and growth, as well as a valuable tool for anticancer therapy[35,80-82].

As a lipophilic weak base[42], FLX quickly diffuses through multiple body-sites[83]. We have already demonstrated that FLX treatment arrested colon tumor cells within the G0/G1 cell-cycle phase without inducing DNA damage[64]. Then, FLX was shown to reduce ROS generation, reversing the melanoma-induced tissue oxidation in mice[50]. In brain tissue of tumor-bearing mice, FLX treatment further reduced OS, enhancing the SOD activity[49]. Actually, FLX was twice reported to stimulate Ca2+ flux reducing the B-cell lymphoma 2 (bcl-2) expression and mitochondrial membrane potential (ΔΨm), which induced DNA fragmentation and apoptosis in Burkitt’s lymphoma cells[52,53]. Another lipophilic weak base ([Z]-5-methyl-2-[2-(1-naphthyl) ethenyl]-4-piperidinopyridine [AU-1421]) was also reported to uncouple mitochondrial oxidative phosphorylation, dissipating the proton motive force during its energized state, which inhibited ATP synthesis[84]. It is known that lipophilic weak bases, such as FLX, reduce ΔΨm (or extra- and intra-mitochondrial motions of H+ atoms generating positive charges in the mitochondrial membrane) in their energized or protonated state, which reduces mitochondrial respiratory rate and energy generation[84-86]. FLX was also found to induce ROS generation in human ovarian cancer cell lines, which induced apoptosis through mitochondrial bcl-2-associated X protein, cytochrome c release, caspase-3 activation and p53 expression levels, whilst this treatment further reduced ΔΨm, BH3 interacting-domain death agonist and bcl-2 levels[54]. Similar findings were reported in human neuroblastomas[55].

Comparing those reports that describe how FLX modulates tumor metabolism[49,50,52-55] with others describing its activity against tumor growth[40,58,87-92], it becomes clear that FLX blocks tumor cell proliferation by impairing the malignant energy generation. The anti-tumor proliferative effects of FLX[40,56,92,93] have been related to different causes, such as delays in cell-cycle progression by inhibiting DNA synthesis and also to a possible binding directly to DNA via groove mode and high attraction force[58,87-90,94]. On a molecular level, FLX was shown to arrest breast tumor cells at G0/G1 phase by disrupting skp2-CKS1 assembly, which is required to enable cell cycle progression[91]. Recent reports have been supporting the idea of FLX acting against tumor proliferating cells by reducing c-Myc and cyclins (D1, D3, E, B and A), whereas cell-cycle checkpoints (p15, p16, p21, p27 and p53) were enhanced[40,91,92].

Perspectives in FLX treatment acting against colon cancer

The application of FLX for tumor patients has so far been limited to its use as an antidepressant, but it might provide much more benefit, potentially making it an interesting co-chemotherapeutic agent. FLX treatment seems to block tumor growth by breaking the malignant metabolism down[49,52-55]. While the pieces for this puzzle are slowly being pulled together, there are already several reports which have given the ground ideas for following investigations[38-40,49,50,52-56,58,60,61,64-67,87-92,95]. Besides the specific idea of FLX acting against the tumor metabolism, there is an open question regarding the effects of FLX treatment against the “reverse Warburg effect”. Pavlides et al[96] have suggested the idea of a reverse Warburg effect taking place in tumors; this idea argues that epithelial cancer cells induce the subepithelial cells to undergo aerobic-glycolysis and secrete lactate and pyruvate, which malignant cells would take up to enhance their tricarboxylic acid cycle, not only to generate more energy through mitochondrial phosphorylation, but further increase redox mechanisms which in turn corroborates with tumor cell survival and proliferation[30,31,82]. Schulze and colleagues have extensively reviewed this topic[30,82]. Such a mechanism would efficiently ensure enough energy production for malignant cells within the hostile tumor environment, allowing not only high proliferative rates, but the enhancement of malignant angiogenesis[97-101]. These authors have further shown that enhancing the subepithelial NF-κB signaling is closely associated with “reverse Warburg effect” in tumors[96].

Our findings, that FLX treatment reduced the nuclear detection of NF-κB protein among preneoplastic subepithelial cells (as related to reduced angiogenesis due to fewer subepithelial cellular proliferation[64,65]), lead towards the idea of FLX treatment having similar effects on subepithelial cells which surround epithelial cells in colon tumors. Figure 5 illustrates that malignant microvessels show high-cytochrome C oxidase activity in colon xenograft tumors. Moreover, our new experiments (unpublished dataset) argue that FLX treatment, in different colon tumor models, takes the malignant metabolism-related energy generation in epithelial cells under control to shrink tumors. We strongly believe that FLX counteracts aerobic glycolysis reducing the activity of lactate transporters that inhibits oxidative phosphorylation due to increased intracellular levels of lactate. This might bring down the ipH values blocking the tumor energy generation machinery. After having this hypothesis challenged in experimental models and by different research groups, we could think of clinical trials for FLX as a co-chemotherapeutic agent in colon cancer patients. Because of the low costs of FLX, this would also be transferable to developing countries with their tightly limited budget for cancer therapy.

Figure 5
Figure 5 Tumor metabolism and malignant angiogenesis. Histopathological images show double staining between cytochrome C oxidase (COX) and anti-CD31 antibody (clone 1A10 at 1:100; Novocastra, United States). Microvessel walls are traced with sectioned white lines (horizontal view of sectioned tumor microvessels). Black arrow indicates a microvessel lumen with double-stained cells (boxed region; transversal view of a tumor microvessel). Picture was taken at × 100 magnification and 45 μm scale bars are inserted in all images. Inset (C) shows the same boxed region at × 200 magnification. Double-stained cells are pointed out by a black arrow at the microvessel wall (inset; B). Sectioned green line circulates a niche of double-stained endothelial cells at the edge of a microvessel bifurcation. To build these images, 5 wk (20 ± 2 g) nonobese diabetic, severe combined immunodeficient mice (NOD/SCID) were subcutaneously transplanted with HT29 cells (1.5 × 106 cells per mice) in agreement with the protocol approved by the Internal Animal Care, Ethical and Use Committee (n° 121/2012). All mice were acclimated for 1 wk before starting the experiment and maintained under specific pathogen-free conditions. Tumor volume was monitored throughout the whole experimental period by measures with a caliper. Mice were sacrificed under general anesthesia (1.5% Forane in 98.5% oxygen; 2l min). Tissue samples were frozen within TissueTek (Sakura, Germany) and kept at -80 °C for immunohistochemical analyses. Double-staining was performed according to our standard methods.
CONCLUSION

To summarize, research data concerning the activity of FLX treatment against tumor metabolism are still very limited but exciting enough to warrant new investigations. The fact that FLX was designed as an antidepressant but was further found to act against tumors already highlights that new drugs can be developed from it. Additionally, cancer therapy lacks alternative strategies to overcome chemoresistance. In many cases, chemoresistance is closely associated with tumor metabolism. It seems reasonable to suggest that treatments disrupting metabolic events, as might be possible with FLX, could effectively not only reduce chemoresistance, but also malignant angiogenesis. Whether these new perspectives for FLX treatment will be applicable for colon cancer patients are a matter of time, discussion and deeper research efforts. We strongly suggest that FLX is a promising target for further studies in cancer research.

Footnotes

P- Reviewers: Koukourakis GV, Wang ZH S- Editor: Zhai HH L- Editor: Roemmele A E- Editor: Liu SQ

References
1.  Jemal A, Siegel R, Xu J, Ward E. Cancer statistics, 2010. CA Cancer J Clin. 2010;60:277-300.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 10002]  [Cited by in F6Publishing: 10353]  [Article Influence: 739.5]  [Reference Citation Analysis (0)]
2.  Lea A, Allingham-Hawkins D, Levine S. BRAF p.Val600Glu (V600E) Testing for Assessment of Treatment Options in Metastatic Colorectal Cancer. PLoS Curr. 2010;2:RRN1187.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 6]  [Cited by in F6Publishing: 10]  [Article Influence: 0.7]  [Reference Citation Analysis (0)]
3.  Siegel R, DeSantis C, Virgo K, Stein K, Mariotto A, Smith T, Cooper D, Gansler T, Lerro C, Fedewa S. Cancer treatment and survivorship statistics, 2012. CA Cancer J Clin. 2012;62:220-241.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 1973]  [Cited by in F6Publishing: 2026]  [Article Influence: 168.8]  [Reference Citation Analysis (1)]
4.  Jemal A, Center MM, DeSantis C, Ward EM. Global patterns of cancer incidence and mortality rates and trends. Cancer Epidemiol Biomarkers Prev. 2010;19:1893-1907.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in F6Publishing: 1]  [Reference Citation Analysis (0)]
5.  Dehal AN, Newton CC, Jacobs EJ, Patel AV, Gapstur SM, Campbell PT. Impact of diabetes mellitus and insulin use on survival after colorectal cancer diagnosis: the Cancer Prevention Study-II Nutrition Cohort. J Clin Oncol. 2012;30:53-59.  [PubMed]  [DOI]  [Cited in This Article: ]
6.  Chibaudel B, Tournigand C, André T, de Gramont A. Therapeutic strategy in unresectable metastatic colorectal cancer. Ther Adv Med Oncol. 2012;4:75-89.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 56]  [Cited by in F6Publishing: 61]  [Article Influence: 5.1]  [Reference Citation Analysis (0)]
7.  Cunningham D, Atkin W, Lenz HJ, Lynch HT, Minsky B, Nordlinger B, Starling N. Colorectal cancer. Lancet. 2010;375:1030-1047.  [PubMed]  [DOI]  [Cited in This Article: ]
8.  Fearon ER, Vogelstein B. A genetic model for colorectal tumorigenesis. Cell. 1990;61:759-767.  [PubMed]  [DOI]  [Cited in This Article: ]
9.  Zeki SS, Graham TA, Wright NA. Stem cells and their implications for colorectal cancer. Nat Rev Gastroenterol Hepatol. 2011;8:90-100.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 103]  [Cited by in F6Publishing: 109]  [Article Influence: 8.4]  [Reference Citation Analysis (0)]
10.  Luebeck EG, Hazelton WD. Multistage carcinogenesis and radiation. J Radiol Prot. 2002;22:A43-A49.  [PubMed]  [DOI]  [Cited in This Article: ]
11.  Makovski A, Yaffe E, Shpungin S, Nir U. Down-regulation of Fer induces ROS levels accompanied by ATM and p53 activation in colon carcinoma cells. Cell Signal. 2012;24:1369-1374.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 11]  [Cited by in F6Publishing: 12]  [Article Influence: 1.0]  [Reference Citation Analysis (0)]
12.  Woo DK, Green PD, Santos JH, D’Souza AD, Walther Z, Martin WD, Christian BE, Chandel NS, Shadel GS. Mitochondrial genome instability and ROS enhance intestinal tumorigenesis in APC(Min/+) mice. Am J Pathol. 2012;180:24-31.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 101]  [Cited by in F6Publishing: 103]  [Article Influence: 7.9]  [Reference Citation Analysis (0)]
13.  Barker N, Ridgway RA, van Es JH, van de Wetering M, Begthel H, van den Born M, Danenberg E, Clarke AR, Sansom OJ, Clevers H. Crypt stem cells as the cells-of-origin of intestinal cancer. Nature. 2009;457:608-611.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 1545]  [Cited by in F6Publishing: 1578]  [Article Influence: 98.6]  [Reference Citation Analysis (0)]
14.  Waldner MJ, Wirtz S, Jefremow A, Warntjen M, Neufert C, Atreya R, Becker C, Weigmann B, Vieth M, Rose-John S. VEGF receptor signaling links inflammation and tumorigenesis in colitis-associated cancer. J Exp Med. 2010;207:2855-2868.  [PubMed]  [DOI]  [Cited in This Article: ]
15.  Wong WM, Mandir N, Goodlad RA, Wong BC, Garcia SB, Lam SK, Wright NA. Histogenesis of human colorectal adenomas and hyperplastic polyps: the role of cell proliferation and crypt fission. Gut. 2002;50:212-217.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 101]  [Cited by in F6Publishing: 102]  [Article Influence: 4.6]  [Reference Citation Analysis (0)]
16.  Hinoi T, Akyol A, Theisen BK, Ferguson DO, Greenson JK, Williams BO, Cho KR, Fearon ER. Mouse model of colonic adenoma-carcinoma progression based on somatic Apc inactivation. Cancer Res. 2007;67:9721-9730.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 215]  [Cited by in F6Publishing: 239]  [Article Influence: 14.1]  [Reference Citation Analysis (0)]
17.  Wong WM, Garcia SB, Wright NA. Origins and morphogenesis of colorectal neoplasms. APMIS. 1999;107:535-544.  [PubMed]  [DOI]  [Cited in This Article: ]
18.  Seton-Rogers S. Microenvironment: Making connections. Nat Rev Cancer. 2013;13:222-223.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 3]  [Cited by in F6Publishing: 4]  [Article Influence: 0.4]  [Reference Citation Analysis (0)]
19.  Glaire MA, El-Omar EM, Wang TC, Worthley DL. The mesenchyme in malignancy: a partner in the initiation, progression and dissemination of cancer. Pharmacol Ther. 2012;136:131-141.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 13]  [Cited by in F6Publishing: 15]  [Article Influence: 1.3]  [Reference Citation Analysis (0)]
20.  Quante M, Varga J, Wang TC, Greten FR. The gastrointestinal tumor microenvironment. Gastroenterology. 2013;145:63-78.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 100]  [Cited by in F6Publishing: 105]  [Article Influence: 9.5]  [Reference Citation Analysis (0)]
21.  Achyut BR, Bader DA, Robles AI, Wangsa D, Harris CC, Ried T, Yang L. Inflammation-mediated genetic and epigenetic alterations drive cancer development in the neighboring epithelium upon stromal abrogation of TGF-β signaling. PLoS Genet. 2013;9:e1003251.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 60]  [Cited by in F6Publishing: 65]  [Article Influence: 5.9]  [Reference Citation Analysis (0)]
22.  Bhowmick NA, Chytil A, Plieth D, Gorska AE, Dumont N, Shappell S, Washington MK, Neilson EG, Moses HL. TGF-beta signaling in fibroblasts modulates the oncogenic potential of adjacent epithelia. Science. 2004;303:848-851.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 1046]  [Cited by in F6Publishing: 1067]  [Article Influence: 53.4]  [Reference Citation Analysis (0)]
23.  Franco OE, Jiang M, Strand DW, Peacock J, Fernandez S, Jackson RS, Revelo MP, Bhowmick NA, Hayward SW. Altered TGF-β signaling in a subpopulation of human stromal cells promotes prostatic carcinogenesis. Cancer Res. 2011;71:1272-1281.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 128]  [Cited by in F6Publishing: 141]  [Article Influence: 10.8]  [Reference Citation Analysis (0)]
24.  Schwitalla S, Ziegler PK, Horst D, Becker V, Kerle I, Begus-Nahrmann Y, Lechel A, Rudolph KL, Langer R, Slotta-Huspenina J. Loss of p53 in enterocytes generates an inflammatory microenvironment enabling invasion and lymph node metastasis of carcinogen-induced colorectal tumors. Cancer Cell. 2013;23:93-106.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 204]  [Cited by in F6Publishing: 215]  [Article Influence: 19.5]  [Reference Citation Analysis (0)]
25.  Kitamura T, Kometani K, Hashida H, Matsunaga A, Miyoshi H, Hosogi H, Aoki M, Oshima M, Hattori M, Takabayashi A. SMAD4-deficient intestinal tumors recruit CCR1+ myeloid cells that promote invasion. Nat Genet. 2007;39:467-475.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 211]  [Cited by in F6Publishing: 215]  [Article Influence: 12.6]  [Reference Citation Analysis (0)]
26.  Garcia SB, Park HS, Novelli M, Wright NA. Field cancerization, clonality, and epithelial stem cells: the spread of mutated clones in epithelial sheets. J Pathol. 1999;187:61-81.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in F6Publishing: 2]  [Reference Citation Analysis (0)]
27.  Cohen G, Mustafi R, Chumsangsri A, Little N, Nathanson J, Cerda S, Jagadeeswaran S, Dougherty U, Joseph L, Hart J. Epidermal growth factor receptor signaling is up-regulated in human colonic aberrant crypt foci. Cancer Res. 2006;66:5656-5664.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 47]  [Cited by in F6Publishing: 48]  [Article Influence: 2.7]  [Reference Citation Analysis (0)]
28.  Tetsu O, McCormick F. Beta-catenin regulates expression of cyclin D1 in colon carcinoma cells. Nature. 1999;398:422-426.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 2796]  [Cited by in F6Publishing: 2806]  [Article Influence: 112.2]  [Reference Citation Analysis (0)]
29.  Firestein R, Bass AJ, Kim SY, Dunn IF, Silver SJ, Guney I, Freed E, Ligon AH, Vena N, Ogino S. CDK8 is a colorectal cancer oncogene that regulates beta-catenin activity. Nature. 2008;455:547-551.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 497]  [Cited by in F6Publishing: 525]  [Article Influence: 32.8]  [Reference Citation Analysis (0)]
30.  Jones NP, Schulze A. Targeting cancer metabolism--aiming at a tumour’s sweet-spot. Drug Discov Today. 2012;17:232-241.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 117]  [Cited by in F6Publishing: 118]  [Article Influence: 9.1]  [Reference Citation Analysis (0)]
31.  Cairns RA, Harris IS, Mak TW. Regulation of cancer cell metabolism. Nat Rev Cancer. 2011;11:85-95.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 3445]  [Cited by in F6Publishing: 3503]  [Article Influence: 269.5]  [Reference Citation Analysis (0)]
32.  Pouysségur J, Dayan F, Mazure NM. Hypoxia signalling in cancer and approaches to enforce tumour regression. Nature. 2006;441:437-443.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 1202]  [Cited by in F6Publishing: 1264]  [Article Influence: 70.2]  [Reference Citation Analysis (0)]
33.  Barrow H, Rhodes JM, Yu LG. The role of galectins in colorectal cancer progression. Int J Cancer. 2011;129:1-8.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 74]  [Cited by in F6Publishing: 79]  [Article Influence: 6.1]  [Reference Citation Analysis (0)]
34.  Waldner MJ, Neurath MF. The molecular therapy of colorectal cancer. Mol Aspects Med. 2010;31:171-178.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 36]  [Cited by in F6Publishing: 44]  [Article Influence: 3.1]  [Reference Citation Analysis (0)]
35.  Brahimi-Horn C, Pouysségur J. The role of the hypoxia-inducible factor in tumor metabolism growth and invasion. Bull Cancer. 2006;93:E73-E80.  [PubMed]  [DOI]  [Cited in This Article: ]
36.  Cardone RA, Casavola V, Reshkin SJ. The role of disturbed pH dynamics and the Na+/H+ exchanger in metastasis. Nat Rev Cancer. 2005;5:786-795.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 654]  [Cited by in F6Publishing: 649]  [Article Influence: 34.2]  [Reference Citation Analysis (0)]
37.  Fuller RW, Perry KW, Molloy BB. Effect of an uptake inhibitor on serotonin metabolism in rat brain: studies with 3-(p-trifluoromethylphenoxy)-N-methyl-3-phenylpropylamine (Lilly 110140). Life Sci. 1974;15:1161-1171.  [PubMed]  [DOI]  [Cited in This Article: ]
38.  Koh SJ, Kim JM, Kim IK, Kim N, Jung HC, Song IS, Kim JS. Fluoxetine inhibits NF-κB signaling in intestinal epithelial cells and ameliorates experimental colitis and colitis-associated colon cancer in mice. Am J Physiol Gastrointest Liver Physiol. 2011;301:G9-G19.  [PubMed]  [DOI]  [Cited in This Article: ]
39.  Coogan PF, Palmer JR, Strom BL, Rosenberg L. Use of selective serotonin reuptake inhibitors and the risk of breast cancer. Am J Epidemiol. 2005;162:835-838.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 36]  [Cited by in F6Publishing: 40]  [Article Influence: 2.1]  [Reference Citation Analysis (0)]
40.  Frick LR, Palumbo ML, Zappia MP, Brocco MA, Cremaschi GA, Genaro AM. Inhibitory effect of fluoxetine on lymphoma growth through the modulation of antitumor T-cell response by serotonin-dependent and independent mechanisms. Biochem Pharmacol. 2008;75:1817-1826.  [PubMed]  [DOI]  [Cited in This Article: ]
41.  Arimochi H, Morita K. Characterization of cytotoxic actions of tricyclic antidepressants on human HT29 colon carcinoma cells. Eur J Pharmacol. 2006;541:17-23.  [PubMed]  [DOI]  [Cited in This Article: ]
42.  Kornhuber J, Reichel M, Tripal P, Groemer TW, Henkel AW, Mühle C, Gulbins E. The role of ceramide in major depressive disorder. Eur Arch Psychiatry Clin Neurosci. 2009;259 Suppl 2:S199-S204.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 36]  [Cited by in F6Publishing: 41]  [Article Influence: 2.7]  [Reference Citation Analysis (0)]
43.  Bertrand PP, Hu X, Mach J, Bertrand RL. Serotonin (5-HT) release and uptake measured by real-time electrochemical techniques in the rat ileum. Am J Physiol Gastrointest Liver Physiol. 2008;295:G1228-G1236.  [PubMed]  [DOI]  [Cited in This Article: ]
44.  Khanzode SD, Dakhale GN, Khanzode SS, Saoji A, Palasodkar R. Oxidative damage and major depression: the potential antioxidant action of selective serotonin re-uptake inhibitors. Redox Rep. 2003;8:365-370.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 307]  [Cited by in F6Publishing: 306]  [Article Influence: 15.3]  [Reference Citation Analysis (0)]
45.  Zafir A, Ara A, Banu N. Invivo antioxidant status: a putative target of antidepressant action. Prog Neuropsychopharmacol Biol Psychiatry. 2009;33:220-228.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 138]  [Cited by in F6Publishing: 143]  [Article Influence: 9.5]  [Reference Citation Analysis (0)]
46.  Zafir A, Banu N. Antioxidant potential of fluoxetine in comparison to Curcuma longa in restraint-stressed rats. Eur J Pharmacol. 2007;572:23-31.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 115]  [Cited by in F6Publishing: 114]  [Article Influence: 6.7]  [Reference Citation Analysis (0)]
47.  Chung ES, Chung YC, Bok E, Baik HH, Park ES, Park JY, Yoon SH, Jin BK. Fluoxetine prevents LPS-induced degeneration of nigral dopaminergic neurons by inhibiting microglia-mediated oxidative stress. Brain Res. 2010;1363:143-150.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 54]  [Cited by in F6Publishing: 61]  [Article Influence: 4.4]  [Reference Citation Analysis (0)]
48.  Novío S, Núñez MJ, Amigo G, Freire-Garabal M. Effects of fluoxetine on the oxidative status of peripheral blood leucocytes of restraint-stressed mice. Basic Clin Pharmacol Toxicol. 2011;109:365-371.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 39]  [Cited by in F6Publishing: 44]  [Article Influence: 3.4]  [Reference Citation Analysis (0)]
49.  Qi H, Ma J, Liu YM, Yang L, Peng L, Wang H, Chen HZ. Allostatic tumor-burden induces depression-associated changes in hepatoma-bearing mice. J Neurooncol. 2009;94:367-372.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 14]  [Cited by in F6Publishing: 14]  [Article Influence: 0.9]  [Reference Citation Analysis (0)]
50.  Kirkova M, Tzvetanova E, Vircheva S, Zamfirova R, Grygier B, Kubera M. Antioxidant activity of fluoxetine: studies in mice melanoma model. Cell Biochem Funct. 2010;28:497-502.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 26]  [Cited by in F6Publishing: 30]  [Article Influence: 2.1]  [Reference Citation Analysis (0)]
51.  Kim HJ, Choi JS, Lee YM, Shim EY, Hong SH, Kim MJ, Min DS, Rhie DJ, Kim MS, Jo YH. Fluoxetine inhibits ATP-induced [Ca(2+)](i) increase in PC12 cells by inhibiting both extracellular Ca(2+) influx and Ca(2+) release from intracellular stores. Neuropharmacology. 2005;49:265-274.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 18]  [Cited by in F6Publishing: 19]  [Article Influence: 1.0]  [Reference Citation Analysis (0)]
52.  Serafeim A, Grafton G, Chamba A, Gregory CD, Blakely RD, Bowery NG, Barnes NM, Gordon J. 5-Hydroxytryptamine drives apoptosis in biopsylike Burkitt lymphoma cells: reversal by selective serotonin reuptake inhibitors. Blood. 2002;99:2545-2553.  [PubMed]  [DOI]  [Cited in This Article: ]
53.  Serafeim A, Holder MJ, Grafton G, Chamba A, Drayson MT, Luong QT, Bunce CM, Gregory CD, Barnes NM, Gordon J. Selective serotonin reuptake inhibitors directly signal for apoptosis in biopsy-like Burkitt lymphoma cells. Blood. 2003;101:3212-3219.  [PubMed]  [DOI]  [Cited in This Article: ]
54.  Lee CS, Kim YJ, Jang ER, Kim W, Myung SC. Fluoxetine induces apoptosis in ovarian carcinoma cell line OVCAR-3 through reactive oxygen species-dependent activation of nuclear factor-kappaB. Basic Clin Pharmacol Toxicol. 2010;106:446-453.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 44]  [Cited by in F6Publishing: 54]  [Article Influence: 3.6]  [Reference Citation Analysis (0)]
55.  Levkovitz Y, Gil-Ad I, Zeldich E, Dayag M, Weizman A. Differential induction of apoptosis by antidepressants in glioma and neuroblastoma cell lines: evidence for p-c-Jun, cytochrome c, and caspase-3 involvement. J Mol Neurosci. 2005;27:29-42.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 113]  [Cited by in F6Publishing: 118]  [Article Influence: 6.2]  [Reference Citation Analysis (0)]
56.  Tutton PJ, Barkla DH. Influence of inhibitors of serotonin uptake on intestinal epithelium and colorectal carcinomas. Br J Cancer. 1982;46:260-265.  [PubMed]  [DOI]  [Cited in This Article: ]
57.  Brandes LJ, Arron RJ, Bogdanovic RP, Tong J, Zaborniak CL, Hogg GR, Warrington RC, Fang W, LaBella FS. Stimulation of malignant growth in rodents by antidepressant drugs at clinically relevant doses. Cancer Res. 1992;52:3796-3800.  [PubMed]  [DOI]  [Cited in This Article: ]
58.  Volpe DA, Ellison CD, Parchment RE, Grieshaber CK, Faustino PJ. Effects of amitriptyline and fluoxetine upon the in vitro proliferation of tumor cell lines. J Exp Ther Oncol. 2003;3:169-184.  [PubMed]  [DOI]  [Cited in This Article: ]
59.  Jia L, Shang YY, Li YY. Effect of antidepressants on body weight, ethology and tumor growth of human pancreatic carcinoma xenografts in nude mice. World J Gastroenterol. 2008;14:4377-4382.  [PubMed]  [DOI]  [Cited in This Article: ]
60.  Coogan PF, Strom BL, Rosenberg L. Antidepressant use and colorectal cancer risk. Pharmacoepidemiol Drug Saf. 2009;18:1111-1114.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 51]  [Cited by in F6Publishing: 54]  [Article Influence: 3.9]  [Reference Citation Analysis (0)]
61.  Chubak J, Boudreau DM, Rulyak SJ, Mandelson MT. Colorectal cancer risk in relation to antidepressant medication use. Int J Cancer. 2011;128:227-232.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 32]  [Cited by in F6Publishing: 36]  [Article Influence: 2.6]  [Reference Citation Analysis (0)]
62.  Lee HK, Eom CS, Kwon YM, Ahn JS, Kim S, Park SM. Meta-analysis: selective serotonin reuptake inhibitors and colon cancer. Eur J Gastroenterol Hepatol. 2012;24:1153-1157.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 11]  [Cited by in F6Publishing: 13]  [Article Influence: 1.1]  [Reference Citation Analysis (0)]
63.  Tutton PJ, Barkla DH. Serotonin receptors influencing cell proliferation in the jejunal crypt epithelium and in colonic adenocarcinomas. Anticancer Res. 1986;6:1123-1126.  [PubMed]  [DOI]  [Cited in This Article: ]
64.  Kannen V, Hintzsche H, Zanette DL, Silva WA, Garcia SB, Waaga-Gasser AM, Stopper H. Antiproliferative effects of fluoxetine on colon cancer cells and in a colonic carcinogen mouse model. PLoS One. 2012;7:e50043.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 41]  [Cited by in F6Publishing: 47]  [Article Influence: 3.9]  [Reference Citation Analysis (0)]
65.  Kannen V, Marini T, Turatti A, Carvalho MC, Brandão ML, Jabor VA, Bonato PS, Ferreira FR, Zanette DL, Silva WA. Fluoxetine induces preventive and complex effects against colon cancer development in epithelial and stromal areas in rats. Toxicol Lett. 2011;204:134-140.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 29]  [Cited by in F6Publishing: 33]  [Article Influence: 2.5]  [Reference Citation Analysis (1)]
66.  Peer D, Dekel Y, Melikhov D, Margalit R. Fluoxetine inhibits multidrug resistance extrusion pumps and enhances responses to chemotherapy in syngeneic and in human xenograft mouse tumor models. Cancer Res. 2004;64:7562-7569.  [PubMed]  [DOI]  [Cited in This Article: ]
67.  Argov M, Kashi R, Peer D, Margalit R. Treatment of resistant human colon cancer xenografts by a fluoxetine-doxorubicin combination enhances therapeutic responses comparable to an aggressive bevacizumab regimen. Cancer Lett. 2009;274:118-125.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 35]  [Cited by in F6Publishing: 34]  [Article Influence: 2.1]  [Reference Citation Analysis (0)]
68.  Vandoros GP, Konstantinopoulos PA, Sotiropoulou-Bonikou G, Kominea A, Papachristou GI, Karamouzis MV, Gkermpesi M, Varakis I, Papavassiliou AG. PPAR-gamma is expressed and NF-kB pathway is activated and correlates positively with COX-2 expression in stromal myofibroblasts surrounding colon adenocarcinomas. J Cancer Res Clin Oncol. 2006;132:76-84.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 53]  [Cited by in F6Publishing: 58]  [Article Influence: 3.1]  [Reference Citation Analysis (0)]
69.  Hardwick JC, van den Brink GR, Offerhaus GJ, van Deventer SJ, Peppelenbosch MP. NF-kappaB, p38 MAPK and JNK are highly expressed and active in the stroma of human colonic adenomatous polyps. Oncogene. 2001;20:819-827.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 86]  [Cited by in F6Publishing: 93]  [Article Influence: 4.0]  [Reference Citation Analysis (0)]
70.  Yang Z, Li C, Wang X, Zhai C, Yi Z, Wang L, Liu B, Du B, Wu H, Guo X. Dauricine induces apoptosis, inhibits proliferation and invasion through inhibiting NF-kappaB signaling pathway in colon cancer cells. J Cell Physiol. 2010;225:266-275.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 55]  [Cited by in F6Publishing: 61]  [Article Influence: 4.4]  [Reference Citation Analysis (0)]
71.  Paul S, DeCastro AJ, Lee HJ, Smolarek AK, So JY, Simi B, Wang CX, Zhou R, Rimando AM, Suh N. Dietary intake of pterostilbene, a constituent of blueberries, inhibits the beta-catenin/p65 downstream signaling pathway and colon carcinogenesis in rats. Carcinogenesis. 2010;31:1272-1278.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 95]  [Cited by in F6Publishing: 98]  [Article Influence: 7.0]  [Reference Citation Analysis (0)]
72.  Ngan BY, Forte V, Campisi P. Molecular angiogenic signaling in angiofibromas after embolization: implications for therapy. Arch Otolaryngol Head Neck Surg. 2008;134:1170-1176.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 13]  [Cited by in F6Publishing: 14]  [Article Influence: 0.9]  [Reference Citation Analysis (0)]
73.  Tammali R, Reddy AB, Srivastava SK, Ramana KV. Inhibition of aldose reductase prevents angiogenesis in vitro and in vivo. Angiogenesis. 2011;14:209-221.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 43]  [Cited by in F6Publishing: 40]  [Article Influence: 3.1]  [Reference Citation Analysis (0)]
74.  Hristov M, Erl W, Weber PC. Endothelial progenitor cells: mobilization, differentiation, and homing. Arterioscler Thromb Vasc Biol. 2003;23:1185-1189.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in F6Publishing: 1]  [Reference Citation Analysis (0)]
75.  Sovalat H, Scrofani M, Eidenschenk A, Pasquet S, Rimelen V, Hénon P. Identification and isolation from either adult human bone marrow or G-CSF-mobilized peripheral blood of CD34(+)/CD133(+)/CXCR4(+)/ Lin(-)CD45(-) cells, featuring morphological, molecular, and phenotypic characteristics of very small embryonic-like (VSEL) stem cells. Exp Hematol. 2011;39:495-505.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 25]  [Cited by in F6Publishing: 45]  [Article Influence: 3.5]  [Reference Citation Analysis (0)]
76.  Meregalli M, Farini A, Belicchi M, Torrente Y. CD133(+) cells isolated from various sources and their role in future clinical perspectives. Expert Opin Biol Ther. 2010;10:1521-1528.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 30]  [Cited by in F6Publishing: 31]  [Article Influence: 2.2]  [Reference Citation Analysis (0)]
77.  Li H, Zimmerlin L, Marra KG, Donnenberg VS, Donnenberg AD, Rubin JP. Adipogenic potential of adipose stem cell subpopulations. Plast Reconstr Surg. 2011;128:663-672.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 99]  [Cited by in F6Publishing: 344]  [Article Influence: 26.5]  [Reference Citation Analysis (0)]
78.  Ye C, Bai L, Yan ZQ, Wang YH, Jiang ZL. Shear stress and vascular smooth muscle cells promote endothelial differentiation of endothelial progenitor cells via activation of Akt. Clin Biomech (Bristol, Avon). 2008;23 Suppl 1:S118-S124.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 44]  [Cited by in F6Publishing: 47]  [Article Influence: 2.9]  [Reference Citation Analysis (0)]
79.  Krause DS, Fackler MJ, Civin CI, May WS. CD34: structure, biology, and clinical utility. Blood. 1996;87:1-13.  [PubMed]  [DOI]  [Cited in This Article: ]
80.  Beasley NJ, Wykoff CC, Watson PH, Leek R, Turley H, Gatter K, Pastorek J, Cox GJ, Ratcliffe P, Harris AL. Carbonic anhydrase IX, an endogenous hypoxia marker, expression in head and neck squamous cell carcinoma and its relationship to hypoxia, necrosis, and microvessel density. Cancer Res. 2001;61:5262-5267.  [PubMed]  [DOI]  [Cited in This Article: ]
81.  Verrax J, Beck R, Dejeans N, Glorieux C, Sid B, Pedrosa RC, Benites J, Vásquez D, Valderrama JA, Calderon PB. Redox-active quinones and ascorbate: an innovative cancer therapy that exploits the vulnerability of cancer cells to oxidative stress. Anticancer Agents Med Chem. 2011;11:213-221.  [PubMed]  [DOI]  [Cited in This Article: ]
82.  Schulze A, Harris AL. How cancer metabolism is tuned for proliferation and vulnerable to disruption. Nature. 2012;491:364-373.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 651]  [Cited by in F6Publishing: 682]  [Article Influence: 56.8]  [Reference Citation Analysis (0)]
83.  Lefebvre M, Marchand M, Horowitz JM, Torres G. Detection of fluoxetine in brain, blood, liver and hair of rats using gas chromatography-mass spectrometry. Life Sci. 1999;64:805-811.  [PubMed]  [DOI]  [Cited in This Article: ]
84.  Nagamune H, Fukushima Y, Takada J, Yoshida K, Unami A, Shimooka T, Terada H. The lipophilic weak base (Z)-5-methyl-2-[2-(1-naphthyl)ethenyl]-4-piperidinopyridine (AU-1421) is a potent protonophore type cationic uncoupler of oxidative phosphorylation in mitochondria. Biochim Biophys Acta. 1993;1141:231-237.  [PubMed]  [DOI]  [Cited in This Article: ]
85.  Song JH, Marszalec W, Kai L, Yeh JZ, Narahashi T. Antidepressants inhibit proton currents and tumor necrosis factor-α production in BV2 microglial cells. Brain Res. 2012;1435:15-23.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 20]  [Cited by in F6Publishing: 22]  [Article Influence: 1.7]  [Reference Citation Analysis (0)]
86.  Hroudová J, Fišar Z. In vitro inhibition of mitochondrial respiratory rate by antidepressants. Toxicol Lett. 2012;213:345-352.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 58]  [Cited by in F6Publishing: 59]  [Article Influence: 4.9]  [Reference Citation Analysis (0)]
87.  Hoose SA, Duran C, Malik I, Eslamfam S, Shasserre SC, Downing SS, Hoover EM, Dowd KE, Smith R, Polymenis M. Systematic analysis of cell cycle effects of common drugs leads to the discovery of a suppressive interaction between gemfibrozil and fluoxetine. PLoS One. 2012;7:e36503.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 6]  [Cited by in F6Publishing: 7]  [Article Influence: 0.6]  [Reference Citation Analysis (0)]
88.  Eddahibi S, Fabre V, Boni C, Martres MP, Raffestin B, Hamon M, Adnot S. Induction of serotonin transporter by hypoxia in pulmonary vascular smooth muscle cells. Relationship with the mitogenic action of serotonin. Circ Res. 1999;84:329-336.  [PubMed]  [DOI]  [Cited in This Article: ]
89.  Pitt BR, Weng W, Steve AR, Blakely RD, Reynolds I, Davies P. Serotonin increases DNA synthesis in rat proximal and distal pulmonary vascular smooth muscle cells in culture. Am J Physiol. 1994;266:L178-L186.  [PubMed]  [DOI]  [Cited in This Article: ]
90.  Lee SL, Wang WW, Lanzillo JJ, Fanburg BL. Regulation of serotonin-induced DNA synthesis of bovine pulmonary artery smooth muscle cells. Am J Physiol. 1994;266:L53-L60.  [PubMed]  [DOI]  [Cited in This Article: ]
91.  Krishnan A, Hariharan R, Nair SA, Pillai MR. Fluoxetine mediates G0/G1 arrest by inducing functional inhibition of cyclin dependent kinase subunit (CKS)1. Biochem Pharmacol. 2008;75:1924-1934.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 46]  [Cited by in F6Publishing: 51]  [Article Influence: 3.2]  [Reference Citation Analysis (0)]
92.  Stepulak A, Rzeski W, Sifringer M, Brocke K, Gratopp A, Kupisz K, Turski L, Ikonomidou C. Fluoxetine inhibits the extracellular signal regulated kinase pathway and suppresses growth of cancer cells. Cancer Biol Ther. 2008;7:1685-1693.  [PubMed]  [DOI]  [Cited in This Article: ]
93.  Yue CT, Liu YL. Fluoxetine increases extracellular levels of 3-methoxy-4-hydroxyphenylglycol in cultured COLO320 DM cells. Cell Biochem Funct. 2005;23:109-114.  [PubMed]  [DOI]  [Cited in This Article: ]
94.  Kashanian S, Javanmardi S, Chitsazan A, Omidfar K, Paknejad M. DNA-binding studies of fluoxetine antidepressant. DNA Cell Biol. 2012;31:1349-1355.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 20]  [Cited by in F6Publishing: 23]  [Article Influence: 1.9]  [Reference Citation Analysis (0)]
95.  Peer D, Margalit R. Fluoxetine and reversal of multidrug resistance. Cancer Lett. 2006;237:180-187.  [PubMed]  [DOI]  [Cited in This Article: ]
96.  Pavlides S, Tsirigos A, Vera I, Flomenberg N, Frank PG, Casimiro MC, Wang C, Fortina P, Addya S, Pestell RG. Loss of stromal caveolin-1 leads to oxidative stress, mimics hypoxia and drives inflammation in the tumor microenvironment, conferring the “reverse Warburg effect”: a transcriptional informatics analysis with validation. Cell Cycle. 2010;9:2201-2219.  [PubMed]  [DOI]  [Cited in This Article: ]
97.  Martinez-Outschoorn UE, Pestell RG, Howell A, Tykocinski ML, Nagajyothi F, Machado FS, Tanowitz HB, Sotgia F, Lisanti MP. Energy transfer in “parasitic” cancer metabolism: mitochondria are the powerhouse and Achilles’ heel of tumor cells. Cell Cycle. 2011;10:4208-4216.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 121]  [Cited by in F6Publishing: 124]  [Article Influence: 9.5]  [Reference Citation Analysis (0)]
98.  Whitaker-Menezes D, Martinez-Outschoorn UE, Lin Z, Ertel A, Flomenberg N, Witkiewicz AK, Birbe RC, Howell A, Pavlides S, Gandara R. Evidence for a stromal-epithelial “lactate shuttle” in human tumors: MCT4 is a marker of oxidative stress in cancer-associated fibroblasts. Cell Cycle. 2011;10:1772-1783.  [PubMed]  [DOI]  [Cited in This Article: ]
99.  Sotgia F, Whitaker-Menezes D, Martinez-Outschoorn UE, Flomenberg N, Birbe RC, Witkiewicz AK, Howell A, Philp NJ, Pestell RG, Lisanti MP. Mitochondrial metabolism in cancer metastasis: visualizing tumor cell mitochondria and the “reverse Warburg effect” in positive lymph node tissue. Cell Cycle. 2012;11:1445-1454.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 127]  [Cited by in F6Publishing: 142]  [Article Influence: 11.8]  [Reference Citation Analysis (0)]
100.  Balliet RM, Capparelli C, Guido C, Pestell TG, Martinez-Outschoorn UE, Lin Z, Whitaker-Menezes D, Chiavarina B, Pestell RG, Howell A. Mitochondrial oxidative stress in cancer-associated fibroblasts drives lactate production, promoting breast cancer tumor growth: understanding the aging and cancer connection. Cell Cycle. 2011;10:4065-4073.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 98]  [Cited by in F6Publishing: 98]  [Article Influence: 7.5]  [Reference Citation Analysis (0)]
101.  Pavlides S, Whitaker-Menezes D, Castello-Cros R, Flomenberg N, Witkiewicz AK, Frank PG, Casimiro MC, Wang C, Fortina P, Addya S. The reverse Warburg effect: aerobic glycolysis in cancer associated fibroblasts and the tumor stroma. Cell Cycle. 2009;8:3984-4001.  [PubMed]  [DOI]  [Cited in This Article: ]