When cells sense a decrease in oxygen availability (hypoxia), they develop adaptive responses in order to sustain this condition and survive. If hypoxia lasts too long or is too severe, the cells eventually die. Hypoxia is also known to modulate the p53 pathway, in a manner dependent or not of HIF-1 (hypoxia-inducible factor-1), the main transcription factor activated by hypoxia. The p53 protein is a transcription factor, which is rapidly stabilised by cellular stresses and which has a major role in the cell responses to these stresses. The aim of this review is to compile what has been reported until now about the interconnection between these two important pathways. Indeed, according to the cell line, the severity and the duration of hypoxia, oxygen deficiency influences very differently p53 protein level and activity. Conversely, p53 is also described to affect HIF-1α stability, one of the two subunits of HIF-1, and HIF-1 activity. The direct and indirect interactions between HIF-1α and p53 are described as well as the involvement in this complex network of their respective ubiquitin ligases von Hippel Lindau protein and murine double minute 2. Finally, the synergistic or antagonistic effects of p53 and HIF-1 on some important cellular pathways are discussed.

To investigate the correlation between tumour accumulation of In-111-bevacizumab and VEGF-A expression in patients with colorectal liver metastases.

Two weeks before resection of the liver metastases 12 patients were intravenously injected with In-111-labelled bevacizumab. Ten minutes and 7 d after injection a whole body scan was acquired. Seven days after the injection, 3D acquisition SPECT of the liver was performed.

Enhanced uptake of In-111-bevacizumab in the liver metastases was observed in 9 of the 12 patients. The level of antibody accumulation in these lesions varied considerably. There was no correlation between the level of In-111-antibody accumulation and the level of VEGF-A expression in the tissue as determined by in situ hybridisation and ELISA.

In this study, we investigated the correlation between tumour accumulation of radiolabelled bevacizumab and VEGF-A expression in patients with colorectal liver metastases. No clear-cut correlation between the level of antibody accumulation and expression of VEGF-A was found.

Therapy targeting hypoxia-inducible factor-1 (HIF-1) to reverse the hypoxia-related drug resistance has received much interest. Despite a close interaction between HIF-1 and p53 and that p53 mutation is seen in >50% of tumors, whether HIF-1 silencing by targeted therapy depends on tumor p53 status remains unknown. Two isogenic fibrosarcoma cells HT1080 (wild-type p53) and HT1080-6TG (mutant p53) were transduced with HIF-1alpha-specific RNAi lentiviral vectors and selected with blasticidin. Real-time PCR and western blot analysis of HIF-1alpha mRNA and protein respectively validated the silencing effects. Cells were first preconditioned under hypoxia (0.5% O(2)) for 4 h and then co-treated with cisplatin for another 24 h. MTT was used for assessment of chemosensitivity to cisplatin. Moreover, annexin V and propidium iodide staining was detected on flow cytometry for analysis of cisplatin-induced apoptosis. Furthermore, changes of some Bcl-2 family members were detected on western blotting. Exposure to hypoxia significantly increased resistance to cisplatin than exposure to normoxia. HIF-1alpha knockdown could reverse hypoxia-related resistance to cisplatin and apoptotic resistance only in HT1080 cells, but had little effect on HT1080-6TG cells. With HIF-1alpha knockdown, Bid expression was higher in HT1080 than in HT1080-6TG under hypoxia. In summary, HIF-1 targeted therapy to reverse hypoxia-related cisplatin resistance depends on normal p53 status. Changes of Bid expression levels under hypoxia might contribute in part to the differential response to HIF-1alpha silencing in cells with different p53 status.

Hypoxia-inducible factor (HIF-1) which contains oxygen regulated HIF-1alpha subunit maintains cytoprotective defence against hypoxic injury by induction of numerous genes. However, apoptotic regulators such as Bcl-xL, Bax and P53 have not been associated with HIF-1 dependent regulation in immunohistochemical evaluation of human colorectal cancer tumours so far. Thus, we visualised these proteins immunohistochemically and using Spearman's test compared for the first time their expression in regard to different clinicopathological traits in 123 (113 for P53 evaluation) human colorectal cancers.

HIF-1alpha correlated with Bcl-xL or Bax in all patients and particularly in node negative and node positive cancers, deeper intramural tumours (pT3+pT4) and adenocarcinomas. There was no significance in a small group of tumours with lesser extent through intestinal walls (pT1+pT2). In addition HIF-1alpha associated with Bcl-xL in mucinous cancers. Moreover, HIF-1alpha correlated with Bcl-xL or Bax in moderately (G2) and poorly differentiated (G3) cancers, rectal and colonic tumours and in different sex and age groups. P53 correlated only with Bax exclusively in younger patients.

HIF-1alpha may influence expression of Bax or Bcl-xL, at least indirectly, as correlations between HIF-1alpha and Bax or Bcl-xL occur constantly.

The human homologue of murine double minute 2 (HDM2) oncogene is amplified in approximately 7% of all human cancers. Overexpression of HDM2 protein impairs cell cycle control and confers growth advantage to cancer cells. In several cancers the progression of tumor growth and formation of distant metastases are found to be dependent on tumor angiogenesis, a process that is regulated by vascular endothelial growth factor (VEGF). In this study, we have investigated the co-expression of HDM2 and VEGF in various types of human cancer cell lines and have shown that the co-expression is not cell-type-specific. Furthermore, when different types of cell lines were treated with a HDM2 gene specific antisense phosphorothioate oligodeoxynucleotide (HDMAS5), the expression of VEGF mRNA as well as the levels of VEGF protein was found to be decreased. Interestingly, the higher basal levels of VEGF mRNA and the protein observed in HDM2 transfected LNCaP-MST cells were effectively suppressed by HDMAS5 treatment. On the contrary, the mutant oligodeoxynucleotide containing 4 mismatched bases (M4) did not alter the expression of either HDM2 or VEGF in any of the cell lines tested. In conclusion, our findings are the first time evidence showing that HDM2 and VEGF are co-expressed in various cancer cell lines that have aggressive growth and high metastatic abilities. Furthermore, the decrease in VEGF expression observed at the transcriptional as well as translational levels, subsequent to HDMAS5 treatment of p53 null cells, strongly suggests that HDM2 has a regulatory role on VEGF expression in a p53 independent manner.

There is much controversy in the literature regarding the role of p53 status response on hypoxia inducible factor (HIF) signaling in response to chronic relative hypoxia (CRH). The goal of this paper was to methodically examine this response in isogenically matched tumor cells. We report that p53-mutant (MUT) cells, versus p53-wild-type (WT) cells, showed decreased apoptosis, increased cell proliferation with higher basal HIF-1alpha levels in response to CRH. In addition, we found increased HIF-mediated transactivation and increased VEGF release with decreased HIF-1alpha/p53 and HIF-1alpha/MDM-2 partnering in p53-MUT versus p53-WT cells in response to CRH.

Pathways adopted by developing cancer cells for evasion of cellular surveillance mechanism deserve attention for therapeutic exploitation as well as for better prognosis. A novel mitotic kinase, PDZ-binding kinase or PBK, which is upregulated in a variety of neoplasms including hematological malignancies, has been the focus of our attention with a goal to understand its role in malignant conversion and to examine as a possible new therapeutic target in disparate types of cancer. Earlier, we reported that PBK expression was downregulated during macrophage differentiation of HL60 promyelocytic leukemia cells, during doxorubicin-induced growth arrest in G2/M phase and that PBK was regulated by cell cycle-specific transcription factors E2F and CREB/ATF. Here, we demonstrate that HT1080 fibrosarcoma cells become adapted to doxorubicin-induced DNA damage checkpoint upon ectopic expression of a phosphomimetic mutant of PBK as indicated by the accumulation of polyploid cells. Aberrant entry into the mitotic phase by these cells is suggested by the appearance of a mitotic phase-specific marker, MPM-2. We propose that the effect is due to downregulation of p53 caused by direct physical interaction with PBK as detected by both a biochemical means as well as by yeast two-hybrid analysis. Together, our studies provide a plausible explanation for the role of PBK augmenting tumor cell growth following transient appearance in different types of progenitor cells in vivo as reported.