Copyright
©The Author(s) 2021.
World J Stem Cells. Jul 26, 2021; 13(7): 841-860
Published online Jul 26, 2021. doi: 10.4252/wjsc.v13.i7.841
Published online Jul 26, 2021. doi: 10.4252/wjsc.v13.i7.841
Table 1 Pathways and factors influencing cancer stem cells
Factors/pathways | Role in cancer stem cells | Ref. |
MicroRNAs | Involved in modulation of genes associated with CSC pathways such as Notch, Wnt/β-catenin, hedgehog, PI3K, NF-κB, etc. miR-9, miR-22, miR-155, mi-181, miR-221/222 and miR-373 are upregulated in CSCs and promote tumor invasiveness and stemness | Akbarzadeh et al[28] and Lapidot et al[29] |
Notch | Aberrant expression in CSCs with upregulation of stemness genes such as ALDH, Sox2, Oct4, klf4 lead to increased self-renewal stem cell property. Notch 1 upregulates transcription of RTK ErbB2 gene, influencing self-renewal property of CSCs. Notch 4 induces the expression of Snail homolog 2, an EMT mediator hence imparting quiescent mesenchymal phenotype in BCSCs | Pannuti et al[39], Suman et al[40] and Harrison et al[41] |
Hedgehog | Hh signaling regulates self-renewal property of stem cells by activating polycomb gene BMI-1. GLI1/GLI2 transcription factors or Hh ligand overexpression cause mammosphere formation and cancer stem cell growth. Hh signaling leads to upregulation of stemness markers c-myc, Nanog, Oct 4. BCSCs markers CD44 and ALDH1. Invasion and EMT promoting Snail and Wnt and jagged ligands | Liu et al[48] |
Wnt | Elevated Wnt signaling in BCSCs increases tumorigenicity and metastases, and conversely abrogation of Wnt decreases tumorigenicity. CSCs shows upregulated expression of various Wnt downstream molecules; LEF1, β-catenin and TCF-4. β-catenin complexes with the TCF/LEF and leads to the transcription of several target genes involved in CSC initiation, maintenance, invasion and metastasis such as lgr5, c-Myc, c-Jun, cyclin D1, MMP7 and fibronectin | Monteiro et al[109], Jang et al[110], and Kalluri and Weinberg [111] |
PI3K | Differentially expressed in the cancer stem cell subpopulation leading to enhanced survival. Strong correlation between PI3K pathway and programmed cell death-ligand 1 could account for stemness in claudin low breast cancer subtypes, as it causes the upregulation of Oct-4A, Nanog and Bmi1 genes. Bmi1 plays a significant role in the self-renewal of BCSCs (CD44+/CD24–/Lin–) as it transcriptionally downregulates PTEN, thereby leading to enhanced PI3K signaling | Liu et al[48] and Magee et al[75] |
HER2 | HER2 containing heterodimers can activate key signaling proliferative pathways like RAS/Raf/MAPK pathway and the cell survival PI3K/Akt pathway. HER2 overexpression generates multidrug resistance phenotype acting via the PI3K/ Akt pathway | Karunagaran et al[112] and Ren and Schaefer[113] |
NF-κB | One important target of transcription factor NF-κB is CD44 whose expression is increased in cancer stem cells. NF-kB regulates the ECM modifying matrix MMP9. Inhibition of NF-κB could result in repression of CD44 and MMP9 and lead to decreased invasiveness in breast cancer cells | So et al[114], Yu and Stamenkovic[115], and Smith et al[116] |
BRCA1 | Loss of BRCA1 responsible for aggressive basal-like breast cancer and expansion of BCSCs. Silencing of BRCA1 expression by siRNA transitions cells to acquire stemness features | Miki et al[24], Lim et al[25] and Heerma van Voss et al[117] |
Hypoxia | Upregulates genes associated with CSCs thereby allowing long-term self-renewal capacity and a blocking of differentiation. Inhibits BRCA1 expression and downregulation of BRCA1 protein. Upregulates BCSC pool | Ungefroren et al[118], Lin and Yun[119], and Xie et al[120] |
Table 2 Clinical trials targeting stemness pathways
Drug | Action | Clinical trial phase | NCT number |
Glasdegib | Notch pathway inhibitor | Phase I | NCT02027376 |
LGK-974 | Inhibitor of the endogenous Wnt palmitoleoylase | Phase I | NCT01351103 |
Sonidegib | Smo inhibitor of the Hedgehog signaling pathway | Phase I/II | NCT02027376 |
Gedatolisib | Targets the PI3K/mTOR pathway in TNBC or advanced breast cancers | Phase I/II | NCT03911973 |
Bevacizumab | Targets VEGF signaling | Phase I/II | NCT01190345 |
Ribociclib | CDK4/6 inhibitors in metastatic breast cancer | Phase II | NCT02738866 |
Anti-PTK7 antibody-drug conjugate | Targets PTK7 in BCSCs | Phase I/II | NCT03243331 |
MEDI4736 | Antibody against PD-L1 | Phase II | NCT02685059 |
Abemaciclib | CDK4/6 inhibitors in metastatic breast cancer | Phase II | NCT03703466 |
Bivatuzumab | Targeting stem cell surface marker CD44v6 | Phase 1 | NCT02254005 |
- Citation: Khan S, Suryavanshi M, Kaur J, Nayak D, Khurana A, Manchanda RK, Tandon C, Tandon S. Stem cell therapy: A paradigm shift in breast cancer treatment. World J Stem Cells 2021; 13(7): 841-860
- URL: https://www.wjgnet.com/1948-0210/full/v13/i7/841.htm
- DOI: https://dx.doi.org/10.4252/wjsc.v13.i7.841