Targeting proapoptotic protein BAD inhibits survival and self-renewal of cancer stem cells

Seetharama S. Konduru, Mariam Al-Muftah, Pu Li, Moza K. Al-Kowari, E. Wang, Aouatef Ismail EP Chouchane, D. Kizhakayil, G. Kulik, F. M. Marincola, A. Haoudi, Lotfi Chouchane

Research output: Contribution to journalArticle

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Abstract

Emerging evidence suggests that the resistance of cancer stem cells (CSC) to many conventional therapies is one of the major limiting factors of cancer therapy efficacy. Identification of mechanisms responsible for survival and self-renewal of CSC will help design new therapeutic strategies that target and eliminate both differentiated cancer cells and CSC. Here we demonstrated the potential role of proapoptotic protein BAD in the biology of CSC in melanoma, prostate and breast cancers. We enriched CD44(+)/CD24(-) cells (CSC) by tumorosphere formation and purified this population by FACS. Both spheres and CSC exhibited increased potential for proliferation, migration, invasion, sphere formation, anchorage-independent growth, as well as upregulation of several stem cell-associated markers. We showed that the phosphorylation of BAD is essential for the survival of CSC. Conversely, ectopic expression of a phosphorylation-deficient mutant BAD induced apoptosis in CSC. This effect was enhanced by treatment with a BH3-mimetic, ABT-737. Both pharmacological agents that inhibit survival kinases and growth factors that are involved in drug resistance delivered their respective cytotoxic and protective effects by modulating the BAD phosphorylation in CSC. Furthermore, the frequency and self-renewal capacity of CSC was significantly reduced by knocking down the BAD expression. Consistent with our in vitro results, significant phosphorylation of BAD was found in CD44(+) CSC of 83% breast tumor specimens. In addition, we also identified a positive correlation between BAD expression and disease stage in prostate cancer, suggesting a role of BAD in tumor advancement. Our studies unveil the role of BAD in the survival and self-renewal of CSC and propose BAD not only as an attractive target for cancer therapy but also as a marker of tumor progression.

Original languageEnglish
Pages (from-to)1936-1949
Number of pages14
JournalCell Death and Differentiation
Volume21
Issue number12
DOIs
Publication statusPublished - 1 Dec 2014

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Neoplastic Stem Cells
Protein Transport
Phosphorylation
Neoplasms
Prostatic Neoplasms
Breast Neoplasms
Therapeutics
Tumor Biomarkers
Drug Resistance
Melanoma
Intercellular Signaling Peptides and Proteins
Phosphotransferases
Up-Regulation
Stem Cells
Pharmacology

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology

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Targeting proapoptotic protein BAD inhibits survival and self-renewal of cancer stem cells. / Konduru, Seetharama S.; Al-Muftah, Mariam; Li, Pu; Al-Kowari, Moza K.; Wang, E.; Ismail EP Chouchane, Aouatef; Kizhakayil, D.; Kulik, G.; Marincola, F. M.; Haoudi, A.; Chouchane, Lotfi.

In: Cell Death and Differentiation, Vol. 21, No. 12, 01.12.2014, p. 1936-1949.

Research output: Contribution to journalArticle

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abstract = "Emerging evidence suggests that the resistance of cancer stem cells (CSC) to many conventional therapies is one of the major limiting factors of cancer therapy efficacy. Identification of mechanisms responsible for survival and self-renewal of CSC will help design new therapeutic strategies that target and eliminate both differentiated cancer cells and CSC. Here we demonstrated the potential role of proapoptotic protein BAD in the biology of CSC in melanoma, prostate and breast cancers. We enriched CD44(+)/CD24(-) cells (CSC) by tumorosphere formation and purified this population by FACS. Both spheres and CSC exhibited increased potential for proliferation, migration, invasion, sphere formation, anchorage-independent growth, as well as upregulation of several stem cell-associated markers. We showed that the phosphorylation of BAD is essential for the survival of CSC. Conversely, ectopic expression of a phosphorylation-deficient mutant BAD induced apoptosis in CSC. This effect was enhanced by treatment with a BH3-mimetic, ABT-737. Both pharmacological agents that inhibit survival kinases and growth factors that are involved in drug resistance delivered their respective cytotoxic and protective effects by modulating the BAD phosphorylation in CSC. Furthermore, the frequency and self-renewal capacity of CSC was significantly reduced by knocking down the BAD expression. Consistent with our in vitro results, significant phosphorylation of BAD was found in CD44(+) CSC of 83{\%} breast tumor specimens. In addition, we also identified a positive correlation between BAD expression and disease stage in prostate cancer, suggesting a role of BAD in tumor advancement. Our studies unveil the role of BAD in the survival and self-renewal of CSC and propose BAD not only as an attractive target for cancer therapy but also as a marker of tumor progression.",
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