ABSTRACT
Survivin overexpression, frequently found in breast cancers and others, is associated with poor prognosis. Its dual regulation of cell division and apoptosis makes it an attractive therapeutic target but its exact functions that are required for tumor maintenance are still elusive. Survivin protects cancer cells from genotoxic agents and this ability is generally assigned to a universal anti-apoptotic function. However, a specific role in cancer cell protection from DNA damage has been overlooked so far. We assessed DNA damage occurrence in Survivin-depleted breast cancer cells using γH2AX staining and comete assay. QPCR data and a gene conversion assay indicated that homologous recombination (HR) was impaired upon Survivin depletion. We conducted the analysis of Survivin and HR genes' expression in breast tumors. We revealed BRCAness phenotype of Survivin-depleted cells using cell death assays combined to PARP targeting. Survivin silencing leads to DNA double-strand breaks in breast cancer cells and functionally reduces HR. Survivin depletion decreases the transcription of a set of genes involved in HR, decreases RAD51 protein expression and impairs the endonuclease complex MUS81/EME1 involved in the resolution of Holliday junctions. Clinically, EME1, RAD51, EXO1, BLM expressions correlate with that of BIRC5 (coding for Survivin) and are of prognostic value. Functionally, Survivin depletion triggers p53 activation and sensitizes cancer cells to of PARP inhibition. We defined Survivin as a constitutive actor of HR in breast cancers, and implies that its inhibition would enhance cell vulnerability upon PARP inhibition.
Subject(s)
Breast Neoplasms/genetics , Breast Neoplasms/metabolism , DNA Repair , Homologous Recombination , Inhibitor of Apoptosis Proteins/metabolism , Aurora Kinase B/genetics , Aurora Kinase B/metabolism , Cdc20 Proteins/genetics , Cdc20 Proteins/metabolism , Cell Line, Tumor , DNA Breaks, Double-Stranded , Drug Resistance, Neoplasm , Female , Gene Expression , Gene Knockdown Techniques , Gene Silencing , Histones/metabolism , Humans , Inhibitor of Apoptosis Proteins/genetics , Poly(ADP-ribose) Polymerase Inhibitors/pharmacology , Prognosis , Survivin , Tumor Suppressor Protein p53/genetics , Tumor Suppressor Protein p53/metabolismABSTRACT
Specific overexpression in cancer cells and evidence of oncogenic functions make Survivin an attractive target in cancer therapy. The small molecule compound YM155 has been described as the first "Survivin suppressant" but molecular mechanisms involved in its biological activity and its clinical potential remain obscure. We herein show that YM155 exerts single agent toxicity on primary breast cancer cells grown in an ex vivo assay preserving tumor microenvironment. In vitro assays indicate that YM155 more efficiently triggers cell death in breast cancer cells (including these with stem-cell like properties) than in non tumorigenic mammary cells. YM155-induced cell death is critically dependent on autophagy and NF-kB but independent of p53 and it coïncides with DNA damage and a DNA damage response in p53-proficient cells. Our results point out a crosstalk between NF-kB and autophagy controlling YM155-induced death in breast cancer cells and argue for the potential use of YM155 as a genotoxic agent in breast cancer therapy.
Subject(s)
Breast Neoplasms/drug therapy , Imidazoles/pharmacology , NF-kappa B/metabolism , Naphthoquinones/pharmacology , Antineoplastic Agents/pharmacology , Autophagy/drug effects , Breast Neoplasms/genetics , Breast Neoplasms/metabolism , Breast Neoplasms/pathology , Cell Death/drug effects , Cell Line, Tumor , Cell Proliferation/drug effects , DNA Damage , Female , Humans , MCF-7 Cells , NF-kappa B/antagonists & inhibitors , Signal Transduction/drug effects , Transfection , Xenograft Model Antitumor AssaysABSTRACT
Attacking cancer cell survival defense by targeting B-Cell Lymphoma 2 (BCL2) family of anti-apoptotic proteins may provide a powerful means to improve chemotherapy efficiency. This could be particularly relevant to anti-mitotic-based therapy, where tumor response relates to a competing network between mitotic cell death signaling and mitotic slippage as an adaptative response to a leaky mitotic checkpoint. In this review, we focus on recent findings that point out the major role played by BCL2 family members in response to anti-mitotic agents, which reveal dependence of cancer cell survival on BCL2 homologs during mitotic arrest and after mitotic slippage. Finally, we discuss pre-clinical data combining anti-mitotic agents with BCL2 inhibitors.
