BH3 Mimetic ABT-737 and a Proteasome Inhibitor Synergistically Kill Melanomas through Noxa-Dependent Apoptosis

Abstract

The Bcl-2 family is important in modulating sensitivity to anticancer drugs in many cancers, including melanomas. The BH3 mimetic ABT-737 is a potent small molecule inhibitor of the anti-apoptotic proteins Bcl-2/Bcl-X(L)/Bcl-w. In this report, we examined whether ABT-737 is effective in killing melanoma cells in combination with the proteasome inhibitor MG-132, and further evaluated the mechanisms of action. Viability, morphological, and Annexin V apoptosis assays showed that ABT-737 alone exhibited little cytotoxicity, yet it displayed strong synergistic lethality when combined with MG-132. In addition, the detection of Bax/Bak activation indicated that the combination treatment synergistically induced mitochondria-mediated apoptosis. Furthermore, mechanistic analysis revealed that this combination treatment induced expression of the pro-apoptotic protein Noxa- and caspase-dependent degradation of the anti-apoptotic protein, Mcl-1. Finally, siRNA-mediated inhibition of Mcl-1 expression significantly increased sensitivity to ABT-737 in these cells, and knocking down Noxa expression protected the cells from cytotoxicity induced by the combination treatment. These findings demonstrate that ABT-737 combined with MG-132 synergistically induced Noxa-dependent mitochondrial-mediated apoptosis. In summary, this study indicates promising therapeutic potential of targeting anti-apoptotic Bcl-2 family members in treating melanoma, and it validates rational molecular approaches that target anti-apoptotic defenses when developing cancer treatments.

The BH3 α-Helical Mimic BH3-M6 Disrupts Bcl-XL, Bcl-2, and MCL-1 Protein-Protein Interactions with Bax, Bak, Bad, or Bim and Induces Apoptosis in a Bax- and Bim-dependent Manner

“…Indeed, our findings support this prediction by demonstrating that that the combination of BH3-M6 with the proteasome inhibitor CEP-1612 synergistically kills A549 cells. Our results are consistent with others that show that ABT-737 synergizes with the proteasome inhibitors bortezomib (50) or MG-132 (51).…”

Restraining FOXO3-dependent transcriptional BMF activation underpins tumour growth and metastasis of E-cadherin-negative breast cancer

“…42,43 Recent studies indicated that BH3-mimetics can be used to treat nonlymphoid cancers but mostly in combination with oestrogen antagonists, proteasome inhibitors, specific PI3K-mTOR inhibitors or chemotherapy. 24,[44][45][46][47][48][49] As previous findings from our laboratory demonstrated that E-cadherin-negative lobular breast cancer depends on p120-catenin-mediated activation of RhoA, Rock and subsequent actomyosin contraction, 26 we anticipate that dual inhibition of these pathways might be successful in E-cadherin-negative cancers that are not driven by oncogenic activation of GFR pathways. Although we do not yet know whether RhoA-Rock signals converge onto the GFR-AKT-FOXO axis in the regulation of anoikis resistance, the fact that FOXO expression had no effect on survival of B-RAF/KRAS-mutated MDA-MB-231 cells seems to be in line with this assumption.…”

BCL-2 inhibition with ABT-737 prolongs survival in an NRAS/BCL-2 mouse model of AML by targeting primitive LSK and progenitor cells

“…11 The efficacy of ABT-737 has already shown in vitro inducing apoptosis of carcinoma and AML cell lines, 12 ex vivo on patients' blasts, 11 in vivo on a mouse model of lymphoma 13 and on a xenograft model of small cell lung cancer. 14 The combination of ABT-737 with chemotherapeutic agents [15][16][17] or other targeted therapy molecules 18,19 has synergistic efficacy. A related orally bioavailable derivative, ABT-263 (Navitoclax) has been tested in a phase I clinical trial on patients with both small cell lung cancer and other solid tumors 20,21 and chronic lymphocytic leukemia 22,23 in which acceptable toxicity and promising efficacy has been reported.…”