Abstract 2502: Targeting anti-apoptotic Bcl-2 family for cancer therapy

Introduction: Despite the recent advancement in treating melanoma, options are still limited for patients without BRAF mutations or in relapse from current treatments, and promising, immunotherapies are not without caveats. Thus, alternative options are still in need. Bcl-2 protein is the main member of a family whose best-characterized function is to regulate apoptosis in several pathologies, including melanoma. To evade apoptotic checkpoints, melanoma cells often overexpress Bcl-2 and other antiapoptotic proteins. Consequently, along with the fact that antiapoptotic proteins play a critical role in the efficacy of most chemotherapeutics and play a relevant role in melanoma progression, they have emerged as attractive targets for therapeutic development. Structure-based efforts led to the development of ABT-199 (also known as venetoclax), recently approved by the Food and Drug Administration for the treatment of chronic lymphocytic leukaemia patients. Experimental procedures: To identify new possible selective inhibitors towards antiapoptotic proteins belonging to the bcl-2 family, a computational medicinal chemistry protocol was set up. Both the PubMed/ChEMBL databases, containing known ligands for bcl-2, bcl-w and bcl-xL proteins and their associated affinities, and the RCSB Protein Data Bank listing 65 bcl-2 family protein structures, were used to build preliminary Quantitative Structure-Activity Relationships (QSAR) models. The QSAR models were used to screen the VITAS-M Laboratory database to select 60 chemical scaffolds as hypothetical novel Bcl-2 inhibitors. Surface Plasmon Experiments were carried out to assess affinity of compounds for Bcl-2. The sensitivity of human leukemia and melanoma cells to these compounds was evaluated in terms of cell survival, cell cycle distribution and apoptosis induction, by using different concentrations and time exposure. Results: 9 out of 60 compounds (15%) were able to reduce cell viability at concentrations lower than 50µM, and to induce cell death in a dose-dependent manner, even though at different extend depending on the compound tested. Inclusion of the 60 selected compounds led to a new QSAR model to perform a second virtual screen on the NIH database from which 40 putative Bcl-2 target molecules were selected and whose efficacy to inhibit cell viability of both leukemia and melanoma cells was measured. 11 compounds are endowed with high affinity for Bcl-2, 2 out of 40 compounds were demonstrated to induce apoptosis in both tumor histotypes in a dose-dependent manner, while they did not affect cell viability of human normal fibroblasts. Conclusion: Machine learning application coupled with experimental data have provided new insights into bcl-2 family9s regulation of the apoptotic pathway both in leukemia and in melanoma, and suggest that inhibiting the major anti-apoptotic proteins is sufficient to induce cell death. Note: This abstract was not presented at the meeting. Citation Format: Elisabetta Valentini, Marta Di Martile, Marianna Desideri, Simona Carcasole, Alexandros Patsilinakos, Manuela Sabatino, Antonello Mai, Gianni Colotti, Rino Ragno, Daniela Trisciuoglio, Donalella Del Bufalo. Targeting anti-apoptotic Bcl-2 family for cancer therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2502.