abt-199 and birinapant

Due to the lack of effective treatments for glioblastoma (GBM), we here studied the responsiveness of GBM cell lines to the combination of death ligand, TRAIL and the IAP antagonist, TL32711 (Birinapant). Responses were highly heterogeneous, with synergistic apoptosis as well as treatment resistance observed. Caspase-8 and Bid, together with caspase-3, form a nonlinear signalling hub that efficiently induced apoptosis in responder cell lines. Cells resistant to TRAIL/TL32711 expressed low amounts of procaspase-8 and Bid and poorly activated caspase-3. We therefore hypothesised that improving caspase-8 activation or sensitising mitochondria to truncated Bid (tBid) could convert non-responder GBM cell lines to responders. Mathematical simulations of both strategies predicted mitochondrial sensitization to tBid would outperform enhancing caspase-8 activation. Indeed, antagonising Bcl-2 by ABT-199 allowed TRAIL/TL32711 response synergies to manifest in otherwise TRAIL resistant cell lines. These findings were further corroborated in experiments with a translationally relevant hexavalent TRAIL variant. Our study therefore demonstrates that a high caspase-8/Bid signature is associated with synergistic TRAIL/TL32711-induced apoptosis in GBM cells and outlines Bcl-2 antagonism as a highly potent intervention to sensitize highly TRAIL-resistant GBM cells to TRAIL/TL32711 combination treatment.

Topics: Antineoplastic Combined Chemotherapy Protocols; Apoptosis; BH3 Interacting Domain Death Agonist Protein; Bridged Bicyclo Compounds, Heterocyclic; Caspase 8; Cell Line, Tumor; Dipeptides; Drug Resistance, Neoplasm; Drug Synergism; Gene Expression Regulation, Neoplastic; Humans; Indoles; Inhibitor of Apoptosis Proteins; Mitochondria; Neuroglia; Proto-Oncogene Proteins c-bcl-2; Signal Transduction; Sulfonamides; TNF-Related Apoptosis-Inducing Ligand

High expression levels of Inhibitors of Apoptosis Proteins (IAPs) have been correlated with poor cancer prognosis and block the cell death pathway by interfering with caspase activation. SMAC-mimetics are small-molecule inhibitors of IAPs that mimic the endogenous SMAC and promote the induction of cell death by neutralizing IAPs.. In this study, anti-tumour activity of new SMAC-mimetics Birinapant and AT-406 is evaluated against colorectal adenocarcinoma cells and IAP cross-talk with either oncogenic BRAF or BCL-2, or with the TRAIL are further exploited towards rational combined protocols.. It is shown that pre-treatment of SMAC-mimetics followed by their combined treatment with BRAF inhibitors can decrease cell viability, migration and can very efficiently sensitize colorectal tumour cells to apoptosis. Moreover, co-treatment of TRAIL with SMAC-mimetics can efficiently sensitize resistant tumour cells to apoptosis synergistically, as shown by median effect analysis. Finally, Birinapant and AT-406 can synergise with BCL-2 inhibitor ABT-199 to reduce viability of adenocarcinoma cells with high BCL-2 expression.. Proposed synergistic rational anticancer combined protocols of IAP antagonists Birinapant and AT-406 in 2D and 3D cultures can be later further exploited in vivo, from precision tumour biology to precision medical oncology.

Topics: Antineoplastic Agents; Azocines; Benzhydryl Compounds; Bridged Bicyclo Compounds, Heterocyclic; Caco-2 Cells; Cell Culture Techniques; Cell Line, Tumor; Cell Proliferation; Cell Survival; Colorectal Neoplasms; Dipeptides; Drug Resistance, Neoplasm; Drug Synergism; Gene Expression Regulation, Neoplastic; HCT116 Cells; HT29 Cells; Humans; Indoles; Mutation; Proto-Oncogene Proteins B-raf; Sulfonamides; TNF-Related Apoptosis-Inducing Ligand