BCL-XL blockage in TNBC models confers vulnerability to inhibition of specific cell cycle regulators

Abstract

Cell cycle regulators are frequently altered in Triple-Negative Breast Cancer (TNBC). Emerging agents targeting these signals offer the possibility to design new combinatorial therapies. However, preclinical models that recapitulate TNBC primary resistance and heterogeneity are essential to evaluate the potency of these combined treatments. Methods: Bioinformatic processing of human breast cancer datasets was used to analyse correlations between expression levels of cell cycle regulators and patient survival outcome. The MMTV-R26Met mouse model of TNBC resistance and heterogeneity was employed to analyse expression and targeting vulnerability of cell cycle regulators in the presence of BCL-XL blockage. Robustness of outcomes and selectivity was further explored using a panel of human breast cancer cells. Alterations of protein expression, phosphorylation, and/or cellular localisation were analysed by western blots, reverse phase protein array, and immunocytochemistry. Bioinformatics was performed to highlight drug's mechanisms of action. Results: We report that high expression levels of BCL-XL and specific cell cycle regulators correlate with poor survival outcomes of TNBC patients. Blockage of BCL-XL confers vulnerability to drugs targeting CDK1/2/4, but not FOXM1, CDK4/6, Aurora A and Aurora B, to all MMTV-R26Met and human TNBC cell lines tested. Mechanistically, we show that, co-targeting of BCL-XL and CDK1/2/4 synergistically inhibited cell growth by combinatorial depletion of survival and RTK/AKT signals, and concomitantly restoring FOXO3a tumour suppression actions. This was accompanied by an accumulation of DNA damage and consequently apoptosis. Conclusions: Our studies illustrate the possibility to exploit the vulnerability of TNBC cells to CDK1/2/4 inhibition by targeting BCL-XL. Moreover, they underline that specificity matters in targeting cell cycle regulators for combinatorial anticancer therapies.

MYC and MET cooperatively drive hepatocellular carcinoma with distinct molecular traits and vulnerabilities

“…Immunocytochemical analyses on cultured cells. Human HCC cell lines were xed and processed for immuno uorescent staining as previously reported [27,28,32]. Brie y, after 36h treatment with 10058-F4 and cabozantinib, alone or in combination, Huh7 cells were xed in 4% paraformaldehyde (PFA) for 10 min and then washed three times with PBS for 5-10 min.…”

“…Overall, the evidence implicating MET in HCC is su ciently strong to have warranted several clinical trials of MET inhibitors [24]. Using a unique genetic setting in which expression of wild-type MET can be slightly enhanced above its endogenous level in a tissue-speci c manner (R26 stopMet mice) [25][26][27][28], we have documented how liver enhanced MET leads progressively to tumorigenesis with age, reaching approximately 80% frequency (Alb-R26 Met mice) [29,30]. The Alb-R26 Met can be considered as a predisposition model, as the slightly enhanced MET levels leave hepatocytes vulnerable to the emergence of molecular events that trigger preneoplastic lesions and progression towards HCC.…”