Journal Article

Synergistic apoptotic effects in cancer cells by the combination of CLK and Bcl-2 family inhibitors

Ebara, Shunsuke, Sasaki, Satoshi, Murai, Aiko, Nomura, Toshiyuki, Araki, Shinsuke, Ohashi, Tomohiro, Miyazaki, Tohru

2020

Overview

Emerging evidence indicates that alternative splicing plays a critical role in cancer progression through abnormal expression or mutation of splicing factors. Small-molecule splicing modulators have recently attracted considerable attention as a novel class of cancer therapeutics. CDC-like kinases (CLKs) are central to exon recognition in mRNA splicing and CLK inhibitors exhibit anti-tumour activities. Most importantly, molecular mechanism-based combination strategies for cancer therapy must be considered. However, it remains unclear whether CLK inhibitors modulate expression and splicing of apoptosis-related genes, and whether CLK inhibitors enhance cytotoxicity in combination with apoptosis inducers. Here we report an appropriate mechanism-based drug combination approach. Unexpectedly, we found that the CLK inhibitor T3 rapidly induced apoptosis in A2780 cells and G2/M cell cycle arrest in HCT116 cells. Regardless of the different phenotypes of the two cancer cell types, T3 decreased the levels of anti-apoptotic proteins (cIAP1, cIAP2, XIAP, cFLIP and Mcl-1) for a short period of exposure and altered the splicing of the anti-apoptotic MCL1L and CFLAR isoform in A2780 and HCT116 cells. In contrast, other members of the Bcl-2 family (i.e., Bcl-xL and Bcl-2) were resistant to T3-induced expression and splicing modulation. T3 and a Bcl-xL/Bcl-2 inhibitor synergistically induced apoptosis. Taken together, the use of a CLK inhibitor is a novel therapeutic approach to sensitise cancer cells to Bcl-xL/Bcl-2 inhibitors.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Alternative splicing / Alternative Splicing - drug effects / Anticancer properties / Antimitotic agents / Antineoplastic agents / Antineoplastic Agents - chemistry / Antineoplastic Agents - pharmacology / Apoptosis / Apoptosis - drug effects / Apoptosis - genetics / Bcl-2 protein / Bcl-x protein / Biology and Life Sciences / Breast cancer / c-FLIP protein / Cancer / Cancer cells / CASP8 and FADD-Like Apoptosis Regulating Protein - metabolism / Cell cycle / Cell Cycle Checkpoints - drug effects / Cell growth / Cell Line, Tumor / Cell Proliferation - drug effects / Control / Cytotoxicity / Drug Synergism / G2 Phase - drug effects / Growth / Humans / Inhibitors / Kidney cancer / Kinases / Mcl-1 protein / Mechanistic Target of Rapamycin Complex 2 - metabolism / Medicine and Health Sciences / Modulators / mRNA / Mutation / Myeloid Cell Leukemia Sequence 1 Protein - genetics / Myeloid Cell Leukemia Sequence 1 Protein - metabolism / Pharmaceutical industry / Phenotypes / Physiological aspects / Proteasome Endopeptidase Complex - metabolism / Protein Kinase Inhibitors - chemistry / Protein Kinase Inhibitors - pharmacokinetics / Protein Kinase Inhibitors - pharmacology / Protein-Serine-Threonine Kinases - antagonists & inhibitors / Protein-Tyrosine Kinases - antagonists & inhibitors / Proteins / Proto-Oncogene Proteins c-bcl-2 - antagonists & inhibitors / RNA Precursors - genetics / RNA Precursors - metabolism / RNA splicing / Splicing factors / Testing / Toxicity / Tumors / XIAP protein