Abstract
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.
MeSH terms
-
Alternative Splicing / drug effects
-
Antineoplastic Agents / chemistry
-
Antineoplastic Agents / pharmacology*
-
Apoptosis / drug effects*
-
Apoptosis / genetics
-
CASP8 and FADD-Like Apoptosis Regulating Protein / metabolism
-
Cell Cycle Checkpoints / drug effects
-
Cell Line, Tumor
-
Cell Proliferation / drug effects
-
Drug Synergism
-
G2 Phase / drug effects
-
Humans
-
Mechanistic Target of Rapamycin Complex 2 / metabolism
-
Myeloid Cell Leukemia Sequence 1 Protein / genetics
-
Myeloid Cell Leukemia Sequence 1 Protein / metabolism
-
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*
-
Proto-Oncogene Proteins c-bcl-2 / antagonists & inhibitors*
-
RNA Precursors / genetics
-
RNA Precursors / metabolism
Substances
-
Antineoplastic Agents
-
BCL2 protein, human
-
CASP8 and FADD-Like Apoptosis Regulating Protein
-
CFLAR protein, human
-
Myeloid Cell Leukemia Sequence 1 Protein
-
Protein Kinase Inhibitors
-
Proto-Oncogene Proteins c-bcl-2
-
RNA Precursors
-
Clk dual-specificity kinases
-
Protein-Tyrosine Kinases
-
Mechanistic Target of Rapamycin Complex 2
-
Protein Serine-Threonine Kinases
-
Proteasome Endopeptidase Complex
Grants and funding
Takeda Pharmaceutical Company Limited provided support in the form of salaries for authors but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.