Research, Takeda Pharmaceutical Company Limited, Fujisawa, Kanagawa, Japan.
PLoS One. 2020 Oct 16;15(10):e0240718. doi: 10.1371/journal.pone.0240718. eCollection 2020.
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.
新出现的证据表明，通过剪接因子的异常表达或突变，可变剪接在癌症进展中起着关键作用。小分子剪接调节剂作为一种新型的癌症治疗药物，最近引起了相当大的关注。CDC 样激酶（CLKs）是 mRNA 剪接中外显子识别的核心，CLK 抑制剂具有抗肿瘤活性。最重要的是，必须考虑基于分子机制的癌症治疗联合策略。然而，CLK 抑制剂是否调节凋亡相关基因的表达和剪接，以及 CLK 抑制剂是否与凋亡诱导剂联合增强细胞毒性，目前尚不清楚。在这里，我们报告了一种适当的基于机制的药物联合方法。出乎意料的是，我们发现 CLK 抑制剂 T3 可迅速诱导 A2780 细胞凋亡，并使 HCT116 细胞停滞在 G2/M 细胞周期。无论两种癌细胞类型的表型不同，T3 在短时间内降低了抗凋亡蛋白（cIAP1、cIAP2、XIAP、cFLIP 和 Mcl-1）的水平，并改变了 A2780 和 HCT116 细胞中抗凋亡 MCL1L 和 CFLAR 异构体的剪接。相比之下，Bcl-2 家族的其他成员（即 Bcl-xL 和 Bcl-2）对 T3 诱导的表达和剪接调节具有抗性。T3 和 Bcl-xL/Bcl-2 抑制剂协同诱导细胞凋亡。总之，CLK 抑制剂的使用是一种使癌细胞对 Bcl-xL/Bcl-2 抑制剂敏感的新治疗方法。
