In vitro therapeutic effects and molecular mechanisms of targeted inhibition of CDK12/13 in high-grade gliomas

Abstract

Objective·To find novel and common targeting strategies for high-grade gliomas (HGGs) from the perspective of epigenetic and transcriptional modulators, test the therapeutic effect in vitro and investigate the related molecular mechanisms.Methods·Glioblastoma (GBM) and diffuse intrinsic pontine glioma (DIPG) cell lines with high malignancy and mortality in HGGs were selected for screening of targeted small molecule drug library related to epigenetic transcription and for functional genome screening based on the CRISPR-Cas9 technology. The effect of selected targeted epigenetic transcriptional modulators on growth, proliferation, and apoptosis of GBM and DIPG cell lines were then measured either by CRISPR-Cas9 knockout or treatment with targeted small molecule inhibitors of genes in vitro. Anti-tumor molecular mechanisms of the modulators in corresponding small molecule inhibitors-treated GBM and DIPG cells were explored via RNA-seq transcriptome analysis and further verified by real time quantitative PCR (RT-qPCR), Western blotting and flow cytometry.Results·Targeted small molecule drug library combined with functional genome screening for epigenetic transcriptional modulators identified CDK12/13 as the novel therapeutic targets for both GBM and DIPG. Knockout out of CDK12 by CRISPR-Cas9 in multiple GBM and DIPG cell lines significantly reduced their in vitro cellular activity. CDK12/13 inhibitors SR-4835 and THZ531 also significantly inhibited the growth of these two types of HGGs cell lines in vitro by antagonizing cell proliferation and promoting cell apoptosis. RNA-seq transcriptome analysis of GBM and DIPG cell lines after SR-4835 treatment showed that genes significantly down-regulated by CDK12/13 inhibitors in HGGs cells were mainly enriched in transcriptional regulation, DNA damage response (DDR) pathway, ubiquitin-proteasome pathway, and cell cycle. Furthermore, a series of experiments demonstrated that targeted inhibition of CDK12/13 significantly down-regulated the transcription of DDR-related genes, resulting in the accumulation of DNA damage, and induced G2-M cell cycle arrest.Conclusion·CDK12/13 is a common potential therapeutic target of these two types of HGGs, providing theoretical support for the follow-up in vivo verification and combination therapy test. The research also lays the foundation for further clinical application.

Keywords

• glioblastoma (gbm)
• diffuse intrinsic pontine glioma (dipg)
• molecular targeted therapy
• anti-tumor drug screening
• crispr-cas9
• cdk12
• cdk13