Therapeutic targeting of PLK1 in TERT promoter‐mutant hepatocellular carcinoma

Abstract Background Hotspot mutations in the promoter of telomerase reverse transcriptase (TERT) gene are the most common genetic variants in hepatocellular carcinoma (HCC) and associated with poor prognosis of the disease. However, no drug was currently approved for treating TERT promoter mutation positive HCC patients. Here, we aim to explore the potential therapeutic strategy for targeting TERT promoter mutation in HCC. Methods The Liver Cancer Model Repository database was used for screening potential drugs to selectively suppress the growth of TERT promoter mutant HCC cells. RNA‐seq, CRISPR‐Cas9 technology and siRNA transfection were performed for mechanistic studies. Cell counting kit‐8 (CCK8) assay and the xenograft tumour models were used for cell growth detection in vitro and in vivo, respectively. Cell apoptosis and cell cycle arrest were analysed by Annexin V‐FITC staining and/or propidium iodide staining. Results PLK1 inhibitors were remarkably more sensitive to HCC cells harbouring TERT promoter mutation than wild‐type cells in vitro and in vivo, which were diminished after TERT promoter mutation was edited to the wild‐type nucleotide. Comparing the HCC cells with wild‐type promoter of TERT, PLK1 inhibitors specifically downregulated Smad3 to regulate TERT for inducing apoptosis and G2/M arrest in TERT mutant HCC cells. Moreover, knockout of Smad3 counteracted the effects of PLK1 inhibitors in TERT mutant HCC cells. Finally, a cooperative effect of PLK1 and Smad3 inhibition was observed in TERT mutant cells. Conclusions PLK1 inhibition selectively suppressed the growth of TERT mutant HCC cells through Smad3, thus contributed to discover a novel therapeutic strategy to treat HCC patients harbouring TERT promoter mutations. Key points TERT promoter mutation confers sensitivity to PLK1 inhibitors in HCC. The selective growth inhibition of TERT mutant HCC cells induced by PLK1 inhibitor was mediated by Smad3. Combined inhibition of PLK1 and Smad3 showed a cooperative anti‐tumor effect in TERT mutant HCC cells.