BI6727, a polo-like kinase 1 inhibitor, synergizes with gefitinib to suppress hepatocellular carcinoma cells via a G2/M arrest mechanism.

Hepatocellular carcinoma (HCC) is the second leading cause of cancer death, which indicates that efficient intervention agents or strategies against HCC are urgently needed. In the present study, we firstly found that a combination of gefitinib (an ep i dermal growth factor receptor (EGFR) inhibitor) and B I 6727 (a pol o -like kinase 1 (PLK1) inhibitor) could significantly inhibit cell proliferation of HCC cells, which attenuated acquired resistance of gefitinib in HCC cells. Interestingly, our results showed that these anti-tumor effects of gefitinib in combination with BI6727 were associated with G2/M arrest. Moreover, further study revealed that BI6727 could downregulate the protein levels of cell division cycle 25C (Cdc25C) via ubiquitination-dependent pathway, which subsequently induced G2/M arrest. Furthermore, two critical checkpoints proteins ataxia telangiectasia-mutated (p-ATM)/ ATM and Rad-3 related(p-ATR) and another hallmark phosphorylated H2AX (γ-H2AX ) of DNA damage were positively regulated in HCC cells exposed to gefitinib in combination with BI6727. These results indicated that co-treatment induced G2/M arrest was closely related to DNA damage. In summary, the present study discovered that gefitinib synergizing with BI6727 could significantly facilitate DNA damage and overcome acquired resistance of HCC cells to gefitinib. Our study provides a promising approach for the combination of EGFR inhibitors and PLK1 inhibitors in the clinical treatment for HCC.