Upregulation of the ErbB family by EZH2 in hepatocellular carcinoma confers resistance to FGFR inhibitor

PURPOSE: Hepatocellular carcinoma (HCC), the most common manifestation of liver cancer, is one of the leading causes of cancer-related mortality worldwide with limited treatment options. Infigratinib, a pan-FGFR inhibitor, has shown a potent antitumour effect in HCC. However, drug resistance is often observed in long-term treatment. In this study, we examined the potential feedback mechanism(s) leading to infigratinib and explored a combination therapy to overcome resistance in HCC. METHODS: Patient-derived xenograft (PDX) tumours were subcutaneously implanted into SCID mice and were subsequently treated with infigratinib. Tumour growth was monitored over time, and tumour samples were subjected to immunohistochemistry and Western blotting. For drug combination studies, mice were treated with infigratinib and/or varlitinib. Gene overexpression and knockdown studies were conducted to investigate the relationship between EZH2 and ErbB activity in infigratinib resistance. RESULTS: Infigratinib-resistant tumours exhibited higher levels of p-ErbB2 and p-ErbB3, concomitant with an increase in EZH2 expression. Gene overexpression and knockdown studies revealed that EZH2 directly regulates the levels of p-ErbB2 and p-ErbB3 in acquired resistance to infigratinib. The addition of varlitinib effectively overcame infigratinib resistance and prolonged the antitumour response, with minimal toxicity. CONCLUSION: The upregulation of the ErbB family by EZH2 appears to contribute to infigratinib resistance. The combination of infigratinib and varlitinib showed a potent antitumour effect and did not result in additional toxicity, warranting further clinical investigation. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00432-021-03703-6.