GOLM1 dictates acquired Lenvatinib resistance by a GOLM1-CSN5 positive feedback loop upon EGFR signaling activation in hepatocellular carcinoma
Lenvatinib is a multiple receptor tyrosine kinases inhibitor (TKI) authorized for first-line treatment of hepatocellular carcinoma (HCC). However, Lenvatinib resistance is common in HCC clinical treatment, highlighting the urgent need to understand mechanisms of resistance. Here, we identified Golgi membrane protein 1 (GOLM1), a type II transmembrane protein originally located in the Golgi apparatus, as a novel regulator of Lenvatinib resistance. We established Lenvatinib resistance in human HCC cell lines PLC/PRF/5. Through RNA-seq, we found that GOLM1 was significantly upregulated, which was further validated in patients derived tumor tissue and peripheral blood. GOLM1 overexpression contributes to Lenvatinib resistance and HCC progression in vitro and in vivo. Mechanistically, GOLM1 upregulates CSN5 expression through EGFR-STAT3 pathway. Reversely, CSN5 deubiquitinates and stabilizes GOLM1 protein by inhibiting ubiquitin-proteasome pathway of GOLM1. Collectively, our data demonstrate that GOLM1 is one of the key driver of Lenvatinib resistance in HCC and depicts a molecular network in Lenvatininb resistant HCC cells. Overall design: To investigate the petential molecule reponsible for Lenvatinib resistance,  PLC/PRF/5 cells were cultured with increasing doses of Lenvatinib (Selleck) at 20 µmol/L initially.The cell culture media was replaced every 48 h until the cells have occupied 90% of the culture dish, at which point they were passaged and replated. After passage, the concentration of Lenvatinib was increased by 0.5 mmol/L until PLC/PRF/5 cells proliferated rapidly at 40 mmol/L. The resistant cell strains were named PLC/PRF/5 LR.