N7-Methylguanosine tRNA modification promotes hepatocellular carcinoma metastasis after insufficient radiofrequency ablation. Homo sapiens

Radiofrequency heat ablation is an ideal radical cure for HCC treatment; however, insufficient radiofrequency ablation (IRFA) could lead to a high recurrence rate. N7-methylguanosine (m7G) on tRNAs is a heat-responding modification that is critical for yeast survival under high temperature, while its function and mechanism in HCC recurrence after IRFA are unknown. Here, we found that IRFA significantly up-regulates the level of m7G tRNA modification and its methyltransferase complex components METTL1 and WDR4 in multiple systems including HCC patient-derived xenograft (PDX) mouse, HCC tissues of patients, sublethal-heat-treated models of HCC cell lines and organoids. Functionally, gain- or loss-of function assays showed that METTL1 mediated m7G tRNA modification promotes HCC metastasis under sublethal heat exposure both in vitro and in vivo. Mechanistically, we found that METTL1 and m7G tRNA modification enhance the translation of SLUG and SNAIL in a codon frequency dependent manner under sublethal heat exposure. Overexpression of SLUG and SNAIL rescued the malignant potency of METTL1 knockdown HCC cells after sublethal heat stress. Our study uncovers the important physiological functions of m7G tRNA modification in heat stress responses and HCC recurrence after IRFA and suggests that targeting METTL1-m7G-SLUG and SNAIL axis could be a promising strategy to prevent HCC metastasis after radiofrequency heat ablation treatment.