Insufficient Radiofrequency Ablation Promotes Hepatocellular Carcinoma Metastasis through m 6 A mRNA Methylation Dependent Mechanism

The dynamic N6-methyladenosine (m6 A) mRNA modification is essential for acute stress response and cancer progression. Sublethal heat stress from insufficient radiofrequency ablation (IRFA) has been confirmed to promote hepatocellular carcinoma (HCC) progression, however, whether m6 A machinery is involved in IRFA-induced HCC recurrence remains unknown. Using IRFA HCC orthotopic mouse model, we detected higher level of m6 A reader YTHDF1 in the sublethal-heat-exposed transitional zone close to the ablation center than that in the farther area. In addition, we validated the increased m6 A modification and elevated YTHDF1 protein level in sublethal-heat-treated HCC cell lines, HCC patient-derived xenograft (PDX) mouse model and patients' HCC tissues. Functionally, gain-/loss-of function assays showed that YTHDF1 promotes HCC cell viability and metastasis. Knockdown of YTHDF1 drastically restrains the tumor metastasis evoked by sublethal heat treatment in tail vein injection lung metastasis and orthotopic HCC mouse models. Mechanistically, we found that sublethal heat treatment increases EGFR m6 A modification in the vicinity of 5'UTR region and promotes its binding with YTHDF1, which enhances the translation of EGFR mRNA. The sublethal heat induced up-regulation of EGFR level was further confirmed in IRFA HCC PDX mouse model and patients' tissues. Combination of YTHDF1 silencing and EGFR inhibition suppressed the malignancies of HCC cells synergically. CONCLUSION: The m6 A-YTHDF1-EGFR axis promotes HCC progression after IRFA, supporting the rationale for targeting m6 A machinery in combined with EGFR inhibitors to suppress HCC metastasis after RFA.