IDDF2024-ABS-0337 Targeting METTL5-mediated fatty acid metabolism via peroxisome prevents hepatocellular carcinoma recurrence after thermal ablation

<h3>Background</h3> Radiofrequency ablation (RFA) is a critical curative therapy for hepatocellular carcinoma (HCC). However, high recurrence rate remains a major clinical challenge. Methyltransferase 5 (METTL5), an enzyme for 18S m⁶A rRNA modification, is reported to modulate stress response, however, its role in HCC recurrence after RFA remains unknown. Here, we explored the function and mechanism of METTL5 in mediating HCC recurrence after RFA. <h3>Methods</h3> <i>In vivo</i> and <i>in vitro</i> insufficient RFA (iRFA) models of HCC were established to evaluate the expression of METTL5 after heat stress, while gain or loss functional assay were performed to investigate the effect of METTL5 on aggressive biological behavior of HCC after iRFA. Ribosome profile sequencing (Ribo-seq) and ribosome-nascent chain complex-sequencing (RNC-seq) were applied to explore the critically involved pathways and genes regulated by METTL5. <h3>Results</h3> By constructing <i>in vitro</i> and<i> in vivo</i> iRFA models, we observed that METTL5 was significantly upregulated in post-iRFA HCC, which was also verified in patients’ recurrent HCC tumors after RFA (IDDF2024-ABS-0337 Figure 1). METTL5-mediated m⁶A rRNA modification promoted HCC proliferation and metastasis under heat stress by gain-/loss-of-function assays (IDDF2024-ABS-0337 Figure 2, IDDF2024-ABS-0337 Figure 3). Mechanically, heat-mediated METTL5 upregulation enhanced the translational efficiency of the peroxisome pathway and its fatty acid oxidation, which in turn promoted mitochondrial respiration and activated downstream peroxisome proliferators-activated receptors γ pathway (PPARγ) to mediate HCC progression (IDDF2024-ABS-0337 Figure 4). The translation efficacy (TE) of PEX16, one of the essential genes for peroxisome construction, was promoted by METTL5-mediated 18S rRNA m⁶A modification (IDDF2024-ABS-0337 Figure 4). Knockdown of METTL5 or PEX16 significantly mitigated tumor progression and metastasis induced by iRFA (IDDF2024-ABS-0337 Figure 5). we demonstrated that PPARγ inhibitor T0070907 was effective and could reduce HCC proliferation, invasion and metastasis <i>in vivo</i> (IDDF2024-ABS-0337 Figure 6). <h3>Conclusions</h3> Our study uncovers that METTL5 promotes tumor aggressiveness after iRFA through fatty acid metabolism mediated by peroxisome from the perspective of 18S rRNA m⁶A modification, and provides novel mechanistic insights and targets to prevent and treat HCC recurrence after thermal ablation.