METTL3-mediated SMPDL3A promotes cell growth, metastasis and immune process of hepatocellular carcinoma by regulating LRPPRC.

BACKGROUND

Methyltransferase-like protein 3 (METTL3) has been confirmed to act as a tumor promoter to regulate hepatocellular carcinoma (HCC) progression. Therefore, more roles and mechanisms of METTL3 in HCC progression deserve to be further revealed.

METHODS

The mRNA and protein levels of METTL3, sphingomyelin phodiesterase acid-like 3 A (SMPDL3A), and leucine rich pentatricopeptide repeat containing (LRPPRC) were determined by qRT-PCR and western blot. Cell proliferation, apoptosis, invasion and migration were detected by CCK8 assay, EdU assay, flow cytometry, transwell assay and wound healing assay. HCC cells were co-cultured with phytohemagglutinin-stimulated peripheral blood mononuclear cells, cytokine-induced killer cells, or CD8 + T-cells. IFN-γ, TNF-α levels, HCC cell survival rate and CD8 + T-cell apoptosis were determined to assess cell immune process. The interaction between METTL3, SMPDL3A and LRPPRC was assessed by MeRIP assay, RIP assay, dual-luciferase reporter assay or Co-IP assay. Animal experiments were performed to evaluate the effect of METTL3 knockdown on HCC tumorigenesis and lung metastasis.

RESULTS

METTL3 was upregulated in HCC tissues and cells, and its knockdown repressed HCC cell proliferation, invasion, migration, immune process and promoted apoptosis. METTL3 increased SMPDL3A mRNA stability by m6A methylation modification, and this modification could be recognized by IGF2BP1. SMPDL3A overexpression reversed the inhibitory effect of METTL3 knockdown on HCC cell growth, metastasis and immune process. SMPDL3A interacted with LRPPRC to positively regulate its expression, and LRPPRC overexpression also eliminated the regulation of SMPDL3A silencing on HCC progression. In addition, downregulation of METTL3 repressed HCC tumorigenesis and lung metastasis via mediating SMPDL3A/LRPPRC axis.

CONCLUSION

METTL3 accelerated HCC cell growth, metastasis and immune process by regulating SMPDL3A/LRPPRC axis, providing a potential target for HCC treatment.