m6A regulator-mediated methylation modification patterns and tumor microenvironment infiltration characterization in hepatocellular carcinoma.

Background: There is increasing evidence of the epigenetic regulation of the immune response in cancer. However, the specific functions and mechanisms of RNA N6-methyladenosine (m6A) modification in the cell infiltration in the hepatocellular carcinoma (HCC) tumor microenvironment (TME) is unknown.

Methods: We systematically analyzed the m6A-modification patterns of 371 HCC samples based on 23 m6A regulators, and determined their correlation with TME cell-infiltrating characteristics. Principal-component analysis algorithms was used to calculate the m6Ascore and clarify the m6A-modification patterns of individual tumors.

Results: Three different m6A-modification patterns were identified in HCC, wherein the m6Acluster B and m6Acluster A had the best and worst prognosis, respectively. These three patterns had different TME cell infiltration characteristics and biological behavior. An m6A-scoring signature was constructed to evaluate the m6A-modification patterns within individual tumors. A low m6Ascore was associated with a low overall survival and high clinical stage. Moreover, the m6A-scoring signature was characterized by distinct immunotherapeutic landscapes; a high m6A score indicated a higher immune checkpoint inhibitor score in the anti-PD-1 treatment alone, anti-CTLA-4 treatment alone, or combined anti-CTLA-4/PD-1 treatment cohorts, which reflected significant treatment and clinical benefits.

Conclusions: Our study highlights the significant role of the m6A modification in the HCC TME. A scoring signature to clarify the individual m6A-modification pattern would help us understand the HCC TME infiltration characterization and, thus, would guide the selection of more effective immunotherapeutic strategies.