m1A inhibition fuels oncolytic virus-elicited antitumor immunity via downregulating MYC/PD-L1 signaling

N¹-methyladenosine (m¹A) RNA methylation is critical for regulating mRNA translation; however, its role in the development, progression, and immunotherapy response of head and neck squamous cell carcinoma (HNSCC) remains largely unknown. Using Tgfbr1 and Pten conditional knockout (2cKO) mice, we found the neoplastic transformation of oral mucosa was accompanied by increased m¹A modification levels. Analysis of m¹A-associated genes identified TRMT61A as a key m¹A writer linked to cancer progression and poor prognosis. Mechanistically, TRMT61A-mediated tRNA-m¹A modification promotes MYC protein synthesis, upregulating programmed death-ligand 1 (PD-L1) expression. Moreover, m¹A modification levels were also elevated in tumors treated with oncolytic herpes simplex virus (oHSV), contributing to reactive PD-L1 upregulation. Therapeutic m¹A inhibition sustained oHSV-induced antitumor immunity and reduced tumor growth, representing a promising strategy to alleviate resistance. These findings indicate that m¹A inhibition can prevent immune escape after oHSV therapy by reducing PD-L1 expression, providing a mutually reinforcing combination immunotherapy approach.