NSUN2 mediated-aberrant 5-methylcytosine methylation regulates autophagy-related ferroptosis in oral squamous cell carcinoma progression.

Oral squamous cell carcinoma (OSCC) is a common malignant tumor with high metastasis rates and poor prognosis. This study investigated the role of NOP2/Sun RNA methyltransferase family member 2 (NSUN2), a key 5-methylcytosine (m5C) methyltransferase, and m5C methylation in the progression of OSCC, particularly in relation to ferroptosis resistance. NSUN2 is significantly overexpressed in OSCC tissues and cell lines and its high expression correlates with poor prognosis and aggressive tumor characteristics. Knockdown of NSUN2 in ferroptosis-resistant OSCC cells resulted in increased sensitivity to ferroptosis. Conversely, NSUN2 overexpression conferred ferroptosis resistance, reducing iron accumulation and restoring GPX4 expression even under erastin treatment. Mechanistically, NSUN2 mediates m⁵C modification of sequestosome 1 (SQSTM1)/P62 mRNA, and the m5C reader protein Y-box binding protein 1 (YBX1) enhances SQSTM1/P62 mRNA stability. This regulation suppresses autophagy and thereby inhibits autophagy-dependent ferroptosis in OSCC. In vivo xenograft models confirmed that NSUN2 knockdown significantly inhibited tumorigenicity. Notably, treatment with an autophagy inhibitor (3-MA) or a ferroptosis inhibitor (Fer-1) partially restored tumor growth in NSUN2-knockdown cells, validating the critical role of autophagy and ferroptosis in NSUN2-mediated OSCC progression. These findings identify the NSUN2-YBX1-SQSTM1/P62 axis as a key regulator of autophagy-dependent ferroptosis in OSCC, highlighting NSUN2 as a promising epitranscriptomic target to enhance ferroptosis induction for OSCC therapy.