GPRC5B Identified by m5C meRIP-Seq Suppresses Apoptosis in Osteosarcoma Through NSUN2-Mediated RNA Methylation.

Osteosarcoma, the most common primary malignant bone tumor with poor prognosis, underscores the need for a deeper understanding of its molecular mechanisms. Recent studies have highlighted the importance of RNA modifications, including 5-methylcytosine (m5C), in cancer progression, yet the m5C modification landscape in osteosarcoma remains unexplored. Here, we performed transcriptome-wide profiling of m5C modifications in osteosarcoma using meRIP-seq and RNA-seq, analyzing four pairs of osteosarcoma and adjacent normal tissues. Furthermore, through conjunction analyses of meRIP-seq and RNA-seq data, we identified 637 genes with significant changes in both the m5C modification and mRNA levels. Among these, GPRC5B emerged as a key prognostic gene, with its high expression and m5C hypermethylation significantly associated with poor survival in osteosarcoma patients. Functional experiments demonstrated that GPRC5B suppresses apoptosis and promotes osteosarcoma cell proliferation and migration. Mechanistically, NSUN2-mediated m5C modification upregulates GPRC5B expression, and the anti-apoptotic effects of NSUN2 are primarily dependent on its ability to modulate GPRC5B m5C modification and expression. Knockdown of GPRC5B partially rescues the anti-apoptotic effects of NSUN2, highlighting the critical role of GPRC5B in osteosarcoma survival. Our study identified an m5C-dependent NSUN2-GPRC5B regulatory axis, providing insights into osteosarcoma progression and revealing its therapeutic potential.