Our observations suggest a potential role for epigenetic dysregulation in C1Q expression during tumorigenesis, and underscore the dynamic interconnection between DNA methylation and gene expression in C1QA, C1QB, and C1QC across various tumor types, shedding light on the intricate relationship between epigenetic modifications and the switching of transcriptional activation and deactivation processes. Here, C1QA is linked to neoplasm.