STK31 (serine/threonine kinase 31) is a cancer-testis gene that functions as an oncogenic driver across multiple cancer types. In pancreatic cancer, STK31 promotes cell proliferation, migration, and invasion, with expression regulated by DNA methylation 1. In lung cancer, STK31 drives tumor growth and immune evasion through direct interaction with STAT3, activating the STAT3-IL-6 signaling pathway that induces CD8+ T cell exhaustion 2. STK31 regulates lung cancer cell proliferation via the Wnt/β-catenin pathway, with c-myc serving as a transcription factor that promotes STK31 expression in a positive feedback loop 3. In pancreatic cancer, miR-543 directly binds STK31 to suppress its expression, correlating with improved patient survival 4. STK31 is significantly upregulated in colorectal cancer tissues and circulating mRNA levels serve as noninvasive biomarkers for early diagnosis, with elevated expression correlating with poor disease-free survival and overall survival 56. Mechanistically, STK31 associates with PIWI and Tudor protein families and regulates genes involved in signal transduction and metabolism 7. Clinical significance includes its potential as a therapeutic target given its consistent upregulation across pancreatic, lung, and colorectal cancers with prognostic value.