RPS6KA6 encodes ribosomal S6 kinase 4 (RSK4), a serine/threonine kinase that functions as a constitutively active growth-factor-independent kinase 1. RSK4 participates in the Ras-MAPK signaling pathway and regulates multiple cellular processes including growth, proliferation, survival, and mobility 2. The gene exhibits complex regulation through alternative splicing, producing at least 50 mRNA variants encoding 35 protein isoforms that respond differentially to cellular stress conditions 3. Functionally, RPS6KA6 shows context-dependent roles: it suppresses thyroid cancer proliferation and promotes apoptosis through FOXP2-mediated transcriptional regulation and PI3K/AKT pathway modulation 4, while simultaneously promoting clear cell renal cell carcinoma metastasis via RUNX1-mediated angiogenesis and VEGF secretion 2. Clinically, RPS6KA6 deletions associate with X-linked mental retardation and contiguous gene syndromes affecting the Xq21 region 5, with high expression in brain and kidney tissues. The gene's expression is downregulated in esophageal adenocarcinoma through epigenetic mechanisms involving miRNA and DNA methylation 6. Rare deleterious variants appear in keratoconus patients 7, and linkage evidence implicates RPS6KA6 in autism spectrum disorder susceptibility 8. The dichotomous oncogenic versus tumor-suppressive roles depend on tissue context, protein isoform expressed, and cellular stress conditions.