Ribosomal protein S6. It is a component of the 40S subunit. It is the major substrate of protein kinases in the ribosome. Phosphorylation is induced by a wide range of stimuli, including growth factors, tumor-promoting agents, and mitogens. Dephosphorylation occurs at growth arrest. The protein may contribute to the control of cell growth and proliferation through the selective translation of particular classes of mRNA. Overexpressed in esophageal squamous cell carcinoma, renal cell carcinoma metastases and hyperphosphorilated in lung cancer [146–148]. This evidence concerns the gene RPS6 and esophageal squamous cell carcinoma.