SOX9 is a member of the SOX transcription factor family [15] defined by a common HMG box domain originally identified in SRY, a sex-determining gene on the Y chromosome of SOX9 belonging to group E (SOX8, SOX9, and SOX10), which is involved in epithelial invasion, migration, and proliferation in prostate development and cancer [16,17]. The gene discussed is SOX10; the disease is cancer.