LY6S and breast cancer: LY6A is aberrant expressed in pituitary tumors and can be a tumor-initiating biomarker of lung cancer [47,48]; LY6E can serve as an independent prognostic factor for CC and is closely associated with the migration and invasion of CC [23,24]; and LY6K promotes the progression of bladder, ovarian, and breast cancers [25,26,27,28,29,30].