ISG15 and posterior cortical atrophy: To further characterized the role of ISG15 and CST2 in PCa metastasis in vivo, we established PCa cells stably expressing luciferase-22Rv1-shCtrl, 22Rv1-shISG15, 22Rv1-shCST2, PC3-shCtrl, PC3-sh ISG15, or PC3-sh CST2.