Conversely, pharmacological inhibition by ACK1 inhibitor, (R)-9bMS mitigated CD44+PSA−/lo sphere formation, overcame resistance to radiation-induced cell death, induced significant apoptosis in PCSCs and inhibited CD44+PSA−/lo xenograft tumor growth in castrated mice suggesting dependency of PCSCs on ACK1 for survival. This evidence concerns the gene CD44 and neoplasm.