Blockade of ACK1/TNK2 To Squelch the Survival of Prostate Cancer Stem-like Cells.
Sci Rep 2018;
8:1954. [PMID:
29386546 PMCID:
PMC5792546 DOI:
10.1038/s41598-018-20172-z]
[Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Accepted: 01/15/2018] [Indexed: 01/08/2023] Open
Abstract
Prostate cancer stem-like cells (PCSCs) are not only enriched in the CD44+PSA-/lo subpopulation but also employ androgen-independent signaling mechanisms for survival. CD44+ PCSCs defy androgen deprivation, resist chemo- and radiotherapy and are highly tumorigenic. Human prostate tissue microarray (TMA) staining revealed an increased membranous staining of CD44 in the luminal compartment in higher grade G7-G9 tumors versus staining of the basal layer in benign hyperplasia. To uncover tyrosine kinase/s critical for the survival of the CD44+PSA-/lo subpopulation, we performed an unbiased screen targeting 87 tyrosine kinases with gene specific siRNAs. Among a subset of tyrosine kinases crucial for PCSC survival, was a non-receptor tyrosine kinase, ACK1/TNK2, a critical regulator of castration resistant prostate cancer (CRPC) growth. Consistently, activated ACK1 as measured by phosphorylation at Tyr284 was significant in the CD44+PSA-/lo population. 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. Thus, blockade of ACK1/TNK2 could be a new therapeutic modality to target recalcitrant PCSCs.
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