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Supplementary Figure 6 from ATPase Copper Transporting Beta (ATP7B) Is a Novel Target for Improving the Therapeutic Efficacy of Docetaxel by Disulfiram/Copper in Human Prostate Cancer

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posted on 2024-06-04, 07:42 authored by Liankun Song, Vyvyan Nguyen, Jun Xie, Shang Jia, Christopher J. Chang, Edward Uchio, Xiaolin Zi

Western blotting analysis of COMMED1, Skp2, p21, and α-Clusterin protein expression in vehicle control and DSF/CuCl2 treated 22Rv1-DR xenograft tumors.

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National Cancer Institute (NCI)

United States Department of Health and Human Services

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U.S. Department of Veterans Affairs (VA)

National Institute of General Medical Sciences (NIGMS)

United States Department of Health and Human Services

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ARTICLE ABSTRACT

Docetaxel has been the standard first-line chemotherapy for lethal metastatic prostate cancer (mPCa) since 2004, but resistance to docetaxel treatment is common. The molecular mechanisms of docetaxel resistance remain largely unknown and could be amenable to interventions that mitigate resistance. We have recently discovered that several docetaxel-resistant mPCa cell lines exhibit lower uptake of cellular copper and uniquely express higher levels of a copper exporter protein ATP7B. Knockdown of ATP7B by silencing RNAs (siRNA) sensitized docetaxel-resistant mPCa cells to the growth-inhibitory and apoptotic effects of docetaxel. Importantly, deletions of ATP7B in human mPCa tissues predict significantly better survival of patients after their first chemotherapy than those with wild-type ATP7B (P = 0.0006). In addition, disulfiram (DSF), an FDA-approved drug for the treatment of alcohol dependence, in combination with copper, significantly enhanced the in vivo antitumor effects of docetaxel in a docetaxel-resistant xenograft tumor model. Our analyses also revealed that DSF and copper engaged with ATP7B to decrease protein levels of COMM domain–containing protein 1 (COMMD1), S-phase kinase–associated protein 2 (Skp2), and clusterin and markedly increase protein expression of cyclin-dependent kinase inhibitor 1 (p21/WAF1). Taken together, our results indicate a copper-dependent nutrient vulnerability through ATP7B exporter in docetaxel-resistant prostate cancer for improving the therapeutic efficacy of docetaxel.

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