Ammonium tetrathiomolybdate treatment targets the copper transporter ATP7A in cisplatin-resistant breast cancer TM and cisplatin sensitize resistant breast cancer.

Chemotherapy resistance presents a major hurdle for cancer treatment. We proposed to identify the molecular changes through which breast cancer cells evolve resistance to conventional treatment, here cisplatin, so targeted therapy can be developed. Candidate approach RNAi screening was combined with cisplatin treatment in order to identify molecular pathways conferring survival advantages. The screening identified ATP7A, a copper transport ATPase responsible for the intercellular movement and sequestering of cisplatin, as a therapeutic target. Copper chelation with tetrathiomolybdate (TM) targets ATP7A. TM in combination with cisplatin sensitized drug-resistant breast cancer cells. Allograft and xenograft models in aythymic mice treated with TM/cisplatin combination therapy inhibited tumor growth and increased survival compared with monotreated mice. Examination of the molecular effects of TM on cisplatin efficacy in drug-resistant tumors revealed reduced levels of APT7A, reduced cisplatin sequestering by ATP7A and increased nuclear availability of cisplatin. Further, we showed that TM treatment combined with cisplatin reduced the half-life of ATP7A in human breast cancer cell lines. This finding offered the potential to combat drug platinum-resistant tumors and sensitize patients to conventional breast cancer treatments by identifying and targeting resistant tumors unique molecular adaptations.

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Chisholm CL, Wang H, Wong AH, Vazquez-Ortiz G, Chen W, Xu X, Deng CX