RESUMO
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.
Assuntos
Adenosina Trifosfatases , Proteínas de Transporte de Cátions , ATPases Transportadoras de Cobre , Cobre , Dissulfiram , Docetaxel , Resistencia a Medicamentos Antineoplásicos , Neoplasias da Próstata , Taxoides , Ensaios Antitumorais Modelo de Xenoenxerto , Masculino , Humanos , Dissulfiram/farmacologia , Dissulfiram/uso terapêutico , ATPases Transportadoras de Cobre/genética , ATPases Transportadoras de Cobre/metabolismo , Docetaxel/farmacologia , Docetaxel/uso terapêutico , Neoplasias da Próstata/tratamento farmacológico , Neoplasias da Próstata/patologia , Neoplasias da Próstata/metabolismo , Neoplasias da Próstata/genética , Proteínas de Transporte de Cátions/metabolismo , Proteínas de Transporte de Cátions/genética , Taxoides/farmacologia , Taxoides/uso terapêutico , Animais , Linhagem Celular Tumoral , Camundongos , Adenosina Trifosfatases/metabolismo , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Antineoplásicos/farmacologia , Antineoplásicos/uso terapêutico , Apoptose/efeitos dos fármacosRESUMO
We have previously demonstrated the in vivo chemopreventive efficacy of flavokawain A (FKA), a novel chalcone from the kava plant, in prostate carcinogenesis models. However, the mechanisms of the anticarcinogenic effects of FKA remain largely unknown. We evaluated the effect of FKA on prostate tumor spheroid formation by prostate cancer stem cells, which were sorted out from CD44+/CD133+ prostate cancer cells 22Rv1 and DU145. FKA treatment significantly decreased both the size and numbers of the tumor spheroids over different generations of spheroid passages. In addition, the dietary feeding of FKA-formulated food to Nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice bearing CD44+/CD133+ 22Rv1 xenograft tumors resulted in a significant reduction of tumor growth compared to those fed with vehicle control food-fed mice. Furthermore, the expression of stem cell markers, such as Nanog, Oct4, and CD44, were markedly downregulated in both tumor spheroids and tumor tissues. We also observed that FKA inhibits Ubc12 neddylation, c-Myc, and keratin-8 expression in both CD44+/CD133+ prostate tumor spheroids and xenograft tumors. Our results suggest that FKA can reduce the tumor-initiating properties and stemness of prostate cancer, which provides a new mechanism for the chemoprevention efficacy of FKA.
