大电导Ca2+激活的K+通道,KCa1.1在癌症进展中起着关键作用,转移,以及化学抗性的获得。先前的研究表明,在人前列腺癌LNCaP的三维球体模型中,通过下调多药耐药相关蛋白,KCa1.1的药理学抑制克服了对多柔比星(DOX)的耐药性,骨肉瘤MG-63和软骨肉瘤SW-1353细胞。最近的研究集中在肿瘤内的关键作用,化学耐药中的药物代谢细胞色素P450酶(CYPs)。在本研究中,我们在癌症球体模型中检查了CYPs参与DOX抗性的获得及其通过抑制KCa1.1克服。在参与DOX代谢的CYP亚型中,CYP3A4通过球状体形成上调,并通过CCAAT/增强子结合蛋白的转录抑制而被KCa1.1的抑制显着抑制,CEBPB,它是Nrf2信号通路的下游转录因子。通过siRNA介导的CYP3A4抑制和用有效的CYP3A4抑制剂治疗克服了DOX抗性,酮康唑,在癌症球体模型中。抑制KCa1.1可显著降低癌球体模型中Akt的磷酸化水平,和KCa1.1诱导的CYP3A4的下调通过用Akt和Nrf2激活剂处理而逆转。总的来说,目前的结果表明,CYP3A4的上调负责在癌症球体模型中获得DOX抗性,KCa1.1的抑制主要通过Akt-Nrf2-CEBPB轴抑制CYP3A4转录来克服DOX抗性。
The large-conductance Ca2+-activated K+ channel,
KCa1.1, plays a pivotal role in cancer progression, metastasis, and the acquisition of chemoresistance. Previous studies indicated that the pharmacological inhibition of
KCa1.1 overcame resistance to doxorubicin (DOX) by down-regulating multidrug resistance-associated proteins in the three-dimensional spheroid models of human prostate cancer LNCaP, osteosarcoma MG-63, and chondrosarcoma SW-1353 cells. Investigations have recently focused on the critical roles of intratumoral, drug-metabolizing cytochrome P450 enzymes (CYPs) in chemoresistance. In the present study, we examined the involvement of CYPs in the acquisition of DOX resistance and its overcoming by inhibiting
KCa1.1 in cancer spheroid models. Among the CYP isoforms involved in DOX metabolism, CYP3A4 was up-regulated by spheroid formation and significantly suppressed by the inhibition of KCa1.1 through the transcriptional repression of CCAAT/enhancer-binding protein, CEBPB, which is a downstream transcription factor of the Nrf2 signaling pathway. DOX resistance was overcome by the siRNA-mediated inhibition of CYP3A4 and treatment with the potent CYP3A4 inhibitor, ketoconazole, in cancer spheroid models. The phosphorylation levels of Akt were significantly reduced by inhibiting
KCa1.1 in cancer spheroid models, and
KCa1.1-induced down-regulation of CYP3A4 was reversed by the treatment with Akt and Nrf2 activators. Collectively, the present results indicate that the up-regulation of CYP3A4 is responsible for the acquisition of DOX resistance in cancer spheroid models, and the inhibition of KCa1.1 overcame DOX resistance by repressing CYP3A4 transcription mainly through the Akt-Nrf2-CEBPB axis.