Triple-negative breast cancer is characterized by aggressive tumours whose cells lack oestrogen and progesterone receptors and do not over-express HER2. It accounts for approximately 10-15% of breast cancer cases. We sought to generate a cellular model of chemotherapy drug resistance for this type of disease to provide the tools for the development of new therapies. Doxorubicin is a component of some chemotherapy regimes used to treat this form of cancer but resistance preventing disease eradication frequently occurs, mainly due to over-expression of drug transporters such as P-glycoprotein. CALDOX cells were generated by exposure of CAL51 to doxorubicin. Resistance to doxorubicin did not involve drug transporters, as the both parental and resistant cells accumulated doxorubicin to comparable levels. CALDOX cells had slower proliferation rate and an extended G1 cell cycle stage than the parental line, mainly due to an intrinsic activation of CDNK1 (p21), but this cell cycle block was not involved in the mechanism of resistance. CALDOX cells had reduced levels of TOP2A (topoisomerase IIα) and were cross resistant to the topoisomerase II inhibitors etoposide and mitoxantrone. CALDOX cells showed collateral sensitivity to carmustine due to the lack of O⁶-methylguanine-DNA-methyltransferase (MGMT) expression, related to the hypermethylation of its promoter. The collateral sensitivity of CALDOX cells to carmustine provides the rationale to evaluate MGMT promoter methylation status to design better therapeutic strategies for triple negative breast cancer.

译文

三阴性乳腺癌的特征是侵袭性肿瘤,其细胞缺乏雌激素和孕激素受体,并且不会过度表达her2。它约占乳腺癌病例的10-15%。我们试图为这种类型的疾病生成化学疗法耐药性的细胞模型,以为开发新疗法提供工具。阿霉素是用于治疗这种癌症的某些化学疗法方案的组成部分,但经常发生抗药性预防疾病根除,这主要是由于药物转运蛋白 (例如P-糖蛋白) 的过表达。CALDOX细胞是通过将CAL51暴露于阿霉素而产生的。对阿霉素的耐药性不涉及药物转运蛋白,因为亲本和耐药细胞都积累了阿霉素的水平相当。与亲本系相比,钙氧化细胞的增殖速度较慢,G1细胞周期阶段延长,这主要是由于CDNK1 (p21) 的内在激活,但这种细胞周期阻滞不参与抗性机制。钙氧化细胞的TOP2A (拓扑异构酶II α) 水平降低,并且对拓扑异构酶II抑制剂依托泊苷和米托蒽醌具有交叉抗性。由于缺乏o-甲基鸟嘌呤-DNA-甲基转移酶 (MGMT) 表达,CALDOX细胞对卡莫司汀表现出附带敏感性,这与其启动子的高甲基化有关。CALDOX细胞对卡莫司汀的附带敏感性为评估MGMT启动子甲基化状态以设计更好的三阴性乳腺癌治疗策略提供了依据。

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