P-glycoprotein in breast cancer
Resistance to cytotoxic chemotherapy is a major impediment to the successful treatment of breast cancer. Adjuvant chemotherapy, though given under theoretically optimal conditions of low tumor bulk , often fails to eradicate micrometastasis. Once metastasis is grossly evident, most breast cancers have intrinsic resistance to single-agent chemotherapy. The response rate of such advanced disease to doxorubicin is less than 40%; the response rate to vinca alkyloids is only 21% [2,3]. Though higher initial response rates can be achieved with combination chemotherapy , essentially all breast cancers will become resistant to cytotoxic therapy. This might occur either through the outgrowth of resistant subclones under the selection pressure of chemotherapy , or through the induction of a resistant phenotype in surviving cancer cells. In either case, this resistance frequently includes a component of cross-resistance to unrelated agents, as second-line chemotherapy is marked by lower response rates and brief response durations .
KeywordsGlutathione Oncol Progesterone NADPH Phenylalanine
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