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Resistance to 5-fluorouracil (5-FU) and its induced immune suppression have prevented its extensive application in the clinical treatment of breast cancer. In this study, the combined effect of 50 Hz-EMFs and 5-FU in the treatment of breast cancer was explored. MCF-7 and MCF10A cells were pre-exposed to 50 Hz-EMFs for 0, 2, 4, 8 and 12 h and then treated with different concentrations of 5-FU for 24 h; cell viability was analyzed by MTT assay and flow cytometry. After pre-exposure to 50 Hz-EMFs for 12 h, apoptosis and cell cycle distribution in MCF-7 and MCF10A cells were detected via flow cytometry and DNA synthesis was measured by EdU incorporation assay. Apoptosis-related and cell cycle-related gene and protein expression levels were monitored by qPCR and western blotting. Pre-exposure to 50 Hz-EMFs for 12 h enhanced the antiproliferative effect of 5-FU in breast cancer cell line MCF-7 in a dose-dependent manner but not in normal human breast epithelial cell line MCF10A. Exposure to 50 Hz-EMFs had no effect on apoptosis and P53 expression of MCF-7 and MCF10A cells, whereas it promoted DNA synthesis, induced entry of MCF-7 cells into the S phase of cell cycle, and upregulated the expression levels of cell cycle-related proteins Cyclin D1 and Cyclin E. Considering the pharmacological mechanisms of 5-FU in specifically disrupting DNA synthesis, this enhanced inhibitory effect might have resulted from the specific sensitivity of MCF7 cells in active S phase to 5-FU. Our findings demonstrate the enhanced cytotoxic activity of 5-FU on MCF7 cells through promoting entry into the S phase of the cell cycle via exposure to 50 Hz-EMFs, which provides a novel method of cancer treatment based on the combinatorial use of 50 Hz-EMFs and chemotherapy. [ABSTRACT FROM AUTHOR]

Abstract: Mucositis arising from cancer chemotherapy is a common problem for which there is no definitive treatment. 5-fluorouracil (5-FU) is a common cytotoxic agent used to treat solid tumors. A global gene expression array was performed to identify genetic signals involved in the pathogenesis of mucositis. The chemokine (C-X-C motif) ligand 9 (CXCL9) was one of the candidates identified that presented a characteristic gene expression profile; its temporal expression pattern was correlated with the damage and regeneration phases of the small intestine upon 5-FU chemotherapy. We found that prophylactic CXCL9 administration was able to attenuate the severity of mucositis, weight loss and diarrhea caused by chemotherapy. CXCL9 also increased the tolerance of the mice to lethal-dose chemotherapy. Moreover, we demonstrated that CXCL9 was able to promote the proliferation and regeneration of intestinal cells by inhibiting the proliferation of normal intestinal mucosal cells prior to chemotherapy and by reducing the 5-FU-induced apoptosis in intestinal crypts. Thus, pretreatment with CXCL9 is a new and promising strategy for the alleviation of chemotherapy-induced intestinal mucositis in clinical settings. [Copyright &y& Elsevier]