2054:

Article Outline

• Purpose/Objective(s)
• Materials/Methods
• Results
• Conclusions
• Copyright

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Purpose/Objective(s) 

The use of complementary/alternative therapies such as green tea by patients undergoing treatment for cancer has been extensively documented. However, little is known about how such practices influence the response to radiation, an integral component of the treatment for many malignancies, including breast cancer. We therefore investigated the effects of green tea extract (GTE) on human breast cancer cells.

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Materials/Methods 

MCF7 and SKBR3 cells were exposed to GTE at varying concentrations and for different lengths of time. Mock- and GTE-exposed cells were assessed for cellular growth. . Cell cycle and viability status were assessed via flow-assisted cytometric analysis (FACS), complemented with propidium iodide exclusion and clonogenic survival assays. Levels of the transcription factor Sp1, and the DNA-damage-related proteins ATM, Rad51, Mre11, and BRCA1 were determined via Western blotting. mRNA levels were assessed via reverse-transcriptase polymerase chain reaction. BRCA1 promoter activity was assessed via a luciferase-based reporter.

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Results 

GTE led to decreased cell growth and increased death of both cell lines in a dose-dependent manner. Interestingly, Sp1, ATM and BRCA1 protein levels were substantially diminished by GTE in both cell lines while Mre11 was largely unaffected, and Rad51 was diminished only in MCF-7. Both cell lines were radiosensitized by GTE. The decrease in BRCA1 protein was associated with decreased mRNA levels, as well as reduced BRCA1 promoter activity.

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Conclusions 

The anticancer effects of green tea may be due at least in part to transcription repression, through decreased Sp1 levels as well as reduced promoter activity. These mechanisms may contribute to decreased levels of DNA repair proteins, potentially leading to radiosensitization. If cancer-specific, these findings may provide reassurance that ingestion of green tea does not impair the anti-breast cancer efficacy of radiation therapy.