The Effect of Laser Irradiation on Proliferation of Human Breast Carcinoma, Melanoma, and Immortalized Mammary Epithelial Cells

Objective: This study compared the effects of different doses (J/cm 2 ) of laser phototherapy at wavelengths of either 780, 830, or 904 nm on human breast carcinoma, melanoma, and immortalized human mammary epithelial cell lines in vitro . In addition, we examined whether laser irradiation would malignantly transform the murine fibroblast NIH3T3 cell line. Background: Laser phototherapy is used in the clinical treatment of breast cancer-related lymphoedema, despite limited safety information. This study contributes to systematically developing guidelines for the safe use of laser in breast cancer-related lymphoedema. Methods: Human breast adenocarcinoma (MCF-7), human breast ductal carcinoma with melanomic genotypic traits (MDA-MB-435S), and immortalized human mammary epithelial (SVCT and Bre80hTERT) cell lines were irradiated with a single exposure of laser. MCF-7 cells were further irradiated with two and three exposures of each laser wavelength. Cell proliferation was assessed 24 h after irradiation. Results: Although certain doses of laser increased MCF-7 cell proliferation, multiple exposures had either no effect or showed negative dose response relationships. No sign of malignant transformation of cells by laser phototherapy was detected under the conditions applied here. Conclusion: Before a definitive conclusion can be made regarding the safety of laser for breast cancer-related lymphoedema, further in vivo research is required.