Abstract 969: The effects of low level laser therapy (LLLT) on human breast cancer cell lines in vitro.

Abstract

PURPOSE: This research examined the response of two breast cancer cell lines (MCF-7 and MB-435) in vitro to a range of laser doses at two commonly used wavelengths (780nm and 830nm). RELEVANCE: LLLT is being used increasingly for the management of post-mastectomy lymphoedema without undisputed evidence of its effectiveness in this disorder. In particular, information regarding dose-response relationships and safety (in malignant conditions) remains elusive. This research set out to clarify dose/response relationships in cell culture as a starting point towards making clinical recommendations for use. PARTICIPANTS: In vitro cell cultures. METHODS: Well-differentiated human breast adenocarcinoma (MCF-7) and less differentiated human breast ductal carcinoma (MB-435) cell lines were grown and passaged using standard aseptic tissue culture protocols. 96-well tissue culture plates were seeded with 1 x 104 cells per well in fresh growth medium, and allowed to grow for 48-72hrs before exposure to laser. A single dose of laser was performed at energy densities of 0.5, 1, 2.5, 10 and 12J/cm2 for 780nm laser, and 0.5, 1, 2.5, 10 and 15J/cm2 for 830nm laser. Cell proliferation was assessed 24hrs after laser treatment by calorimetric spectrophotometry. ANALYSIS: Percentage growth differences between treated and control means, and Student t-tests with 95% confidence limit were calculated. Alpha level was set at 0.05 for all tests. RESULTS: Laser irradiation at 780nm using doses from 0.5 to 5J/cm2 produced no significant difference in proliferation of MCF-7 (adenocarcinoma) cells. A positive trend in MCF-7 cell proliferation was evident at a dose of 10J/cm2 (13.37% mean percentage increase) becoming significantly increased at 12J/cm2 (p < 0.05). In the MB-435 (ductal carcinoma) cells, laser irradiation at 780nm (doses from 0.5 to 5J/cm2) also resulted in no significant difference, but at 10J/cm2 there was a significant increase in cell proliferation compared to negative controls (p < 0.05). At 830nm, laser irradiation using doses from 0.5 to 2.5J/cm2 did not affect MCF-7 cell proliferation, however, at higher doses of 10 and 12J/cm2, significant increases (p < 0.05) in growth were noted. There were no effects observed in MB-435 cells after laser irradiation at 830nm for doses from 0.5 to 10J/cm2, but at 15J/cm2 there was a statistically significant increase (p < 0.05) in cell proliferation. CONCLUSIONS: The findings suggest that 780nm and 830nm laser at doses up to 5J/cm2 do not stimulate cell proliferation in the two breast cancer cell lines studied, however higher doses do appear to stimulate cell proliferation irrespective of wavelength, and in both human breast carcinoma cell lines. We plan to investigate further the in vitro effects of other typical laser wavelengths used in lymphoedema treatment prior to extending the research to in vivo and clinical models. IMPLICATIONS: The results of this research imply that low doses of laser of less than 5J/cm2 at the wavelengths stipulated are potentially safe for clinical use in the presence of the two types of human breast cancers studied. Whilst findings from in vitro research cannot be considered transferable to clinical application, the findings provide some guidance on targeting potential foci for future work using in vivo models of treatment and in clinical applications. KEYWORDS: laser therapy, cancer. FUNDING ACKNOWLEDGEMENTS: Griffith University. CONTACT: L.Laakso@griffith.edu.au