Low level light therapy on breast tumor. In vitro and in vivo studies

Abstract

Low Level Light Therapy (LLLT) has been gaining prominence in health areas due to search for less invasive and cost-effective treatments. However, its use is not indicated to treat patients with cancer due to a few studies in vivo. The aim of this work was to evaluate the effects of LLLT on breast tumor 4T1 cells in vitro and in a murine model. For the in vitro assay, 4T1 cells were submitted to a single session of LLLT with red light (660 ± 20 nm) delivering energies of 1.2 J and 6 J. The cell viability was measured by MTT assay. For in vivo study, nine BALB/c female mice (6 weeks old) received 4T1 cells transfected with luciferase (4T1-Luc) into the mammary fat pad. After two weeks, the animals were divided into control (n=3) and test groups were submitted to LLLT with same parameters described above. The tumor progression was monitored by a caliper and bioluminescence. The anti-fatigue effect of LLLT was assessed by a forced swimming test. Our results showed that LLLT was not able to increase cell viability regardless the energy used. In vivo, the lower energy promoted an increase of the tumor volume compared to control group. On the other hand, the higher energy was able to arrest tumor progression as well as increase the swimming time. Taken together, our results suggest that LLLT triggers opposite effects on breast tumor depending on the type of assay.