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Open Access Highly Accessed Research article

The effect of low-level laser irradiation (In-Ga-Al-AsP - 660 nm) on melanoma in vitro and in vivo

Lúcio Frigo1, Juliana SS Luppi1, Giovani M Favero2, Durnavei A Maria3, Sócrates C Penna4, Jan M Bjordal56, Rene J Bensadoun7 and Rodrigo AB Lopes-Martins4*

Author Affiliations

1 Biological Sciences and Health Center, Cruzeiro do Sul University. Av. Dr. Ussiel Cirilo, 225 São Miguel Paulista, 08060-070 São Paulo, SP - Brasil

2 State University of Ponta Grossa, General Biology Department, Av. Gal. Carlos Cavalvcanti, 4748 Ponta Grossa 84030-900, PR - Brasil

3 Laboratory of Biochemistry and Biophysics, Butantan Institute, Av. Dr. Vital Brasil, 1500 São Paulo 05599-000, SP - Brasil

4 Laboratory of Pharmacology and Phototherapy of Inflammation, Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo - São Paulo 05508-900 SP - Brasil

5 Institute for Physiotherapy, Bergen University College, Moellendalsvn. 6, 5009 Bergen, Norway

6 Section of Physiotherapy Science, Institute of Public Health and Primary Health Care, University of Bergen, Kalfarveien 31, 5018 Bergen, Norway

7 Service d'Oncologie Radiothérapique, CHU de Poitiers, 2, rue de la Milétrie, BP 577, 86021 - Poitiers Cedex, France

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BMC Cancer 2009, 9:404  doi:10.1186/1471-2407-9-404

Published: 20 November 2009

Abstract

Background

It has been speculated that the biostimulatory effect of Low Level Laser Therapy could cause undesirable enhancement of tumor growth in neoplastic diseases. The aim of the present study is to analyze the behavior of melanoma cells (B16F10) in vitro and the in vivo development of melanoma in mice after laser irradiation.

Methods

We performed a controlled in vitro study on B16F10 melanoma cells to investigate cell viability and cell cycle changes by the Tripan Blue, MTT and cell quest histogram tests at 24, 48 and 72 h post irradiation. The in vivo mouse model (male Balb C, n = 21) of melanoma was used to analyze tumor volume and histological characteristics. Laser irradiation was performed three times (once a day for three consecutive days) with a 660 nm 50 mW CW laser, beam spot size 2 mm2, irradiance 2.5 W/cm2 and irradiation times of 60s (dose 150 J/cm2) and 420s (dose 1050 J/cm2) respectively.

Results

There were no statistically significant differences between the in vitro groups, except for an increase in the hypodiploid melanoma cells (8.48 ± 1.40% and 4.26 ± 0.60%) at 72 h post-irradiation. This cancer-protective effect was not reproduced in the in vivo experiment where outcome measures for the 150 J/cm2 dose group were not significantly different from controls. For the 1050 J/cm2 dose group, there were significant increases in tumor volume, blood vessels and cell abnormalities compared to the other groups.

Conclusion

LLLT Irradiation should be avoided over melanomas as the combination of high irradiance (2.5 W/cm2) and high dose (1050 J/cm2) significantly increases melanoma tumor growth in vivo.