The effect of low-level laser irradiation (In-Ga-Al-AsP - 660 nm) on melanoma in vitro and in vivo.
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 mm(2), irradiance 2.5 W/cm(2) and irradiation times of 60s (dose 150 J/cm(2)) and 420s (dose 1050 J/cm(2)) 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/cm(2) dose group were not significantly different from controls. For the 1050 J/cm(2) dose group, there were significant increases in tumor volume, blood vessels and cell abnormalities compared to the other groups.


CONCLUSIONS
LLLT Irradiation should be avoided over melanomas as the combination of high irradiance (2.5 W/cm(2)) and high dose (1050 J/cm(2)) significantly increases melanoma tumor growth in vivo.
Frigo
Lúcio
L
Laboratory of Pharmacology and Phototherapy of Inflammation, Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo - São Paulo 05508-900 SP - Brasil. luciofrigo@uol.com.br
Luppi
Juliana S S
JS
Favero
Giovani M
GM
Maria
Durnavei A
DA
Penna
Sócrates C
SC
Bjordal
Jan M
JM
Bensadoun
Rene J
RJ
Lopes-Martins
Rodrigo A B
RA
D000818:Animals; D017209:Apoptosis / Q000528:radiation effects; D049109:Cell Proliferation / Q000528:radiation effects*; D007834:Lasers; D028022:Low-Level Light Therapy / Q000009:adverse effects*; D008297:Male; D008546:Melanoma, Experimental / Q000532:radiotherapy*; D051379:Mice; D008807:Mice, Inbred BALB C