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Lasers Med Sci. 2018 Aug;33(6):1215-1223. doi: 10.1007/s10103-018-2461-5. Epub 2018 Apr 5.

High doses of laser phototherapy can increase proliferation in melanoma stromal connective tissue.

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Biological Sciences and Health Center, Cruzeiro do Sul University, Av. Dr. Ussiel Cirilo, 225 São Miguel Paulista, São Paulo, SP, 08060-070, Brazil.
General Biology Department, State University of Ponta Grossa, Av. Gal. Carlos Cavalcanti, 4748, Ponta Grossa, PR, 84030-900, Brazil.
Laboratory of Biochemistry and Biophysics, Butantan Institute, Av. Dr. Vital Brasil, 1500, São Paulo, SP, 05599-000, Brazil.
Nove de Julho University (UNINOVE), Rua Vergueiro 235, São Paulo, SP, 01504-001, Brazil.
Institute for Physiotherapy, Bergen University College, Moellendalsvn 6, 5009, Bergen, Norway.
Physiotherapy Research Group, Department of Global and Public Health, University of Bergen, Kalfarveien 31, 5018, Bergen, Norway.
Nove de Julho University (UNINOVE), Rua Vergueiro 235, São Paulo, SP, 01504-001, Brazil.
Biophotonics Applied in Health Sciences, Universidade Nove de Julho, Rua Vergueiro 235, São Paulo, SP, 01504-001, Brazil.
Universidade do Vale do Paraíba, Av. Shishima Hifumi, 2911 - Urbanova, São José dos Campos, SP, 12244-000, Brazil.


It is well established that laser phototherapy (LP) is contraindicated directly over cancer cells, due to its bio modulatory effects in cell and blood vessel proliferation. The aim of the present study was to analyze the influence of typical low-level laser therapy (LLLT) and high intensity laser therapy (HILT) and an in-between dose of 9 J on collagen fibers and blood vessels content in melanoma tumors (B16F10) implanted in mice. Melanoma tumor cells were injected in male Balb C mice which were distributed in four groups: control (no irradiated) or irradiated by 3, 9, or 21 J (150; 450, or 1050 J/cm2). LP was performed in daily sessions for 3 days with a InGaAlP-660 nm (mean output: 50 mW, spot size: 2 mm2). Tumor volume was analyzed using (1) picrosirius staining to quantify collagen fibers content and (2) Verhoeff's method to quantify blood vessels content. Tumor growth outcome measured in the 3-J group was not significantly different from controls. Nine and 21-J groups, presented significant and dose-dependent increases in tumor volume. Quantitative analysis of the intensity of collagen fibers and their organization in stroma and peri-tumoral microenvironment showed significant differences between irradiated and control group. Blood vessels count of 21-J group outnumbered the other groups. High doses (≥ 9 J) of LP showed a dose-dependent tumor growth, different collagen fibers characteristics, and eventually blood vessel growth, while a typical LLLT dose (3 J) appeared harmless on melanoma cell activity.


Bloob vessels; Collagen; Growing tumor; LLLT; Melanoma; Photobiomodulation

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