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.

Curcumin is a natural compound presenting important antitumour activity. However, due to its low aqueous solubility, instability at physiological pH, and low oral bioavailability, its clinical use is limited. Bovine serum albumin (BSA) nanoparticles have been used as drug carriers to improve the drug properties. In this work, curcumin-loaded BSA nanoparticles were developed and the in vitro cytotoxicity over murine melanoma cells and the in vivo antitumour activity in a murine melanoma model were assessed. Nanoparticles presented 150 nm, polydispersity index of 0.16, negative zeta potential, and 45% of curcumin encapsulation efficiency. Curcumin release from nanoparticles was slow and diffusion dependent. In the cytotoxicity assay, free curcumin was more efficient than curcumin-loaded nanoparticles, probably due to the prolonged curcumin release from nanoparticles. However, in a murine melanoma model, curcumin-loaded nanoparticles presented higher antitumour efficiency than free curcumin. BSA nanoparticles are efficient curcumin carriers that may have relevant applications in melanoma treatment.

Apocynin (APO), curcumin (CUR) and vanillin (VAN) are o-methyl catechols widely studied due their antioxidant and antitumour properties. The effect of treatment with these o-methyl catechols on tamoxifen (TAM)-induced cytotoxicity in normal and tumour cells was studied. The cytotoxicity of TAM on red blood cells (RBC) was performed by haemoglobin or K⁺release and on polymorphonuclear leukocytes (PMNs) by trypan blue dye exclusion method. Cytotoxic activity was assessed in human chronic myeloid leukemia (K562) cell line by (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide). According the release of haemoglobin and K⁺, the CUR showed a decrease in TAM cytotoxicity on RBC; however, in PMN, APO, CUR and VAN showed increased of these cells viability. VAN presented the highest cytotoxicity on K562 cells, followed by APO and CUR. These results point the potential therapeutic value of these o-methyl catechols with TAM, particularly of CUR, which potentiates the cytotoxic effects of TAM on K562 cells and also decreases TAM-associated cytotoxicity on RBC and PMN.

Statins induces cell cycle arrest, apoptosis, reduction of angiogenic factors, inhibition of the endothelial growth factor, impairing tissue adhesion and attenuation of the resistance mechanisms. The aim of this study was evaluate the anti-tumoral activity of simvastatin in a B16F10 melanoma-mouse model. Melanoma cells were treated with different concentrations of simvastatin and assessed by viability methods. Melanoma cells (5 × 10⁴) were implanted in two month old C57Bl6/J mice. Around 7 days after cells injection, the oral treatments were started with simvastatin (5 mg/kg/day, p.o.). Tumor size, hematological and biochemical analyses were evaluated. Simvastatin at a concentration of 0.8 μM, 1.2 μM and 1.6 μM had toxic effect. Concentration of 1.6 μM induced a massive death in the first 24 h of incubation. Simvastatin at 0.8 μM induces early cell cycle arrest in G0/G1, followed by increase of hypodiploidy. Tumor size were evaluated and the difference of treated group and control, after ten days, demonstrates that simvastatin inhibited the tumor expansion in 68%. Simvastatin at 1.6 μM, presented cytototoxicity after 72 h of treatment, with an intense death. In vivo, simvastatin being potentially useful as an antiproliferative drug, with an impairment of growth after ten days.