The influence of ALA-mediated photodynamic therapy on secretion of selected growth factors by colon cancer cells in hypoxia-like environment in vitro.

Background: Photodynamic therapy (PDT) affects the immune system and tumor cells' secretory activity. Hypoxia may limit PDT effects. The aim of this study was to determine the influence of PDT with aminolevulinic acid (ALA-PDT) in a hypoxic-like microenvironment on the secretion of growth factors: GM-CSF (granulocyte and macrophage colony stimulating factor), G-CSF (granulocyte colony-stimulating factor) and FGF (fibroblast growth factor) by experimental models of colon cancer cells in vitro.

Methods: Sublethal doses of ALA-PDT (ALA of 1000 μM, light fluence 10J/cm(2), power density rate of 1.5mW/cm(2), wavelength 600-720nm) were administered to two colorectal cancer cell lines varying in malignancy potential: SW480 (local malice) and SW620 (high metastatic activity) under normoxia and hypoxia-like environment. Hypoxia-mimic conditions were achieved by adding environment cobalt (II) chloride. Concentrations of growth factors were analyzed with Bio-Plex Pro™ Assay.

Results: ALA-PDT amplified the secretion of GM-CSF by both cell lines. The decrease in secretion of G-CSF and FGF was noticed in the SW620. SW620 line cells secreted higher levels of FGF and G-CSF, while SW480 cells more actively released GM-CSF. Compared to normoxic condition, no differences in the secretion of these factors in a hypoxic-like environment were found.

Conclusions: ALA-PDT increased GM-CSF secretion, which stimulates antitumor defense and decreased secretion of FGF and G-CSF-factors responsible for tumor progression. No differences in the effects of ALA-PDT in the hypoxic-like environment suggests that the beneficial results of PDT are also continued in the later stages of the reaction.