ALA-mediated photodynamic effect on apoptosis induction and secretion of macrophage migration inhibitory factor (MIF) and of monocyte chemotactic protein (MCP-1) by colon cancer cells in normoxia and in hypoxia-like conditions in vitro.

Background: Photodynamic therapy (PDT) reveals immune modulatory effect. The aim of the study was to evaluate the influence of 5-aminolevulinic acid (ALA) mediated photodynamic effect on secretory activity (MIF, MCP-1) of colon cancer cells in vitro both in normoxia and in hypoxia-like conditions.

Methods: Two colon cancer cell lines differing in malignancy potential: SW480 (lower grade) and SW620 (higher grade) were used. MCP-1 and MIF concentrations in supernatants of cells cultures after pretreatment with ALA at concentrations of 500, 1000 and 1500μM and irradiation with incoherent light (λ=600-720nm) at fluences of 10, 30 and 60J/cm(2), using Bio-Plex ProTM Assay kit and Bio-Plex Suspension Array System apparatus, were measured.

Results: The SW620 cells were more susceptible to ALA-mediated phototoxic effect than SW480 one, however this effect may be partly abolished in hypoxia-like condition. In the case of SW480 cell line, no influence of hypoxia-like conditions on cell susceptibility to ALA-mediated photodynamic effect was found. The MIF concentration increased, contrary to MCP-1 one which decreased after ALA-mediated photodynamic action in both cell lines. No difference between cytokines concentration in supernatant from cells cultures in normoxia or hypoxia-like conditions was observed.

Conclusions: Detected reduction in MCP-1 secretion appears to be advantage because of tumor's growth limiting but an increase in the secretion of MIF, which is responsible for stimulation of tumor cells proliferation, is an unfavorable effect. These results may be explained by the fact that the used cancer cell lines differ from each other in cancer stage.