Secretion of the angiogenic factor VEGF after photodynamic therapy with ALA under hypoxia-like conditions in colon cancer cells

Background: Photodynamic therapy (PDT), eliminates not only the tumor, but also modulates signaling factors release, e.g. vascular endothelial growth factor (VEGF), which plays a crucial role in cancer progression. Assessment of the VEGF-secreting activity of resistant colon cancer cells in different degree of malignancy: SW480 and SW620 under hypoxia-like conditions during delta-aminolevulinic acid (ALA) PDT was the objective of our study. Methods: The colon cancer cell lines SW480 and SW620 were treated in sublethal doses with ALA PDT in hypoxia-like conditions with cobalt chloride (CoCl2). To assess cell viability, MTT assays were performed and the discrimination of the cell death mode was monitored via fluorescence microscopy. The cells cytotoxicity using LDH test was assessed. Determination of VEGF was carried out using the Bio-Plex Assay Prove kit on the Bio-Plex Suspension Array System. Results: ALA PDT used in sublethal doses decreases release of VEGF in more aggressively growing SW620 colon cancer cell line in hypoxia-like conditions. In addition the level of secretion of VEGF in SW620 was much higher than in SW480 cells, which correlates with the grade of aggressive growth of colon cancer cells. Conclusion: Our outcomes offer evidence, that in hypoxia mimic condition sublethal ALA-PDT-mediated VEGF inhibition could be clinically relevant.