ALA-induced photodynamic effect on viability, apoptosis and secretion of S100 protein, secreted by colon cancer cells in vitro.

BACKGROUND

S100 protein is a proven prognostic factor in cancers. In colorectal cancers, its secretion correlates with clinical stage of the disease. Photodynamic therapy (PDT) is used as a supporting therapy in treatment of this particular cancer. The main aim of our study was to estimate the effect of photodynamic therapy with 5-aminolevulinic acid (ALA) in sublethal doses (ALA-PDT) on the secretion of S100 protein by colon cancer cells.

METHODS

Investigations were performed on two colon cancer cell lines. The SW480 cell line is a culture containing locally malignant cancer. The SW620 line is characterized by high metastatic activity. Each line was exposed to different concentrations of photosensitizer's precursor-ALA, and various level of light radiation. Afterwards, cell viability, using MTT and LDH assays and apoptosis of both lines was assessed. Then measurement of S100 protein concentration was performed using a 2-step enzyme immunoassay.

RESULTS

After application of ALA PDT the S100 protein concentration was reduced by 27% in SW480 cell line and by 30% in SW620 cell line. At the same time there has been no increase in the concentration of S100 protein in cells exposed to the light alone. It was demonstrated that the more aggressive line SW620 releases higher levels of S100 proteins in comparison with the line SW480.

CONCLUSION

The outcome of this study presented beneficial effect of ALA-PDT on persistent colon cancer cells. This therapy leads to decrease of S100 protein concentration in both colon cancer cell lines: SW480 and SW620.