The effect of in vitro photodynamic therapy on increase of osteopontin and heat shock protein 70 expression in squamous cell and colon carcinoma

Abstract

The aim of the study was investigating whether the 5-ALA-mediated-photodynamic therapy may cause an increase in osteopontin expression in malignant cells, and whether this was accompanied by a parallel increase in an expression of Heat Shock Protein 70. The heat shock proteins belong to highly conserved stress proteins widely expressed in different cells and playing specific important roles. Osteopontins have been associated with the progression of numerous types of cancer. SCC-4 and SW480 cells were exposed to 3 and 6 mM of 5-aminolevulinic acid for 5 h. Two different light sources were used: first, a halogen lamp; and second, the diode laser. The viability of SCC-4 and SW480 cells following treatment was determined by MTT assay. Protein expression was assessed by immunocytochemistry and Western blot analysis. The apoptosis rate after treatment with different light sources was measured by flow cytometry. Immunocytochemical stainings showed distinct increase of HSP70 and osteopontin protein expression in both cancer cell lines after PDT by means of either halogen lamp or laser light. The effects of a photodamage can both promote cell death and enhance metastasis. This will emphasize the rationale for providing sufficient PDT doses to eradicate malignant cells since a suboptimal dose may have an adverse effect on cancer control.