Effects of Photodynamic Therapy on Protein Expressionin Rat Bladder Cancer Cells

Abstract

Photodynamic therapy (PDT) is an effective treatment involving light and a photosensitizer used in conjunction with molecular oxygen to elicit cell death. The purpose of this study is search for changes in protein expression induced by HAL-PDT-mediated treatment of cytotoxic effect in rat bladder carcinoma cells (AY-27).

A typical protocol for PDT experiments was as follows: AY-27 cells were cultured in RPMI-1640 medium for one day and incubated with hexyl-aminolevulinate. At room temperature, the HAL-treated cells were exposed to blue light (435nm) in PBS and further incubated in serum free culture medium. Protein lysates from non-, HAL- and HAL-PDT treated cells were analyzed by two dimensional difference gel electrophoresis (2D-DIGE). Proteins of interest were then identified by mass spectrometry (MS).

Difference in protein expression between HAL-treated and HAL-PDT samples was clearly displayed in scanning images. Forty proteins were subjected to MS-based peptide map fingerprinting. Of these, fifteen proteins were either post-transcriptional modified (pI-shift) or differentially expressed (down- or up-regulation) due to light treatment. Bioinformatic analysis of the modified proteins has revealed potential affected biological processes, molecular function, pathways and protein interactions in cells. Pre-purification methodologies are now being optimized to allow an in depth study of proteome changes due to PDT.