Selenium enhances the efficacy of Radachlorin mediated-photodynamic therapy in TC-1 tumor development.

Selenium, an essential trace element possessing anti-carcinogenic properties, can induce apoptosis in cancer cells. Our goal was to investigate the enhanced antitumor effects of photodynamic therapy (PDT) plus selenium in TC-1 tumor cells and implanted mice. Cell viability was evaluated at various time intervals after PDT treatment and/or selenium by methyl thiazolyl tetrazolium (MTT) assay. When only PDT treatment was administered to TC-1 tumor cells, TC-1 cell growth recovered over time. On the other hand, co-treatment of PDT and selenium extended the inhibition time of tumor cell growth. Co-treatment of PDT and selenium showed serious morphological changes in TC-1 cells and induced a more apoptotic population by FACS analysis. By signal transduction pathway SuperArray analysis, genes closely involved in the NFκB, p53 and phopholipase C pathways, such as VCAM1, MDM2 and FOS, were significantly downregulated at least 10-fold in TC-1 cells following PDT and selenium cotreatment. In an in vivo study, tumor-bearing mice were intravenously injected with Radachlorin 3 h before irradiation with 300 J/cm2 of light. Selenium was administered daily for 20 days. Combination therapy against the mouse tumors generated by TC-1 cells was more effective than PDT or selenium alone. These data suggest that selenium plus PDT can induce a significant tumor suppression response compared with PDT alone. Additionally, it can be an effective anticancer therapy strategy.