Abstract 2538: The anti-proliferative effect of PUVA treatment on human bladder cancer cell lines

Abstract

Abstract Introduction and Objectives: Although immunotherapy and chemotherapy are the most used intravesical treatments for non-muscle-invasive bladder cancer (NMIBC), progression and recurrence rates are high. So far, several attempts have been done to hire a safer and more efficient treatment. Psoralen (a photoreactive chemical substance) metabolites followed by Ultra Violet A (UVA) irradiation (PUVA therapy) have been previously used to treat a variety of diseases. UVA radiation forms covalent bonds between psoralen molecule and pyrimidine bases of DNA to create interstrand cross-links, which blocks DNA replication, thereby inhibiting cell proliferation. In addition, PUVA therapy leads to apoptosis and local immune reaction. The aim of this study was to evaluate the anti-proliferative effects of PUVA treatment on human bladder cancer cell lines as the first step of further investigations, in order to consider it as a new candidate for NMIBC treatment. Material and Methods: Human bladder cancer cell lines (T24, grade III and RT4, grade I) were cultured in vitro, treated with 500 ng/ml 8-methoxypsoralen (8-MOP, a natural psoralen metabolite) and incubated in the dark room for 45 minutes. Cells were then irradiated with UVA (365 nm) at different doses (0, 0.5, 2 and 5 J/cm2). After 24- or 48-hour PUVA treatment, cells were counted to measure cell growth. MTT assay was performed in order to analyze cell viability and BrdU incorporation assay to evaluate the anti-proliferative effect of PUVA treatment. Cells were also stained with Annexin V-FITC and observed under fluorescence microscope in order to measure the amount of apoptotic cells. Results: Both T24 and RT4 cells treated with 2 and 5 J/cm2 UVA showed a significant decrease (P < 0.05) in the amount of cells after 24 hours, as compared to no UVA-treated cells. After 48 hours of PUVA treatment with all the three doses of UVA, the number of cells was significantly decreased in both cell lines. In MTT assay, PUVA-treated RT4 cells significantly reduced viability with 0.5, 2 and 5 J/cm2 UVA-treatments, as compared to no UVA-treatment. Differently, T24 cells showed a significant reduction of viability with only 5 J/cm2 UVA treatment. BrdU incorporation assay in both cell lines revealed a significant reduction of cell proliferation after PUVA treatment with all the three different UVA doses in comparison to no UVA treatment. Fluorescent microscopic observation of cell lines stained using Annexin V-FITC showed an increased number of apoptotic cells among those particularly treated with 2 and 5 J/cm2 UVA doses, as compared to no UVA-treated cells. Conclusions: PUVA treatment, mostly at higher UVA doses, has a significant anti-proliferative effect on human bladder cancer cell lines by inhibiting cell growth, reducing cell viability and inducing apoptosis. These results suggest a possible relevant use of PUVA therapy for the treatment of NMIBC. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2538. doi:10.1158/1538-7445.AM2011-2538