Hypericum perforatum L. extract – Novel photosensitizer against human bladder cancer cells

The polar methanolic fraction (PMF) of the Hypericum perforatum L. extract has recently been developed and tested as a novel, natural photosensitizer for use in the photodynamic therapy (PDT), and photodynamic diagnosis (PDD). PMF has been tested on HL-60 leukemic cells and cord blood hemopoietic progenitors. In the present study, the efficacy of PMF as a phototoxic agent against urinary bladder carcinoma has been studied using the T24 (high grade metastatic cancer), and RT4 (primary low grade papillary transitional cell carcinoma) human bladder cancer cells. Following cell culture incubation, PMF was excited using 630 nm laser light. The photosensitizer exhibited significant photocytotoxicity in both cell lines at a concentration of 60 μg/ml, with 4–8 J/cm2 light dose, resulting in cell destruction from 80% to 86%. At the concentration of 20 μg/ml PMF was not active in either cell line. These results were compared with the results obtained in the same cell lines, under the same conditions with a clinically approved photosensitizer, Photofrin®. Photofrin® was used in the maximum clinically tolerable dose of 4 μg/ml, and it was also excited with 630 nm laser light. In the T24 cell Photofrin® exhibited slightly less photocytotocixity, compared with PMF, resulting in 77% cell death with 8 J/cm2 light dose. However, against the RT4 cells Photofrin® resulted in minimal cell death (9%) with even 8 J/cm2 light dose. Finally, the type of cell death induced by PMF photoactivation was studied using flow cytometry and DNA laddering. Cell death by PMF photodynamic action in these two bladder cell lines is caused predominently by apoptosis.The reported significant photocytotoxicity, selective localization, natural abundance, easy, and inexpensive preparation, underscore that the PMF extract hold the promise of being a novel, effective PDT photosensitizer.