Assessing the Radioprotecting Effect of ZoPra on Human Prostate Epithelial Cells and Human Fibroblast Cells.

Abstract

Prostate cancer is the most prevalent cancer in men and the second leading cause of cancer-related deaths in men around the world. One of the first-line treatments for lowering tumor size and preventing further cancer development is radiotherapy. Its effectiveness is based on the patient's and tumor cells' radiosensitivity. The radioresistance of tumor cells and harmful effects on the surrounding normal cells, however, greatly limit it.

Radiation exposure to normal tissue can cause both acute and chronic toxicities. Radiotherapy induces DNA double strand breaks and the cell’s response translates into the activation of DSB repair through ATM nucleoshuttling and phosphorylation of H2AX Radioprotectors are chemicals that are meant to decrease the effects of radiation on normal tissues. Numerous disorders linked to bone loss are treated using bisphosphonates, such as zoledronic acid (Zo). Pravastatin (Pra) is one of many statins that are used to control lipid levels.

The ZoPra combination has been found to improve the speed of ATM nucleo-shuttling by blocking nucleus membrane farnesylation. This results in faster and better DSB signaling, which improves the cell's ability to repair DNA. As a result, the combination of Zoledronate and Pravastatin may have a radio protecting effect on normal prostate and fibroblast cells. Therefore, the aim of this study is to assess the radioprotecting effect of Zoledronic acid and Pravastatin, alone and in combination on normal epithelial human prostate cell line, RWPE-1, in vitro, on a cellular and molecular level.

The cytotoxic effect of different concentrations of Zo and Pra was tested using MTT assay. The optimum concentration of both was determined to be 1 μM and was therefore used in further experiments. Cells were treated with 1 μM Zoledronic acid and Pravastatin, alone and in combination, prior to a 2 Gy irradiation. Clonogenic assay was performed to assess cell survival and colony forming ability with treatment. Immunofluorescence analysis of pATM and γH2AX was performed to study DNA DSB repair kinetics.

Pre-treatment with 1 μM ZoPra prior to a 2 Gy irradiation was shown to decrease the residual number of γH2AX foci. However no significant change was observed in cell survival of RWPE-1 cells. This study presents novel findings on the potential use of ZoPra as a radioprotecting agent for normal human prostate epithelial cells.