EUROPEAN RADIATION RESEARCH 2012

Difference in the Radioresistance of DU145 and PC3 Prostate Cancer Cells: Role of Reactive Oxygen Species, GSH and Nrf2

18 Oct 2012, 16:45

1m

Poster Hall (Vietri sul Mare)

poster preferred Modulation of Radiosensitivity Poster Session 3

Speaker

Mr Sundarraj Jayakumar (Radiation Biology and Health Sciences Division, Bhbha Atomic Research Centre, Mumbai, India)

Description

Understanding about the genes which govern tumor radiosensitivity, can help in better selection of patients for radiotherapy protocols, predicting prognosis, and perhaps in decreasing therapy-related side effects. In order to study the molecular determinants of tumor radiosensitivity, we have chosen two prostate tumor cells namely, PC-3 and DU145. These two tumor cell lines showed significant difference in radiosensitivity between them as reflected in clonogenic survival assay and neutral comet assay. Among the two, PC3 cells were found to be more radiosensitive (SF8 = 0.02) than that of DU145 cells (SF8 = 0.06). As these tumor cells have arisen from same tissue background, but exhibits difference in radiosensitivity, they will be ideal to study the differences at molecular level, which can be correlated with their radiosensitivity. When we measured the level of reactive oxygen species (ROS), both basal and inducible levels of ROS seen in PC3 cells were higher than that of DU145 cells. In mitochondrial ROS status also similar trend was observed. DU145 cells also showed significantly high level of basal GSH than that of PC3 cells. The ratio between GSH and GSSG was also higher in DU145 than PC3 cells. Since difference in the ROS and the antioxidant levels observed in these two cell lines, we investigated the role of redox sensitive transcription factors like NRF2 and Nf-κB and its dependent genes in determining the differences in radiosensitivity of these tumor cell lines. The level of Nrf2, Nrf2 dependent genes, and Nf-κB was analysed after irradiation, using real time PCR and electrophoretic mobility shift assay. Basal as well as inducible levels of these genes in DU145 were significantly higher than the PC3 cells. To prove this point further, we have checked the survival fraction of these tumor cells in the presence of inhibitors of Nrf2 and HO1. Presence of these inhibitors significantly reduced the survival fraction of these tumor cells against the radiation exposure further suggesting role of Nrf2 and associated genes in determining the radiosensitivity. This reduction in survival fraction was drastic in radioresistant DU145 cells than that of PC3 cells. This was further confirmed by knocking down the Nrf2 and HO1 expression and then checking the survival fraction. To conclude, the role of Nrf2 and its dependent genes in determining the radioresistance has been established in prostate cancer cells.