Effect of Statins and\ or γ-Radiation on Tumor Cell Line

Abstract

Cancer is the first enemy for all peoples with different societies due to the cancer cases worldwide are forecast to rise 75% and reach close to 25 million over next two decades according to WHO report on world cancer day 2014. There are three main problems in cancer fight; chemotherapy drug resistance, recurrence or metastasis of tumor cells and sever side effects of radiotherapy or chemotherapy which may lead to death in some cases. The present study aims at developing cancer therapy protocols via increasing apoptosis of the tumor cells death by radiation alone or in combination with new cytotoxic drug with safety profile. Statins are a family of drugs which have been used initially as an anti dyslipidemic drug; due to its significant efficacy in blocking mevalonate pathway by inhibition of 3- hydroxy-3-methylglutaryl-coenzyme A reductase and many studies found that the statins have an efficacy on induction of apoptosis and arresting cell cycle of tumor cells. The present study were conducted from twenty five groups (Seventeen groups for primary studies and Eight groups for selected doses and its combinations) to select three doses of γ- radiation from eight doses and one dose of Simvastatin from six doses in preliminary study and the selected doses were Summary 146 repeated again in addition to its combinations in addition to control untreated group. In current experiments, the cells were plated with viability more than 85% and treated with different doses of Simvastatin (0.05μmol/l, 0.1μmol/l, 0.5μmol/l, 1μmol/l, 2μmol/l, 5μmol/l), then the cells were harvested at 24hr, 48hr and 72hr. For Radiation treatment, cells were treated with different doses of γ-radiation (0.25Gy, 0.5Gy, 1Gy, 1.5Gy, 5Gy, 6Gy, 7.5Gy and 10Gy) from Cs137 radioisotope with dose rated 0.45Gy/min or in combination with Simvastatin. For combination treatments, Simvastatin (0.1μmol/l) was added to the culture media 24hr prior to radiation treatment (0.25Gy, 0.5Gy, and 1Gy). The initial experiments which include all different doses of Simvastatin and γ-irradiation were performed in three replicate for each dose and then repeated after choosing the selected dose of Simvastatin (0.1μmol/l) and three doses of γ-irradiation (0.25Gy, 0.5Gy, 1Gy). The viability of cells was estimated through vital dye (Trypan blue 0.2%) by Hemocytometer. Cell viability, induction of apoptosis, cell death, cell cycle, generation of ROS, antioxidant enzymes activity, expression of P53, Bax, Bcl-2, Caspase-3, PARP-1 and Fas genes were estimated. The results indicated that Simvastatin (0.1μM/l) treatment for 24hr prior to Gamma irradiation Summary 147 increased cell death to 37.5% as compared to 4.81% by radiation (0.5Gy) alone. It was found that, simvastatin treatment before irradiation caused an increase in the percentage of cell death which assessed by cell cycle analysis with Flow cytometry causing arresting cells at G0/G1 and G2/M Phases. Interestingly, Simvastatin treatment of P3NS1 cells increased the intracellular ROS production, decreased the antioxidant enzymes activity and increased P53, Bax and Caspase-3 gene expression while the gene expression of Bcl-2 was decreased. Consequently, the present results indicated that pre-treatment with Simvastatin increased radiosensitivity of tumor cells in addition to its apoptotic effect on myeloma cells through intrinsic mitochondrial pathway. RECOMMENDATION The current results concerning with the role of simvastatin increasing radiosensitivity, safety profile, increasing Oxidative stress in tumor cells and achieving a good prognostic indicator. It is recommended that, the physician advice cancer patientsto use oral simvastatin before radiotherapy sessions. Moreover, the current data give us the reason to assure that the using of different antioxidant drugs at different concentrations may lead to best result to arrest tumor Summary 148 cell cycle. To assure these effects, further studies on animal models are needed to verify simvastatin effect in addition to its effect with other anticancer drug combination. Else, more investigation are needed about using specific genes as prognostic and diagnostic marker in radiation hazards and treatment.