Comparison of radiosensitizing effect of Resveratrol on monolayer and spheroid culture of DU145 prostatic cell line

Radiotherapy is an established therapeutic modality for prostate cancer. Resveratrol, a natural antioxidant, has been shown to inhibit carcinogenesis and to block the process of tumor initiation and progression. No data is available on the response of cellular spheroid to Reseveratol. In this study we have examined the effect of Resveratol on the radiation response of human prostate cell line DU145 in monolayer and spheroid cultures. Radiosensitivity was assessed using viability and colony formation assay. Apoptosis and necrosis were assessed using acridine orange/ ethidium bromide double staining. The colony formation assay did not show any significant radio-sensitizing effect, but apoptosis assay showed significant radio-sensitizing effect of Resveratol on DU145 cells grown as monolayer. In the spheroid cells the results of apoptosis test were not significant and corresponded closely to the result of survival curve. While Resveratol could sensitize DU145 cells in monolayer to ionizing radiation, it did not have any effect on sensitivity of cells cultured in spheroid cultures

Megavoltage dose enhancement of gold nanoparticles for different geometric set-ups: Measurements and Monte Carlo simulation

Gold nanoparticles [GNPs] have been shown as a good radiosensitizer. In combination with radiotherapy, several studies with orthovoltage X-rays have shown considerable dose enhancement effects. This paper reports the dose enhancement factor [DEF] due to GNPs in 18 megavoltage [MV] beams. Different geometrical 50-nm GNPs configurations at a concentration of 5 mg/ml were used by both experimental and Monte Carlo [MC] simulation in a deep-seated tumor-like insertion within a phantom. Using MCNP repeated structure capability; a large number of gold nanospheres with a semi-random distribution were applied to simulate this phantom based study. Thermoluminescence dosimetries were used to verify the process of irradiation and MC simulation. Under geometries with different probable combinations of water and GNPs distribution in the tumor, the percentage depth dose and DEF were calculated. Incorporation of GNPs into the radiation field in our set-ups showed a 12% DEF. We show that the method of nanoparticles, distribution, and orientation can effectively change the DEF value

Evaluation of combination effects of 2- methoxyestradiol and methoxyamine on IUdRinduced radiosensitization in glioma spheroids

Glioblastoma is the most common and most malignant cancer of central nervous system. Targeted radiotherapy is an effective method toward its treatment. Iododeoxyuridine [IUdR] is a halogenated thymidine analogue known to be effective as a radiosensitizer in human cancer therapy. In this study we have evaluated the combination effects of 2-Methoxyestradiol, an inhibitor of hypoxia inducible factor 1 alpha [HIF-1 alpha] and Methoxyaminem, an inhibitor of base excision repair [BER] pathway on radiosensitization of IUdR in glioblastoma spheroid culture. The cytotoxic damages of DNA in U87MG cell line were compared using colony formation assay. Experiments were performed in large spheroids with a diameter of approximately 350micro m. Evaluation of the effects of IUdR with 2ME2 and MX pretreatment on spheroid cultured cell followed by ionizing irradiation showed more enhancemented [p

role of Rad51 protein in radioresistance of spheroid model of DU145 prostate carcinoma cell line

Rad51 is a protein with critical role in double strand break repair. Down-regulation of this protein has a significant effect in radiosensitivity of some cell lines like prostate carcinoma. Compared to monolayer cell culture model, the spheroids are more resistant to radiation. The aim of the current study was to determine the Rad51 protein level in DU145 spheroids, and monolayer cells before and after exposure to gamma irradiation. In the present study, western blot was used to determine the level of Rad51 protein in DU145 cell line grown as monolayer and spheroid. Western blot analysis showed that in the spheroid cells, Rad51 had an elevated level before and after radiation in comparison with monolayer cells. Higher doses of radiation induced elevated expression of Rad51 protein in both culture models. The level of at protein after exposure to gamma rays had been time dependent. Rad51 might act as a mediator of radiation resistance in tumor cells. Repression of Rad51 activity could be a prominent strategy to overcome radiation resistance of tumors

Reduced DNA damage in tumor spheroids compared to monolayer cultures exposed to ionizing radiation

Several cell lines when cultured under proper condition can form three dimensional structures called multicellular tumor spheroids. Tumor spheroids are valuable in vitro models for studying physical and biological behavior of real tumors. A number of previous studies using a variety of techniques have shown no relationship between radiosensitivity and DNA strand breaks in monolayer and spheroid model of cell culture. In the present study, the radiosensitivity of cells grown as monolayer and spheroid were measured with colony assay and the role of DNA strand breaks in this sensitivity was examined using single cell gel electrophoresis assay also known as Comet assay. In the present experiment, spheroids showed more radioresistance than monolayers as judged by the number of colonies which they produced after radiation. Under the same experimental conditions, less level of DNA damage was detected in spheroids using "comet assay" technique. It was concluded that the loss of radioresistance which was observed in monolayer cultures might have been attributed to the higher level of DNA damage occurred in the cells