However, as is known, heavy ion irradiation-induced DNA damage arises mainly as a consequence of the direct interaction of the ionizing particles with the DNA molecules [30, 31]

However, as is known, heavy ion irradiation-induced DNA damage arises mainly as a consequence of the direct interaction of the ionizing particles with the DNA molecules [30, 31]. of NADPH oxidase, RAC2 has been found to be involved in the regulation of a diverse array of cellular events, including cell growth, inflammation, chemotaxis, cell polarization, cell adhesion, and macrophage activation [8C13]. It is also reported that functional disruption of RAC2 caused severe myeloid cell dysfunction in both mouse and human [14]. PF-05231023 As is known, ROS of normal physiological level is necessary to host defense and cellular signal transduction. However, excessive ROS will lead to oxidative stress, cell dysfunction, and even apoptosis or necrosis [15]. Many studies have shown that ROS produced by NADPH oxidase is an important mediator for radiobiological effects and is also the decisive factor of cellular radiosensitivity [16C18]. It has been found that the ROS production is tightly associated with the radioresistance of cancer stem cells and removal of ROS scavengers sensitized the cancer stem cells to radiation [19, 20]. Basing on these findings, we speculate that RAC2 is likely to regulate the radiosensitivity of the tumor cells by modulating the activity of NADPH oxidase. Although RAC2 has been studied for the regulation of activity of NADPH oxidase, the studies of the relationship between RAC2 and radiosensitivity of tumor cells are limited. Watanabe et al. used microarray to study the gene expression of tissue samples from rectal cancer patients who received preoperative radiotherapy. It was found that RAC2 expression in nonresponders was significantly lower than that in responders, but the underlying mechanism is not clear [21]. In the previous work, we studied the radiosensitivity of several melanoma cell lines and found that 92-1 was more radiosensitive, while OCM-1 presented radiation resistance [22]. In this study, we chose the melanoma cell lines 92-1 and OCM-1 of different radiosensitivity as a set of experimental models based on the results of previous experiments, for the purpose of revealing the effects and underlying mechanisms of RAC2 on the radiosensitivity of melanoma cells both and = is the length and is the width. All tumor volume data were normalized to those obtained just before irradiation. One month after irradiation, the mice were sacrificed and their tumors were collected for weighing, paraffin section preparation as well as immunohistochemical staining. All mice were maintained in the SPF Animal Laboratory of Soochow University. All animal studies were reviewed and approved by the Soochow University Institutional Animal Care and Use Committee. 2.8. Statistical Analysis Statistical analysis was performed on the means of the data obtained from at least 3 independent experiments. Data are presented as the means SE. values between the indicated samples were additionally presented. < 0.05 was considered to be statistically Rabbit Polyclonal to GRK6 significant. 3. Results 3.1. Effects of RAC2 on Colony Forming of Irradiated Melanoma Cells We detected RAC2 expression in several melanoma cell lines and found that RAC2 expression in 92-1 cells was much higher than that in OCM-1 cells (Fig. S4). Then, 92-shRAC2 and OCM-RAC2, with PF-05231023 RAC2 knock-down in 92-1 cells and radiation-inducible RAC2 overexpression in OCM-1 cells respectively, as well as their negative control cell lines (92-NC and OCM-NC) were established by corresponding lentivirus infection and puromycin selection. The expressions of RAC2 in 4 cell lines after X-ray or carbon ion irradiation were verified by Western blot. As shown in Figure 1(a), RAC2 expression was increased in X-ray-irradiated 92-NC cells while decreased in X-ray-irradiated OCM-NC cells while no significant change was observed upon carbon ion irradiation in both cell lines. However, RAC2 expression was decreased significantly in 92-shRAC2 PF-05231023 cells while increasing markedly in OCM-RAC2 cells exposed to either X-rays or carbon ions. Then, a colony forming assay was employed to examine cell survival fraction following irradiation. Compared with the control group, RAC2 knockdown resulted in a significantly higher survival rate of 92-1 cells exposed to either X-ray or carbon ion irradiation (Figures 1(b) and 1(d)), while radiation-inducible RAC2 overexpression significantly radiosensitized OCM-1 cells to both X-rays and carbon ions (Figures 1(c) and 1(e)). These results indicate that RAC2 is positively correlated.