The Enhancement of Radiation Sensitivity in Nasopharyngeal Carcinoma Cells via Activation of the Rac1/NADPH Signaling Pathway

Abstract

We reported in an earlier study that using mass spectrometry and bioinformatic analysis demonstrated Rac1 protein might be mostly mitochondrial target in the radiosensitization process of nasopharyngeal carcinoma CNE-1 cells. The goal of our current study was to reveal the relationship between Rac1/NADPH pathway and radiosensitization in CNE-1 cells using Rac1 activator, phorbol 12-myristate 13-acetate (PMA) and Rac1 inhibitor NSC23766. The Rac1-GTP expression was determined using a pulldown assay, the Rac1 location using a immunofluorescence with a laser scanning confocal microscope, the NADPH oxidase activity with NBT assay and the reactive oxygen species with DCFH-DA probe. The apoptosis rate was analyzed by flow cytometry, and the expressions of p67(phox) and NFκB-p105/p50 were analyzed by Western blot. After treatment with PMA and 2 Gy radiation (compared to the control), Rac1-GTP was activated and translocated to the cell membrane. NADPH oxidase activity, reactive oxygen species of intracellular concentration and the apoptosis rate increased significantly. The expression of p67(phox) and NFκB-p50 protein also increased. However, in the cells treated with NSC23766 alone or NSC23766 combined with 2 Gy irradiation, the results were just the opposite. Overall, these results indicate that the Rac1 protein may be the key target involved in the radiosensitization of nasopharyngeal carcinoma cells. The activated Rac1/NADPH pathway combined with radiation can increase the radiosensitivity of nasopharyngeal carcinoma cells, and the Rac1/NADPH pathway may be the signaling pathway involved in the radiosensitization process.

Rhein suppresses matrix metalloproteinase production by regulating the Rac1/ROS/MAPK/AP-1 pathway in human ovarian carcinoma cells

“…PMA can activate the NADPH oxidase activity and NSC23766 inhibits its activity. No significant cytotoxicity to SKOV3-PM4 cells was found when the concentration of PMA and NSC23766 was 100 nM and 12.5 µM, respectively (21). Considering that the inhibitory rate of SKOV3-PM4 cells treated with rhein alone was <20%, the concentration of rhein was chosen as ≤11.3 µM.…”

NADPH Oxidase Activation Contributes to Heavy Ion Irradiation–Induced Cell Death

“…28 It has been observed that Nox4 expression continues to increase at all time points from 1 day to 6 months post X-ray radiation in mice lung tissue. 29 Similarly, low-dose γ irradiation is capable of upregulating NADPH oxidase in central nervous system in mice.…”

“…Besides heavy ion radiation, X-ray radiation could also significantly activate NADPH oxidase and enhance the production of ROS, leading to X-radiation-induced growth inhibition of nasopharyngeal carcinoma cells. 28 It has been observed that Nox4 expression continues to increase at all time points from 1 day to 6 months post X-ray radiation in mice lung tissue. 29 Similarly, low-dose g irradiation is capable of upregulating NADPH oxidase in central nervous system in mice.…”

Rac-GEF/Rac Signaling and Metastatic Dissemination in Lung Cancer

“…Rac1 and its effectors can activate mitogenic pathways, including the MAPK cascades, leading to changes in cell cycle progression (Olson et al, 1995;Yang et al, 2008). Rac1 has been consistently involved in the activation of pro-survival pathways in cancer cells, such as NF-κB, thereby counterbalancing the apoptotic responses triggered by chemotherapeutic agents and radiation therapy (Friedland et al, 2007;Han et al, 2013;Wang et al, 2013Wang et al, , 2016Hein et al, 2016). Regarding cellular metabolism, Rac1 has been widely associated with macropinocytosis, a mechanism of endocytic uptake of extracellular fluid that assists in meeting the increased demand of nutrients required for cancer cells to proliferation (Erami et al, 2017;Ramirez et al, 2019).…”