[Effect of REG3A on proliferation and invasion of glioma cells by regulating PI3K/Akt signaling pathway]

Objective: To investigate the effects of regenerating islet-derived protein 3A (REG3A) on the proliferation and invasion of glioma cells and its molecular mechanism. Methods: Five low-grade, five high-grade glioma tissues and ten adjacent tissues from glioma patients who underwent surgery at Linyi People's Hospital from October 17, 2017 to October 18, 2018 were collected. Human glioma cell lines (SF295, U251, TG905, A172, CRT) and a primary glioma cell line PT-1 were cultured in vitro. The protein and mRNA expressions of REG3A in these tissues and glioma cell lines were detected by Western blot and reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR). SF295 cells were infected with lentivirus and labeled as REG3A plasmid transfection group, and the TG905 cells were transfected with si-REG3A by liposome transfection reagent and labeled as si-REG3A transfection group. At the same time, the empty transfection control and blank control groups were set up. Glioma cells were treated with REG3A recombinant protein alone or in combination with Akt1/2 inhibitors. Cell counting kit-8 (CCK-8) and cell scratch assay were used to detect cell proliferation and invasion, respectively. Western blot was used to detect the protein expression of N-cadherin, vimentin and phosphorylation of Akt (p-Akt) in REG3A overexpressed and knockdown glioma cells. Results: RT-qPCR results showed that the mRNA expression levels of REG3A in glioma cells in each group were U251 (2.129±0.13), TG905 (2.22±0.59), CRT (5.02±0.31), A172 (6.62±1.34) and PT-1 (9.18±0.61), respectively, higher than its expression in SF295 cells (1.00±0.18, P<0.001). The mRNA expression level of REG3A in high-grade glioma tissue samples (3.18±2.92) was higher than that in the control group (1.00±1.14, P=0.031) and low-grade glioma group (0.90±0.67, P=0.014). The results of western blot and immunohistochemical staining were consistent with that of RT-qPCR. The migration rate of cells in si-REG3A transfection group [(60.57±5.30)%] was lower than that of the empty transfection group [(84.18±13.63)% (P=0.038)] and blank control group [(79.65±12.09)% (P=0.076)]. The results of the scratch experiment showed that the migration rate of cells in REG3A plasmid transfected cells in the SF295 group was (96.05±6.41)%, which was significantly higher than that of empty transfected cells [(74.47±8.23)%, P=0.021)]. REG3A recombinant protein could up-regulate the expression of N-cadherin, vimentin and p-Akt in SF295 cells. Compared with the control group [(100.00±2.53)%], the proliferation rate in the REG3A recombinant protein group [(117.70±10.24)%] was significantly up-regulated, and the proliferation rate in the REG3A recombinant protein+ Akt inhibitor group [(98.31±3.64)%] was significantly lower than that of the REG3A recombinant protein group (P=0.017). The migration rate of the REG3A recombinant protein+ Akt inhibitor group was (63.35±4.06)%, which was significantly lower than (89.26±11.07)% of the REG3A recombinant protein group (P=0.019). Conclusion: REG3A can promote the proliferation and invasion of human glioma cells by activating the PI3K/Akt signaling pathway.

Temozolomide Drives Ferroptosis via a DMT1-Dependent Pathway in Glioblastoma Cells

PURPOSE

Temozolomide is used in first-line treatment for glioblastoma. However, chemoresistance to temozolomide is common in glioma patients. In addition, mechanisms for the anti-tumor effects of temozolomide are largely unknown. Ferroptosis is a form of programmed cell death triggered by disturbed redox homeostasis, overloaded iron, and increased lipid peroxidation. The present study was performed to elucidate the involvement of ferroptosis in the anti-tumor mechanisms of temozolomide.

MATERIALS AND METHODS

We utilized the CCK8 assay to evaluate cytotoxicity. Levels of lactate dehydrogenase (LDH), malondialdehyde (MDA), iron, and glutathione (GSH) were measured. Flow cytometry and fluorescence microscope were used to detect the production of reactive oxygen species (ROS). Western blotting, RT-PCR and siRNA transfection were used to investigate molecular mechanisms.

RESULTS

Temozolomide increased the levels of LDH, MDA, and iron and reduced GSH levels in TG905 cells. Furthermore, we found that ROS levels and DMT1 expression were elevated in TG905 cells treated with temozolomide and were accompanied by a decrease in the expression of glutathione peroxidase 4, indicating an iron-dependent cell death, ferroptosis. Our results also showed that temozolomide-induced ferroptosis is associated with regulation of the Nrf2/HO-1 pathway. Conversely, DMT1 knockdown by siRNA evidently blocked temozolomide-induced ferroptosis in TG905 cells.

CONCLUSION

Taken together, our findings indicate that temozolomide may suppress cell growth partly by inducing ferroptosis by targeting DMT1 expression in glioblastoma cells.