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PGC-1? coordinates with Bcl-2 to control the cell cycle in U251 cells through reducing ROS*#

ABSTRACT: B-cell lymphoma 2 (Bcl-2) has a dual function, acting as both an oncogene and an anti-tumor gene. It is well known that Bcl-2 exerts its tumor promoting function through the mitochondrial pathway. However, the mechanism by which it suppresses tumor formation is not well understood. We have previously shown that Bcl-2 inhibits cell cycle progression from the G0/G1 to the S phase after serum starvation, and that quiescent Bcl-2 expressing cells maintain a significantly lower level of mitochondrial reactive oxygen species (ROS) than control cells. Based on the fact that ROS mediate cell cycle progression and are controlled by peroxisome proliferator-activated receptor-? co-activator 1? (PGC-1?), a key molecule induced by prolonged starvation and involved in mitochondrial metabolism, we hypothesized that PGC-1? might be related to the cell cycle function of Bcl-2. In this paper, we show that PGC-1? is upregulated by Bcl-2 overexpression and downregulated following Bcl-2 knockdown or downregulation after serum starvation. However, Bcl-2 is negatively regulated by PGC-1? expression. Further, co-immunoprecipitation (co-IP) experiments showed that PGC-1? protein is co-precipitated with Bcl-2 at the G0/G1 phase. Taken together, our results suggest that PGC-1? interacts with Bcl-2 after serum depletion, and that Bcl-2 might recruit PGC-1? to reduce ROS, which in turn delays cell cycle progression in coordination with Bcl-2.

SUBMITTER: Yao K

PROVIDER: S-EPMC6011023 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature

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Project description:Energy metabolic reprogramming (EMR) allows for the rearrangement of a series of metabolic genes and proteins when tumor cells adapt to their microenvironment. EMR is characterized by changes in the metabolic pattern and metabolic intermediates to meet the needs of tumor cells for their malignant proliferation and infiltrative growth. The present study investigated the role of low-dose paclitaxel (PTX) in changing the expression levels of key genes and proteins during glycolysis in CD133+ U251 glioma cells and explored the relevant regulatory mechanisms of action at the molecular level. CD133 immunomagnetic beads were applied to malignant CD133+ U251 glioma cells, which were then divided into a negative control and an experimental group treated with 1, 2, 4 or 8 µM PTX for 72 h. Cell Counting Kit-8 (CCK-8) was used to measure U251 cell proliferation. RNA and protein were extracted from the malignant glioma cells in all groups to observe changes in the expression levels of key glycolytic enzymes, such as glucose transporter 1 (GLUT1), pyruvate kinase M (PKM) and lactate dehydrogenase A (LDHA), using reverse transcription-quantitative PCR and western blot assays. Transwell migration assays were performed to quantify the effects of PTX solution on U251 cells. CD133+ U251 glioma cells were isolated successfully. CD1133+ cells had a higher rate of proliferation compared with CD1133- cells. In CD1133+ cells treated with PTX, a dose-dependent reduction in the expression levels of the key glycolytic enzymes GLUT1, PKM and LDHA was observed at both the mRNA and protein levels. PTX solution also inhibited cell migration. Differences between the control and experimental groups were statistically significant (P<0.05). Since glycolysis plays an indispensable role in the proliferation and migration of stem cell-like glioma cells, PTX may inhibit tumor cell growth by downregulating the gene and protein expression levels of glycolytic enzymes in CD133+ glioma cells.

Project description:ObjectiveRho-associated coiled-coil kinase 2 (ROCK2) is an attractive therapeutic target because it is overexpressed in many malignancies, including glioma. Therefore, we designed the current study to determine whether the downregulation of ROCK2 would sensitize the cytotoxic effect of temozolomide (TMZ) in U251 cells.MethodsGlycol-polyethyleneimine (PEG-PEI) was used to deliver siROCK2 to U251 cells, and the physical characteristics of the PEG-PEI/siROCK2 complex (referred to as the siROCK2 complex) were investigated. The transfection efficiency and cell uptake were determined by flow cytometry (FCM) and confocal laser microscopy (CLSM), respectively. U251 cells were then treated with 100 μM TMZ, siROCK2 complexes or their combination. The apoptosis rate and cell migration were measured by FCM and wound-healing assay, respectively. The levels of Bax, Bcl-2, cleaved caspase-3, MMP-2, and MMP-9 were detected to analyze the degrees of apoptosis and migration.ResultsOur results revealed that the characteristics of the siROCK2 complexes depended closely on the N/P ratios. PEG-PEI served as a good vector for siROCK2 and exhibited low cytotoxicity toward U251 cells. The CLSM assay showed that the siROCK2 complexes were successfully uptaken and that both the protein and mRNA levels of ROCK2 were significantly suppressed. Furthermore, the combination treatment induced a higher apoptosis rate and markedly increased the gap distance of U251 cells in the wound-healing assay. Levels of the proapoptotic proteins Bax and cleaved caspase-3 were significantly increased, whereas levels of the antiapoptotic protein Bcl-2 and the migration-related proteins MMP-2 and MMP-9 were significantly reduced by the combination treatment compared with either treatment alone.ConclusionsIn conclusion, our results demonstrate that the combination of TMZ and siROCK2 effectively induces apoptosis and inhibits the migration of U251 cells. Therefore, the combination of TMZ and siROCK2 complex is a potential therapeutic approach for human glioma.

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PGC-1? coordinates with Bcl-2 to control the cell cycle in U251 cells through reducing ROS*#

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