RESUMEN
BACKGROUND: Esophageal squamous cell carcinoma (ESCC), the predominant type of esophageal cancer, has a 5-year survival rate less than 20%. Although the cause of poor prognosis is the high incidence and mortality of ESCC, the high rate of metastasis after esophageal cancer surgery is the main cause of death after the surgery. Bromodomain-containing protein 4 (BRD4), an epigenetic reader of chromatin-acetylated histones in tumorigenesis and development, plays an essential role in regulating oncogene expression. BRD4 inhibition and BRD4 inhibition-based treatment can potentially suppress ESCC growth. However, the effects and mechanisms of action of BRD4 on ESCC cell migration remain unclear. AIM: To explore the effect of BRD4 on cell migration of ESCC in vitro and its possible molecular mechanism. METHODS: Human ESCC cell lines KYSE-450 and KYSE-150 were used. The 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide assay was performed to examine cell proliferation, and the transwell migration assay was conducted to test ESCC cell migration. JQ1, a BRD4 inhibitor, was applied to cells, and BRD4 siRNA was transfected into ESCC cells to knockdown endogenous BRD4. GFP-RFP-LC3 adenovirus was infected into ESCC cells to evaluate the effect of JQ1 on autophagy. Western blotting was performed to determine the protein levels of BRD4, E-cadherin, vimentin, AMP-activated protein kinase (AMPK), and p-AMPK. RESULTS: BRD4 was either downregulated by small interfering RNA or pretreated with JQ1 in ESCC cells, leading to increased tumor migration in ESCC cells in a dose- and time-dependent manner. Inhibition of BRD4 not only significantly suppressed cell proliferation but also strongly increased cell migration by inducing epithelial-mesenchymal transition (EMT). The protein expression of vimentin was increased and E-cadherin decreased in a dose-dependent manner, subsequently promoting autophagy in KYSE-450 and KYSE-150 cells. Pretreatment with JQ1, a BRD4 inhibitor, inhibited BRD4-induced LC3-II activation and upregulated AMPK phosphorylation in a dose-dependent manner. Additionally, an increased number of autophagosomes and autolysosomes were observed in JQ1-treated ESCC cells. The autophagy inhibitor 3-methyladenine (3-MA) reversed the effects of BRD4 knockdown on ESCC cell migration and blocked JQ1-induced cell migration. 3-MA also downregulated the expression of vimentin and upregulation E-cadherin. CONCLUSION: BRD4 inhibition enhances cell migration by inducing EMT and autophagy in ESCC cells via the AMPK-modified pathway. Thus, the facilitating role on ESCC cell migration should be considered for BRD4 inhibitor clinical application to ESCC patients.
RESUMEN
Objective: To investigate the effects of ACC1 knockdown on human glioma U251 cell migration and its molecular mechanisms. Methods: Human glioma U251 cell line was used. The experiment was carried out in three steps. Experiment 1: knockdown of ACC1 in U251 cells (shACC1) and its control (NC) U251 cells were established by transfection of shACC1 lentivirus and negative control virus. The cell migration was detected by Transwell migration assay and scratch test. Western blot (WB) was performed to detect the levels of ACC1, Vimentin, Fibronectin, N-cadherin, E-cadherin and Slug proteins. Experiment 2: RT-qPCR and WB were performed to verify the RNA-seq result, upregulation effect of ACC1 knockdown on PAI-1 in U251 cells. The cells then were treated with PAI-1 inhibitor PAI-039, and the cell migration was detected by Transwell migration assay and scratch assay. The protein levels of ACC1, PAI-1, Vimentin, Fibronectin, N-cadherin, E-cadherin and Slug were examined by WB. Experiment 3: the molecular mechanisms of knocking down ACC1 to increase PAI-1 were explored. The cells were treated with acetyltransferase inhibitor C646, and cell migration was examined by Transwell migration assay and scratch assay. WB was conducted to test the levels of ACC1, H3K9ac, PAI-1, Vimentin, Fibronectin, N-cadherin, E-cadherin and Slug proteins. Each experiment was repeated three times. Results: Experiment 1: lentivirus transfection was performed on glioma U251 cells. Compared with NC group, the expression level of ACC1 in shACC1 group was decreased significantly, indicating that lentivirus transfection was successful (Pï¼0.01), and the number of migrated cells in shACC1 group was increased significantly (Pï¼0.01). Migration-related proteins Vimentin, Fibronectin, N-cadherin and Slug were up-regulated, while E-cadherin was down-regulated (Pï¼0.01). Experiment 2: Compared with NC group, PAI-1 mRNA level in shACC1 group was up-regulated. Compared with control group, cell migration in shACC1+PAI-039 group was decreased (Pï¼0.01), and migration-related proteins Vimentin, Fibronectin, N-cadherin, and Slug were up-regulated. E-cadherin expression was down-regulated (Pï¼0.01). Experiment 3: Compared with NC group, the concentration of acetyl-coA and the expression level of H3K9ac in shACC1 group were increased significantly (Pï¼0.01); After further treatment with histone acetyl transferase inhibitor C646, PAI-1 mRNA level was decreased, cell migration number and H3K9ac expression level were decreased in shACC1+C646 group compared with control group (Pï¼0.01). Migration-related proteins Vimentin, Fibronectin, N-cadherin and Slug were up-regulated, while E-cadherin was down-regulated (Pï¼0.01). Conclusion: Knockdown of ACC1 promotes the migration of human glioma U251 cells by increasing histone acetylation which elevates the level of PAI-1.
