ABSTRACT
Objective The SOX7 gene plays a tumor-suppressive role in a variety of tumors, but there are few reports on whether it plays a role in bladder cancer. This study aims to investigate the expression of SOX7 gene in bladder cancer as well as to investigate the regulation and significance of SOX7 promoter methylation on bladder cancer. Methods GEPIA, Oncomine, MethHC, and cBioPortal databases were used to speculate the SOX7 expression and promoter methylation in bladder cancer tissues. 40 urine samples were collected from January 2017 to October 2017 in the Department of Urology, Tenth People's Hospital of Shanghai City, including 20 samples from bladder cancer patients and the rest 20 from regular patients as a control group. The methylation difference of SOX7 gene was detected by methylation-specific PCR. The bladder cancer cell line was cultured. The medium containing the methylated drug 5-aza-2’ deoxycytidine (5-aza-dc) was added to the Taza cells as the 5-aza-dc group, while T24 cells were added the same volume of DMSO as the control group. The bladder cancer cell line was transfected with the SOX7 plasmid as the plasmid group, and the transfected with the unloaded plasmid was the empty group. Western blot was used to detect the expression of SOX7 in bladder cancer cell lines, and the proliferation, clone formation, and apoptosis of bladder cancer cells after demethylation were detected by CCK-8 experiments, plate cloning experiments, and flow cytometry, respectively. Results The level of methylation in bladder cancer was significantly higher than that in healthy tissues (P<0.005). The higher levels of SOX7 methylation were observed in the urine of 15 bladder cancer patients (75%), compared with only 7 patients (35%) in normal urine, and the proportion was statistically different (P<0.05). The expression of SOX7 protein in the 5-aza-dc group was up-regulated compared to the control group. The expression of SOX7 protein was relatively high when the concentration reached 20 μmol/L. The expression of SOX7 protein in the plasmid group was significantly higher than that in the unloaded group. CCK-8 results showed that the A value of the 5-aza-dc group was statistically lower than that of the control group on the fifth day (P<0.05), and the A value of T24 cells in the plasmid group was significantly lower than that in the unloaded group. The colony formation experiment showed that the number of colony formation per well in the 5-aza-dc group (167.33 ± 13.65) was significantly lower than that in the control group (328.00 ± 20.81) (P<0.05). The number of clone formation per well in the plasmid group (136.00 ± 15.00) was significantly lower than that in the unloaded group (280.67 ± 13.43) (P<0.05). The apoptosis rate of T24 cells in the 5-aza-dc group (27.89%) was significantly higher than that of the control group (3.79%) (P<0.05), and the apoptosis rate of the plasmid group (21.28%) was higher than that of the no-load group (9.90%). Conclusion SOX7 is lowly expressed in bladder cancer, which is regulated by promoter methylation. It is a potential biological marker of bladder cancer and plays a vital role in the occurrence and development of bladder cancer.