5-azacytidine inhibits the tumorigenesis of esophageal cancer cells through the suppression of NOTCH1 signaling

Background: Esophageal squamous carcinoma (ESCC) and esophageal adenocarcinoma (EAC) are different pathological types of esophageal cancer (EC) with low patient survival. The methyltransferase inhibitor 5-azacytidine (5-azaC) has been approved to treat hematological malignancies and malignant solid tumors for years. NOTCH1 pathway plays an important role in both hematological and esophageal cancer and previous studies demonstrated a NOTCH1/IL-7/IL-7R signal in other cancers. Methods: : TE-1 and OE33 cells were employed to represent ESCC and EAC respectively. The effects of 5-azaC on cells were evaluated by CCK8, wound healing, Transwell assay, and flow cytometry. Pyrosequencing was performed to detect changes of 18 CpG units in cells after being treated with 5-azaC. Western blot and Quantitative Real-time PCR were conducted respectively to test expressions of NOTCH1/IL-7/IL-7R signal for exploring the mechanisms. siRNA transfections were performed to inhibit IL-7R. Results: : 5-azaC showed anticancer effects and NOTCH1 signaling was also downregulated in both cell lines. Although there were abundant CpG islands in NOTCH1 , no change was observed in its methylation level. Moreover, the combination of 5-azaC with NOTCH1 signaling inhibitor DAPT had a synergistic inhibiting effect in EAC but ESCC cells. We proved the existence of the NOTCH1/IL-7/IL-7R signal in the ESCC cell line. Additionally, the activation or inactivation of the IL-7/IL-7R pathway could mitigate or potentiate the potency of 5-azaC on ESCC cells as well. Conclusions: : Our findings showed a possibility of treating esophageal cancer with 5-azaC combining inhibitors of NOTCH1/IL-7/IL-7R signal, hoping to provide novel therapeutic strategies for EC.