Effect of Notch-Pax9 Signaling Pathway in Ethanol-associated Oral Cancer

Objectives: Epidemiological studies have clearly shown a dose- and concentration-dependent effect of alcohol drinking on oral cancer. However, the molecular mechanisms of alcohol drinking-associated oral cancer are still unclear. Our previous data demonstrated that the expression of Pax9 and Notch target gene were decreased in samples from human oral cancer and esophagus cancer. The goal of this study was to investigate the relationship between Pax9 and Notch pathway.
Methods: ChIP test was applied to explore the relationship between Pax9 and Notch signaling pathway. Pax9 knockout mice amd NMBA induced mouse model were established to investigate the relation between Pax9 and Notch.KYSE510 cells were used and treated with DBZ (Notch inhibitor) or Jagged1 (Notch activator) in this study.
Results: ChIP test results showed an association between Pax9 and Notch signaling pathway. RBPJ knockout mice Sox2CreER;RBPJ^fl/fl found down-regulation of Pax9 expression in squamous epithelial cells of tongue, esophagus and stomach.KYSE510 cells were treated with DBZ or Jagged1. The results showed that the alteration of Pax9 expression was consistent with the target gene of Notch signaling pathway. These findings indicated that Pax9 was regulated by Notch signaling pathway and was likely to be downstream of Notch signaling pathway. The activity of cell proliferation was detected in Pax9 knockout mice model Krt5Cre; Pax9 ^loxp/loxp by the fluorescent immunohistochemical staining. The results showed that Pax9-knockout promoted proliferation and inhibited differenciation of esophageal epithelial cells. In addition, Pax9 deficiency promoted NMBA-induced tumors in mouse forestomach and tongue.
Conclusions: In conclusion, our data suggested that Pax9 is likely to be the downstream gene of Notch signaling pathway, and Notch-Pax9 inhibition may be involved in the development of alcohol associated oral cancer by promoting proliferation and inhibiting differentiation.