Abstract
Notch signaling induced interleukin (IL)-22 secretion by CD4+ T cells via retinoid-related orphan nuclear receptor γt (RORγt) or aryl hydrocarbon receptor (AhR). Previous studies have demonstrated that Notch-AhR-IL-22 axis took part in the pathogenesis of chronic viral infection, however, its role in cancer has not been fully elucidated. Thus, the aim of current study was to investigate the involvement of Notch-AhR-IL-22 axis in the pathogenesis of lung adenocarcinoma. A total of 37 late-stage lung adenocarcinoma patients and 17 healthy individuals were enrolled. CD4+ T cells were purified from peripheral bloods and bronchoalveolar lavage fluids (BALF), and were stimulated with γ-secretase inhibitor (GSI). mRNA corresponding to Notch receptors and transcriptional factors were measured by real-time PCR. IL-22 concentration was investigated by ELISA. The bioactivity (including cellular proliferation, cell cycle, apoptosis, and invasion) of lung adenocarcinoma cell line A549 was also assessed in response to recombinant IL-22 stimulation in vitro. Notch1 mRNA expression was significantly elevated in CD4+ T cells purified from peripheral bloods and tumor site BALF in lung adenocarcinoma patients. IL-22 expression and RORγt/AhR mRNA in BALF was also remarkably increased in tumor site. Inhibition of Notch signaling by GSI did not affect cellular proliferation, but reduced IL-22 production in CD4+ T cells from BALF, along with down-regulation of AhR, but not RORγt. Moreover, IL-22 stimulation promoted A549 cells invasion. The current data indicated that elevated Notch1 induced higher IL-22 secretion by CD4+ T cells in lung adenocarcinoma patients, and Notch-AhR-IL-22 axis took part in the pathogenesis of lung adenocarcinoma.