Effect of Notch1 Signaling on Cellular Proliferation and Apoptosis of Human Laryngeal Carcinoma

Abstract The pathological processes of occurrence and development of malignancies include the excessive proliferation and apoptosis resistance of neoplastic cells. The study aims to identify the effects of Notch1 signaling on the proliferation and apoptosis of laryngeal cancer cells in hypoxic microenvironment. Notch1 and Ki-67 expression in laryngeal squamous cell carcinoma (LSCC) tissue samples were detected by immunohistochemistry. The apoptotic index (AI) of LSCC was evaluated by TUNEL method. In laryngeal cancer cells, small interfering RNA (siRNA) technology was to inhibit Notch1 expression. Meanwhile, Real-time PCR detected Notch1, Hes1 and Hey1 mRNA expression, and Western blot detected Notch1 and Notch1 intracellular domain (N1ICD) protein expression. Annexin V-FITC/propidium iodide staining and Cell Counting Kit‑8 methods measured cell apoptosis and proliferation, respectively. Notch1 expression was detected in 63.55％(68/107) of LSCC samples and was significantly related to the proliferation index (PI) (P < 0.05) and AI (P < 0.05) in LSCC tissues. Furthermore, it was confirmed that hypoxia could induce proliferation and inhibit apoptosis of laryngeal carcinoma cells (P < 0.05). Meanwhile, Notch1 expression and Notch1 signaling activity could be upregulated by hypoxia (P < 0.05). In contrast, suppression of Notch1 signaling activity in hypoxic neoplastic cells could obviously decrease cell proliferation and increase cell apoptosis (both P<0.05). Our study has demonstrated that hypoxia may promote cell proliferation and inhibit cell apoptosis of laryngeal carcinoma. Notch1 signalling may exert a pivotal role in regulating the proliferation and apoptosis resistance of laryngeal cancer cells under hypoxia.