Enhanced expression of asparagine synthetase under glucose-deprived conditions promotes esophageal squamous cell...

Background: Cancer cells survive and develop under nutrient deficient microenvironment caused by low blood supply. Although anaerobic metabolism could function through the enhanced uptake of glucose, other mechanisms of tolerance to glucose deficient conditions might be required. Materials and Methods: Expression of asparagine synthetase (ASNS) under normal glucose and glucose-deprived conditions was examined. Cancer cell proliferation and migration were evaluated by in vitro and in vivo assays. In addition, the relationship between ASNS expression and cancer stages was also analyzed. Results: Expression of ASNS was enhanced under glucose deficient conditions. In vitro assays indicated that ASNS could promote the proliferation and migration abilities of esophageal squamous cell carcinoma (ESCC) cells under glucose deficient condition. In mechanism, 2 critical effectors during nutrient deprivation, NRF2 and ATF4, were upregulated and demonstrated to promote ASNS expression. Clinically, high level of ASNS was significantly associated with ESCC with advanced stages and metastasis. In vivo, ASNS could promote tumor growth and metastasis in mouse xenograft models. Conclusion: This study uncovered that glucose deprivation induces the overexpression of ASNS in ESCC cells, which in turn causes cancer cell tolerance to nutrient stress and promotes cancer development. The illustration of the mechanism sheds deep insight on how cell biology was regulated in response to the conditions of limited nutrient availability.