ASCT2 overexpression is associated with poor survival of OSCC patients and ASCT2 knockdown inhibited growth of glutamine-addicted OSCC cells

Background: Alanine-serine-cysteine transporter 2 (ASCT2), a major glutamine transporter, is essential for cell growth and tumor development in a variety of cancers. However, the clinicopathological significance and pathological role of ASCT2 in OSCC (oral squamous cell carcinoma) lesions remain unclear. Methods: Sections from 89 OSCC patients and 10 paracancerous tissue controls were stained by immunohistochemistry (IHC) to detect the expression of ASCT2, glutaminase, and Ki-67. Survival analysis was carried out to determine the predictive value of ASCT2 expression using the log-rank test. Moreover, the critical role of ASCT2 in tumor growth was determined by a series of in vitro and in vivo assays. Cell Counting Kit-8 (CCK8), Western Blotting (WB), Reactive Oxygen Species (ROS), and Glutathione (GSH) detection were applied to explore the molecular mechanism of ASCT2 involvement in tumor development. Results: In OSCC lesions, ASCT2 expression was significantly increased and associated with cell proliferation index (Ki-67) and GLS expression. Moreover, survival analysis showed that OSCC patients with high ASCT2 expression had lower overall survival (P = 0.0365). In OSCC cell lines, the high level of ASCT2 was inherent and related to the glutamine addiction of tumor cells. In vitro and in vivo functional experiments revealed that targeted silencing of ASCT2 can effectively inhibit OSCC cell proliferation and tumor growth. Mechanistically, targeting ASCT2 knockdown reduced glutamine uptake and intracellular GSH levels, which contribute to the accumulation of ROS and induce apoptosis in OSCC cells. Conclusion: ASCT2 is a significant factor for predicting overall survival in patients with OSCC, and targeting ASCT2 to inhibit glutamine metabolism may be a promising strategy for OSCC treatment.