G protein pathway suppressor 2 suppresses gastric cancer by destabilizing epidermal growth factor receptor.

G protein pathway suppressor 2 (GPS2) is expressed in most human tissues, including the stomach. However, the biological functions of GPS2 in cancer, as well as the underlying molecular mechanisms, remain poorly understood. Here, we report that GPS2 expression was aberrantly downregulated in gastric cancer (GC) tissues compared with control tissues. Clinicopathologic analysis showed that low GPS2 expression was significantly correlated with pathological grade, lymph node stage, and invasive depth. Kaplan-Meier analysis indicated that patients with low GPS2 expression showed poorer overall survival rates than those with high GPS2 expression. Moreover, GPS2 overexpression decreased GC cell proliferation, colony formation, tumorigenesis, and invasion. Overexpression of GPS2 reduced the protein expression of epidermal growth factor receptor (EGFR) and inhibited its downstream signaling in GC cells. Interestingly, GPS2 decreased EGFR protein expression, which was reversed by a lysosome inhibitor. Furthermore, GPS2 reduced EGFR protein stability by enhancing the binding of EGFR and an E3 ligase, c-Cbl, which promoted the ubiquitination of EGFR, ultimately leading to its degradation through the lysosomal pathway. Further analysis indicated that GPS2 activated autophagy and promoted the autophagic flux by destabilizing EGFR. Taken together, these results suggest that low GPS2 expression is associated with GC progression and provide insights into the applicability of the GPS2-EGFR axis as a potential therapeutic target in GC.