S100A8/A9-MCAM signaling promotes gastric cancer cell progression via ERK-c-Jun activation.

S100 protein family members S100A8 and S100A9 function primarily as a heterodimer complex (S100A8/A9) in vivo. This complex has been implicated in various cancers, including gastric cancer (GC). Recent studies suggest that these proteins play significant roles in tumor progression, inflammation, and metastasis. However, the exact mechanisms by which S100A8/A9 contributes to GC pathogenesis remain unclear. This study investigates the role of S100A8/A9 and its receptor in GC. Immunohistochemical analysis was performed on GC tissue samples to assess the expression of the S100A8/A9 receptor melanoma cell adhesion molecule (MCAM). In vitro transwell migration and invasion assays were used to evaluate the motility and invasiveness of GC cells. Cell proliferation was assessed using a growth assay, and Western blotting (WB) was employed to examine downstream signaling pathways, including ERK and the transcription factor c-Jun, in response to S100A8/A9-MCAM interaction. S100A8/A9 stimulation enhanced both proliferation and migration through MCAM binding in GC cell lines. These cellular events were accompanied by ERK activation and c-Jun induction. Downregulation of MCAM suppressed both ERK phosphorylation and c-Jun expression, highlighting the importance of the S100A8/A9‒MCAM‒ERK‒c-Jun axis in promoting GC progression. These findings indicate that S100A8/A9 contributes to GC progression via MCAM, which activates the ERK‒c-Jun pathway. The S100A8/A9‒signaling axis may represent a novel therapeutic target in GC.