Objectives <p>This research investigates how the SERPINE1-associated tumor microenvironment influences anti-PD-1 treatment response in gastric carcinoma (GC).</p> Methods <p>Bioinformatics analysis, cellular experiments, and animal models were employed to quantify the levels of NFATC2, SERPINE1, JAK3, STAT3, and to explore their associations with various biological behaviors of GC cells, encompassing proliferation, migration, invasiveness, EMT, and immune cell infiltration. Additionally, by constructing a GC tumor-bearing model, we assessed the efficacy of knocking down SERPINE1 in combination with anti-PD-1 therapy.</p> Results <p>Elevated SERPINE1 expression in GC correlated with enhanced tumor aggressiveness, lymphatic dissemination, and adverse prognostic indicators. NFATC2, a potential transcription factor of SERPINE1, showed high expression that correlated with poor prognosis in GC patients. NFATC2 orchestrates JAK3/STAT3 pathway activation via SERPINE1 induction, culminating in STAT3 upregulation. Concurrently, STAT3 regulates the upregulation of NFATC2, which in turn further enhances SERPINE1 levels, establishing a positive feedback loop. This loop facilitates the proliferation, clonogenic growth, migration, invasion, and EMT processes of GC cells, thereby accelerating the progression of GC. Additionally, the NFATC2/SERPINE1 axis may facilitate immune evasion in GC by increasing the presence of PD-L1⁺ M2 macrophages. Importantly, silencing SERPINE1 enhanced the sensitivity of GC xenografts to anti-PD-1 therapy.</p> Conclusion <p>Our study reveals the critical function of the NFATC2/SERPINE1/JAK3/STAT3 positive feedback loop in gastric carcinogenesis while identifying its plausible contribution to anti-PD-1 therapy resistance mechanisms.</p> Graphical Abstract <p><b>Schematic diagram of NFATC2 in stomach adenocarcinoma.</b> The positive feedback loop of NFATC2/SERPINE1/JAK3/STAT3 reshapes the immune microenvironment to mediate resistance to anti-PD-1 therapy in stomach adenocarcinoma.</p> <p></p>