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Figure 4. Elevated serum IL-31 levels are associated with resistance to anti-PD-1 in GC. (A) ELISA measuring IL-31 expression levels in the peripheral blood of 24 gastric cancer patients receiving anti-PD-1 treatment, with Kaplan-Meier analysis showing differences in PFS between high and low IL-31 expression groups; (B and C) Establishment of gastric cancer mouse models using MFC cells, examining the relationship between high IL-31 expression and sensitivity of gastric cancer to anti-PD-1 treatment (n = 5). ^***P < 0.001; ^****P < 0.0001; NS: no significance; bars: means ± standard deviation. GC: Gastric cancer; PFS: progression-free survival.