In a Balb/c nu/nu tumor transplantation model, CD4+ T cells are reported to upregulate PD-L1 expression in gastric cancer-derived MSCs (GC-MSCs) via the p-STAT3 signaling pathway, and to activate the PD-1/mTOR signaling pathway, thereby promoting gastric cancer growth (21). The gene discussed is STAT3; the disease is gastric cancer.