FGF4 and neoplasm: Immunofluorescence in liver-infiltrating tumor tissues showed that AAV-SHH or AAV-FGF4 successfully activated the positive feedback regulation between FGF4/SHH and GREM1 in macrophages (F4/80+) (Fig. 8F), which contributed to an increase in CD206+F4/80+ macrophages and a decline in CD8+CD3+ T cells (Fig. 8G).