To investigate the effects of IDO1 and COL12A1 on GC metastasis in vivo, we injected HGC-27_NC, HGC-27_IDO1, HGC-27_shCOL12A1 and HGC-27_IDO1 + shCOL12A1 cells into mouse footpads to construct a footpad xenograft model (Fig. 8a). Here, IDO1 is linked to gastric cancer.