In this work, for the first time, we studied the co-expression of a set of IC genes—ADAM17, PVR, TDO2, CD274, CD276, CEACAM1, IDO1, LGALS3, LGALS9, and HHLA2—in GC tumors at the early stages of its development and during metastasis. Here, TDO2 is linked to gastric cancer.