Given the dependence of NK cell activity on MHC class I expression, we investigated the effect of HPK1 overexpression in NK cells on pulmonary metastasis of TC‐1 lung cancer cells that express a high level of MHC class I surface expression (Figure S5a, Supporting Information) and are resistant to NK cell‐mediated cytolysis.[41, 42] The TC‐1‐derived metastatic load in Ncr1iCreMAP4K1Tg mice was comparable to that in Ncr1iCre mice (Figure S5b,c, Supporting Information), confirming the selective effect of HPK1 overexpression in NK cells on metastasis control of NK‐sensitive tumor cells. Here, MAP4K1 is linked to neoplasm.