To obtain mouse cancer tissues for further analysis of T‐cell activity in TME and distinguish whether RNase1‐promoting cancer growth is from its immunosuppressive function, we knocked down RNase1 in 4T1 cells (Figure S3C, Supporting Information) and compared the cancer growth between 4T1‐sh‐Ctrl and 4T1‐sh‐mR1#1 cells in both immunocompetent and non‐obese diabetic severe combined immune deficiency (NOD SCID) mice. Here, RNASE1 is linked to cancer.