RNASE1 and breast cancer: Additionally, we expressed RNase1 (R1) in the low‐endogenous RNase1 expressing cells, SAS human oral squamous cell carcinoma cells or MDA‐MB‐231 breast cancer cells (Figure S2F,H, Supporting Information) and discovered that RNase1 or catalytically inactive RNase1 mutant (R1‐H12A) expression reduced T‐cell cytotoxicity against cancer cells (Figure 3H,I; right panels).