STAT1 and neoplasm: The results showed that R1‐5A expressed in MDA‐MB‐231 abolished the RNase1‐promoted increases in tumor volume and weight (Figure 6O and Figure S5H,I, Supporting Information), suggesting that the RNase1‐STAT1 interaction in CD8+ T cells may be crucial for RNase1 to inhibit CD8+ T‐cell cytotoxicity against cancer cells in vivo.