Unlike previous findings showing that RNase1 increases tumor weight in J:NU immunocompromised nude mice 24 who lack functional T lymphocytes but preserve lineages such as macrophages and natural killer (NK) cells, our results surprisingly suggest that RNase1-mediated tumor shrinkage occurs in a lymphocyte-dependent manner in the syngeneic tumor system. The gene discussed is RNASE1; the disease is neoplasm.