The introduction of a tumor that secretes TNF results in notable muscle wasting in mice (Tracey et al. 1990), and administration of TNF or IL-1 in living organisms leads to an increase in nitrogen excretion from skeletal muscle and a decline in body protein levels in otherwise unaffected animals (Fong et al. 1989; Hoshino et al. 1991). This evidence concerns the gene TNF and neoplasm.