Increased circulating levels of S-RNase (serum ribonuclease), an enzyme with immunosuppressive properties, were demonstrated in 14 of 19 patients with prostatic carcinoma, 6 of 6 patients with renal cell carcinoma, 5 of 6 patients with bladder carcinoma, but only 1 of 8 patients with testis tumors. A significant correlation between S-RNase levels and the extent of tumor was demonstrated in patients with prostatic carcinoma, but not in patients with other urologic malignant conditions. Moreover, a significant correlation was demonstrated between S-RNase and host cell-mediated immunocompetence as measured by delayed cutaneous hypersensitivity to DNCB (dinitrochlorobenzene). The results suggest that the S-RNase assay may be of clinical use in experimental treatment programs to reflect fluctuations of tumor status when subtle effects on tumor growth may be obscured by the advanced tumor state.
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