The activity of neutral ribonuclease (RNase) was determined in human tumor tissues of stomach, livers, lungs, bladder, prostate, uterrus, ovary and bones to evaluate the role of the enzyme in the tumor tissues. Also analyzed was neutral RNase in human tumor tissues to find out the enzyme specific to the tumors.
1. The activity of neutral RNase was significantly increased in tumor tissues of small cell and large cell carcinoma of lungs, mucinous cystadenocarcinoma and endodermal sinus tumor of ovary, osteosarcoma and giant cell carcinoma of bones. The positive rate of the enzyme activity in the tumor tissues as a biochemical marker of the tumors was over 60%.
2. The activity of neutral RNase in the tumor tissues was significantly decreased in stomach cancer, liver cancer, and serous cystadenocarcinoma, but was unchanged in epidermoid carcinoma and adenocarcinoma of lungs, renal cell cancer, bladder cancer and prostate cancer.
3. DEAE-cellulose column chromatographical analyses of neutral RNase in human tumor tissues revealed that the neutral RNase in the tumor tissues was not present in the form of a single enzyme, but present in the form of multiple isozymes, and that the neutral RNases specific to the tumors were found one in epidermoid carcinoma tissue of lungs and two in osteosarcoma tissue of bones. It was also demonstrated that the neutral RNase isozymes present in normal control tissues disappeared one each in bladder cancer, prostate cancer and serous cystadenocarcinoma tissue of ovary and two in osteosarcoma tissue, and that some of neutral RNase isozymes in the tumor tissues were activated or suppressed.
The pattern of change in the neutral RNase activity and the isolation pattern of the neutral RNase isozymes present in multiple in human tumor tissues were different from one tumor tissue to another, and this might suggest the multifunctional roles of neutral RNase in tumor tissues.
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