A neutral ribonuclease(RNase) specific to the epidermoid carcinoma of the lung was isolated from the lung cancer tissue to investigate processes involved in carcinogenesis an suppression of the lung cancer. Also studied were the substrate
specificity ad
mechanism of action of the neural RNase specific to the lung cancer.
Neutral RNase activity in the lung tissue obtained by surgery was unchanged in four varieties of lung cancers (epidermoid carcinoma in 20 cases, 4721±1859 umole/g/hr ; adenocarcinoma in 5 cases, 5165±1575 umole/g/hr ; large cell carcinoma in 3
cases,
5870±2305 umole/g/hr ; small cell carcinoma in 3 cases, 5405±2822 umole/g/hr ; control in 31 cases, 4380±1502 umole/g/hr), indicating that RNase assay in the lung tissue could not be used as a biochemical marker for the lung cancer. Neutral
RNases in
the in the epidermoid carcinoma tissue of the lung were separated by a DEAE-cellulose column chromatography into 6 peaks, of which the peak I neutral RNase isozyme was specific to the epidermoid cancer of the lung.
High performance liquid chromatography (HPLC) and polyacryamide gel electrophoresis (PAGE) patterns for peak I protein from epidermoid carcinoma tissue of the lung appeared to be different from those of control lung tissue. The subpeak I5~8(in
HPLC
pattern) that was supposed to be associated with RNase was greatly increased in the lung cancer, indicating that peak I protein from epidermoid carcinoma tissue of the lung was specific to the lung cancer and that peak I RNase specific to the
cancer was
laced in HPLC subpeak 1-5~8.
The peak I neutral RNase was observed to be highly active toward poly C, poly AC and poly ACU and less active toward poly U and RNA, indicating that the peak I neutral RNase was the secretory type of RNase. No activity was found toward
polydeoxyribonucleotides and double stranded polyribonucleotides. Majority of products of poly C digest by the peak I neutral RNase was analyzed to be oligoribonucleotides, indication that the RNase was endonuclease in nature.
Observations that the peak I neutral RNase was specific to the epidermoid carcinoma of the lung and that the enzyme was endonuclease in nature suggested that the RNase might play an importnat role in process involved in the suppression of the
lung
cancer.
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