Activity of acid deoxyribonuclease (DNase) known to be involved in DNA integration and carcinogenesis was determined in seven human cancer tissues, hepatocellular carcinoma, lung epidermoid carcinoma, serous cystadenocarcinoma of ovary, cervical cancer of uterus, urological epithelial cancer, stomach cancer and osteosarcoma. The positive rate of the enzyme as a biochemical cancer marker was also determined. The acid DNases purified partially from uterine cervical cancer, lung epidermoid cancer and gastric cancer tissues were studied for substrate specificity and for mode of enzymatic action to find out a possible role of the enzyme in carcinogenesis process.
1. The activity of acid DNase, was greatly increased in seven human cancer tissues
studied and the positive rate of the enzyme activity as a biochemical marker for
the cancer was observed to be high in value.
2. Out of seven cancer tissues studied, the activity of neutral DNase was significantly increased in uterine cervical cancer, lung epidermoid cancer and gastric cancer tissues and the activity of alkaline DNase in uterine cervical cancer tissue.
3. The acid DNase purified patially from uterine cervical cancer tissue preferentially hydrolyzed double stranded DNA, but single stranded nucleic acids such as single stranded DNA, RNA and polyribonucleotides were highly resistant to the enzyme. The enzymes purified partially from lung epidermoid cancer and gastric cancer tissues hydrolyzed double stranded DNA more rapidly than did single stranded DNA, but did not exhibit absolute specificity toward double stranded DNA.
4. Product analyses of enzymatic hydrolysis of DNA by acid DNase revealed that the enzyme purified from uterine cervical cancer tissue cleaved DNA by endonucleolytic manner and that the enzyme purified from gastric cancer tissue by both endonucleolytic and exonucleolytic manners.
The assumption that acid DNase might play a role in transforming normal cells into cancer cells by integrating foreign DNA into host DNA or by modifying a part of host genome might be suggestive in the development of uterine cervical cancer, but not of gastric cancer.
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