Acid deoxyribonuclease(DNase) has been reported to be associated with carcinogenesis processes in human cancer tissues. In order to investigate a role of acid DNase in carcinogenesis of laryngeal tissue, the enzyme was isolated and purified from the laryngeal cancer tissue, and the substrate specificity and mode of action of the enzyme were studied. Also studied was inhibitory effect of polyribonucleotides on the acid DNase to understand the regulation of the enzyme in the cancer tissue.
Activity of acid DNase was markedly increased in the laryngeal cancer tissue, suggesting the use of the enzyme for a biochemical marker of the laryngeal cancer. The acid DNase both in laryngeal cancer and control tissues were isolated by a DEAE-cellulose column chromatography into a single peak, the activity of the enzyme being greater in the cancer tissue than in the control tissue. This indicates that the acid DNase in the cancer tissue is activated, but may not be different from that in the control tissue.
The acid DNase in the laryngeal cancer tissue was highly active toward double stranded(ds) DNA over single stranded(ss) DNA. A considerable activity toward as DNA(5% of that of ds DNA) was, however, observed, indicating that the enzyme in the cancer tissue does not exhibit absolute specificity toward ds DNA.
Analyses of the ds DNA digest by the action of the acid DNase from the laryngeal cancer tissue demonstrated that the majority of the products was ologodeoxyribonucleotides with nucleotide length of 5 to 25. This indicated that the acid DNase was an endonuclease in nature.
The acid DNase from the laryngeal tissue was inhibited by RNA and polyribonucleotides, the degree of inhibition being highest with poly G and the lowest with poly C of the polyribonucletotides studied.
The results obtained in the present study indicated that the acid DNase activity was markedly incresed in the laryngeal tissue, the enzyme was highly active toward ds DNA over ss DNA. The acid DNase was found to be endonuclease in nature and the enzyme was inhibited by RNA and polyribonucleotides, suggesting that the acid DNase in the laryngeal tissue might play a crucial role in the process involved in carcinogenesis of the laryngeal tissue and that the process could be regulated by polyribonucleotides and RNA.
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