Topoisomerase I (TOP I) and II (TOP II) activities and their corresponding levels were analyzed in 27 primary brain tumors and 32 lung cancers (28 NSCLC, 4 SCLC). The TOP I and II activities in primary brain tumors varied from 500-2,000 units/mg and 100-3,000 units/mg respectively. Their corresponding levels varied from <0.01-3.30 (TOP I) and 0.24-8.30 (TOP II) arbitrary units. In lung cancer, the TOP I and II activities ranged from 1,000-4,000 and 500-4,000 units/mg respectively with their levels ranging from 0.30-61.60 and 0.2-14.2 arbitrary units respectively. These parameters were compared in both tumors using the Wilcoxon rank sums test, the difference were statically significance for all four parameters with a p<0.0001 for TOP I and II activities and TOP I levels and p<0.09 for TOP II levels. Using linear regression analysis, there was no correlation between TOP I and II activities and their corresponding levels in primary brain tumor. However, in lung cancer, the relationship between TOP I activities and levels were linear with r(2)=0.2 and p<0.0094, but not for TOP II activity and their levels. There was no relationship between TOP I and TOP II levels in the same tumor for both types of cancer. The future clinical implication of these findings are discussed.

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