DNA-TOPOISOMERASE-I ACTIVITY AND CONTENT IN EPITHELIAL OVARIAN-CANCER

Background. The levels and activity of topoisomerase I were determined in 35 biopsies from patients with ovarian cancer. Patients and method s: The activity was defined by the ability to relax supercoiled DNA pl asmid, and levels were determined by Western blotting and immunohistoc hemistry. Results. We detected topoisomerase I activity in all samples , although at different levels. Enzymatic activity was the same in fre sh and frozen tissues. Western blotting analysis detected topoisomeras e I in 29 of 35 tumor samples but in the remaining six the levels were below the detection limit. We analyzed the distribution of topoisomer ase I in tumor cells and normal infiltrating cells by immunohistochemi stry. The enzyme was mainly associated with tumor cells although there were four samples in which tumor cells were negative but ill which no rmal cells, mainly lymphocytes, yielded a positive result. Conclusions : The results indicate that topoisomerase I enzymatic activity is dete ctable in human ovarian tumors, varying among patients. No correlation s were found between the levels of the enzyme and its activity Because of the high heterogeneity observed, enzymatic activity assays should be combined with immunohistochemical evaluation of Topo I in the tumor and normal cells present in the tissue.