van der Zee A G, de Jong S, Keith W N, Hollema H, Boonstra H, de Vries E G
Department of Gynecology, University Hospital, Groningen, The Netherlands.
Cancer Res. 1994 Feb 1;54(3):749-55.
Quantitative and qualitative aspects of topoisomerase (Topo) I and II were studied in 17 malignant ovarian tumors [eight untreated and nine after platinum/cyclophosphamide (Pt/Cy) chemotherapy]. Median Topo II catalytic activity was lower (P < 0.05) in tumors after Pt/Cy chemotherapy in comparison to untreated tumors, while no differences were found for Topo I catalytic activity in tumors before and after chemotherapy, as was also found in a previous study (Van der Zee et al. Cancer Res., 51: 5915-5920, 1991). Teniposide (VM-26)-induced cleavable complex formation correlated (r = 0.60; P < 0.05) with Topo II activity, while Topo II decatenation activity was equally but incompletely inhibited by VM-26 in all tumors. No differences were found in Topo II cleavage site patterns in plasmid BR322 DNA for all tumors using an indirect end-labeling procedure. Cleavable complex formation of Topo I by camptothecin (Cpt) did not correlate with Topo I catalytic activity, while Topo I catalytic activity could equally and completely be inhibited by Cpt. By Western blotting, Topo II alpha protein expression was detected in four of eight untreated tumors and three of nine tumors after Pt/Cy chemotherapy, whereas in all tumors a M(r) 150,000 degradation product of Topo II beta was detected. Topo I protein was detected in all tumors at varying levels, but the protein levels did not correlate with Topo I catalytic activity or cleavable complex formation by Cpt. Our study shows that Topo I and II, isolated from human malignant tumors, can be stimulated by Cpt and VM-26, respectively, to induce DNA cleavage, which suggests that topoisomerases are real targets for chemotherapy in patients with ovarian cancer. From in vitro data from the literature it appears that the cleavable complex assay reflects both quantitative and qualitative changes as well as changes in the phosphorylation state of Topo I and II. In combination with the feasibility of the cleavable complex assay for Topo I and II in human malignant tumors, which was found in the present study, it appears that at present the determination of cleavable complex formation by tumors seems to be the most promising parameter of Topo I or II expression in human tumors to be related to response to Topo I- or II-targeted chemotherapy.
对17例恶性卵巢肿瘤[8例未经治疗，9例接受铂/环磷酰胺（Pt/Cy）化疗后]的拓扑异构酶（Topo）I和II的定量及定性方面进行了研究。与未经治疗的肿瘤相比，Pt/Cy化疗后的肿瘤中Topo II催化活性中位数较低（P<0.05），而化疗前后肿瘤中Topo I催化活性未发现差异，这与先前的一项研究（Van der Zee等人，《癌症研究》，51:5915 - 5920，1991）结果一致。替尼泊苷（VM - 26）诱导的可切割复合物形成与Topo II活性相关（r = 0.60；P<0.05），而在所有肿瘤中，VM - 26对Topo II解连环活性的抑制程度相同但不完全。使用间接末端标记法，在所有肿瘤的质粒BR322 DNA中，Topo II切割位点模式未发现差异。喜树碱（Cpt）诱导的Topo I可切割复合物形成与Topo I催化活性不相关，而Cpt可同等且完全抑制Topo I催化活性。通过蛋白质印迹法，在8例未经治疗的肿瘤中有4例以及9例Pt/Cy化疗后的肿瘤中有3例检测到Topo IIα蛋白表达，而在所有肿瘤中均检测到Topo IIβ的分子量为150,000的降解产物。所有肿瘤中均检测到不同水平的Topo I蛋白，但蛋白水平与Topo I催化活性或Cpt诱导的可切割复合物形成不相关。我们的研究表明，从人类恶性肿瘤中分离出的Topo I和II可分别被Cpt和VM - 26刺激以诱导DNA切割，这表明拓扑异构酶是卵巢癌患者化疗的真正靶点。从文献中的体外数据来看，可切割复合物测定反映了Topo I和II的定量及定性变化以及磷酸化状态的变化。结合本研究中发现的在人类恶性肿瘤中对Topo I和II进行可切割复合物测定的可行性，目前肿瘤中可切割复合物形成的测定似乎是与Topo I或II靶向化疗反应相关的人类肿瘤中Topo I或II表达的最有前景的参数。
