Demeter A, Abonyi M, Look K Y, Keszler G, Staub M, Weber G
Laboratory for Experimental Oncology, Indiana University School of Medicine, Indianapolis, Indiana 46202-5200, USA.
Anticancer Res. 2001 Jan-Feb;21(1A):353-8.
Thymidine kinase 1 (TK 1 EC. 2.7.1.21) the most specific and cell-cycle regulated salvage enzyme for pyrimidine nucleoside supply of DNA synthesis is a promising target to rationally designed chemo- and other therapies. The present study was undertaken to compare the heat stability of TK isoenzymes of both normal ovarian and epithelial ovarian cancer cells. Tissue extracts of epithelial ovarian carcinomas (N = 7) and normal ovaries (N = 9) were analyzed for thymidine kinase activity using the polyethyleneimine-cellulose disc radioassay. The TK activity in extracts of ovarian carcinomas was 12-fold higher than in extracts of normal ovaries. The TK activity of ovarian carcinomas decreased significantly even after 30 minutes incubation at 37 degrees C while, the enzyme activity of normal ovarian extracts was more stable and decreased to the same extent after 120 minutes. The half-life time of the enzyme activity was 82 min in the normal but only 36 minutes in the cancer tissue extract at 37 degrees C.
The TK activity of malignant ovarian cells was much higher but more unstable (t1/2 = 36 minutes) than the enzyme isolated from healthy ovaries (t1/2 = 82 minutes). This profound difference in thermostability might provide the molecular background for hyperthermia combined with chemotherapy as a promising treatment for ovarian malignancies.
胸苷激酶1（TK 1，EC. 2.7.1.21）是DNA合成中嘧啶核苷供应最具特异性且受细胞周期调控的补救酶，是合理设计化疗及其他疗法的一个有前景的靶点。本研究旨在比较正常卵巢细胞和上皮性卵巢癌细胞中TK同工酶的热稳定性。使用聚乙烯亚胺-纤维素圆盘放射分析法分析了上皮性卵巢癌组织提取物（N = 7）和正常卵巢组织提取物（N = 9）的胸苷激酶活性。卵巢癌提取物中的TK活性比正常卵巢提取物中的高12倍。即使在37℃孵育30分钟后，卵巢癌提取物中的TK活性也显著降低，而正常卵巢提取物中的酶活性更稳定，在120分钟后才降低到相同程度。在37℃时，该酶活性在正常组织提取物中的半衰期为82分钟，而在癌组织提取物中仅为36分钟。
恶性卵巢细胞中的TK活性比从健康卵巢中分离出的酶高得多，但更不稳定（t1/2 = 36分钟），而健康卵巢中的酶半衰期为82分钟。这种热稳定性的显著差异可能为热疗联合化疗作为卵巢恶性肿瘤的一种有前景的治疗方法提供分子背景。
