Physiological function of thymidine phosphorylase and the involvement of the enzyme in tumor growth

胸苷磷酸化酶的生理功能及其在肿瘤生长中的参与

基本信息

批准号：
10470043
负责人：
AKIYAMA Shinichi
金额：
$ 8万
依托单位：
Kagoshima University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

Thymidine phosphorylase (TP) is an enzyme involved in the reversible conversion of thymidine to thymine and is identical to an angiogenic factor, platelet-derived endothelial cell growth factor (PD-ECGF), TP is expressed at higher levels in a wide variety of solid tumors than in the adjacent nonneoplastic tissues. KB/TP cells transfected with a PD-ECGF/TP cDNA were resistant to hypoxia-induced apoptosis. Among the degradation products of thymidine produced by PD-ECGF/TP, 2-deoxy-D-ribose partially prevented hypoxia-induced apoptosis, 2-Deoxy-L-ribose abrogated the effects of 2-deoxy-D-ribose. These findings suggested that TP can confer resistance to apoptosis induced by hypoxia and the degeadation products of thymidine are involved in this resistance.In hypoxic condition, the level of HIF-1 α is elevated and the expression levels of Bcl-2 and Bcl-XL are lowered. 2-Deoxy-D-ribose inhibited the response of the cells to hypoxia. Patients with TP-positive colon and esophageal tumors have a … More poorer prognosis than those with TP-negative tumors. We have recently synthesized a new TP inhibitor (TPI), 5-chloro-6-[1-(2-iminopyrrolidinyl)methyl] uracil hydrochloride. We investigated the effect of TPI on angiogenesis in KB cells transfected with PD-ECGF cDNA, KB/TP, and a mock transfecta, KB/CV, using the mouse dorsal air sac assay model. We found that KB/TP cells had a higher angiogeneic ability than KB/CV cells and that TPI completely suppressed angiogenesis by KB/TP. Furthermore, at a dose of 50 mg/kg/day, TPI considerably decreased the growth rate of KB/TP cells xenografted into nude mice. Microvessel density in KB/TP tumors was higher than that in KB/CV tumors, and TPI did not significantly change the density in either of the tumors. The apoptotic index in KB/TP tumors was significantly lower than that in KB/CV tumors, and TPI significantly increased the apoptotic index in KB/TP tumors but not in KB/CV tumors. TPI inhibited the high chemotactic motility and basement membrane invasion of KB/TP cells. In nude mice, oral administration of TPI suppressed macroscopic liver metastases of highly metastasizing KB/TP cells. These findings demonstrate that TP plays a key role in invasiveness and metastasis of TP-expressing solid tumors, and TPI might be a novel anti-metastatic agent for blood-borne metastasis. Less

胸苷磷酸化酶 (TP) 是胸苷可逆转化为胸腺嘧啶的酶，与血管生成因子、血小板源性内皮细胞生长因子 (PD-ECGF) 相同，TP 在多种固体中以较高水平表达转染 PD-ECGF/TP cDNA 的 KB/TP 细胞对缺氧诱导的细胞凋亡具有抵抗力。 PD-ECGF/TP 产生的胸苷、2-脱氧-D-核糖部分阻止了缺氧诱导的细胞凋亡，2-脱氧-L-核糖消除了 2-脱氧-D-核糖的作用。这些发现表明 TP 可以赋予耐药性。缺氧条件下，HIF-1α水平升高，胸腺嘧啶核苷脱失产物参与了这种抵抗。 Bcl-2 和 Bcl-XL 降低，抑制细胞对缺氧的反应。 TP 阳性结肠和食管肿瘤患者的预后比 TP 阴性肿瘤患者的预后更差。最近合成了一种新的TP抑制剂（TPI），5-氯-6-[1-(2-亚氨基吡咯烷基)甲基]尿嘧啶盐酸盐，我们研究了其作用。使用小鼠背气囊测定模型，TPI 对用 PD-ECGF cDNA、KB/TP 和模拟转染物 KB/CV 转染的 KB 细胞中血管生成的影响，我们发现 KB/TP 细胞具有比 KB/ 更高的血管生成能力。 CV细胞和TPI通过KB/TP完全抑制血管生成此外，在50mg/kg/天的剂量下，TPI显着降低KB/TP细胞的生长速率。裸鼠移植瘤中KB/TP的微血管密度高于KB/CV肿瘤，TPI没有显着改变两种肿瘤的密度，而KB/TP肿瘤的细胞凋亡指数明显低于KB/TP肿瘤。 KB/CV 肿瘤中，TPI 增加了 KB/TP 肿瘤中的凋亡指数，但在 KB/CV 肿瘤中，TPI 显着抑制了 KB/TP 细胞的高趋化运动和基底膜侵袭。在裸鼠中，口服 TPI 抑制了高度转移的 KB/TP 细胞的宏观肝转移。这些发现表明 TP 在表达 TP 的实体瘤的侵袭和转移中发挥着关键作用，TPI 可能是一种新型的抗转移剂。对于血源性转移较少。