Partially purified samples of thymidine phosphorylase were obtained from four preparations of human uterine leiomyomas and uteri using the method of Yoshimura et al. (1990), Biochim. Biophys. Acta 1034, 107-113. Among the studied twelve pyrimidine derivatives, 5- bromouracil. 5-nitrouracil, 5-fluorouracil, 6-aminouracil, 4,6-dihydroxy-5-nitropyrimidine are competitive inhibitors, while allyloxymethylthymine is an uncompetitive inhibitor of thymidine phosphorylase activity. 6-benzyl-2-thiouracil inhibits the activity of the enzyme in a mixed way. The most potent inhibitor of the thymidine phosphorylase activity is 5-bromouracil and uracil the weakest one. Stronger inhibition of these compounds on the activity of thymidine phosphorylase was found in uterine leiomyomas than in uteri
The platelet-derived endothelial cell growth factor (PD-ECGF) is one of the potent angiogenic factors. Recently, its homology with thymidine phosphorylase (dThdPase), an enzyme involved in pyrimidine nucleoside metabolism, has been shown. In the present study, dThdPase activity was evaluated spectrophotometrically in 43 breast carcinomas and in 19 cases of non-neoplastic breast tissues. The mean dThdPase activity in breast cancer was almost six fold higher than in normal, non-neoplastic breast tissues (1.92 and 0.29 μmol thymine (T) x mg prot. -1 x h -1 respectively). The enzyme activity significantly correlated with axillary lymph node status (p = 0.0076) and with tumor size (p = 0.0099). Besides, the intratumoral microvessel density (MD) was evaluated using the CD 31 mouse anti-human monoclonal antibody, and there was no correlation between the level of enzymatic activity and a number of microvessels. The positive significant correlation of thymidine phosphorylase activity with prognostic factors in breast cancer patients with no relation to the number of microvessels needs further examination to confirm the prognostic significance of the level of dThdPase.
The activity of thymidine phosphorylase (dThdPase) in the myometrium and uterine myomas has been investigated in perimenopausal women. Differences in the activity of dThdPase have been found depending on the myoma type, menopause stage and the phase of the menstrual cycle in which the surgery was performed. The enzyme in the cytoplasmatic soluble fraction obtain ed at 50 000 x g was the most active in cellular leiomyomas of the follicular phase, the least in adenomyom as of the luteal phase of the menstrual cycle, whereas its activity in myometrium was always unchanged. Greater differences can be observed in the activity of dThdPase after a partial purification of the enzyme from myomas. It seems that the increase in dThdPase activity may point to its correlation with transient, premalignant tumor which may later transform into malignant forms.
Background: Thymidine phosphorylase (TP) is identical with platelet-derived endothelial cell growth factor (PD-ECGF) which promotes angiogenesis. The aim of this study was to evaluate the cytosol activity of TP in tumor samples from patients with endometrial cancer.
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