Thymidine phosphorylase expression in progression of cervical cancer: correlation with microvessel count, proliferating cell nuclear antigen, and apoptosis

Insights from the SNP analysis of TYMP gene linking MNGIE

TYMP gene, which codes for thymidine phosphorylase (TP) is also known as platelet-derived endothelial cell growth factor (PD-ECGF). TP plays crucial roles in nucleotide metabolism and angiogenesis. Mutations in the TYMP gene can lead to Mitochondrial Neurogastrointestinal Encephalopathy (MNGIE) syndrome, a rare genetic disorder. Our main objective was to evaluate the impact of detrimental non-synonymous single nucleotide polymorphisms (nsSNPs) on TP protein structure and predict harmful variants in untranslated regions (UTR). We employed a combination of predictive algorithms to identify nsSNPs with potential deleterious effects, followed by molecular modeling analysis to understand their effects on protein structure and function. Using 13 algorithms, we identified 119 potentially deleterious nsSNPs, with 82 located in highly conserved regions. Of these, 53 nsSNPs were functional and exposed, while 79 nsSNPs reduced TP protein stability. Further analysis of 18 nsSNPs through 3D protein structure analysis revealed alterations in amino acid interactions, indicating their potential impact on protein function. This will help in the development of faster and more efficient genetic tests for detecting TYMP gene mutations.

Thymidine phosphorylase: A potential new target for treating cardiovascular disease

We recently found that thymidine phosphorylase (TYMP), also known as platelet-derived endothelial cell growth factor, plays an important role in platelet activation in vitro and thrombosis in vivo by participating in multiple signaling pathways. Platelets are a major source of TYMP. Since platelet-mediated clot formation is a key event in several fatal diseases, such as myocardial infarction, stroke and pulmonary embolism, understanding TYMP in depth may lead to uncovering novel mechanisms in the development of cardiovascular diseases. Targeting TYMP may become a novel therapeutic for cardiovascular disorders. In this review article, we summarize the discovery of TYMP and the potential molecular mechanisms of TYMP involved in the development of various diseases, especially cardiovascular diseases. We also offer insights regarding future studies exploring the role of TYMP in the development of cardiovascular disease as well as in therapy.

The dual role of thymidine phosphorylase in cancer development and chemotherapy

Thymidine phosphorylase (TP), also known as "platelet-derived endothelial cell growth factor" (PD-ECGF), is an enzyme, which is upregulated in a wide variety of solid tumors including breast and colorectal cancers. TP promotes tumor growth and metastasis by preventing apoptosis and inducing angiogenesis. Elevated levels of TP are associated with tumor aggressiveness and poor prognosis. Therefore, TP inhibitors are synthesized in an attempt to prevent tumor angiogenesis and metastasis. TP is also indispensable for the activation of the extensively used 5-fluorouracil prodrug capecitabine, which is clinically used for the treatment of colon and breast cancer. Clinical trials that combine capecitabine with TP-inducing therapies (such as taxanes or radiotherapy) suggest that increasing TP expression is an adequate strategy to enhance the antitumoral efficacy of capecitabine. Thus, TP plays a dual role in cancer development and therapy: on the one hand, TP inhibitors can abrogate the tumorigenic and metastatic properties of TP; on the other, TP activity is necessary for the activation of several chemotherapeutic drugs. This duality illustrates the complexity of the role of TP in tumor progression and in the clinical response to fluoropyrimidine-based chemotherapy.

Enzymatic activities of uridine and thymidine phosphorylase in normal and cancerous uterine cervical tissues

In this study, the preliminary analyses were conducted of enzymatic activities of uridine phosphorylase (UP) and thymidine phosphorylase (TP) in normal tissues and cancer tissues of the uterine cervix. The study was performed on 27 patients of cervical cancer, treated first in our hospital. Normal cervical tissues obtained from 15 patients undergoing hysterectomy for benign diseases were used as controls. The supernatant of the homogenated cervical tissues and the stroma (5-FU and ribose-1-P or deoxyribose-1-P) were analyzed by high performance liquid chromatography, and then the UP and TP activities calculated. TP activity was significantly greater than UP activity (P < 0.0001). Both UP and TP showed significantly greater activity in cancer tissues than in normal tissues (P < 0.0001). In the TP activity of the cancer tissues, there was no significant difference among the histological types, while the TP activity tended to be significantly higher in the cases with lymph node metastasis. These results showed that the TP-mediated route seemed important as the 5FU metabolic pathway in the uterine cervical tissues, and TP enzymatic activity might be associated with lymph node metastasis.

Expression of thymidine phosphorylase as an effect prediction factor for uterine cervical squamous cell carcinoma after radiotherapy: an immunohistochemical study

Prognoses in cases of uterine cervical squamous cell carcinoma treated with radiotherapy were investigated in association with immunohistochemical expression of an angiogenic factor, thymidine phosphorylase (TP). Forty-six cases of uterine cervical squamous cell carcinoma mainly treated with radiotherapy during 1992-2001 at our clinic were studied. All were diagnosed as stages IIB to IVA. Paraffin-embedded biopsy specimens excised before radiotherapy were stained immunohistochemically using anti-TP monoclonal antibody. The extent of staining in both tumor and interstitial cells was graded as (-), (+/-), (+), and (2+). Specimens with TP expression levels of (2+) and (+) were regarded as positively stained and those with TP expression levels of (+/-) and (-) as negatively stained. The efficacy of radiotherapy in both groups was analyzed by the Kaplan-Meier method. With tumor cells, 5-year survival rates for the positive (n= 38) and negative (n= 8) staining groups were 73.9% and 42.9%, respectively; the rate being significantly higher for the TP-positive group (log rank, P= 0.0096). Contrarily, with staining for interstitial cells, the 5-year survival rates for the positive (n= 20) and negative (n= 26) staining groups were 74.1% and 64.6%, respectively, with no significant difference (log rank, P= 0.406). The efficacy of radiotherapy in the group with positive staining of tumor cells was significantly better than in the negative staining group. Immunohistochemical expression of TP in tumor cells is suggested as a useful prognostic factor for uterine cervical squamous cell carcinomas treated with radiotherapy. Choosing therapy for individual cases by referring to factors including TP expression should contribute to an improved prognosis.

Identification of the angiogenic endothelial-cell growth factor-1/thymidine phosphorylase as a potential target for immunotherapy of cancer

Characterization of the antigens recognized by tumor-reactive T cells isolated from patients successfully treated with allogeneic HLA-matched hematopoietic stem cell transplantation (SCT) can lead to the identification of clinically relevant target molecules. We isolated tumor-reactive cytotoxic CD8(+) T-cell (CTL) clones from a patient successfully treated with donor lymphocyte infusion for relapsed multiple myeloma after allogeneic HLA-matched SCT. Using cDNA expression cloning, the target molecule of an HLA-B7-restricted CTL clone was identified. The CTL clone recognized a minor histocompatibility antigen produced by a single nucleotide polymorphism (SNP) in the angiogenic endothelial-cell growth factor-1 (ECGF1) gene also known as thymidine phosphorylase. The SNP leads to an Arg-to-His substitution in an alternatively translated peptide that is recognized by the CTL. The ECGF1 gene is predominantly expressed in hematopoietic cells, although low expression can also be detected in other tissues. The patient from whom this CTL clone was isolated had mild graft-versus-host disease despite high numbers of circulating ECGF-1-specific T cells as detected by tetramer staining. Because solid tumors expressing ECGF-1 could also be lysed by the CTL, ECGF-1 is an interesting target for immunotherapy of both hematologic and solid tumors.

Dihydropyrimidine dehydrogenase in normal and malignant endometrium: relationship with cell proliferation and thymidine phosphorylase

Dihydropyrimidine dehydrogenase (DPD) is a pyrimidine salvage enzyme responsible for degradation of thymine, which is produced from thymidine by thymidine phosphorylase (TP). Our purpose was to determine the relationship between DPD, cell proliferation and TP expression in human endometrium. We examined DPD gene expression using reverse transcription-polymerase chain reaction, DPD protein levels using enzyme-linked immunosorbent assay, and DPD protein localization using immunohistochemistry in 58 normal endometria and 28 endometrial cancers. DPD gene expression was then related to the proliferating cell nuclear antigen index and to TP gene expression. DPD gene expression, which was correlated with DPD protein level, was relatively stable throughout various menstrual phases but was significantly elevated in postmenopausal status. It was significantly lower in endometrial cancer than in normal endometrium. Localization analysis revealed that DPD protein was located primarily in epithelial cells, but was also present in stromal cells. DPD gene expression correlated inversely with the PCNA index. TP gene expression pattern contrasted with that of DPD in postmenopausal and malignant endometrium. A high ratio of TP to DPD gene expression was significantly more frequent in endometrial cancer than in normal endometrium in any menstrual phase. DPD may act cooperatively with TP to affect cell function by maintaining the pyrimidine nucleotide pool balance in normal and malignant endometrium.

Correlation between apoptotic index and angiogenesis in non-small cell lung cancer: comparison between CD105 and CD34 as a marker of angiogenesis

Only a few clinical studies have documented a significant correlation between intratumoral microvessel density (IMVD), a measurement of angiogenesis, and apoptotic index (AI), an incidence of apoptosis, although many experimental studies have confirmed that insufficient angiogenesis induces accelerated apoptotic cell death. In the present study, therefore, to assess AI in correlation with IMVD in resected non-small cell lung cancer, a total of 236 patients with pathologic stage I to IIIa were reviewed. IMVDs were determined immunohistochemically with an antibody against a pan-endothelial marker, CD34 (CD34-IMVD), and an antibody against a proliferation-related endothelial marker, CD105 (CD105-IMVD). AI was defined as the number of tumor cells positive for the terminal deoxynucleotidyl tranferase-mediated dUTP-biotin nick end-labeling staining per 1000 tumor cells. When CD34 was used as a marker of angiogenesis, the mean AIs for the lower-IMVD and the higher-IMVD patients were 20.1 and 17.5, respectively, demonstrating no significant difference between the lower- and the higher-IMVD patients. In contrast, when CD105 was used, the mean AI for the lower-IMVD patients was significantly higher than that for the higher-IMVD patients (22.0 and 15.6, respectively; P=0.019). There was no significant correlation between proliferative activity and CD34-IMVD or CD105-IMVD. These results demonstrated that that decreased angiogenesis may induce enhanced apoptotic tumor-cell death without affecting cell proliferation.

Thymidine phosphorylase expression in oral squamous cell carcinoma

Thymidine phosphorylase (TP), as an enzyme involved in DNA synthesis, catalyzes the reversible conversion of thymidine to thymine. It is also identical to the angiogenic factor, platelet-derived endothelial cell growth factor. We examined TP expression using immunohistochemistry in 66 archival samples obtained from the patients with primary oral squamous cell carcinoma (SCC) and investigated its relation to tumor vascularity, cell proliferation, apoptosis, clinicopathological features and survival. TP expression was identified in cytonucleus and/or cytoplasm in carcinomas, but was not identified in histologically normal epithelia distant to tumor in most cases. No significant difference of microvessel density (MVD) was found between the carcinomas with high TP expression (H-TP) and low TP expression (L-TP). The percentages of proliferative cells marked by Ki-67 staining in H-TP carcinomas was significantly higher than that in L-TP carcinomas (P=0.0222). The apoptotic indice (AI) in H-TP carcinomas tended to be lower than that in L-TP carcinomas (P=0.0723). Moreover, the level of TP expression was significantly correlated the pattern of tumor invasion (P=0.0146) and marginally correlated with lymph nodal metastasis (P=0.0804). Our results suggested that TP enzyme may play a role in promotion of tumor growth in oral SCC, and that its expression can be indicative of tumor aggressiveness in this tumor type.

Gene expression for dihydropyrimidine dehydrogenase and thymidine phosphorylase influences outcome in epithelial ovarian cancer

PURPOSE

Dihydropyrimidine dehydrogenase (DPD) is a pyrimidine salvage enzyme responsible for degradation of thymine, which is produced from thymidine by thymidine phosphorylase (TP). Our purpose was to determine whether DPD affects prognosis in patients with epithelial ovarian cancer and how the two enzymes may interact in such effects.

PATIENTS AND METHODS

DPD gene expression was analyzed by reverse transcription-polymerase chain reaction in 27 samples from normal ovaries and the 85 epithelial ovarian cancers previously studied with regard to TP gene expression.

RESULTS

DPD gene expression was significantly lower in epithelial ovarian cancers than in normal ovaries (P: <.0001), whereas TP gene expression and the ratio of TP to DPD gene expression (TP:DPD) were significantly higher in epithelial ovarian cancer (P: <.0001 for both). In patients with epithelial ovarian cancer, DPD gene expression and the TP:DPD ratio did not significantly correlate with any clinicopathologic factors. Patients with a high TP:DPD ratio (higher than the median) had significantly poorer outcomes than those with lower ratios (P: =.0002). The difference in survival between groups with high and low TP:DPD ratios was greater than the difference between groups with high and low TP gene expression. Multivariate analysis showed the TP:DPD ratio to be the independent prognostic factor (P: =.0002). In tumors with high TP gene expression, low DPD gene expression significantly correlated with poor survival (P: =. 04).

CONCLUSION

Downregulation of DPD gene expression may enhance the negative prognostic effect of high TP gene expression in patients with epithelial ovarian cancer. Certain newly available chemotherapeutic choices may take the TP:DPD ratio into consideration.