Orotate phosphoribosyltransferase levels measured by a newly established enzyme-linked immunosorbent assay in gastric carcinoma

Role of pH in Regulating Cancer Pyrimidine Synthesis

Replication is a fundamental aspect of cancer, and replication is about reproducing all the elements and structures that form a cell. Among them are DNA, RNA, enzymes, and coenzymes. All the DNA is doubled during each S (synthesis) cell cycle phase. This means that six billion nucleic acids must be synthesized in each cycle. Tumor growth, proliferation, and mutations all depend on this synthesis. Cancer cells require a constant supply of nucleotides and other macromolecules. For this reason, they must stimulate de novo nucleotide synthesis to support nucleic acid provision. When deregulated, de novo nucleic acid synthesis is controlled by oncogenes and tumor suppressor genes that enable increased synthesis and cell proliferation. Furthermore, cell duplication must be achieved swiftly (in a few hours) and in the midst of a nutrient-depleted and hypoxic environment. This also means that the enzymes participating in nucleic acid synthesis must work efficiently. pH is a critical factor in enzymatic efficiency and speed. This review will show that the enzymatic machinery working in nucleic acid synthesis requires a pH on the alkaline side in most cases. This coincides with many other pro-tumoral factors, such as the glycolytic phenotype, benefiting from an increased intracellular pH. An increased intracellular pH is a perfect milieu for high de novo nucleic acid production through optimal enzymatic performance.

Orotate phosphoribosyltransferase as a predictor of benefit from S-1 adjuvant chemotherapy for cholangiocarcinoma patients

BACKGROUND AND AIM

To improve the prognosis of cholangiocarcinoma, we investigated potential biomarkers that may enable the selection of patients for whom postoperative adjuvant chemotherapy is likely effective.

METHODS

The cohort of this retrospective study included 170 surgically resected cholangiocarcinoma patients, 26 with gemcitabine adjuvant chemotherapy (GEM group), 36 with S-1 adjuvant chemotherapy (S-1 group), and 103 receiving no adjuvant chemotherapy (NC group). Propensity score matching was performed to adjust patient backgrounds; 36 patients from the NC group then were selected. Immunohistochemistry of orotate phosphoribosyltransferase (OPRT) and human equilibrative nucleoside transporter 1 (hENT1) was performed to determine the correlation between their expression and disease-free survival (DFS).

RESULTS

After matching, the backgrounds of these three groups were unbiased. No significant improvement of DFS by adjuvant chemotherapy was observed in the whole cohort. However, among the high-OPRT-expression patients, DFS of GEM, S-1, and NC groups at 5 years was 28.8%, 53.8%, and 25.5%, respectively. The DFS of the S-1 group was significantly longer than that of the NC group (P = 0.034). On the other hand, no significant differences in DFS were observed among the low OPRT expression patients. hENT1 expression was shown to have no predictive value. Multivariate analysis of the high-OPRT-expression patients demonstrated that S-1 adjuvant chemotherapy can reduce tumor recurrence (HR, 0.303; P = 0.013).

CONCLUSION

Cholangiocarcinoma patients with high OPRT expression would benefit from postoperative adjuvant S-1 therapy, which increases the DFS. Assessment of OPRT expression may contribute to the optimization of adjuvant chemotherapy for cholangiocarcinoma.

The relationship between the expression of thymidylate synthase, dihydropyrimidine dehydrogenase, orotate phosphoribosyltransferase, excision repair cross-complementation group 1 and class III β-tubulin, and the therapeutic effect of S-1 or carboplatin plus paclitaxel in non-small-cell lung cancer

Previous studies have reported that the expressions of specific proteins may predict the efficacy of chemotherapy agents for non-small cell lung cancer (NSCLC) patients. The present study evaluated the expression of proteins hypothesized to be associated with the effect of chemotherapeutic agents in 38 NSCLC patients with pathological stage II and IIIA. The subjects received carboplatin plus paclitaxel (CP) or S-1 as adjuvant chemotherapy following complete resection. The protein expressions evaluated were those of thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD) and orotate phsphoribosyltransferase (OPRT), which were suspected to be associated with the effect of S-1 agents, excision repair cross-complementation group 1 (ERCC1), which was suspected to be associated with the effect of platinum-based agents, and class III β-tubulin (TUBB3), which was suspected to be associated with the effect of taxane-based agents. The positive rate of TS was 55.3% (n=21/38), DPD was 57.9% (n=22/38), OPRT was 42.1% (n=16/38), ERCC1 was 47.4% (n=18/38) and TUBB3 was 44.7% (n=17/38). Among the patients who received S-1 adjuvant chemotherapy, TS-negative cases demonstrated a significantly better disease-free survival than positive cases. Thus, TS protein expression may have been a factor that predicted the effect of S-1 agent as adjuvant chemotherapy.

Orotate phosphoribosyl transferase mRNA expression and the response of cholangiocarcinoma to 5-fluorouracil

AIM: To determine whether expression of certain enzymes related to 5-fluorouracil (5-FU) metabolism predicts 5-FU chemosensitivity in cholangiocarcinoma (CCA).

METHODS: The histoculture drug response assay (HDRA) was performed using surgically resected CCA tissues. Tumor cell viability was determined morphologically with hematoxylin and eosin- and terminal deoxynucleotide transferase-mediated dUTP nick-end labeling-stained tissues. The mRNA expression of thymidine phosphorylase (TP), orotate phosphoribosyl transferase (OPRT), thymidylate synthase (TS), and dihydropyrimidine dehydrogenase (DPD) was determined with real-time reverse transcriptase-polymerase chain reaction. The levels of gene expression and the sensitivity to 5-FU were evaluated.

RESULTS: Twenty-three CCA tissues were obtained from patients who had been diagnosed with intrahepatic CCA and who underwent surgical resection at Srinagarind Hospital, Khon Kaen University from 2007 to 2009. HDRA was used to determine the response of these CCA tissues to 5-FU. Based on the dose-response curve, 200 μg/mL 5-FU was selected as the test concentration. The percentage of inhibition index at the median point was selected as the cut-off point to differentiate the responding and non-responding tumors to 5-FU. When the relationship between TP, OPRT, TS and DPD mRNA expression levels and the sensitivity of CCA tissues to 5-FU was examined, only OPRT mRNA expression was significantly correlated with the response to 5-FU. The mean expression level of OPRT was significantly higher in the responder group compared to the non-responder group (0.41 ± 0.25 vs 0.22 ± 0.12, P < 0.05).

CONCLUSION: OPRT mRNA expression may be a useful predictor of 5-FU chemosensitivity of CCA. Whether OPRT mRNA could be used to predict the success of 5-FU chemotherapy in CCA patients requires confirmation in patients.

5-Fluorouracil: mechanisms of resistance and reversal strategies

The purpose of this work is to review the published studies on the mechanisms of action and resistance of 5-fluorouracil. The review is divided into three main sections: mechanisms of anti-tumor action, studies of the resistance to the drug, and procedures for the identification of new genes involved in resistance with microarray techniques. The details of the induction and reversal of the drug resistance are also described.

Levels and expressions of orotate phosphoribosyltransferase in gastric carcinoma and normal gastric mucosa tissues

BACKGROUND

Orotate phosphoribosyltransferase (OPRT; EC 2.4.2.10), a key enzyme that catalyzes one of the primary steps in the phosphorylation of fluoropyrimidine, was recently recognized as an important enzyme that determines the anticancer effects of the dihydropyrimidine dehydrogenase-inhibitory fluoropyrimidine, S-1.

METHODS

Levels of OPRT were examined in 97 gastric carcinoma tissues and 65 normal gastric mucosa tissues obtained from patients with gastric carcinoma. The relation between OPRT levels and clinicopathological variables was evaluated, and correlations of OPRT with thymidylate synthase and dihydropyrimidine dehydrogenase levels in gastric carcinoma tissues were evaluated.

RESULTS

Although OPRT levels were high in well-differentiated and localized carcinomas, they were not correlated with other clinicopathological variables or with the pathological stage of gastric carcinoma. Levels of OPRT were significantly higher in gastric carcinoma tissue than in normal gastric mucosa. OPRT levels were not correlated with levels of either thymidylate synthase or dihydropyrimidine dehydrogenase. In samples of gastric carcinoma tissues and normal gastric mucosa tissues obtained simultaneously from 24 patients, no correlation was found between OPRT levels in gastric carcinoma and levels in normal gastric mucosa.

CONCLUSION

These results suggest that the OPRT level is significantly higher in gastric carcinoma tissue than in normal gastric mucosa and that the OPRT level in gastric carcinoma is a novel variable that is independent of the levels of other previously known enzymes related to 5-fluorouracil (FU) metabolism.

Quantitative double-fluorescence immunohistochemistry (qDFIHC), a novel technology to assess protein expression: a pilot study analyzing 5-FU sensitive markers thymidylate synthase, dihydropyrimidine dehydrogenase and orotate phosphoribosyl transferases in gastric cancer tissue specimens

To evaluate the protein expression level in formalin-fixed cancer tissue specimens, the authors devised quantitative double-fluorescence immunohistochemistry (qDFIHC). Using this method, the 17 gastric cancer biopsy specimens, before undergoing S-1 based neoadjuvant chemotherapy, were assessed in order to determine the expression levels of the thymidylate synthase (TS), orotate phosphoribosyltransferase (OPRT) and dihydropyrimidine dehydrogenase (DPD) which determines S-1 efficacy. The ratios of OPRT/TS, OPRT/DPD and OPRT/(DPD+TS) which have been proposed to show a good correlation with S-1 efficacy, were calculated and compared with the clinical response. A significant difference was thus observed in OPRT/TS (P=0.0049), OPRT/DPD (P=0.0067) and OPRT/(DPD+TS) (P=0.0013) between the responder and the non-responder groups. Therefore, the ratios assessed by qDFIHC may be a potentially effective predictor of the S-1 efficacy. Furthermore, qDFIHC may also be a useful method for assessing various protein levels in cancer tissues.

Expression of orotate phosphoribosyltransferase (OPRT) in hepatobiliary and pancreatic carcinoma

The purpose of this study was to clarify the role of orotate phosphoribosyltransferase (OPRT) in the progression of hepatobiliary and pancreatic carcinomas. Representative sections from 8 surgically resected pancreatic carcinomas, 5 gallbladder carcinomas and 19 hepatocellular carcinomas (HCCs) were examined microscopically. Sites of pancreatic intraepithelial neoplasia (PanIN) were counted, and histologic subtypes of invasive ductal carcinoma of the pancreas (IDC) were determined. Gallbladder carcinomas and HCCs were examined histologically, and the subtypes and spread patterns were assessed. Expression of OPRT was examined immunohistochemically. A total of 75 PanINs were identified. Expression of OPRT increased as lesions progressed from early to high-grade PanINs (PanIN-1A and -1B versus PanIN-2 and -3, p=0.0004). Three (37.5%) of the 8 pancreatic IDCs were positive for OPRT. In the remaining 5 cases, OPRT was expressed only in the neoplastic ducts adjacent to PanIN-3s. In gallbladder carcinomas, mucosal neoplastic epithelium showed dense cytoplasmic expression in 4 of the 5 cases, but expression was absent in the deeply invasive lesions. Among HCCs, 15 of the 19 cases were negative for OPRT in the central area of the tumor, but 8 of the 19 cases expressed OPRT in vascularly invasive lesions. Our data suggest that OPRT is involved in early events of pancreatic and gallbladder carcinogenesis and invasion of HCC.

Molecular markers for gastric adenocarcinoma: an update

Gastric cancer is the second most common cancer worldwide. Treatment of localized gastric cancer relies primarily on surgical intervention, although growing evidence suggests that the addition of chemoradiation may improve disease-free intervals and overall survival. In this regard, the current high rates of recurrence and subsequent poor survival have prompted an ever-increasing use of multimodal strategies, even for early-stage disease. However, these therapies are often limited by debilitating toxicities and varying degrees of response efficacy. As a result, pharmacogenomics, the study of specific genetic and molecular signatures that may be predictive of treatment outcomes, has gained considerable interest. For example, studies have demonstrated that the expression of enzymes involved in the metabolism or conjugation of commonly used chemotherapy agents, such as fluoropyrimidines and cisplatin, can serve as surrogate markers predictive of chemotherapy response. Polymorphisms in the genes encoding these enzymes have also been identified and may further account for altered expression patterns, resulting in varied clinical responses. Future work is necessary to further refine the list of molecular genetic markers and to identify novel markers for prognostic and predictive purposes. Technologies such as microarray analysis may be useful in identifying new molecular genetic markers, and further work may determine whether these markers can be employed to help stratify patients into different multimodal treatment regimens.