Comparison of histologic subtype and growth pattern in intraductal papillary-mucinous carcinoma of the pancreas.

The purpose of this study was to compare histologic subtype and growth pattern, including invasion and intraductal spread to branch ducts, in main duct-type intraductal papillary-mucinous carcinoma (IPMC) by histopathology and immunohistochemistry. Five surgically resected samples of main duct-type IPMC from five patients, were studied. Main lesions, invasive components, and adjacent secondary ducts were examined microscopically. We performed immunohistochemistry with monoclonal mucin 2 (MUC2) and polyclonal orotate phosphoribosyltransferase (OPRT) antibodies. Three cases showed adenoma components in the main duct. Two of these showed intestinal-type accompanied by intraductal spread to branch ducts, neoplastic changes in branch ducts consisting of high-grade pancreatic intraepithelial neoplasia-like ducts positive for MUC2, and ducts filled with arborizing neoplastic cells, resembling pancreatobiliary type. The other case showed gastric-type adenoma and intestinal-type carcinoma in situ (CIS) in the main duct, with minimal tubular invasion. The two remaining cases showed no adenoma components in the main duct, but showed abrupt transition from normal epithelium to CIS (pancreatobiliary type or oncocytic type) and massive invasion diffusely positive for OPRT. These results suggest that IPMC with adenoma components in the main duct undergoes intraductal spread to branch ducts and has low malignant potential. The progression of one subtype to another is associated with intraductal spread of intraductal papillary-mucinous neoplasm (IPMN). However, IPMC without adenoma components is associated with marked invasion.

Clinical role of orotate phosphoribosyl transferase and dihydropyrimidine dehydrogenase in colorectal cancer treated with postoperative fluoropyrimidine.

BACKGROUND: Orotate phosphoribosyl transferase (OPRT) is an essential enzyme for activation of 5-fluorouracil (5-FU) and its derivatives. Dihydropyrimidine dehydrogenase (DPD) is a rate-limiting enzyme for degradation of 5-FU. In colorectal cancer (CRC), few studies have evaluated the relationship between OPRT, DPD, and clinicopathologic features. METHODS: The study included 150 patients whose CRCs were classified into stage II to IV, and resected operatively. OPRT and DPD expression were evaluated using immunohistochemistry with new antibodies. Relationships between their expressions and clinicopathologic features. Survival curves were calculated using Kaplan-Meier method, and differences were evaluated with log-rank test. Cox proportional hazards model was also used. RESULTS: OPRT expression showed a negative correlation with advances in venous invasion (P=.041), though DPD expression showed positive correlations with advances in venous invasion (P=.0053), and cancer stage (P=.0064). The patients survival rates were higher in those OPRT(+) than in those OPRT(-) (P=.004), and higher in those DPD(-) than in those DPD(+) (P=.008). The estimated hazard ratio for patients death with OPRT and DPD expression were 2.43 and 6.55 (P=.0047 and .0096) respectively. CONCLUSIONS: OPRT expression was associated negatively with CRC progression and related with better prognosis, although DPD expression was positively correlated with CRC progression and related with poor prognosis. The overall patients survival rates were best in the patients OPRT(+)DPD(-), and worst in those OPRT(-)DPD(+) in treatment with fluoropyrimidine after operation.

Preparation of anti-orotate phosphoribosyltransferase antibody and its application to immunochemical detection in human tumor cells.

Orotate phosphoribosyltransferase (OPRT) is a key enzyme in the anabolism of 5-fluorouracil (5-FU), and its expression in tumors is thought to increase the efficacy of 5-FU against the tumor. To detect the OPRT protein by immunoblot and/or immunohistochemical methods, we prepared highly specific antibody to the peptides contained in the human OPRT amino acid sequence. The anti-OPRT polyclonal antibodies, obtained by immunizing rabbits with the OPRT peptides, had a high specificity for the OPRT protein in human tumor xenografts when it was analyzed by immunoblotting, and furthermore, there was a positive correlation between OPRT activity and protein content in 12 human tumors (R2 = 0.632). These results suggest that immunohistochemical detection of tumoral OPRT protein expression with our anti-OPRT antibodies may provide a useful method for predicting the clinical response to 5-FU-based chemotherapy.

[Preparation of anti-OPRT antibody for immunochemical detection].

Orotate phosphoribosyl transferase (OPRT, EC 2.4.2.10) is a key enzyme in the anabolism of 5-fluorouracil (5 FU), and its expression in tumor is thought to increase the efficacy of 5-FU against the tumor. To detect the OPRT protein by immunoblotting and/or immunohistochemical methods, we tried to prepare highly specific antibody against the peptide including human OPRT amino acid sequence. The anti-OPRT polyclonal antibody obtained by immunization of OPRT peptides to rabbits had high specificity for the OPRT protein in human tumor xenografts in immunoblot and immunohistochemical analysis. Furthermore, there was a positive correlation between the activity and proteins of OPRT (R2=0.632) in 12 human tumors. These results suggest that immunohistochemical detection of tumoral OPRT protein expression using our anti-OPRT antibody may provide useful methods to predict the clinical response to 5-FU-based chemotherapy.

Potential for ambiguity in the interpretation of immunochemical studies on multienzymic proteins. The case of uridylate synthase.

Rabbit antibodies directed against homogeneous uridylate synthase multienzyme from mouse Ehrlich ascites carcinoma precipitate both the orotidine-5'-monophosphate decarboxylase (EC 4.1.1.23) and orotate phosphoribosyltransferase (EC 2.4.2.10) activities of mouse and human erythrocyte uridylate synthase. When the partially purified human enzyme is used as antigen the two activities coprecipitate with the same apparent titer; however, when the mouse carcinoma protein was studied under the same conditions the decarboxylase activity immunoprecipitated with significantly higher avidity than did the transferase activity. Since the mouse multienzyme has been shown to be a single polypeptide that contains both activities (McClard, R.W., Black, M.J., Livingstone, L.R. and Jones, M.E. (1980) Biochemistry 19, 4699-4706), these results were, at face value, surprising. However, when the mouse orotate phosphoribosyltransferase activity (which is largely lost upon dilution into the immunoassay medium) was stabilized with 5-phosphoribosyl 1-pyrophosphate, both enzyme activities displayed the same apparent antibody titer. The immunochemical studies indicate that the antibodies, as a population, preferentially bind to a form or forms of the enzyme which contain(s) denatured transferase domains. A calculation based on a simple model yields a value of approximately 100 for the relative selectivity of the antibody for the denatured form of uridylate synthase. These results illustrate an ambiguity that is inherent in the interpretation of immunochemical studies on such multienzymic proteins; that is, it is possible to conclude incorrectly that two enzyme activities are not functionally associated if one of the catalytic domains is particularly unstable and thereby displays greater immunoreactivity for the specific antiserum.