Chromosomal imbalances associated with acquired resistance to fluoropyrimidines in human colorectal cancer cells

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.

Genome-wide screening of loci associated with drug resistance to 5-fluorouracil-based drugs

Resistance to chemotherapeutic agents represents the chief cause of mortality in cancer patients with advanced disease. Chromosomal aberration and altered gene expression are the main genetic mechanisms of tumor chemoresistance. In this study, we have established an algorithm to calculate DNA copy number using the Affymetrix 10K array, and performed a genome-wide correlation analysis between DNA copy number and antitumor activity against 5-fluorouracil (5-FU)-based drugs (S-1, tegafur + uracil [UFT], 5'-DFUR and capecitabine) to screen for loci influencing drug resistance using 27 human cancer xenografts. A correlation analysis confirmed that the single nucleotide polymorphism (SNP) showing significant associations with drug sensitivity were concentrated in some cytogenetic regions (18p, 17p13.2, 17p12, 11q14.1, 11q11 and 11p11.12), and we identified some genes that have been indicated their relations to drug sensitivity. Among these regions, 18p11.32 at the location of the thymidylate synthase gene (TYMS) was strongly associated with resistance to 5-FU-based drugs. A change in copy number of the TYMS gene was reflected in the TYMS expression level, and showed a significant negative correlation with sensitivity against 5-FU-based drugs. These results suggest that amplification of the TYMS gene is associated with innate resistance, supporting the possibility that TYMS copy number might be a predictive marker of drug sensitivity to fluoropyrimidines. Further study is necessary to clarify the functional roles of other genes coded in significant cytogenetic regions. These promising data suggest that a comprehensive DNA copy number analysis might aid in the quest for optimal markers of drug response.

Evaluations of biomarkers associated with 5-FU sensitivity for non-small-cell lung cancer patients postoperatively treated with UFT

The sensitivity to 5-fluorouracil (5-FU) has been reported to be associated with target molecule thymidylate synthase (TS), fluoropyrimidine-metabolising enzymes such as orotate phosphoribosyltransferase (OPRT), and dihydropyrimidine dehydrogenase (DPD). We performed an immunohistochemical study on the clinical significance of TS, OPRT, and DPD expression using 151 resected non-small-cell lung cancer (NSCLC) patients postoperatively treated with a combination of tegafur and uracil (UFT). Eighty-two carcinomas were TS-positive, 105 carcinomas were OPRT-positive, 68 carcinomas were DPD-positive. No correlation was observed in the HSCORE between the TS and OPRT expression (r=0.203), between the TS and DPD expression (r=0.098), or between the OPRT and DPD expression (r=0.074). Regarding the survival of NSCLC patients treated with UFT, the 5-year survival rate of patients with TS-negative tumours was significantly higher than that with TS-positive tumours (P=0.0133). The 5-year survival rate of patients with OPRT-positive stage II to III tumours was significantly higher than that with OPRT-negative stage II to III tumours (P=0.0145). In addition, the 5-year survival rate of patients with DPD-negative tumours was also significantly higher than that with DPD-positive tumours (P=0.0004). A Cox multivariate regression analysis revealed the TS status (hazard ratio 2.663; P=0.0003), OPRT status (hazard ratio 2.543; P=0.0005), and DPD status (hazard ratio 2.840; P<0.0001) to all be significant prognostic factors for the survival of resected NSCLC patients postoperatively treated with UFT.

Orotate phosphoribosyl transferase mRNA expression in oral squamous cell carcinoma and its relationship with the dihydropyrimidine dehydrogenase expression and the clinical effect of 5-fluorouracil

In this study, we investigated whether orotate phosphoribosyl transferase (OPRT) correlates with the clinicopathological features and effect of 5-fluorouracil (5-FU) in human oral carcinoma. We examined the expression of OPRT mRNA by in situ hybridization in surgical specimens of oral squamous cell carcinoma. The expression of OPRT mRNA in oral carcinoma was observed in all specimens and such expression was higher than that seen in normal control tissue specimens. There was no correlation between the expression of OPRT mRNA and clinical factors, but the expression of OPRT mRNA was significantly associated with histological differentiation. The expression of OPRT mRNA showed correlation with effect of 5-FU for oral carcinoma in either in vivo or in vitro. These results suggest that the OPRT expressions may therefore be a prognostic factor of 5-FU efficacy in patients with oral squamous cell carcinoma.

Chromosomal imbalances associated with drug resistance and thermoresistance in human pancreatic carcinoma cells

Resistance to therapeutic treatment is the major obstacle to advances in the successful management of pancreatic cancer. To characterize chromosomal alterations associated with different phenotypes of acquired multidrug resistance (MDR) and thermoresistance, comparative genomic hybridization (CGH) was applied to compare human pancreatic carcinoma-derived cells. This panel of cell lines consists of the parental, drug- and thermosensitive pancreatic carcinoma cell line EPP85 - 181P, its atypical MDR variant EPP85-181RNOV, the classical MDR subline EPP85-181RDB, and their thermoresistant counterparts EPP85-181P-TR, EPP85-181RNOV-TR, and EPP85 - 181RDB-TR, respectively. CGH using genomic DNA prepared from these cell lines as probes successfully identified genomic gains and/or losses in chromosomal regions encoding putative genes associated with drug resistance and/or thermoresistance. These genes included 23 members of the family of ABC transporters, 27 members of the family of cytochrome P450 (CYP) monooxygenases, various molecular chaperones, DNA repair enzymes, and factors involved in the regulation of cell cycle and apoptosis. The importance of these cell variant-specific genomic imbalances in the development of MDR and thermoresistance is discussed and remains to be elucidated.

Genomic changes identified by comparative genomic hybridisation in docetaxel-resistant breast cancer cell lines

Docetaxel is one of the most effective chemotherapeutic agents in the treatment of breast cancer. Breast cancers can have an inherent or acquired resistance to docetaxel but the causes of this resistance remain unclear. In this study high-level, docetaxel-resistant human breast cancer cell lines (MCF-7 and MDA-MB-231) were created, and comparative genomic hybridisation was used to identify genomic regions associated with resistance to docetaxel. MCF-7 resistant cells showed an amplification of chromosomes 7q21.11-q22.1, 17q23-q24.3, 18, and deletion of chromosomes 6p, 10q11.2-qter and 12p. MDA-MB-231 resistant cells showed a gain of chromosomes 5p, 7q11.1-q35, 9, and loss of chromosomes 4, 8q24.1-qter, 10, 11q23.1-qter, 12q15-q24.31, 14q and 18. Whole chromosome paints confirmed these findings. Amplification of 7q21 and loss of 10q may represent a common mechanism of acquired docetaxel resistance in breast cancer cells. This study is the first description of a genomic approach specifically to identify genomic regions involved in resistance to docetaxel.