Thymidylate synthetase (TS) genotype and TS/dihydropyrimidine dehydrogenase mRNA level as an indicator in determining chemosensitivity to 5-fluorouracil in advanced gastric carcinoma

BACKGROUND: One of the target enzymes of 5-fluorouracil (5-FU) is thymidylate synthetase (TS). The DNA sequence of the TS gene includes either double or triple tandem 28-bp repeats within the promoter region, such that TS genotypes can be classified as homozygous 3R/3R heterozygous 2R/3R or homozygous 2R/2R Several recent studies have shown that TS genotype affects mRNA expression, with 3R/3R homozygotes showing higher TS mRNA expression compared to the other genotypes. PURPOSE: We analyzed the TS genotype and TS and dihydropyrimidine dehydrogenase (DPD) mRNA expression levels in 22 advanced gastric carcinoma patients, and analyzed results with respect to patient 5-FU chemosensitivity, as detected by the tetrazolium-based colorimetric (MTT) assay and survival outcome. PATIENTS AND METHODS: Between September 2001 and April 2002, 22 Japanese patients with advanced gastric carcinoma were evaluated. Informed written consent was obtained from all patients and the study was approved by the ethical committee at our University Hospital Fresh surgical specimens from carcinoma lesions were enzymatically dissociated and incubated with 5-FU at a concentration of 50 microg/ml for 48 hours to determine the inhibition rate as detected by MTT assay. Normal and tumor tissue and peripheral blood samples were collected and stored at -80 degrees C until assay for TS genotype and TS and DPD mRNA level The TS genotype was assessed by PCR assay using peripheral monocytes, since monocyte genotypes represent the genotype of normal and tumor tissues. Quantification of TS and DPD mRNA levels was performed using real-time PCRP Survival outcome was assessed according to the disease-free survival period in cases with similar clinical backgrounds. RESULTS: TS genotyping revealed 19 3R/3R homozygotes and 3 2R/3R heterozygotes. After analysis of normal and tumor tissues, samples from homozygote 3R/3R cases showed higher TS mRNA expression than heterozygote 2R/3R cases, which was statistically significant at p<0.05. We also observed a statistically significant correlation in TS mRNA levels between normal and tumor tissues, while no significant correlation was observed for DPD mRNA levels between normal and tumor tissues. While no relationship between 5-FU chemosensitivity and TS genotype or mRNA expression was observed, cases with high DPD mRNA expression were resistant to 5-FU and exhibited poor survival outcomes. CONCLUSION: While TS genotype affected TS mRNA expression in both normal and tumor tissues in advanced gastric cancer, there is no relationship between TS genotype or mRNA expression level and 5-FU chemosensitivity. CONCLUSION: Our finding, that DPD mRNA expression appears to be a factor in determining 5-FU chemosensitivity and the survival outcome of advanced gastric cancer patients, is comparable with previous reports.     

Gene expression in colorectal cancer and in vitro chemosensitivity to 5-fluorouracil: a study of 88 surgical specimens

To predict the sensitivity of colorectal cancer to 5-fluorouracil (5-FU), we compared the gene expression of surgically obtained colorectal cancer specimens with chemosensitivity to 5-FU as detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H tetrazolium bromide (MTT) assay. Eighty-eight patients with advanced and/or metastatic colorectal cancer provided written informed consent and entered the trial from September 2000 to October 2001. Fresh surgical specimens were used for the MTT assay, and sensitivity to 5-FU was evaluated at a cutoff concentration of 50 μg/ml and 48-h incubation time. Frozen samples were stored at −80°C until mRNA analysis of thymidylate synthetase (TS), dihydropyri-midine dehydrogenase (DPD), thymidine phosphorylase (TP), es-nucleoside transporter (NT), and E2F1 by real-time RT-PCR. The correlations between the variables were analyzed, and the predictive value of these mRNAs was assessed statistically using a receiver operating characteristic (ROC) curve. NT and DPD, TP and DPD, and TP and NT mRNA expression levels correlated significantly, while TS and E2F1 showed no correlations. High NT expression was associated with low sensitivity to 5-FU (P<0.013), as were high DPD and E2F1 expression ( P <0.022 for both). High TP mRNA expression correlated with low sensitivity to 5-FU ( P <0.034), although high TS mRNA expression did not. ROC curves indicated that DPD and NT mRNAs were possible predictors of sensitivity to 5-FU, with cutoff values of 0.6 and 0.4, respectively. The sensitivity of colorectal cancer to 5-FU may be regulated by DPD, the rate-limiting enzyme of catabolism, and NT, an important transmembrane transporter of nucleosides.     

Dihydropyrimidine dehydrogenase activity and mRNA expression in advanced gastric cancer analyzed in relation to effectiveness of preoperative 5-fluorouracil-based chemotherapy

Dihydroxypyrimidine dehydrogenase (DPD) is an enzyme involved in degradation and inactivation of 5-fluorouracil (5-FU). The amount of its expression in a tumor is thought to be a factor determining the response of the tumor to 5-FU therapy. We compared DPD activity and DPD mRNA expression in resected tumors between two groups of patients, i.e., a group of 14 patients with advanced gastric cancer who received preoperative chemotherapy (neoadjuvant chemotherapy; NAC) and surgery and a group of 24 patients with advanced gastric cancer who underwent surgery without preoperative chemotherapy. Tumor DPD activity was found to correlate well with tumor DPD mRNA expression. In the surgery alone group, DPD activity decreased significantly as the tumor stage advanced. This change was not observed in the NAC plus surgery group. Neither tumor depth (T factor) nor lymph node metastasis was found to correlate with DPD activity. Patients who responded to preoperative chemotherapy had lower DPD mRNA levels. Based on these results, we anticipate that measurement of DPD expression in clinical specimens may be clinically useful in managing advanced gastric cancer.     

A retrospective study on TS mRNA expression and prediction of the effects of adjuvant oral 5-fluorouracil in breast cancer

Nucleic acid-metabolizing enzymes, such as thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD), thymidine phosphorylase (TP) and orotate phosphoribosyl transferase (OPRT), have attracted attention as candidates for response determinants of 5-fluorouracil (5-FU). Whether the expression levels of these enzymes can be adopted as valuable parameters for 5-FU sensitivity in breast cancer has yet to be elucidated. In the present study, intratumoral mRNA expression of TS, DPD, TP and OPRT were determined in formalin-fixed paraffin-embedded surgical specimens collected from 217 breast cancer patients, using the Danenberg Tumor Profile method, which combines microdissection and real-time-polymerase chain reaction. The significance of these enzymes as prognostic and 5-FU efficacy-predicting factors was evaluated. Our data showed that a low DPD expression is related to a high nuclear grade and other factors including hormone receptor-negativity. Low expression levels of TP were found in hormone receptor-negative tumors. TS and OPRT expression were not related to various clinicopathological factors, but patients with a high TS mRNA expression showed a significantly poorer prognosis in cases where 5-FU was not administered. The efficacy of 5-FU was more significant when administered for more than 6 months in the group with a high TS mRNA expression. These data suggest that TS mRNA expression in breast cancer tissue is an ideal predictor of outcomes for patients with no administration of 5-FU, and of the efficacy of 5-FU.     

Thymidylate synthase and dihydropyrimidine dehydrogenase are related to histological effects of 5-fluorouracil and cisplatin neoadjuvant chemotherapy for primary gastric cancer patients

Thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD), and vascular endothelial growth factor (VEGF) are associated with the effect of 5-fluorouracil (5-FU) based adjuvant chemotherapy. However, very few studies have investigated the relationship between these factors and 5-FU neoadjuvant chemotherapy for primary gastric cancer patients. In this study, we studied the correlation between these markers and the histological chemotherapeutic effect in advanced gastric cancer with neoadjuvant chemotherapy. METHODS: Sixty-two primary advanced gastric cancer patients were recruited into the study. One cycle of continuous infusion of 5-FU (300 mg/m2/day, 14 days) plus drip infusion of cisplatin (15 mg/m2/day, Day one and Day two) was performed as neoadjuvant chemotherapy. Histological chemotherapeutic responses of the resected specimens were classified into responders and nonresponders. TS, DPD, VEGF expressions both before and after neoadjuvant chemotherapy were examined immunohistochemically. RESULTS: There was an association between the TS-low group and the responders (p < 0.05); the DPD-low group and the responders in both biopsy and surgical specimens (p < 0.01). A combination of the low-TS and low-DPD group was further associated with responders (p < 0.01). The immunoexpressions of biopsied and surgical specimens were significantly associated with each other. CONCLUSION: Neoadjuvant chemotherapy for primary gastric cancer with one cycle of 5-FU and cisplatin was associated with histological findings in patients with low baseline TS and DPD. This dual determination may predict for efficacy of neoadjuvant treatment with these drugs.     

Preoperative endoscopic analysis of thymidine phosphorylase and dihydropyrimidine dehydrogenase in gastrointestinal cancer

Thymidine phosphorylase (TP) and dihydropyrimidine dehydrogenase (DPD) are considered to be key enzymes affecting the prognosis for patients with advanced gastrointestinal cancer. Preoperative examination of TP and DPD expression levels and assessment of these enzymes in inoperable cancer patients may contribute to successful treatment. We tried to prove the correlation of TP and DPD expression in preoperative specimens by endoscopy and in surgical specimens. The present study was designed to quantify TP and DPD levels by enzyme-linked immunosorbent assay (ELISA) in tumor tissue obtained from 30 gastrointestinal cancer patients by preoperative endoscopy and surgery, including 15 gastric and 15 colorectal cancers. Successful cases as those in which cancer cells were demonstrated histologically in preoperative specimens by endoscopy were 12 (success rate: 80%) in gastric cancer patients, and 15 (success rate: 100%) in colorectal cancer patients. In successful cases, there were almost significant correlations in all cases, gastric cancer, and colorectal cancer among the expression of TP, DPD, and TP/DPD ratio in each preoperative specimen by endoscopy and surgical specimen, respectively. On the other hand, in the gastric cancer group, 3 unsuccessful cases resulted in a significant departure from ideal equation compared with 12 successful cases. In actual clinical care, physicians should pay attention to and evaluate carefully the data from endoscopical biopsy specimens in which cancer cells may not be demonstrated histologically. Thus, endoscopic analysis of TP and DPD expression in preoperative or inoperable cancer patients may contribute to successful treatment.     

The expression profiles of orotate phosphoribosyltransferase and dihydropyrimidine dehydrogenase in gastric cancer and their clinical significance

Orotate phosphoribosyltransferase (OPRT) is an enzyme that causes the activation of 5-fluorouracil (5-FU). Dihydropyrimidine dehydrogenase (DPD) is known to catabolize 5-FU, which is widely used in chemotherapeutic treatments for patients with a variety of malignant tumors including gastric and colorectal cancer. The expression and activities of these two enzymes therefore play important roles in the response of cancer patients to chemotherapy. However, little is known about the expression of these enzymes in gastric cancer. In the present study, we further elucidate the expression patterns of ORPT and DPD and their clinicopathological significance by immunohistochemical analysis in 221 and RT-PCR in 36 gastric cancer samples. The expression of OPRT by immunohistochemical analysis was detected in 117 (52.9%) cases, whereas DPD was detected in 66 (29.9%) cases. Moreover, the level of expression of OPRT was found to correlate with the depth of tumor invasion and a poorer prognosis. Although the mRNA and protein expression of OPRT and DPD levels did not correlate, an inverse correlation in the expression of OPRT and DPD was observed by RT-PCR. The survival benefit of post-operative adjuvant chemotherapy could not be confirmed in our present analysis. However, among the patients who had received such treatment with 5-FU or its derivatives, the prognosis in cases with low DPD levels was better than that in cases with high DPD expression by immunohistochemical analysis. These results indicate that the expression of OPRT and DPD are important predictors of both survival and the response to adjuvant chemotherapy in gastric cancer patients.     

Molecular factors of 5-fluorouracil metabolism in colorectal cancer: analysis of primary tumor and lymph node metastasis

Thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD) and thymidine phosphorylase (TP) are predictive markers for tumor response to 5-fluorouracil-based therapies. To determine whether gene expression values measured in primary cancer tissue would be useful for prediction of response of lymph node metastases, the expressions of these genes were quantitatively analyzed in 35 pairs of primary colorectal cancer (CRC) and corresponding lymph node metastases using real-time PCR. DPD and TP mRNA levels were significantly lower in the primary colorectal tumor and lymph node metastases compared with the normal adjacent stroma tissue (p<0.01), whereas TS mRNA levels were significantly higher in the primary tumor and lymph node metastases than in the normal adjacent tissue (p<0.001). Median gene expression levels of TP and TS did not differ significantly between primary colorectal tumor and corresponding lymph node metastasis but median DPD gene expression levels in the lymph node metastases were significantly higher compared to matched primary colorectal tumors (p=0.015). There was a significant correlation for DPD, TP and TS gene expression levels between primary colorectal tumor specimens and the matched lymph node metastasis. These results suggest that biopsies of the tumor of origin may be valid for determining predictive markers for chemotherapy response in patients with metastatic CRC.     

Expression of mRNA levels of thymidylate synthase, thymidine phosphorylase, dihydropyrimidine dehydrogenase and orotate phosphoribosyltransferase in diffusely infiltrating colorectal cancer

Little is known about the expression levels of thymidylate synthase (TS), thymidine phosphorylase (TP), dihydropyrimidine dehydrogenase (DPD), and orotate phosphoribosyltransferase (OPRT) in diffusely infiltrating colorectal cancer. We semiquantified the mRNA levels of these enzymes in colorectal cancer specimens from 10 patients with diffusely infiltrating type and 20 patients with other types (control) matched by the maximal diameter and pathological stage, using the Dannenberg tumor profiling method. The relative expression of these enzymes did not significantly differ between diffusely infiltrating and other types of tumors. There were no significant relationships among the relative expression of the four enzymes in the diffusely infiltrating tumors, while the following three combinations were found to be correlated with each other in the control tumors: TS versus TP,TS versus DPD, and TP versus DPD. In 5 patients who received 5-fluorouracil-based chemotherapy for evaluable lesions, there were no specific relationships between the expression of these enzymes and therapeutic response. In conclusion, diffusely infiltrating colorectal cancer does not appear to have any characteristics in terms of the expression of these enzymes, which may not alter the effect of 5-fluorouracil-based chemotherapy.     

Intratumoral induction of thymidylate synthase mRNA by 5-FU in colorectal cancer patients: association with survival

Dihydropyrimidine dehydrogenase (DPD) is the rate-limiting enzyme in 5-fluorouracil (5-FU) catabolism. Thymidylate synthase (TS) is inhibited to form an inactive ternary complex by 5-fluoro-dUMP and is considered to be a target enzyme of 5-FU treatment. Two enzymes, DPD and TS, have been reported to be major determinants of individual sensitivity to 5-FU, and it has been reported that TS mRNA levels are modified by 5-FU treatment. We investigated their impact on treatment efficacy in colorectal cancer patients. TS and DPD mRNA levels, which correlated to the corresponding enzyme activities, were quantified in tumor tissues before and after treatment in 40 advanced colorectal cancer patients who had been treated with Doxifluridine (5'-DFUR) for 14 days before surgery. Furthermore inter-individual variations of TS mRNA levels after 5-FU treatment were found, and the individual TS induction varied between patients (0.2-2.4). Increased TS mRNA levels were found in 19 out of 40 cases. The samples were divided into two groups according to their TS mRNA induction (< or >1; TS/beta-actin ratio after treatment divided by values prior treatment) and compared with tumor reduction and survival. TS and DPD mRNA levels in tumor biopsies before treatment were not related to 5-FU responses by histological evaluations in this study. However the efficacy of 5-FU treatment was enhanced in patients with no or low TS mRNA induction (odds ratio: 6.2, p<0.05). Furthermore, longer periods of survival were observed in the group without increased TS mRNA levels. These findings suggest that TS mRNA was induced by 5-FU treatment, and the overall induction level varied between individuals. Therefore, the estimation of TS mRNA induction may be useful to predict the efficacy of 5-FU treatment.     

Thymidylate synthase and dihydropyrimidine dehydrogenase gene expression in breast cancer predicts 5-FU sensitivity by a histocultural drug sensitivity test

Thymidylate synthase (TS), Dihydropyrimidine dehydrogenase (DPD) and Thymidine Phosphorylase (TP) gene expressions are reported to be predictive markers for 5-fluorouracil (5-FU) sensitivity in gastrointestinal cancer. However, in breast cancer, it is still controversial whether those molecular markers predict 5-FU sensitivity or not. One possible reason for the difficulty may be the histological heterogeneity in breast cancer specimens. In this study, TS, DPD and TP mRNA expression in 40 breast cancer tumors were semi-quantified separately in cancer cells (Ca), cancerous stroma (Str) and normal glands (Nor) using laser capture microdissection and real time RT-PCR (LCM+RT-PCR). The histoculture drug response assay (HDRA) for 5-FU sensitivity was performed for 22 tumors. TS and TP mRNA expressions were higher in Ca than Str, although DPD gene expression was lower in Ca than Str. The group of high TS and high DPD gene expression in Ca was resistant to 5-FU, and the group of low TS and low DPD gene expression in Ca was sensitive to 5-FU (P=0.048 chi-square test). TS and DPD mRNA expressions measured using LCM+RT-PCR might be useful predictive markers for 5-FU sensitivity in human breast cancer.