Quantitative measurement of thymidylate synthase and dihydropyrimidine dehydrogenase mRNA level in gastric cancer by real-time RT-PCR

An Overview of Clinical Trials in the Treatment of Resectable Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer-related death worldwide. Partial hepatectomy, one of a few curative therapeutic modalities, is plagued by high recurrence rate of up to 70% at 5 years. Throughout the past 3 decades, many clinical trials have attempted to improve HCC recurrence rate following partial hepatectomy using adjuvant and neoadjuvant treatment modalities such as antiviral therapy, brachytherapy, systemic chemotherapy, immunotherapy, transarterial chemoembolization and radioembolization, and radiotherapy. The goal of this review is to discuss the clinical trials pertaining to resectable HCC including surgical technique considerations, adjuvant, and neoadjuvant treatment modalities.

Choice of Capecitabine or S1 in Combination with Oxaliplatin based on Thymidine Phosphorylase and Dihydropyrimidine Dehydrogenase Expression Status in Patients with Advanced Gastric Cancer

Purpose

To study the efficacy of capecitabine or S-1 plus oxaliplatin (CAPOX or SOX) for treating thymidine phosphorylase (TP)- or dihydropyrimidine dehydrogenase (DPD)-positive advanced gastric cancer.

Materials and Methods

Eighty-six patients with stage IIIC to IV gastric cancer were assessed for TP and DPD expression by immunohistochemistry. The association between CAPOX or SOX efficacy and TP/DPD expression was retrospectively analyzed.

Results

There were no significant differences in the objective remission rate (ORR, 52.27% vs. 47.62%; P>0.05), disease control rate (72.73% vs. 73.81%, P>0.05), progression-free survival (hazard ratio [HR], 1.119; 95% confidence interval [CI], 0.739-1.741; P=0.586), and overall survival (OS; HR, 0.855; 95% CI, 0.481-1.511; P=0.588) between CAPOX and SOX. A higher number of stage IV patients showed TP positivity, while DPD-positive patients predominantly showed intestinal type of gastric cancer. In TP-positive patients, the ORRs associated with CAPOX and SOX treatments were 57.14% and 38.10%, respectively; OS was better with CAPOX than with SOX (HR, 0.447; 95% CI, 0.179-0.978; P=0.046). Among DPD-positive patients, the SOX treatment-associated ORR (60.87%) was significantly higher than the CAPOX treatment-associated ORR (43.48%). Furthermore, SOX treatment resulted in better OS than did CAPOX treatment (HR, 2.020; 95% CI, 1.019-4.837; P=0.049).

Conclusions

No significant difference in clinical efficacy was found between CAPOX and SOX. TP-positive patients might respond better to CAPOX while DPD-positive patients may respond better to SOX. Our findings might serve as a guide for personalized chemotherapy for gastric cancer.

Anticancer activity of the intraperitoneal-delivered DFP-10825, the cationic liposome-conjugated RNAi molecule targeting thymidylate synthase, on peritoneal disseminated ovarian cancer xenograft model

Introduction

Peritoneal disseminated ovarian cancer is one of the most difficult cancers to treat with conventional anti-cancer drugs and the treatment options are very limited, although an intraperitoneal (ip) paclitaxel has shown some clinical benefit. Therefore, treatment of peritoneal disseminated ovarian cancer is a highly unmet medical need and it is urgent to develop a new ip delivered drug regulating the fast DNA synthesis.

Methods

We developed a unique RNAi molecule consisting of shRNA against the thymidylate synthase (TS) and a cationic liposome (DFP-10825) and tested its antitumor activity and PK profile in peritoneally disseminated human ovarian cancer ascites models by the luciferase gene-transfected SCID mice. DFP-10825 alone, paclitaxel alone or combination with DFP-10825 and paclitaxel were administered in an ip route to the tumor-bearing mice. The TS expression level was measured by conventional RT-PCR. The anti-tumor activity and host survival benefit by DFP-10825 treatment on tumor-bearing mice were observed as resulting from the specific TS mRNA knock-down in tumors.

Results

DFP-10825 alone significantly suppressed the growth of SKOV3-luc tumore ascites cells and further extended the survival time of these tumor-bearing mice. Combination with the ip paclitaxel augmented the antitumor efficacy of DFP-10825 and significantly prolonged the survival time in the tumor-bearing mice. Short-hairpin RNA for TS (TS shRNA) levels derived from DFP-10825 in the ascetic fluid were maintained at a nM range across 24 hours but not detected in the plasma, suggesting that TS shRNA is relatively stable in the peritoneal cavity, to be able to exert its anti-tumor activity, but not in blood stream, indicating little or no systemic effect.

Conclusion

Collectively, the ip delivery of DFP-10825, TS shRNA conjugated with cationic liposome, shows a favorable antitumor activity without systemic adverse events via the stable localization of TS shRNA for a sufficient time and concentration in the peritoneal cavity of the peritoneally disseminated human ovarian cancer-bearing mice.

P53 represses pyrimidine catabolic gene dihydropyrimidine dehydrogenase (DPYD) expression in response to thymidylate synthase (TS) targeting

Nucleotide metabolism in cancer cells can influence malignant behavior and intrinsic resistance to therapy. Here we describe p53-dependent control of the rate-limiting enzyme in the pyrimidine catabolic pathway, dihydropyrimidine dehydrogenase (DPYD) and its effect on pharmacokinetics of and response to 5-fluorouracil (5-FU). Using in silico/chromatin-immunoprecipitation (ChIP) analysis we identify a conserved p53 DNA-binding site (p53BS) downstream of the DPYD gene with increased p53 occupancy following 5-FU treatment of cells. Consequently, decrease in Histone H3K9AC and increase in H3K27me3 marks at the DPYD promoter are observed concomitantly with reduced expression of DPYD mRNA and protein in a p53-dependent manner. Mechanistic studies reveal inhibition of DPYD expression by p53 is augmented following thymidylate synthase (TS) inhibition and DPYD repression by p53 is dependent on DNA-dependent protein kinase (DNA-PK) and Ataxia telangiectasia mutated (ATM) signaling. In-vivo, liver specific Tp53 loss increases the conversion of 5-FU to 5-FUH₂ in plasma and elicits a diminished 5-FU therapeutic response in a syngeneic colorectal tumor model consistent with increased DPYD-activity. Our data suggest that p53 plays an important role in controlling pyrimidine catabolism through repression of DPYD expression, following metabolic stress imposed by nucleotide imbalance. These findings have implications for the toxicity and efficacy of the cancer therapeutic 5-FU.

The Impact of the Expression Level of Intratumoral Dihydropyrimidine Dehydrogenase on Chemotherapy Sensitivity and Survival of Patients in Gastric Cancer: A Meta-Analysis

The potential impact that the intratumoral expression level of dihydropyrimidine dehydrogenase (DPD) has on chemotherapy sensitivity and long-term survival for gastric cancer (GC) patients remains controversial; therefore, this study seeks to clarify this issue. Our meta-analysis was performed using Review Manager (RevMan) 5.3 software. In vitro drug sensitivity tests, correlation coefficients between sensitivity to 5-fluorouracil (5-FU), and expression levels of intratumoral DPD were used as effective indexes to analyse. Overall survival (OS) and progression-free survival (PFS) were used as endpoints for patient outcome, and hazard ratios (HRs) and 95% confidence intervals (CIs) were noted as measures of effect. There were 15 eligible studies including 1805 patients for the final analysis. The analysis revealed a statistically significant difference between the expression level of intratumoral DPD activity, DPD mRNA levels, and sensitivity to 5-FU in GC patients, with high expression levels of intratumoral DPD resulting in low sensitivity to 5-FU. However, no matter what therapeutic regimens were used, there was no significant difference for patient outcomes between high and low DPD expression groups, either in OS or in PFS. In conclusion, high levels of intratumoral DPD expression have a negative impact on sensitivity to 5-FU in GC patients, but no prognostic value for long-term survival was uncovered.

Histone H3K27 Trimethylation Modulates 5-Fluorouracil Resistance by Inhibiting PU.1 Binding to the DPYD Promoter

The antimetabolite 5-fluorouracil (5-FU) is one of the most widely used chemotherapy drugs. Dihydropyrimidine dehydrogenase (DPD) is a major determinant of 5-FU response and toxicity. Although DPYD variants may affect 5-FU metabolism, they do not completely explain the reported variability in DPD function or the resultant differences in treatment response. Here, we report that H3K27 trimethylation (H3K27me3) at the DPYD promoter regulated by Ezh2 and UTX suppresses DPYD expression by inhibiting transcription factor PU.1 binding, leading to increased resistance to 5-FU. Enrichment of H3K27me3 at the DPYD promoter was negatively correlated with both DPYD expression and DPD enzyme activity in peripheral blood specimens from healthy volunteers. Lastly, tumor expression data suggest that DPYD repression by Ezh2 predicts poor survival in 5-FU-treated cancers. Collectively, the findings of the present article suggest that a previously uncharacterized mechanism regulates DPD expression and may contribute to tumor resistance to 5-FU. Cancer Res; 76(21); 6362-73. ©2016 AACR.

Cancer chemoresistance; biochemical and molecular aspects: a brief overview

The effectiveness of chemotherapy is one of the main challenges in cancer treatment and resistance to classic drugs and traditional treatment processes is an obstacle to this goal. Drug resistance that may be inherent or adventitious can cause poor treatment outcome and tumor relapse. In most cases, resistance to a drug can lead to resistance to many other drugs structure and function of which is not necessarily similar to the first drug. This phenomenon is the main mechanism behind failure of many of metastatic cancers. There are various molecular mechanisms involved in multidrug resistance, including change in the activity of membrane transporters (such as ABC transporters), increase of drug metabolism, change of the target enzyme (such as mutations that change thymidylate synthase and topoisomerases), promotion of DNA damage repair, and escape from drug induced apoptosis. Clinical and laboratory investigations on biomarkers involved in the response to chemotherapy have characterized the key factors behind the failure of treatments. Knowing the molecular factors involved in drug resistance may help us to develop new strategies for more promising chemotherapy and reduce the rate of relapse. In this brief review, molecular mechanisms and tumor microenvironment leading to decreased drug sensitivity, and strategies of reversing drug resistance are described.

Correlations between expression levels of thymidylate synthase, thymidine phosphorylase and dihydropyrimidine dehydrogenase, and efficacy of 5-fluorouracil-based chemotherapy for advanced colorectal cancer

The efficacy of 5-fluorouracil (5-FU)-based chemotherapy for colorectal cancer (CRC) widely varies among patients; therefore, it is difficult to accurately predict chemotherapeutic responses. Some recent studies have found that key enzymes in the various metabolic pathways activated by 5-FU present potential predictors of treatment outcome. Of these enzymes, thymidylate synthase (TS), thymidine phosphorylase (TP), and dihydropyrimidine dehydrogenase (DPD) are known to play important roles in the efficacy of therapeutic agents. Here, we measured expression levels of TS, TP, and DPD in formalin-fixed, paraffin-embedded, CRC specimens and paracancerous tissue with normal mucosa by immunohistochemical and fluorescence real-time quantitative polymerase chain reaction techniques. We found no significant differences in TS, TP, and DPD expression levels between CRC specimens and paracancerous tissues (P > 0.05), although overall survival and the chemotherapeutic effect were relatively poor in CRC patients with relatively high expression levels of TS, TP, and DPD, as compared to those with comparatively low expression levels (P < 0.05). Therefore, TS, TP, and DPD mRNA levels appear to be suitable indicators of the efficacy of 5-FU-based chemotherapy and prognosis of CRC.

Impact of intratumoral expression levels of fluoropyrimidine-metabolizing enzymes on treatment outcomes of adjuvant S-1 therapy in gastric cancer

We analyzed the expression levels of fluoropyrimidine-metabolizing enzymes (thymidylate synthase [TS], dihydropyrimidine dehydrogenase [DPD], thymidine phosphorylase [TP] and orotate phosphoribosyltransferase [OPRT]) to identify potential biomarkers related to treatment outcomes in gastric cancer (GC) patients receiving adjuvant S-1 chemotherapy. In this study, 184 patients who received curative gastrectomy (D2 lymph node dissection) and adjuvant S-1 were included. Immunohistochemistry and quantitative reverse transcription polymerase chain reaction were performed to measure the protein and mRNA levels of TS, DPD, TP, and OPRT in tumor tissue. In univariate analysis, low intratumoral DPD protein expression was related to poorer 5-year disease-free survival (DFS; 78% vs. 88%; P = 0.068). Low intratumoral DPD mRNA expression (1st [lowest] quartile) was also related to poorer DFS (69% vs. 90%; P < 0.001) compared to high intratumoral DPD expression (2nd to 4th quartiles). In multivariate analyses, low intratumoral DPD protein or mRNA expression was related to worse DFS (P < 0.05), irrespective of other clinical variables. TS, TP, and OPRT expression levels were not related to treatment outcomes. Severe non-hematologic toxicities (grade ≥ 3) had a trend towards more frequent development in patients with low intratumoral DPD mRNA expression (29% vs. 16%; P = 0.068). In conclusion, GC patients with high intratumoral DPD expression did not have inferior outcome following adjuvant S-1 therapy compared with those with low DPD expression. Instead, low intratumoral DPD expression was related to poor DFS.

Calpain regulates thymidylate synthase-5-fluoro-dUMP complex levels associated with response to 5-fluorouracil in gastric cancer cells

Thymidylate synthase (TS) plays a major role in the response to 5-fluorouracil (5-FU) by binding directly to the 5-FU metabolite, 5-fluoro-dUMP (FdUMP). The change in the TS expression levels after 5-FU administration was examined in parallel to 5-FU responsiveness in six human gastric adenocarcinoma cell lines to elucidate the source of variability of 5-FU sensitivity. MKN-1, SH-10-TC and MKN-74 cells were more resistant to 5-FU than MKN-28, KATO III and MKN-45 cells. Western blotting analysis revealed that the 5-FU sensitivity of these cells did not correlate with the basal TS expression levels but did correlate with rapid detection of the TS-FdUMP complex after exposure to 5-FU. In 5-FU-resistant cells, very low levels of the TS-FdUMP complex early after 5-FU exposure were elevated by pretreatment with calpain inhibitors such as benzyloxycarbonyl-leucyl-leucinal (ZLLH), benzyloxycarbonyl-leucyl-leucyl-leucinal (ZLLLH) and ALLN, but not by other protease inhibitors. In contrast, ONO-3403, which causes calpain activation, stimulated downregulation of the TS-FdUMP complex in 5-FU-sensitive cells. The expression levels of calpastatin, an endogenous calpain inhibitor, were higher in 5-FU-sensitive cells than in 5-FU-resistant cells. ZLLH increased the 5-FU sensitivity of 5-FU-resistant cells, whereas ONO-3403 decreased the sensitivity of 5-FU-sensitive cells. In addition, knockdown of m-calpain by siRNA increased the 5-FU sensitivity in 5-FU-resistant cells, while knockdown of calpastatin reduced the sensitivity in 5-FU-sensitive cells. These results suggest that calpain might reduce the chemosensitivity of human gastric cancer cells to 5-FU possibly by rapid degradation of the TS-FdUMP complex, a finding that is considered to have novel therapeutic implications.

Resistance may not be futile: microRNA biomarkers for chemoresistance and potential therapeutics

Chemoresistance to many commercially available cancer therapeutic drugs is a common occurrence and contributes to cancer mortality as it often leads to disease progression. There have been a number of studies evaluating the mechanisms of resistance and the biological factors involved. microRNAs have recently been identified as playing a role in the regulation of key genes implicated as cancer therapeutic targets or in mechanisms of chemoresistance including EGFR, MDR1, PTEN, Bak1, and PDCD4 among others. This article briefly reviews chemoresistance mechanisms, discusses how microRNAs can play a role in those mechanisms, and summarizes current research involving microRNAs as both regulators of key target genes for chemoresistance and biomarkers for treatment response. It is clear from the accumulating literature that microRNAs can play an important role in chemoresistance and hold much promise for the development of targeted therapies and personalized medicine. This review brings together much of this new research as a starting point for identifying key areas of interest and potentials for future study.

The role of Sp1 and Sp3 in normal and cancer cell biology

Sp1 and Sp3 are transcription factors expressed in all mammalian cells. These factors are involved in regulating the transcriptional activity of genes implicated in most cellular processes. Dysregulation of Sp1 and Sp3 is observed in many cancers and diseases. Due to the amino acid sequence similarity of the DNA binding domains, Sp1 and Sp3 recognize and associate with the same DNA element with similar affinity. However, others and our laboratory demonstrated that these two factors possess different properties and exert different functional roles. Both Sp1 and Sp3 can interact with and recruit a large number of proteins including the transcription initiation complex, histone modifying enzymes and chromatin remodeling complexes, which strongly suggest that Sp1 and Sp3 are important transcription factors in the remodeling chromatin and the regulation of gene expression. In this review, the role of Sp1 and Sp3 in normal and cancer cell biology and the multiple mechanisms deciding the functional roles of Sp1 and Sp3 will be presented.

The dihydrouracil/uracil ratio in plasma, clinical and genetic analysis for screening of dihydropyrimidine dehydrogenase deficiency in colorectal cancer patients treated with 5-fluorouracil

A rapid and cost-effective reversed phase high performance liquid chromatography (HPLC) method for quantification of dihydrouracil to uracil ratio (UH2/U) in plasma has been developed and used to screen for dihydropyrimidine dehydrogenase (DPD) deficiency in nine patients treated with 5-fluorouracil (5-FU). This HPLC method is based on the use of a simultaneous UV detection at 205 and 268nm during the analysis run of the plasma extract and taking into account the particularity that UH2 shows no absorbance response at 268nm. The plasma UH2/U ratio values evaluated by the use of our HPLC assay were found to be highly correlated with the plasma 5-FU-half-life values and were significantly associated with the toxic side effects, whereas, data set provided from genetic analysis of the coding sequences of the DPD gene (DPYD) were found to be insufficient to explain all the cases of the 5-FU-related toxicity pattern. The proposed HPLC assay could be available for routine clinical use for DPD deficiency assessment in patients prior to 5-FU administration.

Relationship between expression of 5-fluorouracil metabolic enzymes and 5-fluorouracil sensitivity in esophageal carcinoma cell lines

5-Fluorouracil (5-FU) is a key drug in the treatment of esophageal squamous cell carcinoma (ESCC). Gene expression of 5-FU metabolic enzymes such as thymidylate synthase (TS), thymidine phosphorylase (TP), dihydropyrimidine dehydrogenase (DPD) and orotate phosphoribosyl transferase (OPRT), has recently been investigated in order to predict the 5-FU sensitivity of several cancers. We examined the relationship between such gene expression and 5-FU sensitivity in 25 ESCC cell lines. TS, DPD, TP and OPRT mRNA levels were assessed by real-time polymerase chain reaction. The 50% inhibitory concentrations (IC50) of 5-FU in 25 ESCC cell lines were determined by cell proliferation assay. IC50 values for 5-FU ranged from 1.00 to 39.81 micromol/L. There were significant positive correlations between IC50 and TS mRNA expression (R(2) = 0.5781, P < 0.0001) and DPD mRNA expression (R(2) = 0.3573, P = 0.0016). There were no correlations between IC50 and TP or OPRT mRNA expression. TS and DPD mRNA expression levels may be useful indicators in predicting the anti-tumor activity of 5-FU in ESCC.

Synergistic antitumor effect of combined 5-fluorouracil (5-FU) with 5-chloro-2,4-dihydroxypyridine on 5-FU-resistant gastric cancer cells: possible role of a dihydropyrimidine dehydrogenase-independent mechanism

BACKGROUND

S-1 is an oral fluorouracil antitumor drug that combines three pharmacological agents: tegafur, a prodrug of 5-fluorouracil (5-FU); 5-chloro-2,4-dihydroxypyridine (CDHP), an inhibitor of dihydropyrimidine dehydrogenase (DPD); and potassium oxonate, an agent included to reduce gastrointestinal toxicity. S-1 has a potent antitumor effect on gastric cancer, even in 5-FU-refractory cases. However, there is a lack of basic information to account for this clinical outcome. This study was performed to determine the differences in antitumor effects of combined administration of 5-FU and CDHP between NUGC-3 cells and NUGC-3/5FU/L cells, which are resistant to 5-FU (established by repeated cultures of NUGC-3 with escalating concentrations of 5-FU), and to determine the mechanisms involved.

METHODS

Both cell lines were incubated with various concentrations of 5-FU and/or CDHP. The antitumor effect was assessed using an MTS assay and cell counts. DPD levels were assayed by using enzyme-linked immunosorbent assay. Expression of DPD and thymidylate synthase (TS) mRNA was quantified using real-time quantitative polymerase chain reaction analysis.

RESULTS

The combination of 5-FU (IC15) with CDHP exerted a synergistic antitumor effect on NUGC-3/5FU/L, but not on NUGC-3, while CDHP by itself did not affect cell growth in either cell line. Expression of DPD was not detected in NUGC-3/5FU/L. In NUGC-3/5FU/L, 5-FU-enhanced expression of TS mRNA was inhibited by the addition of CDHP. In contrast, in NUGC-3, administration of 5-FU with or without CDHP did not alter TS mRNA expression.

CONCLUSIONS

The inhibitory mechanism of CDHP, which is independent of DPD, may in part contribute to the antitumor effect of S-1 even in 5-FU-resistant gastric cancer cases.

Suppression of DPYD expression in RKO cells via DNA methylation in the regulatory region of the DPYD promoter: a potentially important epigenetic mechanism regulating DPYD expression

Dihydropyrimidine dehydrogenase (DPD) is one of the factors that determine the efficacy and toxicity of 5-fluorouracil. Variations in DPD activity may result from alterations at the transcriptional level of the DPYD gene. Heterogeneity in DPYD expression has been reported, but the molecular mechanisms responsible for this remain unclear. We investigated methylation of the DPYD promoter as a mechanism for transcriptional regulation of DPYD in the RKO colorectal cancer cell line. We demonstrate that the active transcription machinery for DPYD is present in RKO cells, but promoter binding of Sp1, a transactivator of DPYD, was inhibited, which on subsequent examination was shown to be associated with dense promoter methylation. Treatment with 5-aza-2'-deoxycytidine alone or the combination of 5-aza-2'-deoxycytidine and trichostatin A induced demethylation of the promoter and markedly increased the DPYD mRNA level in RKO cells but not in unmethylated WiDr cells. Furthermore, in vitro methylation of the DPYD promoter decreased promoter activity. These data suggest an important role for methylation in DPYD suppression. The transcriptional suppression of DPYD by methylation may be responsible for the increased 5-fluorouracil sensitivity observed in some patients. This may also provide insight into the mechanism underlying the downregulation of DPYD in some colorectal cancers.

Correlation between thymidylate synthase and dihydropyrimidine dehydrogenase mRNA level and in vitro chemosensitivity to 5-fluorouracil, in relation to differentiation in gastric cancer

PURPOSE

It has been suggested that the gene expression levels of thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD) help in the prediction of the response to 5-fluorouracil (5-FU) in vivo and in vitro in gastric cancers.

METHODS

In this study, intratumoral TS and DPD gene expressions were evaluated with real time reverse transcriptional polymerase chain reaction technique to determine the correlation between the expression of these two genes and in vitro sensitivity to 5-FU, assessed by the histoculture drug response assay on 87 patients with gastric adenocarcinoma.

RESULTS

The sensitivity to 5-FU did not show any difference in clinicopathological groups. DPD gene level was higher in undifferentiated (n = 39) than differentiated (n = 48) tumors (P = 0.043). In differentiated tumors, TS gene expression levels were higher in the tumors with relative resistance to 5-FU, while in undifferentiated cases, DPD mRNA levels were higher in tumors that showed resistance to 5-FU in vitro (P = 0.043 and 0.007, respectively). DPD also had significant predictive value for 5-FU sensitivity in undifferentiated cases [R(S) = -0.401, P = 0.011]. TS and DPD gene expression levels were more highly correlated in undifferentiated compared to differentiated cases [R(S) = 0.515 and 0.359, respectively].

CONCLUSIONS

Different gene expression might be responsible for 5-FU sensitivity in gastric cancers of different histologic origin.

Regulation of human dihydropyrimidine dehydrogenase: implications in the pharmacogenetics of 5-FU-based chemotherapy

Dihydropyrimidine dehydrogenase is the enzyme that is critical for the efficacy and toxicity of the anticancer reagent 5-fluorouracil. It has been demonstrated that the regulation of the dihydropyrimidine dehydrogenase gene has an important role in the determination of the enzyme activity of dihydropyrimidine dehydrogenase. The regulation of the gene expression is thus discussed from two aspects: normal regulation by specificity proteins, and the epigenetic regulation by promoter methylation. The influence of the polymorphism on dihydropyrimidine dehydrogenase enzyme activity and other factors that have been suggested to be involved in dihydropyrimidine dehydrogenase regulation are also discussed.

Efficacy of S-1 for patients with peritoneal metastasis of gastric cancer

BACKGROUND

This study was designed to examine the efficacy and compliance of S-1 for the patients with peritoneal metastasis of gastric cancer.

METHODS

Sixteen consecutive patients with peritoneal metastasis of gastric cancer were treated with S-1. Their survival was compared with that of the historical control group (25 patients). Thymidylate synthase, dihydropyrimidine dehydrogenase, thymidine phosphorylase and orotate phosphoribosyl transferase mRNA expression in the tumor were evaluated.

RESULTS

The median survival time of S-1-treated patients was 550 days, which was significantly longer than that of the historical control group (215 days). We elucidated some factors to prolong the survival of the patients treated with S-1 for peritoneal metastasis: peritoneal metastasis without other distant metastases, the combination of S-1 treatment and gastrectomy, and low expression of thymidine phosphorylase mRNA in primary tumors.

CONCLUSIONS

S-1 showed a surprisingly long-term survival with minimum toxicity in patients with peritoneal metastasis of gastric cancer.

The role of Sp1 and Sp3 in the constitutive DPYD gene expression

Dihydropyrimidine dehydrogenase (DPD), the initial and rate-limiting enzyme in the 5-fluorouracil (5-FU) catabolic pathway, has been implicated as one of the factors determining the efficacy and toxicity of the anticancer agent 5-FU. Studies have attributed variation in DPD activity partially to alterations at the transcriptional level of DPYD gene. We investigated the transcription factors implicated in the constitutive expression of DPYD by utilizing a 174-bp fragment of the DPYD promoter region in which three consensus Sp protein binding sites (SpA, SpB and SpC) were predicted. The binding of Sp1 and Sp3 transcription factors to this region was detected by electrophoretic mobility shift and chromatin immunoprecipitation assays. By ectopically expressing human Sp1 and Sp3 in Sp-deficient Drosophila S2 cells, we demonstrated that Sp1 is a strong activator, while Sp3 by its own is a weak activator of the DPYD promoter. Moreover, Sp3 may serve as a competitor of Sp1, thus decreasing the Sp1 induced promoter activity. SpA, SpB and SpC sites are all Sp1 inducible. In the full activation of the DPYD promoter in human cell lines, the SpB site is essential; the SpC site works cooperatively with SpB, while SpA has minor promoter activity. These studies provide further insight into the molecular mechanisms underlying the heterogeneity of DPD activity, and may facilitate the efficacy and safety of 5-FU-based chemotherapy.

The role of thymidylate synthase and dihydropyrimidine dehydrogenase in resistance to 5-fluorouracil in human lung cancer cells

The expressions of thymidylate synthase (TS) and intracellular metabolic enzymes have been reported to be associated with the sensitivity and/or resistance to 5-fluorouracil (5-FU). However, since the role of these enzymes in the mechanism of resistance to 5-FU has not been fully examined in lung cancer, in the present study we measured the expression levels of TS, dihydropyrimidine dehydrogenase (DPD), thymidine phosphorylase (TP), and orotate phosphoribosyltransferase (OPRT) genes in lung cancer cell lines by real-time PCR, and the sensitivity to 5-FU using the MTS assay. The expression of DPD was significantly correlated with the concentration of 5-FU for 50% cell survival in 15 non-small-cell lung cancer (NSCLC) cell lines (p<0.05), but the expressions of TS, TP, and OPRT were not. Treatment with 5-chloro-2,4-dihydroxypyridine, an inhibitor of DPD, altered the sensitivity to 5-FU in DPD-expressing RERF-LC-MT cells, indicating that modulation of DPD activity could increase the 5-FU sensitivity in lung cancer. In contrast, TS expression was dramatically higher in a 5-FU-resistant small-cell lung cancer cell line than in the parent cell line, whereas the expressions of DPD, TP, and OPRT genes were not markedly different. In order to examine the effect of other cytotoxic agents on TS and DPD expression, we compared the expressions of both genes between cisplatin-, paclitaxel-, gemcitabine-, or 7-ethyl-10-hydroxycamptothecin-resistant lung cancer cells and their respective parent cells, but found no differences between any pair of resistant subline and the corresponding parent cell line. Our results indicate that degradation of 5-FU due to DPD is an important determinant in 5-FU sensitivity, while induction of TS contributes to acquired resistance against 5-FU in lung cancer. Therefore, the expression levels of TS and DPD genes may be useful indicators of 5-FU activity in lung cancer.

Influence of chemotherapeutic agents and cytokines on the expression of 5-fluorouracil-associated enzymes in human colon cancer cell lines

BACKGROUND

Several studies have demonstrated that intratumoral expression of catabolizing and anabolizing enzymes for 5-fluorouracil (5-FU) is important in the response of cancers to 5-FU-based chemotherapy. We investigated the influence of other chemotherapeutic agents or cytokines, which are often administered for enhancing the efficacy of 5-FU, on the tumoral expression of 5-FU-associated enzymes, i.e., dihydropyrimidine dehydrogenase (DPD), thymidylate synthase (TS), orotate phosphoribosyl transferase (OPRT), and thymidine phosphorylase (TP).

METHODS

Human colon cancer cell lines (HT-29, Caco-2, and DLD-1) were incubated with 5-FU and with 5-FU combined with cisplatin, camptothecin, paclitaxel, mitomycin C, interferon, or TNF-related apoptosis-inducing ligand. mRNA expression of 5-FU-associated enzymes was assessed by real-time PCR. Activity of each enzyme and intracellular 5-FU accumulation after incubation with such agents were also evaluated.

RESULTS

Each agent had a synergistic effect on the cytotoxicity of 5-FU. All chemotherapeutic agents other than cytokines induced marked alteration of the mRNA expression profile of 5-FU-associated enzymes; depression of DPD, elevation of TS, and slight suppression of OPRT and TP. In accordance with mRNA expression, enzyme activity of DPD was significantly depressed by such agents. Furthermore, although 5-FU itself increased DPD mRNA expression, a mechanism considered to be related to the acquisition of 5-FU resistance, the addition of cisplatin or camptothecin significantly inhibited the 5-FU-induced elevation of DPD.

CONCLUSIONS

5-FU-associated enzymes in colon cancer cells were greatly influenced by various chemotherapeutic agents; in particular, DPD expression was depressed. These results appear important in planning chemotherapy and also in understanding the development of adverse effects of 5-FU.

Tumor quantification of several fluoropyrimidines resistance gene expression with a unique quantitative RT-PCR method. Implications for pretherapeutic determination of tumor resistance phenotype

Pretherapeutic determination of tumor resistance to chemotherapy is a main challenge, hindered by the low number of mechanisms characterized at the same time, the small size of the clinical specimens and the heterogeneity of the techniques or the lack of true quantification. The aim of the present study was to determine in real time quantitative RT-PCR, tumor cell expression of several transcripts involved in cancer cell resistance with a unique cDNA sample from a tumor biopsy. The technique had to be suitable in clinical practice for determination of several factors involved in resistance to a given drug family, for example, fluoropyrimidines resistance factors: thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD), thymidine kinase (TK), dihydrofolate reductase (DHFR), folylpolyglutamate synthetase (FPGS). A frame-shifted artificial construct was designed specifically to work within the same conditions. We validated our technique by quantifying expressions of these 5 genes starting from tissue samples of colorectal carcinoma and the surrounding normal mucosa of 33 different patients. That real time quantitative RT-PCR technique using the frame-shifted artificial construct as a standard provided a real comparison and quantification of different resistance factors. Tumor resistance phenotype determination based on that approach will be investigated in a control study.

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.

Evaluation of sensitivity to 5-FU on the basis of thymidylate synthase (TS)/dihydropyrimidine dehydrogenase (DPD) activity and chromosomal analysis in micro tissue specimens of breast cancer

BACKGROUND

Preoperative assessment of the anticancer drug sensitivity of tumors plays an important role in the selection of therapy. If evaluation of the 5-FU sensitivity of microtissue specimens obtained by techniques such as core needle biopsy could be performed, the addition of fluorouracil to adriamycin and cyclophosphamide may further enhance response rates. In order to evaluate a simple sensitivity test for the anti-tumor agent 5-fluorouracil (5-FU), we examined whether an assay of a small sample could measure mRNA to predict the activities of thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD). In addition, gene abnormalities on chromosomes 1 and 18 corresponding to DPD, TS and the relationships between the gene abnormalities and the amount of mRNA and activity were examined.

METHOD

TS and DPD activity were measured using the fluorodeoxyuridine monophosphate ligand binding assay and radio enzymatic assay, respectively, while mRNA levels were assayed by real-time polymerase chain reaction. Chromosome 1 and 18 aberrations were investigated by fluorescence in situ hybridization (FISH) with centromere probes.

RESULTS

TS mRNA and TS activity showed a positive correlation (r=0.518, p=0.0017). TS activity and TS mRNA were significantly higher in the nuclear grade 3 group than in the other groups (p=0.04, p=0.0072, respectively). TS activity and mRNA in tumor tissue tended to decrease in the progesterone receptor positive groups (p=0.059, p=0.066, respectively). There was no correlation between DPD mRNA and DPD activity in tumor tissue (r=0.139, p=0.4423). DPD mRNA was measured as 282.88+/-170.68 copies/cell in tumor tissue and 635.88+/-310.04 copies/cell in normal tissue, and was thus significantly higher in normal tissue (p<0.001).

CONCLUSIONS

TS mRNA showed a positive correlation with TS activity, suggesting that this method of using small amounts of tissue can replace anti-cancer drug sensitivity tests.

Thymidylate synthase and dihydropyrimidine dehydrogenase gene expression in relation to differentiation of gastric cancer

Thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD) are important enzymes of DNA de novo synthesis and the salvage pathway in cancer cells, respectively. Intratumoral TS and DPD gene expressions were evaluated to determine the correlation between the expression of the 2 genes in both normal stromal tissues and tissues with different degrees of malignant differentiation in primary gastric cancer. The study population consisted of 78 consecutive patients with advanced gastric cancer who underwent surgical treatment. Laser-captured microdissection of malignant or normal stromal tissues was performed in formalin-fixed, paraffin-embedded specimens. After extraction of RNA, TS and DPD gene expressions were measured by the real-time reverse transcriptional PCR method. Apart from degree of differentiation, TS and DPD in malignant tissue showed no correlation with clinicopathologic factors. TS in malignant tissue was higher in differentiated type cases than undifferentiated type cases (p < 0.01). However, DPD in malignant tissue of undifferentiated type cases was statistically higher than that of differentiated type cases (p < 0.05). In normal stromal tissue, neither TS nor DPD had any correlation with clinicopathologic factors. TS in malignant tissue was statistically higher than in normal stromal tissue in both differentiated and undifferentiated types (p < 0.0001). DPD in differentiated type malignant tissue was statistically lower than in normal stromal tissue (p < 0.001), but no difference was seen in undifferentiated type cases. TS and DPD gene expressions in primary gastric cancer differ according to degree of differentiation and between malignant and normal stromal tissue.

Thymidylate synthase and dihydropyrimidine dehydrogenase mRNA levels in tumor tissues and the efficacy of 5-fluorouracil in patients with non-small-cell lung cancer

We examined 116 stage I-IIIA non-small-cell lung cancer (NSCLC) patients for intra-tumoral expression of thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD) using TaqMan reverse transcription polymerase chain reaction (RT-PCR) assay to clarify the correlation between gene expression and the efficacy of 5-fluorouracil (5-FU) in patients with NSCLC. Patients who were administered 5-FU alone after surgery comprised the 5-FU group (n = 30), and those who underwent only surgery comprised the control group (n = 86). When dichotomized at the mean TS and DPD mRNA level, patients with low-DPD tumors who were administered 5-FU had a significantly better prognosis than those who did not receive adjuvant treatment (p = 0.041). In addition, in the 5-FU group, 10 patients with both low-TS and low-DPD tumors have not had any relapse, whereas 8 of the 20 patients with either high-TS or high-DPD tumors developed distant metastasis after surgery. Based on these results, the quantitation of TS and DPD mRNA levels may predict the efficacy of 5-FU after surgery for patient with NSCLC.

Identification of novel genes associated with the response to 5-FU treatment in gastric cancer cell lines using a cDNA microarray

The 5-Fluorouracil (5-FU) is an anticancer drug that is widely used in the treatment of cancer. To identify novel genes associated with 5-FU in gastric cancer, the time-dependent expression profiling of genes in response to 5-FU was examined in 5-FU sensitive and/or resistant gastric cancer cell lines using a 'KUGI 14 K cDNA chip' containing 14,081 unigenes obtained from human gastric cancer cell lines and tissues. By this analysis, we obtained 13 genes which are directly associated with sensitivity or resistance to 5-FU. Of these genes, 11 were found to be commonly up-regulated only in the 5-FU sensitive cell lines, and 2 were oppositely regulated in both of 5-FU sensitive and resistant cell lines. These genes were determined to be involved in cell surface, apoptosis, cell cycle and signal transduction. Of these genes, the expression levels of ZFP100, 4F2hc, FLJ11021, CSTF3, PPP1R14A, DDB2, C6orf139, CDKN1A, HOXC11 and FLJ38860 were confirmed by semi-quantitative RT-PCR. In addition, seven genes containing RRMI, UP1 and K-EST0037597 were found to be commonly up-regulated in both cell lines. In addition, the expression of genes such as TP, OPRT, TS and DPD, which have been previously known to be involved in 5-FU metabolism, were examined in both of 5-FU sensitive and resistant cell lines. These results provide not only predictive biomarkers for 5-FU sensitivity or resistance to human gastric cancer, but also a new molecular basis for understanding the mechanism of cellular cytoxicity to 5-FU.

Decreased expression of osteopontin is related to tumor aggressiveness and clinical outcome of intrahepatic cholangiocarcinoma

BACKGROUND

Osteopontin (OPN) is known to be a secreted adhesive glycoprotein. Recent studies have reported that the overexpression of OPN is correlated with tumorigenesis, tumor aggressiveness, and poor prognosis in several types of human cancer. The aim of this study was to determine whether the expression of OPN in cases of intrahepatic cholangiocarcinoma (ICC) indicates the clinical outcome.

METHODS

The expression of OPN protein was investigated immunohistochemically in surgically resected specimens from 73 patients, and the level of OPN mRNA was also examined by quantitative real-time reverse transcription-polymerase chain reaction (real-time RT-PCR) in nine samples of ICC. We examined the correlation between the expression of OPN and the clinicopathological factors, including overall survival, in patients with ICC.

RESULTS

We detected the positive expression of OPN protein in 31 of 73 (42.5%) of the primary ICCs. Negative expression of OPN protein was significantly related to lymphatic permeation, perineural invasion, intrahepatic metastasis, and lymph node metastasis (P=0.0029, 0.0072, 0.0134, and 0.0101, respectively). Overall survival was significantly lower among the patients with a negative expression of OPN than it was among those with a positive expression of OPN. The negative expression of OPN protein and the lower levels of OPN mRNA were statistically significant (P=0.0139).

CONCLUSIONS

Decreased expression of OPN is considered to be a reliable indicator of tumor aggressiveness and clinical outcome in patients with ICC.

Prediction of sensitivity to fluoropyrimidines by metabolic and target enzyme activities in gastric cancer

BACKGROUND

This study was designed to investigate the role of thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD), and thymidine phosphorylase (TP) in tumor progression and sensitivity to 5-fluorouracil (5-FU).

METHODS

A total of 275 tumor samples from 275 patients with gastric cancer were utilized in this study. TS activity was determined in 130 samples by 5-fluorodeoxyuridine monophosphate binding assay. DPD activity was measured in 140 samples by radioenzymatic assay, and TP protein level was determined in 157 samples by an enzyme-linked immunosorbent assay (ELISA) system. These parameters were compared with several clinicopathologic factors and sensitivity to 5-FU determined by in-vitro ATP assay. The antitumor activities of 5-FU, uracil plus tegafur (UFT), and 1M tegafur--0.4 M 5-chloro-2,4-dihydroxypyridine--1 M potassium oxonate (S-1 [TS-1]) were also compared, using three human gastric cancer xenografts in nude mice.

RESULTS

There was no correlation between either TS or TP and sensitivity to 5-FU. However, a weak inverse correlation was found between DPD activity and sensitivity to 5-FU. High DPD activity in tumor resulted in poor prognosis, especially in patients who received 5-FU-based adjuvant chemotherapy. Although TP was significantly correlated with depth of tumor invasion and with lymphatic and venous invasions, TP alone had no impact on survival. On the other hand, TS, as well as peritoneal, hepatic, and lymph node metastases, was selected as an independent prognostic factor in gastric cancer. In the animal model, there was no significant difference in antitumor activities among the drugs in a tumor with low DPD activity. However, S-1 showed superior antitumor activity to 5-FU or UFT in tumors with high DPD activity.

CONCLUSION

DPD is considered to be a most important predictive factor of 5-FU sensitivity. The use of DPD inhibitory fluoropyrimidines is strongly recommended for tumors with high DPD activity.