Simple combinations of 5-FU pathway genes predict the outcome of metastatic gastric cancer patients treated by S-1

Current Advances and Outlook in Gastric Cancer Chemoresistance: A Review

BACKGROUND

Surgical resection of the lesion is the standard primary treatment of gastric cancer. Unfortunately, most patients are already in the advanced stage of the disease when they are diagnosed with gastric cancer. Alternative therapies, such as radiation therapy and chemotherapy, can achieve only very limited benefits. The emergence of cancer drug resistance has always been the major obstacle to the cure of tumors. The main goal of modern cancer pharmacology is to determine the underlying mechanism of anticancer drugs.

OBJECTIVE

Here, we mainly review the latest research results related to the mechanism of chemotherapy resistance in gastric cancer, the application of natural products in overcoming the chemotherapy resistance of gastric cancer, and the new strategies currently being developed to treat tumors based on immunotherapy and gene therapy.

CONCLUSION

The emergence of cancer drug resistance is the main obstacle in achieving alleviation and final cure for gastric cancer. Mixed therapies are considered to be a possible way to overcome chemoresistance. Natural products are the main resource for discovering new drugs specific for treating chemoresistance, and further research is needed to clarify the mechanism of natural product activity in patients. .

A predictive signature for oxaliplatin and 5-fluorouracil based chemotherapy in locally advanced gastric cancer

Adjuvant chemotherapy(AC) plays a substantial role in the treatment of locally advanced gastric cancer (LAGC), but the response remains poor. We aims to improve its efficacy in LAGC. Therefore, we identified the expression of eight genes closely associated with platinum and fluorouracil metabolism (RRM1, RRM2, RRM2B, POLH, DUT, TYMS, TYMP, MKI67) in the discovery cohort (N=291). And we further validated the findings in TCGA (N=279) and GEO. Overall survival (OS) was used as an endpoint. Univariate and multivariate Cox models were applied. A multivariate Cox regression model was simulated to predict the OS. In the discovery cohort, the univariate Cox model indicated that AC was beneficial to high-RRM1, high-DUT, low-RRM2, low-RRM2B, low-POLH, low-KI67, low-TYMS or low-TYMP patients, the results were validated in the TCGA cohort. The multivariate Cox model showed consistent results. Cumulative analysis indicated that patients with low C-Score respond poorly to the AC, whereas the high and medium C-Score patients significantly benefit from AC. A risk model based on the above variables successfully predicted the OS in both cohorts (AUC=0.75 and 0.67, respectively). Further validation in a panel of gastric cancer cell (GC) lines (N=37) indicated that C-Score is significantly associated with IC50 value to fluorouracil. Mutation profiling showed that C-Score was associated with the number and types of mutations. In conclusion, we successfully simulated a predictive signature for the efficacy of AC in LAGC patients and further explored the potential mechanisms. Our findings could promote precision medicine and improve the prognosis of LAGC patients.

•

We successfully simulated a predictive signature for the efficacy of chemotherapy in LAGC patients and a GC cell line panel.

•

We further explored the potential mechanisms that it may be associated with the number and type of mutations.

•

Our findings could promote precision medicine and improve the prognosis of LAGC patients.

Comprehensive biomarker analyses identifies HER2, EGFR, MET RNA expression and thymidylate synthase 5'UTR SNP as predictors of benefit from S-1 adjuvant chemotherapy in Japanese patients with stage II/III gastric cancer

Purpose: A comprehensive molecular analysis was conducted to identify prognostic and predictive markers for adjuvant S-1 chemotherapy in stage II/III Japanese gastric cancer (GC) patients and to evaluate their potential suitability for alternative cytotoxic or targeted drugs.

Experimental Design: We investigated genetic polymorphisms of enzymes potentially involved in 5-fluoruracil (5-FU) metabolism as well as platinum resistance, previously identified genomic subtypes potentially predicting 5-FU benefit, and mRNA expression levels of receptor tyrosine kinases and KRAS as potential treatment targets in a single institution cohort of 252 stage II/III GC patients treated with or without S-1 after D2 gastrectomy.

Results: 88% and 62% GC had a potentially 5-FU sensitive phenotype by SNP analyses of TS 3'UTR, and TS 5'UTR, respectively. 24%, 46%, 40%, 5%, and 44% GC had a potentially platinum sensitive phenotype by SNP analyses of GSTP1, ERCC1 rs11615, ERCC1 rs3212986, ERCC2, and XRCC1, respectively. High HER2, EGFR, FGFR2, or MET mRNA expression was observed in 49%, 66%, 72%, and 54% GC, respectively. High HER2 expression was the only significant prognosticator (HR=3.912, 95%CI: 1.706-8.973, p=0.0005). High HER2 (p=0.031), low EGFR (p=0.124), high MET (p=0.165) RNA expression, and TS 5'UTR subtype 2R/2R, 2R/3C, or 3C (p=0.058) were significant independent predictors for S-1 resistance.

Conclusions: The present study suggests that platinum-based or RTK targeted agents could be alternative treatment options for a substantial subgroup of Japanese GC patients currently treated with S-1. HER2, EGFR, MET, and TS 5'UTR SNP appear to be promising predictive markers for S-1 resistance warranting validation in an independent GC series.

Tailored therapy in patients treated with fluoropyrimidines: focus on the role of dihydropyrimidine dehydrogenase

Fluoropyrimidines are widely used in the treatment of solid tumors, mainly gastrointestinal, head and neck and breast cancer. Dihydropyrimidine dehydrogenase (DPD) is the rate-limiting enzyme for catabolism of 5-FU and it is encoded by DPYD gene. To date, many known polymorphisms cause DPD deficiency and subsequent increase of 5-FU toxicity. In addition, reduced inactivation of 5-FU could lead to increased 5-FU intracellular concentration and augmented efficacy of this drugs. Therefore DPD expression, particularly intratumoral, has been investigated as predictive and prognostic marker in 5-FU treated patients. There also seems to be a tendency to support the correlation between DPD expression and response/survival in patients treated with fluoropyrimidine even if definitive conclusions cannot be drawn considering that some studies are conflicting. Therefore, the debate on intratumoral DPD expression as a potential predictor and prognostic marker in patients treated with fluoropyrimidines is still open. Four DPD-polymorphisms are the most relevant for their frequency in population and clinical relevance. Many studies demonstrate that treating a carrier of one of these polymorphisms with a full dose of fluoropyrimidine can expose patient to a severe, even life-threatening, toxicity. Severe toxicity is reduced if this kind of patients received a dose-adjustment after being genotyped. CPIC (Clinical Pharmacogenetics Implementation Consortium) is an International Consortium creating guidelines for facilitating use of pharmacogenetic tests for patient care and helps clinicians ensuring a safer drug delivery to the patient. Using predictive DPD deficiency tests in patients receiving 5FU-based chemotherapy, in particular for colorectal cancer, has proven to be a cost-effective strategy.

Expression of thymidylate synthase predicts clinical outcomes of S-1-based chemotherapy in squamous cell lung cancer

Non-small cell lung cancer (NSCLC) patients with squamous cell carcinoma (SCC) histology have limited chemotherapeutic options. Treatment with S-1 combined with carboplatin (CBDCA) has been shown to provide a significant survival benefit in SCC patients compared with treatment with combined CBDCA and paclitaxel. The aim of the present study was to investigate the association between the expression of molecular markers related to the pharmacological action of S-1, including thymidylate synthase (TS), orotate phosphoribosyltransferase (OPRT) and dihydropyrimidine dehydrogenase (DPD), and the clinical efficacy of S-1-based chemotherapy in SCC patients. The immunohistochemical expression of TS, OPRT and DPD were retrospectively analyzed in tumor biopsy and resection specimens from patients with advanced SCC (n=32). Immunohistochemical H-scores were calculated and their association with S-1/CBDCA response was evaluated. Median progression-free survival time was significantly longer in patients with low TS H-scores than in those with high TS H-scores (162.5 vs. 97 days; P=0.004); by contrast, overall survival time was not observed to differ significantly between these groups (P=0.185). In the multivariate analysis, low TS expression was a significant positive factor for progression-free survival rate (hazard ratio, 0.40; P=0.021). A low TS H-score was also associated with an increased response to S-1-based chemotherapy compared with a high TS H-score (P=0.002). This indicates that SCC patients with low TS expression can benefit significantly from S-1-based chemotherapy, and that H-score measurement of intratumoral TS expression may represent a useful predictive biomarker for response to S-1-based chemotherapy by patients with SCC-type NSCLC.

Intratumor dihydropyrimidine dehydrogenase mRNA expression levels are decreased in extramammary Paget's disease

S-1, a 5-fluorouracil (5-FU)-based anti-cancer agent, is an important drug for treating metastatic extramammary Paget's disease (EMPD). Although intratumor expression levels of 5-FU metabolism enzymes have been studied widely in many solid tumors, no studies have examined on the expression levels of thymidylate synthase (TS), orotate phosphoribosyl-transferase (OPRT) or dihydropyrimidine dehydrogenase (DPD) in skin cancers. The aim of this study was to estimate the intratumoral mRNA expression levels of these genes in EMPD by real time PCR. Intratumoral DPD mRNA levels were decreased in EMPD compared to those in normal skin, but its intratumoral DPD mRNA expression levels were not correlated with clinical manifestations. Intratumoral DPD mRNA levels were positively correlated with OPRT mRNA levels in EMPD. Based on these results, low expression of intratumoral DPD mRNA in EMPD may contribute to the pathogenesis of this disease.

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.

Phase II trial of S-1 plus leucovorin in patients with advanced gastric cancer and clinical prediction by S-1 pharmacogenetic pathway

Background

The first one-arm phase II trial aimed to evaluate and predict efficacy and safety of S-1 plus oral leucovorin (S-1/LV) as first-line chemotherapy for patients with advanced gastric cancer (AGC), using S-1 pharmacogenetic pathway approach.

Patients and methods

A total of 39 patients orally took S-1 at conventional dose and LV simultaneously at a dose of 25 mg twice daily for a week, within a 2-week cycle. The primary endpoint was overall response rate (ORR), while the secondary endpoints were progression-free survival (PFS), time to failure (TTF), overall survival (OS), disease control rate (DCR), and adverse events (AEs). Peripheral blood was sampled prospectively for baseline expression of dihydropyrimidine dehydrogenase (DPD), orotate phosphoribosyltransferase (OPRT), thymidine phosphorylase (TP), and thymidylate synthase (TS), CYP2A6 gene polymorphisms, and 5-FU pharmacokinetics.

Results

The ORR and DCR were 41.0 and 76.9%. The median PFS, TTF, and OS were 4.13, 3.70, and 11.40 months. Grade 3–4 AEs occurred in only 13 patients, and grade 4 AEs occurred in only 1 of them. High OPRT/TS and peritoneal metastasis (vs. liver metastasis) independently predicted responding. High OPRT/DPD independently predicted grade 3–4 AEs. High AUC_0–24h of 5-FU and metastatic/recurrent sites ≤2 (vs. >3) independently predicted prolonged PFS. Low baseline plasmic DPD independently predicted prolonged OS.

Conclusions

Two-week, oral S-1/LV regimen demonstrated promising efficacy and safety as first-line chemotherapy for AGC.

ClinicalTrials.gov identifier

NCT02090153

Electronic supplementary material

The online version of this article (doi:10.1007/s00280-016-3209-1) contains supplementary material, which is available to authorized users.

Current Development of Anti-Cancer Drug S-1

S-1 is a novel oral fluoropyrimidine derivative, widely used for treating gastric, pancreatic, lung, head, neck and breast carcinomas. It is designed to enhance the clinical utility of an oral fluoropyrimidine and is associated with low gastrointestinal toxicity. S-1 consists of three pharmacological agents (at a molar ratio of 1:0.4:1)-Tegafur (FT), a prodrug of 5-Fluorouracil (5-FU), 5-Chloro-2-4-Dihydroxypyridine (CDHP), which inhibits the activity of Dihydropyrimidine Dehydrogenase (DPD) and Oxonic Acid (Oxo), which reduces Gastrointestinal (GI) toxicity of 5-FU. The present article reviews the current development of clinical study of S-1.

High/positive expression of 5-fluorouracil metabolic enzymes predicts better response to S-1 in patients with gastric cancer: a meta-analysis

PURPOSE

To provide an assessment by meta-analysis of the relationship between the expression variations of 5-fluorouracil metabolic enzymes and clinical outcomes in patients with gastric cancer treated with S-1.

METHOD

Databases were searched electronically from inception to April 19th, 2015. Studies in gastric cancer patients treated with S-1 investigating the expression variations of 5-fluorouracil metabolic enzymes were included after having been identified systematically. Pooled odds ratios (OR) for the objective response rate (ORR) and median survival ratio were calculated using the Review Manager 5.3 and Stata 12.0 software separately.

RESULTS

A total of 555 patients in 10 studies met our inclusion criteria. There was a significant difference in ORR between patients with high/+ and low/- expression of orotate phosphoribosyl transferase (OPRT) (OR = 8.06; 95% CI, 4.06-16.02; p<0.001) and dihydropyrimidine dehydrogenase (DPD) (OR = 1.95; 95% CI, 1.21-3.13; p = 0.006). There was no significant difference in ORR between different expression levels of thymidylate synthase (TS) and thymidine phosphorylase (TP). Although patients with low/- TS expression, low/- TP expression and high/+ DPD expression showed a trend towards longer survival, no statistical significance was found. The median OS was significantly longer in patients with high/+ expression of OPRT (p = 0.076).

CONCLUSIONS

OPRT and DPD expression can be treated as a potential predictive biomarker for S-1 response in gastric cancer patients. Further investigation is warranted.

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.

How prognostic and predictive biomarkers are transforming our understanding and management of advanced gastric cancer

BACKGROUND

Gastric cancer (GC) is the second leading cause of cancer death worldwide. GC is a heterogeneous disease in terms of histology, anatomy, and epidemiology. There is also wide variability in how GC is treated in both the resectable and unresectable settings. Identification of prognostic and predictive biomarkers is critical to help direct and tailor therapy for this deadly disease.

METHODS

A literature search was done using Medline and MeSH terms for GC and predictive biomarkers and prognostic biomarkers. The search was limited to human subjects and the English language. There was no limit on dates. Published data and unpublished abstracts with clinical relevance were included.

RESULTS

Many potential prognostic and predictive biomarkers have been assessed for GC, some of which are becoming practice changing. This review is focused on clinically relevant biomarkers, including EGFR, HER2, various markers of angiogenesis, proto-oncogene MET, and the mammalian target of rapamycin.

CONCLUSION

GC is a deadly and heterogeneous disease for which biomarkers are beginning to change our understanding of prognosis and management. The recognition of predictive biomarkers, such as HER2 and vascular endothelial growth factor, has been an exciting development in the management of GC, validating the use of targeted drugs trastuzumab and ramucirumab. MET is another potential predictive marker that may be targeted in GC with drugs such as rilotumumab, foretinib, and crizotinib. Further identification and validation of prognostic and predictive biomarkers has the potential transform how this deadly disease is managed.

Gastric cancer pharmacogenetics: progress or old tripe?

Gastric cancer remains the second most frequent cause of cancer-related mortality. While surgery is traditionally the initial treatment for early-stage disease, the addition of chemotherapy has been shown to significantly increase overall survival and progression-free survival in advanced and metastatic stages of disease. However, despite the incorporation of newer chemotherapies and regimens into gastric cancer clinical trials, the response rate and median overall survival for treated patients has not significantly improved throughout the years; therefore, newer therapeutic approaches to improve upon the medication selection process are warranted. Treatment and dose selection based on patient factors, such as genetic variation, may provide a more rational and potentially more powerful means of personalizing chemotherapy. This review provides an update on the current status of pharmacogenetic studies regarding germline DNA mutations that may alter response to chemotherapeutic agents used to treat gastric cancer, including perspectives on clinical translation and future work.

Relapse-associated microRNA in gastric cancer patients after S-1 adjuvant chemotherapy

S-1 has been recommended as adjuvant chemotherapy in patients after curative surgery for gastric cancer. However, some patients suffer recurrence even after S-1 adjuvant chemotherapy. The present study was conducted to find a predictive marker of the efficacy of S-1 adjuvant chemotherapy. We examined the microRNA (miRNA) expression of 35 patients who underwent S-1 adjuvant chemotherapy after curative surgery (R0) for pathological stage II or III gastric cancer. miRNAs were extracted from formalin-fixed, paraffin-embedded specimens for analysis and miRNA expression was examined using miRNA oligo chips. Fifteen patients relapsed and 20 did not over 5 years. Five miRNAs (miR-92b, 422a, 4732-5p, 4758-3p and 221) were highly expressed according to the tumor/normal (T/N) ratio in the patients who relapsed but not in those who did not relapse (P-value <0.05) by microarray analysis. If tumors showed high expression of 4 miRNAs (miR-92b, 422a, 4732-5p and 4758-3p) their positive predictive value of relapse was 93.8% and negative predictive value was 92.3%. In this case, their disease-free survival rate and overall survival rate were very poor. Our findings indicate that miR-92b, miR‑422a, miR-4732-5p and miR-4758-3p are closely associated with relapse following S-1 adjuvant chemotherapy in gastric cancer.

Final results of a phase II study of S-1 in patients with cytokine-refractory metastatic renal cell carcinoma

OBJECTIVE

A planned primary analysis of a Phase II study of S-1 demonstrated that the drug was active and tolerable in Japanese patients with cytokine-refractory metastatic renal cell carcinoma. Furthermore, pharmacogenomic analysis suggested that low expression of thymidylate synthase mRNA may have been associated with clinical outcome in terms of overall response rate and progression-free survival. Here, we report the results of the final analysis assessing the efficacy and safety of S-1 including overall survival.

METHODS

Patients with renal cell carcinoma were eligible if they had had at least one regimen of cytokine for metastatic disease. S-1 was orally administered on Days 1-28 of a 42-day cycle until disease progression. The primary endpoint was the overall response rate, and the secondary endpoint included progression-free survival, overall survival and safety.

RESULTS

A total of 45 patients were treated with S-1 and were fully assessable for efficacy and safety. At the final analysis, a response was seen in 11 patients (overall response rate, 24.4%; 95% confidence interval: 12.9-39.5%), including two patients who achieved a complete response. The final median progression-free and overall survival were 9.2 and 42.8 months, respectively. The safety profile of S-1 was favorable. It was suggested that there was no relation between overall survival and the expression level of thymidylate synthase.

CONCLUSION

This final analysis confirms that S-1 treatment is effective and safe in patients with cytokine-refractory renal cell carcinoma.

Impact of excision repair cross-complementing gene 1 (ERCC1) on the outcomes of patients with advanced gastric cancer: correlative study in Japan Clinical Oncology Group Trial JCOG9912

BACKGROUND

Since the best chemotherapy regimen for each patient with advanced gastric cancer is uncertain, we aimed to identify molecular prognostic or predictive biomarkers from biopsy specimens in JCOG9912, a randomized phase III trial for advanced gastric cancer.

PATIENTS AND METHODS

Endoscopic biopsy specimens from primary lesions were collected in 445 of 704 randomized patients in JCOG9912. We measured the mRNA expression of excision repair cross-complementing group 1 (ERCC1), thymidylate synthase, dihydropyrimidine dehydrogenase, and five other genes, then, categorized them into low and high groups relative to the median, and examined whether gene expression was associated with efficacy end point.

RESULTS

Multivariate analyses showed that high ERCC1 expression [HR 1.37; 95% confidence interval (CI) 1.08-1.75; P = 0.010], performance status ≥ 1 (HR 1.45; 95% CI 1.13-1.86; P = 0.004), and number of metastatic sites ≥ 2 (HR 1.66; 95% CI 1.28-1.86; P < 0.001) were associated with a poor prognosis, and recurrent disease (versus unresectable; HR 0.75; 95% CI 0.56-1.00; P = 0.049) was associated with a favorable prognosis. None of these molecular factors were a predictive marker for choosing irinotecan plus cisplatin or 5-fluorouracil rather than S-1.

CONCLUSION

These correlative analyses suggest that ERCC1 is an independent prognostic factor for overall survival in the first-line treatment of gastric cancer.

CLINICAL TRIAL NUMBER

C000000062, www.umin.ac.jp.

Molecular biomarkers in esophageal, gastric, and colorectal adenocarcinoma

Cancers of the esophagus, stomach and colon contribute to a major health burden worldwide and over 20% of all cancer deaths. Biomarkers that should indicate pathogenic process and are measureable in an objective manner for these tumors are rare and not established in the clinical setting. In general biomarkers can be very useful for cancer management as they can improve clinical decision-making regarding diagnosis, surveillance, and therapy. Biomarkers can be different types of molecular entities (such as DNA, RNA or proteins), which can be detected, in different tissues or body fluids. However, more important is the type of biomarker itself, which allows diagnostic, prognostic or predictive analyses for different clinical problems. This review aims to systematically summarize the recent findings of genetic and epigenetic markers for gastrointestinal tumors within the last decade. While many biomarkers seem to be very promising, especially if used as panels, further development is urgently needed to address practical considerations of biomarkers in cancer treatment.

TMEM158 and FBLP1 as novel marker genes of cisplatin sensitivity in non-small cell lung cancer cells

Even after development of molecular targeting therapies, platinum-based chemotherapy is still a standard care for treatment of locally advanced non-small cell lung cancer (NSCLC). So far, critical molecular markers capable to predict the therapeutic response in NSCLC patients remain undetermined. We here attempted to identify novel biomarker genes for cisplatin (CDDP) for a tailored therapy. Initial screening to explorer association of IC(50) values of CDDP obtained by MTT assay and gene expression levels measured with oligonucleotide microarray and real-time RT-PCR provided 6 candidate genes, namely, NUBPL, C9orf30, ZNF12, TMEM158, GSK3B, and FBLP1 using 9 lung cancer cells consisting of 3 small and 6 NSCLC cells. These 6 genes together with 5 reported biomarkers, i.e., GSTP1, ERCC1, BRCA1, FRAP1, and RRM1, were subjected to a linear regression analysis using 12 NSCLC cell lines including 6 additional NSCLC cells: only FBLP1 and TMEM158 genes showed positive associations with statistical significances (P = .016 and .026, respectively). The biological significance of these genes was explored by in vitro experiments: Knockdown experiments in PC-9/CDDP cells revealed that the reduced expression of TMEM158 significantly decreased the chemo-resistance against CDDP (P <.0001), while 2 transformants of PC-6 cells stably over-expressing FBLP1 resulted in an enhanced resistance to CDDP (P = .004 and P = .001). Furthermore, a stepwise multiple regression analysis demonstrated the best prediction formula could be fixed when we used expression data of TMEM158 and FBLP1 (R(2) = 0.755, P = .0018). TMEM158 and FBLP1 may be powerful predictive biomarkers for CDDP therapy in NSCLC.

Evaluation of prognostic factors for the response to S-1 in patients with stage II or III advanced gastric cancer who underwent gastrectomy

OBJECTIVES

Many studies have reported that low intratumoral mRNA expression of thymidylate synthase (TS) is an important biomarker of response to chemotherapy in patients with unresectable advanced gastric cancer. However, the role of gene expression profile of patients who received postoperative adjuvant chemotherapy remains unclear. In this study, we evaluated how TS and other associated genes related to outcome.

METHODS

Seventy-nine patients with stage II or III advanced gastric cancer who underwent gastrectomy were analyzed. Thirty-nine patients received adjuvant chemotherapy with S-1 after surgery (S-1 group) and 40 patients underwent surgery only (surgery group). Formalin-fixed, paraffin-embedded tumor tissues were dissected by the laser-captured microdissection technique and analyzed for target gene expressions using a quantitative real-time polymerase chain reaction.

RESULTS

There were no significant differences between the S-1 group and the surgery group in gene expressions except TS (P=0.034). In the S-1 group, recurrence-free survival (RFS) and overall survival (OS) were significantly longer in patients with low TS expression compared with patients with high TS expression (P=0.021 and 0.016), whereas there were no correlations in the surgery group. Furthermore, RFS and OS were both correlated with extent of lymph node metastasis (N) (P=0.038 and 0.020) and TS expression (P=0.021 and 0.032). On multivariate analysis it was found that TS expression and N were significant independent prognostic factors of RFS and OS (TS: P=0.027 and 0.050, N: P=0.048 and 0.032).

CONCLUSION

Our results suggested that intratumoral TS expression is an independent prognostic factor in patients with gastric cancer who received postoperative adjuvant chemotherapy with S-1.

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.

Predictive value of thymidylate synthase expression in gastric cancer: a systematic review with meta-analysis

PURPOSE

The relationship between thymidylate synthase (TS) expression and outcomes in gastric cancer (GC) patients remains controversial, although most studies reported poor survival and reduced response to fluoropyrimidine were related to high TS in tumors. We carried out a systematic review of the literature with meta-analysis to estimate the predictive value of TS expression from published studies.

METHODS

We identified 24 studies analysing the outcome data in gastric cancer stratified by TS expression. Effect measures of outcome were hazard ratios (HRs) for overall survival (OS) and event-free survival (EFS), or the odds ratio (OR) for overall response rate (ORR). HRs and ORs from these eligible studies were pooled using random-effects meta- analysis.

RESULTS

Fifteen studies investigated outcomes in a total of 844 patients with advanced GC, and nine studies investigated outcomes in a total of 1,235 patients with localized GC undergoing adjuvant therapy. Meta- analysis of estimates showed high TS expression was significantly associated with poor OS in the advanced setting (HR: 1.43, 95%CI: 1.08 - 1.90), and poor EFS in the adjuvant setting (HR: 1.53, 95%CI: 1.01 - 2.32). Subgroup analysis demonstrated TS expression to have even greater value in predicting OS, EFS and ORR in advanced GC patients treated with fluoropyrimidine monotherapy (HR for OS: 2.32, 95%CI: 1.53 - 3.50; HR for EFS: 1.76, 95%CI: 1.19 - 2.60; OR for ORR: 0.32, 95%CI: 0.11 - 0.95).

CONCLUSION

High levels of TS expression were associated with a poorer OS for advanced GC patients compared with low levels. In the adjuvant setting, high TS expression was also associated with a worse EFS. Additional studies with consistent methodology are needed to define the precise predictive value of TS.

Novel mRNA isoforms and mutations of uridine monophosphate synthetase and 5-fluorouracil resistance in colorectal cancer

The drug fluorouracil (5-FU) is a widely used antimetabolite chemotherapy in the treatment of colorectal cancer. The gene uridine monophosphate synthetase (UMPS) is thought to be primarily responsible for conversion of 5-FU to active anticancer metabolites in tumor cells. Mutation or aberrant expression of UMPS may contribute to 5-FU resistance during treatment. We undertook a characterization of UMPS mRNA isoform expression and sequence variation in 5-FU-resistant cell lines and drug-naive or -exposed primary and metastatic tumors. We observed reciprocal differential expression of two UMPS isoforms in a colorectal cancer cell line with acquired 5-FU resistance relative to the 5-FU-sensitive cell line from which it was derived. A novel isoform arising as a consequence of exon skipping was increased in abundance in resistant cells. The underlying mechanism responsible for this shift in isoform expression was determined to be a heterozygous splice site mutation acquired in the resistant cell line. We developed sequencing and expression assays to specifically detect alternative UMPS isoforms and used these to determine that UMPS was recurrently disrupted by mutations and aberrant splicing in additional 5-FU-resistant colorectal cancer cell lines and colorectal tumors. The observed mutations, aberrant splicing and downregulation of UMPS represent novel mechanisms for acquired 5-FU resistance in colorectal cancer.

CYP2A6 and ERCC1 polymorphisms correlate with efficacy of S-1 plus cisplatin in metastatic gastric cancer patients

Background:

We evaluated the association between polymorphisms of cytochrome P450 2A6 (CYP2A6)/excision repair cross-complementation group 1 (ERCC1)/X-ray repair cross-complementing group 1(XRCC1) and treatment outcomes of metastatic gastric cancer (MGC) patients treated with S-1/cisplatin.

Methods:

Among MGC patients (n=108), who received S-1 (40 mg m⁻² b.i.d., days 1–14) and cisplatin (60 mg m⁻², day 1) every 3 weeks, we analysed the wild-type allele (W) and variants (V) of CYP2A6 (*4, *7, *9, *10), and the polymorphisms of ERCC1 (rs11615, rs3212986) and XRCC1 (rs25487).

Results:

Patients having fewer CYP2A6 variants had better response rates (W/W vs W/V other than *1/*4 vs V/V or *1/*4=66.7 vs 58.3 vs 32.3% P=0.008), time to progression (TTP) (7.2 vs 6.1 vs 3.5 months, P=0.021), and overall survival (23.2 vs 15.4 vs 12.0 months, P=0.004). ERCC1 19442C>A (rs3212986) was also associated with response rate (C/C, 46.7% vs C/A, 55.3% vs A/A, 87.5%) (P=0.048) and TTP (4.4 vs 7.6 vs 7.9 months) (P=0.012). Patients carrying both risk genotypes of CYP2A6 (V/V or 1/*4) and ERCC1 19442C>A (C/C) vs those carrying none showed an adjusted odds ratio of 0.113 (P=0.004) for response, and adjusted hazard ratios of 3.748 (P=0.0001) for TTP and 2.961 (P=0.006) for death.

Conclusion:

Polymorphisms of CYP2A6 and ERCC1 19442C>A correlated with the efficacy of S-1/cisplatin.

Relationship between gene expression of 5-fluorouracil metabolic enzymes and 5-fluorouracil sensitivity in primary cancer cells isolated from malignant ascites

This study was designed to investigate the predictive role of 5-FU metabolic enzymes in malignant ascites. Forty-three malignant ascites were collected and primary cancer cells were isolated. Gene expression was detected by quantitative RT-PCR. We found that DPD mRNA was higher in patients with pancreatic cancers than those with gastric cancers, colon cancers, and liver cancers. Significant correlations were found between expression of DPD and TP, and between TS and OPRT. mRNA levels of TS and OPRT correlated significantly with the chemosensitivity of 5-FU. Assessing gene expression would be useful in predicting 5-FU sensitivity for patients with malignant ascites.

Multicenter Phase II Trial of S-1 in Patients With Cytokine-Refractory Metastatic Renal Cell Carcinoma

Purpose

This phase II multicenter trial was conducted to evaluate the activity and safety of S-1 in Japanese patients with metastatic renal cell carcinoma (mRCC). We also examined the relation between response and mRNA expression levels of enzymes involved in the metabolism of fluorouracil (FU).

Methods

Patients with mRCC who had received nephrectomy in whom cytokine-based immunotherapy was ineffective or contraindicated were studied. S-1 was administered orally at 80-, 100-, or 120-mg daily, assigned according to body surface area, on days 1 to 28 of a 42-day cycle. The primary end point was the objective response rate. The mRNA expression levels of FU-related enzymes were measured by reverse-transcriptase polymerase chain reaction in formalin-fixed, paraffin-embedded specimens of tumors obtained at nephrectomy.

Results

A total of 45 eligible patients were enrolled. Eleven (24.4%) of 45 patients had partial responses to S-1, and 28 (62.2%) had stable disease. Median progression-free survival was 9.2 months. The severity of most adverse events was mild to moderate. The most common grade 3/4 drug-related adverse events were neutropenia (8.9%) and anorexia (8.9%). The expression level of thymidylate synthase (TS) mRNA was significantly lower in patients who responded to treatment (t-test, P = .048), and progression-free survival was significantly longer in patients whose TS mRNA expression levels were below the median value, as compared with those with higher levels (log-rank test, P = .006).

Conclusion

S-1 is active against cytokine-refractory mRCC. Quantification of TS mRNA levels in tumors before treatment may facilitate prediction of the response of mRCC to S-1.

A predictive factor for the response to S-1 plus cisplatin in gastric cancer

AIM: To prove that the protein expression level of thymidylate synthase is a predictive factor for the response to S-1/cisplatin (CDDP) chemotherapy in gastric cancer.

METHODS: We measured the protein expression levels of thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD), and orotate phosphoribosyltransferase (OPRT) in advanced gastric cancer. Before S-1/CDDP chemotherapy, tumor specimens from primary sites were obtained by endoscopic biopsy and analyzed by enzyme-linked immunosorbent assay. The chemotherapeutic effects on the primary sites were evaluated by endoscopic biopsy performed more than once after S-1/CDDP chemotherapy. The effects are a predictive factor for the response to S-1/CDDP chemotherapy in patients with advanced gastric cancer, as evaluated by endoscopic biopsy over time.

RESULTS: The protein expression level of TS was significantly higher (P < 0.05) in the tumor than in the normal tissue, and significantly lower (P < 0.05) in the responders than in the non-responders. We were able to evaluate the correlation between changes in the protein expression levels of TS, DPD and OPRT and chemotherapeutic responses in 7 patients by assessing tumor tissues more than twice. In the responders, the protein expression level of TS was < 40 ng/mg protein. However, there were significant increases in the protein expression levels of TS (P < 0.01) and DPD (P < 0.05) after chemotherapy in 3 patients. In these cases, the patient assessment changed from “responder” to “non-responder”. In the non-responders, the protein expression level of TS was > 40 ng/mg protein.

CONCLUSION: We have confirmed that the protein expression level of TS is a predictive factor for the response to S-1/CDDP chemotherapy in patients with advanced gastric cancer.

Possibility of using mRNA expression levels for nucleic acid-metabolizing enzymes within prostate cancer cells as indices for prognostic factors

Thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD), thymidine phosphorylase (TP) and orotate phosphoribosyl transferase (OPRT) are enzymes involved in nucleic acid metabolism. It has been reported (based on observations of various tumor types) that the extent of the mRNA expression of these enzymes within tumor tissues may be used as a factor to define tumor prognosis. It has also been reported that the mRNA expression patterns differ in each type of tumor. However, few reports are available on the distribution of mRNA expression in prostate cancers. This study was conducted on tissue specimens obtained from 172 patients who were diagnosed with prostate cancer and had undergone total prostatectomies. The mRNA expression of TS, DPD, OPRT and TP was quantitatively analyzed using the Danenberg tumor profile (DTP) method. The results were used to examine the correlations between the distributions of the mRNAs and clinicopathological factors, as well as the significance of their expression as a prognostic factor. Patients with poorly differentiated cancers in their tissues showed a significant increase in the mRNA expression of TS and OPRT. The increases in the TP mRNA content were proportional to an increase in the Gleason scores. The prognosis was significantly poorer in those cases with a high expression of TS or OPRT mRNA and a low expression of DPD mRNA. In conclusion, the expression levels of mRNAs for TS, DPD and OPRT among the enzymes related to nucleic acid metabolism are useful as prognostic factors in patients with prostate cancers.

Biomarker analysis in patients with advanced gastric cancer treated with S-1 plus cisplatin chemotherapy: orotate phosphoribosyltransferase expression is associated with treatment outcomes

This study was performed to analyze the impact of protein expression related to fluoropyrimidine and cisplatin metabolism (thymidylate synthase, dihydropyrimidine dehydrogenase, thymidine phosphorylase, orotate phosphoribosyltransferase [OPRT], excision repair cross-complementation 1, Fanconi anemia complementation group D2, glutathione S-transferase P1, and X-ray repair cross-complementing group 1) on treatment outcomes in patients with metastatic or relapsed gastric cancer (MRGC) receiving S-1/cisplatin chemotherapy. Protein expression was measured by immunohistochemistry (IHC). Of the 43 patients who had received S-1 (80 mg/m2/day; days 1-14) and cisplatin (60 mg/m2; day 1) every 3 weeks and had available tissue blocks, IHC was successfully performed in 41 patients. Patients with high OPRT levels in tumor tissues (IHC score≥6) had superior progression-free survival (PFS) (23.3 vs. 14.1 weeks [median]) and overall survival (OS) (72.4 vs. 55.4 weeks [median]) to those with low OPRT levels (IHC score≤5; P-values<.05). Expression levels of other proteins were not predictive of treatment outcomes. In multivariate analysis, both a good performance status and a high OPRT level were independently associated with prolonged PFS and OS. The OPRT expression level may be a good predictive marker in S-1/cisplatin-treated patients with MRGC.

Impacts of fluorouracil-metabolizing enzymes on the outcomes of patients treated with S-1 alone or S-1 plus cisplatin for first-line treatment of advanced gastric cancer

A phase III trial of S-1 plus cisplatin (SP) versus S-1 alone, for first-line treatment of advanced gastric cancer (SPIRITS trial), has shown that overall survival was better in patients treated with SP than with S-1 alone. In the present retrospective biomarker study, we aimed to develop a methodology to identify the patients with advanced gastric cancer who would respond better to S-1 alone than SP. We studied 120 patients who received S-1 alone or SP for first-line chemotherapy for advanced gastric cancer, and quantitatively evaluated mRNA levels of thymidylate synthase (TS), thymidine phosphorylase (TP), orotate phosphoribosyltransferase (OPRT), dihydropyrimidine dehydrogenase, vascular endothelial growth factor-A, and epidermal growth factor receptor in paraffin-embedded specimens of primary tumors. Multivariate survival analysis in patients who received S-1 monotherapy (66 patients) demonstrated that low TP expression (hazard ratio: 2.55 (95% CI: (1.33 to 4.89)), low TS (2.71 (1.36 to 5.37)), and high OPRT (0.33 (0.13 to 0.86)) were significant predictors of long overall survival. In patients with lower expression of both TP and TS (n = 23) than their cutoff values, the S-1 alone group (n = 15) had longer overall survival than the SP group (n = 8; median overall survival, 18.2 months vs. 9.4 months), whereas the frequency of overall adverse events in the S-1 alone group tended to be lower than that in SP group. Our results suggest that these biomarkers are useful for selection of patients with advanced gastric cancer in whom treatment with S-1 alone will yield survival benefit.

Apocrine metaplasia of breast cancer: clinicopathological features and predicting response

BACKGROUND

Tailor-made therapies are currently gaining prominence, and the clarification of predictive markers for anticancer agents represents an important research issue. From our institutional neoadjuvant experience, apocrine carcinoma showed a high correlation with therapeutic effect against breast cancer. We thus considered that apocrine metaplasia (AM) might represent a predictive marker for breast cancer.

METHODS

A total of 210 primary invasive breast cancers from Japanese patients were scored according to the size of cytoplasmic granules and abundance of cytoplasm, then classified into three categories: non-AM, incomplete AM and complete AM. Clinicopathological features were evaluated based on these classifications.

RESULTS

Distribution according to the classification of AM was: non-AM, 61%; incomplete AM, 36%; and complete AM, 3%. No significant differences with regard to estrogen receptor, progesterone receptor, human epidermal growth factor receptor type 2, androgen receptor or bcl-2 were observed among the three groups. Gross cystic fluid protein-15 showed a high positive rate (83%) for complete AM. Cases of incomplete AM and complete AM were combined to form the AM group. Among lymph node-positive patients without chemotherapy, the 10-year recurrence-free survival (RFS) rate was 85% for non-AM and 44% for AM (p < 0.05). Conversely, among the lymph node-positive group with chemotherapy, the 10-year RFS rate was 45% for non-AM and 75% for AM (p < 0.05). Prognoses for non-AM and AM were turned around by chemotherapy. Lymph node metastasis was related to prognosis in multivariate analysis, although AM did not remain an independent prognosticator.

CONCLUSIONS

Apocrine metaplasia appears to offer an effective predictive marker for anticancer therapy.

A long-time survivor of alpha-fetoprotein-producing gastric cancer successfully treated by fluoropyrimidine-based chemotherapy: a case study

A 67-year-old male with advanced gastric cancer and lymph node metastasis as well as a tumor embolus in the portal vein was treated by S-1/cisplatin therapy. The serum alpha-fetoprotein levels were elevated to 836 ng/ml at the first visit. After one course of chemotherapy, the patient showed stable disease; the serum level of alpha-fetoprotein also decreased to 626 ng/ml after a transient increase, and therefore reduction surgery was performed. A total gastrectomy with a distal pancreatectomy, splenectomy, and regional lymph node dissection was performed. The resected specimen was diagnosed to be alpha-fetoprotein-producing gastric cancer. There were no metastatic foci in the resected lymph nodes, presumably due to the preoperative chemotherapy. S-1/cisplatin therapy was continued after the operation to treat the remaining tumor embolus in the portal vein. After one course of this therapy, the tumor embolus disappeared. However, a lymph node measuring 1.5 cm in diameter appeared in the hepatoduodenal ligament. Therefore, the chemotherapy was changed to paclitaxel monotherapy. After 2 courses of paclitaxel monotherapy, the lymph node swelled, and thus 5'-deoxy-5-fluorouridine was added to the paclitaxel regimen. After 5 courses of this regimen, the lymph node swelling disappeared without any other new lesions and a total of 21 courses were performed. The patient remained stable for over 8 years without recurrence. The expression of chemoresistance-related proteins was retrospectively analyzed by immunohistochemistry to evaluate the chemoresistance. The ortate phosphoribosyltransferase expression was strongly positive, and the good outcome in this case may have been associated with this result.

Pharmacokinetics and pharmacogenomics in gastric cancer chemotherapy

Despite extensive efforts, treatment of gastric cancer by chemotherapy, the globally accepted standard, is yet undetermined, and uncertainty remains regarding the optimal regimen. Recent introduction of active "new generation agents" offers hope for improving patient outcomes. Current chemotherapeutic trials provided several regimens that may become a possible standard treatment, including docetaxel/cisplatin/5-FU (TCF) and cisplatin/S-1 for advanced and metastatic cancer and S-1 monotherapy in the adjuvant setting. Along with the development of novel active regimens, individual optimization of cancer chemotherapy has been attempted in order to reduce toxicity and enhance tumor response. Unlike the rare and limited contribution of pharmacokinetic studies, pharmacogenomic studies are increasing the potential to realize the therapeutics against gastric cancer. Despite the limited data, pharmacogenomics in gastric cancer have provided a number of putative biomarkers for the prediction of tumor response to chemotherapies and of toxicity.

Higher expression of deoxyuridine triphosphatase (dUTPase) may predict the metastasis potential of colorectal cancer

Aims:

5-Fluorouracil (5-FU) is one of the most widely used anticancer drugs; however, the activity of 5-FU is determined by the presence of several enzymes that limit its activation or degradation, and these include dihydropyrimidine dehydrogenase (DPD), orotate phosphoribosyl transferase (OPRT), thymidylate synthase (TS), thymidine kinase (TK), thymidine phosphorylase (TP) and deoxyuridine triphosphatase (dUTPase). The aim of this study was to compare the expression levels of these enzymes between the primary colorectal cancer of patients with and without distant metastases. Furthermore, there was a comparison of these expression levels between the primary tumour and the corresponding metastasis.

Methods:

Of 55 patients with colorectal cancer, 20 had no metastasis and the other 35 had distant metastasis. A strong expression was classified as positive, while weak to moderate or no expression was negative by immunohistochemistry.

Results:

Of the six 5-FU-related enzymes, the numbers of patients with expression of dUTPase (54% versus 15%; p = 0.005), TK (26% versus 0%; p = 0.019) and DPD (17% versus 45%; p = 0.033) were significantly different in those with primary tumours with metastasis compared with those with non-metastasis, respectively. The altered expression of OPRT (34.3%), TS (40.0%) and dUTPase (42.9%) was significantly greater from primary to metastasis among the 35 patients with metastasis. By contrast, the expression of OPRT, TS and dUTPase was decreased in 6, 5 and 7 patients, respectively, in metastatic sites.

Conclusions:

From this comparative study of the six 5-FU-related enzymes in colorectal cancer, the expression of dUTPase was most significantly different between primary tumours and their corresponding metastatic tumour. It is suggested that dUTPase may be a predictive biomarker for the metastatic potential of colorectal cancer.

Challenge for a better combination with basic evidence

5-Fluorouracil (5-FU) has been the most widely accepted and studied chemotherapeutic agent, and many combination chemotherapeutic regimens have been reported. However, until recently, a standard regimen for metastatic gastric cancer had not been established. The combination of S-1 and cisplatin is a good candidate as a standard first-line regimen for metastatic gastric cancer. On the other hand, interest in biochemical modulation has become wide spread recently. The low level of dihydropyrimidine denhydrogenase (DPD), thymidylate synthase (TS) activities, and a high level of orotate phosphoribosyl-transferase (OPRT) activity enhance the antitumor effect of 5-FU and S-1. Docetaxel is one of the agents that modulate these enzyme expressions and activities. Moreover, the response rate of combination therapy of docetaxel and S-1 for metastatic gastric cancer was 56.3% and median survival time was 14.3 months in a phase II study, showing it to be a good candidate for a new standard regimen for gastric cancer. A phase III collaborative study, START (S-1 and Taxotere for advanced gastric cancer randomized phase III trial), is now under way in Japan and Korea.

Evaluating the drug-target relationship between thymidylate synthase expression and tumor response to 5-fluorouracil. Is it time to move forward?

Thymidylate synthase is a target of 5-fluoruracil, a pyrimidine analog used to treat gastrointestinal and other cancers. The 5-fluorouracil metabolite, fluoro-deoxyuridine monophosphate, forms a ternary complex with thymidylate synthase and 5,10-methylene tetrahydrofolate. The purpose of this study was to evaluate the time-honored connection between thymidylate synthase and 5-fluorouracil. From our literature search spanning reports from 1995 to 2007 published in journals having an impact factor greater than 2, we stratified the tumors within each article, according to low versus high thymidylate synthase expression. These groups were subdivided into responders, stable disease or disease progression. The relationship between thymidylate synthase expression and 5-fluorouracil response was analyzed for the overall group, as well as for subsets. Overall, the literature supported an approximately 2-fold inverse relationship between thymidylate synthase expression and response to 5-fluoruracil. We found no change in the trend for a relationship between thymidylate synthase and 5-fluorouracil when the literature was stratified by date of publication, impact factor of the journal in which the report was published, or substrate (mRNA versus protein) for measuring thymidylate synthase expression. Of note, there is no significant change in the trend when comparing 5-fluorouracil treatment alone or in combination with leucovorin. We found a decline of this trend when certain chemotherapeutics were used in combination with 5-fluorouracil. In sum, the connection between thymidylate synthase expression and patient response to 5-fluorouracil does not satisfy expectations for an effective drug-target relationship; and thus, studies of the thymidylate synthase tandem repeat status might only be clinically valuable in regards to patient toxicity. Thus, we question the reliability of thymidylate synthase expression as a clinical predictor of 5-fluorouracil response. Future research could perhaps be directed towards alternate targets and metabolites of 5-fluorouracil, in an effort to find a clinically relevant biomarker panel for response and to optimize fluoropyrimidine-based therapy.

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.

How do we improve outcomes for gastric cancer?

Although the incidence of gastric cancer is decreasing globally, it remains the second leading cause of cancer death, accounting for 600,000 deaths annually worldwide. It is particularly common in Asia and especially in China, Japan and Korea. In Singapore, it is the fourth commonest cancer in men, who have a 1:50 lifetime risk of developing gastric cancer. Gastric cancer traditionally carries a poor prognosis because of late presentation at an advanced stage of disease. If diagnosed at an early stage, it is a curable disease. Four strategies will systematically help to improve outcomes for gastric cancer: (i) early detection by screening of high-risk groups; (ii) clarification of the hypothesis that Helicobacter pylori eradication in endemic areas with a high incidence of gastric cancer is an effective primary prevention strategy; (iii) improvement of treatment by well-designed clinical trials, coupled with molecular characterization of tumors; and (iv) improving our biological understanding of gastric carcinogenesis.

Overexpression of the Orotate Phosphoribosyl-Transferase Gene Enhances the Effect of 5-Fluorouracil on Gastric Cancer Cell Lines

OBJECTIVE

Orotate phosphoribosyl-transferase (OPRT) is the initial enzyme of the 5-fluorouracil (5-FU) metabolic pathway, converting 5-FU into 5-fluorouridinemonophosphate, which is the most important mechanism of 5-FU activation. We therefore investigated whether overexpression of the OPRT gene enhances sensitivity to 5-FU.

METHODS

An expression vector of the OPRT gene (pTARGET-OPRT) was transfected into two gastric cancer cell lines, TMK-1 and MKN-45, with low baseline expression levels of OPRT. The sensitivity to and anti-tumor activity of 5-FU were then investigated in vitro and in vivo in these two transfected clones (TMK-OPRT and MKN-OPRT).

RESULTS

Although cell growth was unaltered compared to parent cells, overexpression of the OPRT gene was confirmed by Western blotting in both the TMK-OPRT and MKN-OPRT cells. OPRT enzyme activity increased 38-fold in TMK-OPRT cells and 8.0 fold in MKN-OPRT cells compared to their parent cells. Interestingly, although the sensitivity to Adriamycin, cis-platinum, mitomycin C and paclitaxel was unaltered in the transfected clones, the sensitivity to 5-FU was increased 14.2- and 6.0-fold in TMK-OPRT and MKN-OPRT cells, respectively, compared to their parent cells. Moreover, enhanced sensitivity was also confirmed in the in vivo study.

CONCLUSION

The results indicate that overexpression of the OPRT gene plays an important role in the antiproliferative effect of 5-FU and might therefore be a predictive factor of response to 5-FU in gastric cancer patients.