Thymidylate synthase expression in stage II and III colon cancer: a retrospective review

Implications of Circadian Rhythm Regulation by microRNAs in Colorectal Cancer

Aim

To establish a connection between microRNA (miRNAs), circadian rhythm, and colorectal cancer patient survival.

Methods

Genomic and clinical data were extracted from The Cancer Genome Atlas (TCGA) colorectal cancer database, and the expression levels of candidate miRNAs and a set of circadian rhythm-related genes (Per1, Per2, Per3, Bmal1), and genes associated with chemosensitivity (thymidylate synthase, dihydrofolate reductase) were assessed for any correlations among their expression. In addition, survival analyses specific to different colorectal cancer stages were performed to determine if these genes contribute to patient outcomes.

Results

Significant inverse correlation between the expression of Per1 and that of miR-192 and miR-194 was observed. In survival analyses, high miR-192 and miR-194 correlate with better overall survival in Stage II patients, but worse survival in more advanced Stage III/IV patients. The expression of Per1, but Per2 or Bmal1, is marginally associated with patient survival for Stage II patients. Low thymidylate synthase expression correlates with better overall survival in Stage II patients but worse survival in Stage III/IV patients.

Conclusion

This study establishes a foundation based on a large genomic database of colorectal cancer, for further investigation into the importance of regulatory mechanisms of circadian rhythm by miRNAs in colorectal cancer.

Thymidylate synthase expression and prognosis in colorectal cancer: a meta-analysis of colorectal cancer survival data

BACKGROUND

Although many studies have investigated the prognostic effect of thymidylate synthase (TS) in colorectal cancer, no consensus has been reached. The aim of this meta-analysis was to obtain a more precise estimate of the prognostic significance of TS expression in localized cancers treated by curative resection and adjuvant chemotherapy.

MATERIALS AND METHOD

Seventeen eligible studies reporting survival in 2,893 patients stratified by TS expression were pooled using a fixed- or random-effects model. The main outcome measure was hazard ratio (HR).

RESULTS

The overall HR for overall survival was 1.01 (95% CI 0.74-1.39, p=0.947), with an I2 of 64.4%. The total HR for disease-free survival was 1.36 (95% CI 0.97-1.89, p=0.072), with an I2 of 75.8%. In the TS protein-tested subgroup, the total HR for disease-free survival was 1.72 (95% CI 1.02-2.89, p=0.042), with an I2 of 81.3%.

CONCLUSION

Our meta-analysis showed that, in the adjuvant setting, TS expression does not predict a poorer disease-free survival or a worse overall survival. Therefore, we believe that it is inappropriate to regard TS expression as a prognostic factor for patients with stage II and stage III colorectal cancer treated by surgery and adjuvant chemotherapy.

Expression and prognostic significance of thymidylate synthase (TS) in pancreatic head and periampullary cancer

BACKGROUND

Pancreatic cancer has a dismal prognosis. Attempts have been made to improve outcome by several 5-FU based adjuvant treatment regimens. However, the results are conflicting. There seems to be a continental divide with respect to the use of 5-FU based chemoradiotherapy (CRT). Furthermore, evidence has been presented showing a different response of pancreatic head and periampullary cancer to 5-FU based CRT. Expression of thymidylate synthase (TS) has been associated with improved outcome following 5-FU based adjuvant treatment in gastrointestinal cancer. This prompted us to determine the differential expression and prognostic value of TS in pancreatic head and periampullary cancer.

PATIENTS AND METHODS

TS protein expression was studied by immunohistochemistry on original paraffin embedded tissue from 212 patients following microscopic radical resection (R0) of pancreatic head (n = 98) or periampullary cancer (n = 114). Expression was investigated for associations with recurrence free (RFS), cancer specific (CSS) and overall survival (OS), and conventional prognostic factors.

RESULTS

High cytosolic TS expression was present in 26% of pancreatic head tumours and 37% of periampullary tumours (p = .11). Furthermore, TS was an independent factor predicting favourable outcome following curative resection of pancreatic head cancer (p = .003, .001 and .001 for RFS, CSS and OS, respectively). In contrast, in periampullary cancer, TS was not associated with outcome (all p > .10).

CONCLUSION

TS, was found to be poorly expressed in both pancreatic head and periampullary cancer and identified as an independent prognostic factor following curative resection of pancreatic head cancer.

Predictive biomarkers with potential of converting conventional chemotherapy to targeted therapy in patients with metastatic colorectal cancer

The availability of systemic chemotherapy regimens for the treatment of patients with metastatic colorectal cancer (mCRC) is based on the results from large prospective, randomized studies. The main chemotherapeutic drugs used in treatment of mCRC are the fluoropyrimidines (5-fluorouracil (5-FU); capecitabine) in combination with either oxaliplatin (FOLFOX) or irinotecan (FOLFIRI). The objective response rate to either combination is approximately 50%, where no significant differences with regard to progression free survival or overall survival have been observed. Interestingly, a number of preclinical and clinical studies have indicated lack of full cross resistance between oxaliplatin based and irinotecan based treatment. Therefore, it is possible that certain mCRC patient subpopulations would benefit more from one drug combination rather than the other. To address this clinical problem there has been much focus on development and validation of predictive biomarkers for these three drugs. Here, we present a thorough review on the current status of predictive biomarkers for 5-FU, oxaliplatin and irinotecan treatment of mCRC patients. The overall conclusions were as follows: Several promising biomarker candidates were identified, notably thymidylate synthase for 5-FU, topoisomerase I for irinotecan and ERCC1 for oxaliplatin. However, these candidates warrant further analysis, where assay performance and clinical trial design should be in focus.

The association of polymorphisms in 5-fluorouracil metabolism genes with outcome in adjuvant treatment of colorectal cancer

AIM

The purpose of this study was to investigate whether specific combinations of polymorphisms in 5-fluorouracil (5-FU) metabolism-related genes were associated with outcome in 5-FU-based adjuvant treatment of colorectal cancer.

METHODS

We analyzed two cohorts of 302 and 290 patients, respectively, one cohort for exploratory analyses and another cohort for validating the exploratory analyses. A total of ten polymorphisms in genes involved in 5-FU pharmacodynamics and pharmacokinetics were studied. End points were disease-free survival (DFS) and overall survival. Multifactor dimensionality reduction was used to identify genetic interaction profiles associated with outcome.

RESULTS

Low-expression alleles in thymidylate synthase (TYMS) were associated with decreased DFS and overall survival (DFS:hazard ratio [HR] exploration 2.65 [1.40-4.65]; p = 0.004, HR validation 1.69 [1.03-2.66]; p = 0.03). A specific multifactor dimensionality reduction derived combination of dihydropyrimidine dehydrogenase and TYMS polymorphisms was associated with increased DFS (HR exploration 0.69 [0.49-0.98]; p = 0.04, HR validation 0.66 [0.45-0.95]; p = 0.03). Specific combinations of functional polymorphisms in DPYD and TYMS were demonstrated to be associated with DFS and overall survival in patients receiving adjuvant 5-FU-based treatment. Specifically high TYMS expression alleles seem to be associated with decreased DFS.

Correlation between thymidylate synthase gene variants, RNA and protein levels in primary colorectal adenocarcinomas

This study was designed to compare thymidylate synthase (TS) genotype, mRNA and protein levels in primary colorectal adenocarcinoma, and to examine the correlation between microsatellite instability (MSI) and TS expression. The TS genotype of 68 patients with colorectal cancer was determined by polymerase chain reaction (PCR) and restriction fragment length polymorphism analysis in peripheral blood mononuclear cells and tumour tissue. The TS mRNA levels in tumour tissue were measured by reverse-transcription PCR, and TS protein levels and MSI status were assessed using immunohistochemistry. Significantly higher mRNA and protein levels were observed in patients with the TS 3R/3R versus the 2R/2R and 2R/3R genotypes. There was no correlation between TS single nucleotide polymorphism and TS expression. Individuals homozygous for the six base-pair insertion in the 3'-untranslated region had significantly higher TS mRNA levels than heterozygous and homozygous wild type individuals. The TS mRNA and protein levels were significantly higher in microsatellite unstable tumours compared with microsatellite stable tumours. There was a significant association between the number of TS enhancer region repeats (in blood) and intratumoural TS mRNA and protein levels. A larger case series investigating the role of TS gene polymorphisms as predictors of sensitivity to 5-fluorouracil-based chemotherapy is required.

Nuclear thymidylate synthase expression in sporadic colorectal cancer depends on the site of the tumor

Colorectal carcinoma (CRC) is a heterogeneous disease with specific epidemiological, pathological, molecular, and clinical characteristics that depend on the location of the tumor relative to the splenic flexure. Thymidylate synthase (TS) is a major target of 5-fluorouracil-based chemotherapy for CRC and high expression of this enzyme in tumor cells can influence the effect of therapy. We examined differences in TS protein expression in nuclei of tumor cells between CRCs located proximal and distal to the splenic flexure. Nuclear TS was detected by immunohistochemistry with a TS 106 monoclonal antibody on tissue microarrays constructed from 269 CRCs. The median histological score of nuclear TS expression of all proximal tumors was two times higher (p = 0.0003) and in men three times higher (p = 0.00023) than that found in distal tumors. In multivariate analysis which included age, sex, Astler-Coller stage, histological grade, and site, only proximal location of the tumor was identified as an independent factor associated with higher TS expression (odds ratio 2.46, 95% confidence interval = 1.29-4.70, p = 0.0062). These results demonstrate significant differences in nuclear TS expression between proximal and distal cancers and suggest the potential importance of the site of the tumor for proper stratification of patients for chemotherapy.

Microsatellite instability in colorectal cancer and association with thymidylate synthase and dihydropyrimidine dehydrogenase expression

Background

Microsatellite instability (MSI) refers to mutations in short motifs of tandemly repeated nucleotides resulting from replication errors and deficient mismatch repair (MMR). Colorectal cancer with MSI has characteristic biology and chemosensitivity, however the molecular basis remains unclarified. The association of MSI and MMR status with outcome and with thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD) expression in colorectal cancer were evaluated.

Methods

MSI in five reference loci, MMR enzymes (hMSH2, hMSH6, hMLH1 and hPMS2), thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD) expression were assessed in paraffin embedded tumor specimens, and associated with outcome in 340 consecutive patients completely resected for colorectal cancer stages II-IV and subsequently receiving adjuvant 5-fluorouracil therapy.

Results

MSI was found in 43 (13.8%) tumors. Absence of repair protein expression was assessed in 52 (17.0%) tumors, which had primarily lost hMLH1 in 39 (12.7%), hMSH2 in 5 (1.6%), and hMSH6 in 8 (2.6%) tumors. In multivariate analysis MSI (instable) compared to MSS (stable) tumors were significantly associated with lower risk of recurrence (hazard ratio (HR) = 0.3; 95% CI: 0.2–0.7; P = 0.0007) and death (HR = 0.4; 95% CI: 0.2–0.9; P = 0.02) independently of the TS and DPD expressions. A direct relationship between MSI and TS intensity (P = 0.001) was found, while there was no significant association with DPD intensity (P = 0.1).

Conclusion

The favourable outcome of MSI colorectal carcinomas is ascribed mainly to the tumor biology and to a lesser extent to antitumor response to 5-fluorouracil therapy. There is no evidence that differential TS or DPD expression may account for these outcome characteristics.

Correlation Between Thymidylate Synthase Protein Expression and Gene Polymorphism with Clinicopathological Parameters in Colorectal Carcinoma

5-Fluorouracil (5-FU) represents the basis of chemotherapy for colorectal carcinoma, inhibiting thymidylate synthase (TS), an essential enzyme for DNA replication. Previous studies have associated high TS protein expression by tumor cells with poor outcome of patients with colorectal carcinoma, but others have refuted these findings. In view of the potential role of TS as predictive parameter and the lack of consensus in the literature, the present study compared 2 methods: protein expression and gene polymorphism, correlating them with clinicopathological findings. Immunohistochemical detection of TS in tumor cells and detection of gene polymorphism in the blood were performed in 32 patients with colorectal carcinoma treated with 5-FU. No correlation was found between TS protein expression and gene polymorphism. Neither method correlated with survival, tumor staging, and tumor histological grading. This result possibly reflects a complex tumor response to 5-FU therapy, where TS is just one of the involved proteins.

Thymidylate synthase genotyping is more predictive for therapy response than immunohistochemistry in patients with colon cancer

Thymidylate synthase (TS) is a potentially valuable marker for therapy response since it is the molecular target of 5-fluorouracil (5-FU). TS can be analyzed at the DNA (gene polymorphisms and amplification) and protein level (immunohistochemistry). This study investigated the predictive role of TS at the DNA and protein levels in patients with N(+) colon cancer (n = 38). Tumor and normal tissues were genotyped using PCR for variable number of tandem repeats (VNTR), a single nucleotide polymorphism (SNP) in the 3R allele and a 6 bp deletion (1494del6) in the TS gene. Tumor tissues were additionally analyzed for loss of heterozygosity (VNTR polymorphism). A newly developed real time PCR assay was used to detect the presence of TS gene amplifications in tumor tissues. VNTR analysis in normal tissue was significantly associated with distant tumor recurrence (8% for 2R/2R vs. 52% for patients carrying a 3R allele, p = 0.038) and cancer-specific survival (p = 0.021). IHC was not found to be significantly associated with patients' outcome. No correlations between TS gene polymorphisms and IHC were found. However, TS gene amplification was correlated with a strong IHC staining intensity. In conclusion, this study indicates that DNA based analysis is more predictive for patients' outcome than TS IHC.

Prognostic and predictive value of thymidylate synthase expression in colon cancer

Thymidylate synthase (TS) is an enzyme responsible for DNA synthesis. Its competitive inhibition constitutes the major mechanism of the antitumor effect of 5-fluorouracil (5-FU) therapy, which significantly improves the survival rate of colon cancer patients. The aim of our study was to examine the clinical importance of TS expression in colon cancer patients and to correlate its expression with various clinicopathological parameters, tumor proliferative capacity, cell cycle-related molecules' expression and patients' survival. Of the 71 colon cancer patients studied, 51 (71.8%) tested positive for TS, with the positive result being statistically significantly correlated with patients' gender (P = 0.012), tumor histological grade (P = 0.032), vascular invasion (P = 0.017) and the expression of cyclin E, pRb and p16 (P = 0.042, P = 0.001 and P = 0.001, respectively). The overall 5-year survival rate was 40% for TS-positive patients and 68.6% for TS-negative ones (P = 0.0134); in patients aged >70 years, this was 30 and 77.8%, respectively (P = 0.0008). In a multivariate analysis of survival, TS expression proved to be of prognostic significance (P = 0.0174). Our findings support evidence for the clinical importance of TS expression in colon cancer patients and define it as an independent prognostic risk factor.

The prognostic significance of thymidylate synthase and dihydropyrimidine dehydrogenase in colorectal cancer of 303 patients adjuvantly treated with 5-fluorouracil

Cytotoxic effect of 5-fluorouracil 5-FU is mediated through inhibition of thymidylate synthase (TS), and 5-FU is catabolised by dihydropyrimidine dehydrogenase (DPD). Efficacy of 5-FU may therefore depend on the TS and DPD activity of colorectal cancer. Archival tumour specimens from 303 consecutive patients were analysed for the expression of TS and DPD using immunohistochemistry. All patients were completely resected for colorectal cancer stages II-III and have subsequently received adjuvant treatment with 5-FU. In a multivariate analysis adjusting for the impact of bowel obstruction and vascular tumour invasion, diffuse TS pattern was significantly associated with increased risk of recurrence (hazard ratio (HR) = 1.9; 95% confidence interval (CI): 1.1-3.2; p = 0.02), but without significant association to death (HR = 1.6; 95% CI: 0.9-2.8; p = 0.08). High TS intensity was not significantly associated with lower risk of recurrence (HR = 0.6; 95% CI: 0.3-1.1; p = 0.07) or death (HR = 0.6; 95% CI: 0.3-1.2; p = 0.2). High DPD intensity was significantly associated with increased risk of recurrence (HR = 1.5; 95% CI: 1.1-2.3; p = 0.03) and death (HR = 1.6; 95% CI: 1.1-2.5; p = 0.02). Patients with a combination of low TS and high DPD intensity were at significantly increased risk of both recurrence (HR = 2.1; 95% CI: 1.0-4.2; p = 0.04) and death (HR = 2.0; 95% CI: 1.0-4.0; p = 0.05). No relationship between tolerability and toxicity of 5-FU and TS and DPD expression was found. It is concluded that characterizing colorectal carcinomas by TS and DPD expression may disclose subsets of patients with significantly greater risk of disease recurrence and early death. This may be utilized in the selection of patients for treatment approaches and for decision on follow-up programs.

Thymidylate synthase expression in resectable and unresectable pancreatic cancer: role as predictive or prognostic marker?

BACKGROUND AND AIMS

Thymidylate synthase (TS) is an important enzyme for DNA synthesis and the target for 5-fluorouracil (5-FU). Its expression may determine the outcome of patients with gastrointestinal cancers. We examined the prognostic and predictive value of TS-protein expression in patients with ductal adenocarcinoma of the pancreas.

METHODS

TS expression from 131 patients with ductal adenocarcinoma of the pancreas was analyzed by immunohistochemistry in paraffin-embedded primary tumour specimens or biopsies.

RESULTS

The median disease-specific survival among all patients (n=131) was 13 months. The invasion depth, the presence of metastases, grading and Union Internationale Contre le Cancer [International Union Against Cancer] (UICC) stage were associated with survival. Among resected patients (n=98), a difference in median survival was seen in the group receiving postoperative adjuvant treatment (21.1 months) compared with the group treated by surgery alone (12.4 months) (p=0.025). Low- and high-TS immunoreactivity was present in 74 (56%) and 56 (43%) of the cancers, respectively. One sample was not evaluable. No difference in median survival was observed among low- and high-TS-expressing tumours. Among patients undergoing resection and receiving postoperative intra-arterial chemotherapy (n=23), a marked trend to a longer median survival was seen for the group with low-TS-expressing tumours compared with the corresponding high-TS group (25.0 vs 16.0 months) (p=0.3834). There was no difference in survival among all palliative treated patients with low- and high-TS-expressing tumours.

CONCLUSION

Especially patients undergoing tumour resection with low-TS values seemed to have taken advantage from an intensified postoperative chemotherapeutic protocol. However due to the heterogeneous group of patients in the present report, larger trials of more homogenous patient populations will be necessary to confirm this hypothesis.

Predictive role of thymidylate synthase, dihydropyrimidine dehydrogenase and thymidine phosphorylase expression in colorectal cancer patients receiving adjuvant 5-fluorouracil

OBJECTIVE

The combined assessment of thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD) and thymidine phosphorylase (TP) gene expressions in metastatic colorectal cancer has been reported to be able to predict the efficacy of fluoropyrimidine-based chemotherapy. In order to evaluate the prognostic role in the adjuvant setting, we investigated the TS, DPD and TP expression in primary tumors of colorectal cancer patients treated with 5-fluorouracil (5-FU).

METHODS

TS, DPD and TP expression levels were determined by immunohistochemistry in paraffin-embedded primary tumor tissues from 62 patients with Dukes' stage B and C colorectal cancers who underwent surgery and received adjuvant systemic chemotherapy with 5-FU. The median follow-up was 90 months (range 17-127).

RESULTS

Dukes' stage C cancer and high TS expression were independent markers of poor prognosis for disease-free survival (DFS; p = 0.0009 and p = 0.007, respectively) and overall survival (OS; p = 0.0005 and p = 0.011, respectively). By multivariate analysis, patients with high DPD expression had significantly shorter DFS (p = 0.007) and OS (p = 0.005) compared to patients with low DPD expression. In the combined analysis of 2 markers, patients with low TS and low DPD had the best outcome in terms of DFS (p = 0.007) and OS (p = 0.03). The analysis of all 3 proteins showed that the patients with low expression of all 3 markers had significantly longer DFS (p = 0.04) and OS (p = 0.01) than patients with a high value of any one of the protein expressions. However, the joint analysis of 3 markers (group with TS-/DPD-/TP-) could not identify a subgroup of patients with a better prognosis compared to the analysis of 2 markers (group with TS-/DPD-). The analysis of Dukes' stage C cancer patients confirmed a significant benefit in terms of DFS and OS (p = 0.001 and p = 0.006, respectively) when all 3 markers had low expression. We also found a positive significant correlation between TS and TP protein expression (p = 0.033).

CONCLUSIONS

This retrospective investigation suggests that the combined assessment of TS and DPD may be useful to evaluate the prognosis of patients with Dukes' B and C colon carcinoma receiving 5-FU adjuvant chemotherapy. The role of TP as a predictor for 5-FU-based therapy needs further investigations.

How may anticancer chemotherapy with fluorouracil be individualised?

Fluorouracil is used clinically against various solid tumours. Both fluorouracil toxicity and pharmacokinetics vary highly within and between individuals. The reasons why doses are not individualised routinely are difficulties in defining, predicting and achieving an optimal fluorouracil exposure or dose because of a narrow therapeutic index, nonlinear pharmacokinetics, variabilities in administration rates and metabolism, and in targets like thymidylate synthase. To individualise fluorouracil administration before the first dose, assessment of the individual dihydropyrimidine dehydrogenase (DPD) activity may be useful, because this genetically highly polymorphic enzyme controls approximately 80% of fluorouracil elimination. A complete or partial loss of DPD activity in 0.1 and 3-5% of Caucasians, respectively, leads to increased fluorouracil exposure and toxicity. Several methods to assess DPD activity in patients have been proposed (genotyping, various phenotyping methods), but each of them has limitations, as has the fluorouracil test dose approach. To adapt exposure towards fluorouracil a priori, a combination of genotyping and phenotyping may yield better prediction of toxicity than one method alone. A prerequisite for dose adaptation is the definition of fluorouracil exposure ranges with sufficient therapeutic activity, but without serious toxicity. While an increased risk of leukopenia, diarrhoea, stomatitis, and hand-foot syndrome during continuous 5-day infusions was related to fluorouracil exposures above an area under the plasma concentration-time curve (AUC) threshold of 25-30 mg.h/L, tumour response was higher when an AUC of approximately 30 mg.h/L was achieved, illustrating the extremely narrow therapeutic window of fluorouracil. Pharmacokinetic target values are less clear for other regimens, including chronomodulated regimens, which yielded a superior clinically efficacy and tolerability in several trials. However, the monitoring of fluorouracil plasma concentrations seems principally useful for individual a posteriori dose adjustment. Whether an adaptation of the fluorouracil starting dose to the results of two DPD activity tests before fluorouracil administration a priori, and the adaptation of doses to fluorouracil exposure a posteriori is a reasonable approach to better prevent toxicity and increase efficacy, remains to be evaluated in randomised clinical studies comparing these strategies to routine clinical safety monitoring.

A prospective, blinded analysis of thymidylate synthase and p53 expression as prognostic markers in the adjuvant treatment of colorectal cancer

BACKGROUND

Despite previous studies, uncertainty has persisted about the role of thymidylate synthase (TS) and p53 status as markers of prognosis in colorectal cancer (CRC).

PATIENTS AND METHODS

A total of 967 patients accrued to a large adjuvant trial in CRC were included in a prospectively planned molecular substudy, and of them, 59% had rectal cancer and about 90% received adjuvant chemotherapy (either systemically or randomly allocated to intraportal 5-fluorouracil infusion or both). TS and p53 status were determined, blinded to any clinical data, by immunohistochemistry using a validated polyclonal antibody or the DO-7 clone, respectively, and their relationships with overall survival were examined.

RESULTS

High TS expression was observed in 58% and overexpression of p53 in 60% of tumours. TS expression correlated with tumour stage, and p53 overexpression, with rectal cancers. There was no evidence that either marker was significantly associated with survival by either univariate (TS hazard ratio (HR) = 0.94, 95% CI 0.76-1.18 and P = 0.6 and p53 HR = 0.98, 95% CI 0.78-1.23 and P = 0.9) or multivariate analyses (TS HR = 0.99, 95% CI 0.79-1.25 and P = 0.9 and p53 HR = 0.98, 95% CI 0.78-1.23 and P = 0.8).

CONCLUSIONS

Neither TS nor p53 expression has significant prognostic value in the adjuvant setting of CRC.

Advances and challenges in fluoropyrimidine pharmacogenomics and pharmacogenetics

In cancer pharmacogenetics (the study of how variability in a single or set of known genes influences drug response) and pharmacogenomics (the study of variability on a genome-wide scale), one of the most important fields of research focuses on the fluoropyrimdines (FPs) and, in particular, 5-fluorouracil (5-FU). After over 40 years of use, FPs remain one of the most commonly used cancer chemotherapy agents and their application includes a wide spectrum of cancer types. FPs also continue to be the baseline component for many new regimens with novel molecular-targeted agents that are being rapidly introduced. Hence, it would seem appropriate that pharmacogenetic/genomic models for optimizing cancer patient management would involve indicators of FP response. In this article, the current trends in FP pharmacogenetics and pharmacogenomics are reviewed based on the advances made to date and the challenges faced in realizing their full potential.

Immunohistochemical analysis of thymidylate synthase, thymidine phosphorylase, and dihydropyrimidine dehydrogenase in rectal cancer (cUICC II/III): correlation with histopathologic tumor regression after 5-fluorouracil-based long-term neoadjuvant chemoradiotherapy

In locally advanced rectal cancer, neoadjuvant 5-fluorouracil (5-FU)-based long-term chemoradiotherapy leads to marked tumor reduction and decrease of local recurrence rate. Thymidylate synthase (TS), thymidine phosphorylase (TP), and dihydropyrimidine dehydrogenase (DPD) are known to be important biomarkers to predict tumor response to 5-FU-based therapy. The aim of this study was to examine the correlation between TS, TP, and DPD protein expression and histopathologic tumor regression after neoadjuvant chemoradiotherapy. The results were compared with the recently published mRNA data. Preoperative biopsies (n = 25) and resection specimens (n = 40) from patients with rectal carcinoma (clinical UICC stage II/III) receiving neoadjuvant 5-FU-based chemoradiotherapy were studied for TS, TP, and DPD protein expression by immunohistochemistry using three different scoring systems (intensity, pattern, intensity + pattern). Results were compared with histopathologic tumor regression. A significant correlation between protein expression and tumor response was only seen when both staining intensity and staining pattern were considered. With this method, a significant association was seen between high TS expression in tumor biopsies as well as resection specimens and nonresponse of the tumor to therapy (P = 0.04). Furthermore, low TP expression in the resection specimens was significantly associated with lack of response (P = 0.02). For DPD no significant correlations were found at all. In conclusion, these results suggest that immunohistochemistry like RT-PCR is a suitable method to determine the correlation between TS, TP, and DPD expression and histopathologic tumor regression. However, precise results can only be achieved if staining intensity as well as staining pattern within the tumors are evaluated.

Predictive value of thymidylate synthase and dihydropyrimidine dehydrogenase protein expression on survival in adjuvantly treated stage III colon cancer patients

BACKGROUND

The predictive value of thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD) expression on long-term survival by influencing 5-fluorouracil (5-FU) effect were determined in primary tumours and node metastases of stage III colon cancer patients treated adjuvantly with 5-FU regimens (n=391). The effect of TP 53 mutation status, which is thought to be functionally linked to TS inhibition, was also examined.

PATIENTS AND METHODS

TS and DPD protein expression was determined by immunohistochemical analysis using tissue microarrays of these colon tumours. Two hundred and twenty tumours had already been screened in a previous study for TP 53 mutations.

RESULTS

Low TS protein levels in primary stage III colon tumours appeared to be associated with mucinous histology and low DPD protein levels with young age at time of randomisation. Concordance between TS and DPD expression in primary and metastatic tumours was low. No associations were found between disease-free survival (DFS) and TS or DPD protein levels. When stratified by TP 53 mutation status DFS did not differ with TS expression.

CONCLUSIONS

Expression of TS and DPD proteins is not predictive for survival in patients with stage III colon cancer treated adjuvantly with 5-FU regimens. TS protein levels did not alter the effect of TP 53 mutation status.

Adjuvant therapy for stage II colon cancer: an elephant in the living room?

At present, standard adjuvant treatment for patients with stage III colon cancer after surgical resection is represented by 6 months of chemotherapy based on 5-fluorouracil/leucovorin regimens. Even elderly patients enjoy the benefit of chemotherapy in terms of superior overall survival with no detrimental effects on quality of life. More questionable is the role of adjuvant chemotherapy for stage II colon cancer patients, the standard of care for whom is surgical resection alone. Although a majority of patients will be cured with resection, a significant minority will ultimately relapse, suggesting the need to identify patients who may benefit from adjuvant therapy. Putative prognostic markers for stage II patients, as well as the state-of-the-art of the adjuvant treatment in this setting, are reviewed in this paper.

Modulation of 5-fluorouracil cytotoxicity through thymidylate synthase and NF-κB down-regulation and its application on the radiolabelled iododeoxyuridine therapy on human hepatoma cell

The inhibition of thymidylate synthase (TS) by 5-fluorouracil (5-FU) was known to increase the incorporation of radiolabelled iododeoxyuridine (IdUrd) into DNA. The relatively non-toxic compounds such as thiol-containing antioxidant pyrrolidinodithiocarbamte (PDTC) or aromatic fatty acid phenylbutyrate (PB) had been reported to enhance the cytotoxic efficacy of 5-FU. We designed a novel strategy through triplet combination of PB, PDTC and 5-FU to increase the radiolabelled IdUrd uptake and investigated the underlying mechanisms. The growth inhibition and [(125)I]IdUrd-DNA incorporation by PB, PDTC, 5-FU in different combinations were tested on parent or p21(Waf1) transfected Hep3B cells. The combination of PB and PDTC was more effective in enhancing 5-FU cytotoxicity than either drug alone. The combination of PB/PDTC and 5-FU blocked cells in S-phase and resulted in 8.5-fold increase of radiolabelled IdUrd-DNA incorporation. The transfection of p21(Waf1) did not change the general pattern of enhancement. Intriguingly, the combination of PB and PDTC effectively down-regulated NF-kappaB and TS and prevented their up-regulation from 5-FU treatment than either drug alone through a p21(Waf1)-independent mechanism. Based on this strategy, the 3-drug combination offered potential for improved radiolabelled IdUrd molecular radiotherapy for hepatoma treatment.

Thymidylate synthase expression and prognosis of patients with gastrointestinal cancers receiving adjuvant chemotherapy: a review

BACKGROUND AND AIMS

Many studies have been published that report an association between thymidylate synthase (TS) and response to fluoropyrimidine-based chemotherapy and the overall outcome of patients with gastrointestinal cancer. The results have given rise to the possibility that, by determination of TS levels, the physician may decide if the patient has a potential benefit from fluoropyrimidine-based treatment, similar to measurements of oestrogen receptors in breast cancer. The purpose of this review is to summarize critically the reports on TS measurement in gastrointestinal cancer, focusing on the adjuvant fluoropyrimidine treatment situation.

METHODS

We reviewed more than 20 studies that reported the association of TS with the clinical outcome in patients with gastrointestinal cancer who had undergone complete resection of the primary tumour only or were receiving additional adjuvant chemotherapy.

RESULTS

Patients with metastasized disease who expressed high TS levels display a low probability of responding to fluoropyrimidine-based treatment and have a poorer survival rate. Patients with high TS levels who undergo complete surgical resection of the primary tumour also have a poorer prognosis than those with tumours with low TS expression. In contrast to advanced disease and to surgery alone, patients with high TS levels appear to benefit, especially, from adjuvant fluoropyrimidine-based chemotherapy after complete primary tumour resection, while patients with low TS levels do not.

CONCLUSION

Patients with gastrointestinal cancers that express high TS levels have a poor prognosis with regard to fluoropyrimidine-based palliative chemotherapy or complete primary tumour resection. In contrast, patients with high TS levels might benefit from adjuvant fluoropyrimidine-based treatment after primary tumour resection. However, additional prospective studies are mandatory to define the precise role of TS in adjuvant therapy.

Topoisomerase-I, thymidylate synthase primary tumour expression and clinical efficacy of 5-FU/CPT-11 chemotherapy in advanced colorectal cancer patients

While several studies have reported that thymidylate synthase (TS) tumour expression can be a reliable predictive marker of clinical response to 5-Fluorouracil (5-FU) for advanced colorectal cancer patients, only a few studies that searched for predictive factors of irinotecan (CPT-11) clinical response are available. The aim of the present study has been to verify the predictive value of immunohistochemical topoisomerase-I (Topo-I) and TS primary tumour expression in a consecutive series of 62 advanced colorectal cancer patients that received a first line 5-FU/CPT-11 chemotherapy. TS and Topo-I immunostaining was observed in 76% and 43% of tumours, respectively, resulting in a significant relationship within each tumour (r=0.365, p<0.004). Patients with different TS tumour expression showed a similar percentage of Objective Clinical Response, OR (40% vs. 28% of OR in low and high TS-expressing tumours, respectively, p=ns); also, patients with different Topo-I tumour expression did not show a different probability of OR (39% vs. 29% of OR in high and low Topo-I expressing tumours, respectively; p=ns). The tumour expression of these 2 biomarkers also did not impact on time to progression and overall survival of patients. Furthermore, the combined analysis of TS and Topo-I tumour status did not permit to individualize subgroups of patients with different probability of OR. With multivariate analysis, only patient Performance Status significantly impacted on OS (Hazard ratio 4.87; p=0.02) of these patients. We can conclude that high TS tumour expression seems not to preclude a clinical activity for 5-FU/CPT-11 polichemotherapy in advanced colorectal cancer patients; furthermore, clinical response and prognosis of colorectal cancer patients treated with 5-FU/CPT-11 regimen do not differ in tumours with different TS or Topo-I expression.

Thymidylate synthase expression and prognosis in colorectal cancer: a systematic review and meta-analysis

PURPOSE

A number of studies have investigated the relationship between thymidylate synthase (TS) expression and survival in colorectal cancer (CRC) patients. Although most have reported poorer overall and progression-free survival with high TS expression, estimates of the hazard ratio (HR) between studies differ wildly. To derive a more precise estimate of the prognostic significance of TS expression, we have reviewed published studies and carried out a meta-analysis.

MATERIALS AND METHODS

Twenty studies stratifying overall survival and/or progression-free survival in CRC patients by TS expression status were eligible for analysis. The principal outcome measure was the HR. Data from these studies were pooled using standard meta-analysis techniques.

RESULTS

Thirteen studies investigated outcome in a total of 887 cases with advanced CRC, and seven studies investigated outcome in a total of 2,610 patients with localized CRC. A number of methods were used both to assess TS expression and to assign TS status. Sample sizes varied greatly, small sample sizes being a feature of the advanced disease studies. The combined HR estimate for overall survival (OS) was 1.74 (95% CI, 1.34 to 2.26) and 1.35 (95% CI, 1.07 to 1.80) in the advanced and adjuvant settings, respectively, but there was evidence of heterogeneity and possible publication bias.

CONCLUSION

Tumors expressing high levels of TS appeared to have a poorer OS compared with tumors expressing low levels. Additional studies with consistent methodology are needed to define the precise prognostic value of TS.

Role of biological markers in the clinical outcome of colon cancer

We investigated a number of biological markers, evaluated under strict intralaboratory quality control conditions, in terms of their role in predicting clinical outcome of patients with colon cancer treated with 5-FU-containing regimens. Colon cancer tissue from 263 patients enrolled onto two randomised clinical trials were studied for their cytofluorimetrically determined DNA content and their immunohistochemically evaluated microvessel density, vascular endothelial growth factor expression, thymidylate synthase expression and tumour lymphocyte infiltration. Disease-free survival and overall survival of patients were analysed as a function of the different variables. At a median follow up of 57 months, age, gender and Dukes' stage showed an impact on disease-free survival, whereas no biological marker emerged as an indicator of better or worse disease-free survival. Only histological grade and Dukes' stage were found to influence overall survival. The different biological variables, studied with particular attention for determination reliability, proved to have no impact on the clinical outcome of patients with colon cancer. Therefore, other markers must be identified to complement clinico-pathological variables in the management of this disease.

The impact of pharmacogenomics on gastrointestinal cancer therapy

Recently, we have seen major advances in the chemotherapy of gastrointestinal tumors, in particular colorectal cancer, leading to a substantial increase in overall survival of the patients. However, clinical efficacy and also toxicity of a given chemotherapy are still largely unpredictable for the individual patient. Amongst other variables, genetic polymorphisms determine the interindividual heterogeneity in both toxicity and therapeutic efficacy. In this review we present current evidence on host genetic polymorphisms that affect the toxicity or efficacy of three drugs commonly used for the treatment of gastrointestinal malignancies, 5-fluorouracil, irinotecan and oxaliplatin.