The role of thymidylate synthase expression in prognosis and outcome of adjuvant chemotherapy in patients with rectal cancer

Histone deacetylase inhibitor enhances 5-fluorouracil cytotoxicity by down-regulating thymidylate synthase in human cancer cells

Thymidylate synthase (TS) overexpression is a key determinant of 5-fluorouracil (5-FU) resistance in human cancer cells. TS is also acutely up-regulated with 5-FU treatment, and, thus, novel strategies targeting TS down-regulation seem to be promising in terms of modulating 5-FU resistance. Here, we report that histone deacetylase inhibitors can reverse 5-FU resistance by down-regulating TS. By using cDNA microarrays and validation experiments, we found that trichostatin A reduced the expression of both TS mRNA and TS protein. Cotreatment with trichostatin A and cycloheximide restored TS mRNA expression, suggesting that TS mRNA is repressed through new protein synthesis. On the other hand, TS protein expression was significantly reduced by lower doses of trichostatin A (50 nmol/L). Mechanistically, TS protein was found to interact with heat shock protein (Hsp) complex, and trichostatin A treatment induced chaperonic Hsp90 acetylation and subsequently enhanced Hsp70 binding to TS, which led to the proteasomal degradation of TS protein. Of note, combined treatment with low-dose trichostatin A and 5-FU enhanced 5-FU-mediated cytotoxicity in 5-FU-resistant cancer cells in accordance with TS protein down-regulation. We conclude that a combinatorial approach using histone deacetylase inhibitors may be useful at overcoming 5-FU resistance.

Significance of Biological Markers for Predicting Prognosis and Selecting Chemotherapy Regimens of Advanced Gastric Cancer Patients between Continuous Infusion of 5-FU and a Combination of 5-FU and Cisplatin

BACKGROUND

Our previous phase II study of 5-fluorouracil (5-FU) and cisplatin (FP) for treatment of advanced gastric cancer showed that strong immunoreactivity for vascular endothelial growth factor (VEGF) is associated with chemoresponse. Patients with four or five of the favorable phenotypes, p53 (-), bcl-2 (-), gluthathione S-transferase pi (-), thymidylate synthase (-), and VEGF (+), survived longer than those with three or less of these phenotypes. The purpose of this study is to confirm our previous results and to compare the significance of those markers between continuous infusion of 5-FU (5-FUci) and FP.

METHODS

Pretreatment biopsies from 131 of 210 advanced gastric cancer patients enrolled to JCOG9205 were analyzed immunohistochemically for the presence of the five markers.

RESULTS

Median survival times of patients treated with 5-FUci (n = 65) or FP (n = 66) were 216 and 253 days, respectively (P = 0.6953). After FP treatment, patients with four or five favorable phenotypes (n = 20) survived longer than those with three or less favorable phenotypes (n = 46) (334 days and 243 days, respectively; P = 0.0463), and the survival times of 34 and 32 patients with VEGF (-) and (+) were similar (269 days and 253 days, respectively; P = 0.6317). After 5-FUci, 30 patients with VEGF (+) survived for a shorter time than 35 patients with VEGF (-) (142 days and 302 days, respectively; P = 0.0043).

CONCLUSION

The number of favorable phenotypes is prognostic for gastric cancer patients treated with FP, and VEGF has a different impact on survival between treatment with 5-FUci and FP.

Current Issues in Rectal Cancer Chemotherapy

PURPOSE

In this review we intend to provide a synthesized review of relevant studies and articles relating to the use of chemotherapy in the treatment of rectal cancer. The focus will be on the adjuvant and neoadjuvant treatment of stage II and III rectal cancer. The importance of risk stratification in the decisions to treat rectal cancer, both through clinical evaluation of patients as well as molecular analysis of tumors will be reviewed. Symptomatology associated with rectal cancer and rectal cancer therapy will be discussed as an increasingly important element of trial design. Additionally, new agents in the treatment of rectal cancer will be discussed. Finally, the design of 2 current studies incorporating these issues in their trial design will be presented.

METHODS

A MEDLINE search for clinical trials and reviews was performed, with selection of the most relevant clinical trials pertaining to the treatment of rectal cancer with chemotherapeutic agents.

RESULTS

Adjuvant and neoadjuvant treatments with chemotherapeutic agents have served to improve rates of local recurrence as well as overall survival. Trials evaluating the efficacy of orally active fluoropyrimidines, newer generation platinum agents, and inhibitors to vascular endothelial growth factors in the treatment of rectal cancer are currently underway.

CONCLUSIONS

The large U.S. trials that are currently underway will provide answers to several outstanding questions, including the efficacy of orally active fluoropyrimidines, newer generation platinum agents, and inhibitors to vascular endothelial growth factors in rectal cancer. These trials will also include rigorous assessments of symptomatology by validated symptom measures, as well as the evaluation of molecular tumor markers and their correlation with outcomes. Finally, the identification of low-risk groups of patients who do not require radiotherapy remains an important question in the treatment of rectal cancer.

Shifting from clinical to biologic indicators of prognosis after resection of hepatic colorectal metastases

Following resection of hepatic colorectal metastases, there are few criteria for predicting which patients have more aggressive disease and are, therefore, more likely to experience recurrence and reduced survival. Traditionally, primary tumor stage, preoperative carcinoembryonic antigen level, time from primary tumor treatment to diagnosis of hepatic metastases (disease-free interval), hepatic tumor size, number of hepatic metastases, and presence of extrahepatic disease have been reported to be predictors of survival after resection. However, the data regarding the prognostic importance of these clinicopathologic factors are inconsistent and conflicting. Therefore, conventional clinicopathologic factors may be inadequate for the purposes of prognostication. More recently, there has been increased interest in identifying biologic indicators that may help better define patients at risk for recurrence after hepatic resection for colorectal metastases. Recent studies have shown that proliferation markers such as p53 expression, tritiated thymidine uptake, thymidylate synthase, Ki-67, and human telomerase reverse transcriptase may be better predictors of outcome after resection of hepatic colorectal metastases. Moreover, tumor response to preoperative chemotherapy may also prove to be a useful predictor of outcome following liver resection for colorectal metastases.

Thymidylate synthase expression in primary colorectal tumours is correlated with its expression in metastases

OBJECTIVE

Thymidylate synthase (TS) is the rate-limiting enzyme in the synthesis of pyrimidine nucleotides and as such a critical target for fluoropyrimidines, which are widely used in the treatment of colorectal cancer (CRC). The purpose of this study was to investigate TS expression in the primary tumours (PTs) and their metastases (M) in advanced CRC.

MATERIAL AND METHODS

TS expression was determined immunohistochemically in paraffin-embedded biopsies of PT-M pairs in 39 CRC patients, as related to the clinical data.

RESULTS

There was no difference in the mean TS index of PTs compared with that of M, 1.25 and 1.14, respectively (p=0.12). TS expression of PTs was above the mean more often than that of M (61.5% and 41.0%, respectively, p=0.035). High TS expression in PTs was significantly related to high expression in M (the Fisher exact test, p=0.001). Using the absolute index values, TS expression in PT and M was significantly correlated (Pearson R=0.501, p=0.001). In 29/39 (74.3%) pairs, PT and M had concordant expression levels (Cohen's kappa 0.508, 95% CI 0.260-0.756, p=0.001; intraclass correlation coefficient (ICC) = 0.679, 95% CI 0.358-0.836, p=0.0001). No significant association was found between TS expression and any of the clinicopathological variables, disease outcome (DFS, DSS) or its response to treatment in univariate or multivariate analysis.

CONCLUSIONS

Albeit usually higher, TS expression in PT was closely correlated with TS expression in M. This suggests that measurement of TS in primary CRC accurately predicts TS expression in subsequent metastases, which may help in selecting those patients most likely to respond to 5-FU-based regimens.

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.

A phase II study of combined chemotherapy with methotrexate, 5-fluorouracil, and low-dose cisplatin (MFP) for histologically diffuse-type advanced and recurrent gastric cancer (KDOG9501)

BACKGROUND

Histologically diffuse-type gastric cancer is well known to have a poor prognosis and is often complicated with abdominal and pleural effusions. We evaluated the efficacy of a low dose of cisplatin combined with methotrexate and 5-fluorouracil (MFP therapy) in diffuse-type advanced gastric cancer.

METHODS

The study group comprised 47 patients. Patients with pleural effusion or ascites were actively enrolled. Methotrexate (30 mg/m(2) per day) plus 5-fluorouracil (600 mg/m(2) per day) was administered on days 1 and 8. Cisplatin (6 mg/m(2) per day) was given daily for 14 days after which there was 14 day's rest. Calcium leucovorin (15 mg) was administered after methotrexate.

RESULTS

The overall response rate was 38.3%. Ascites disappeared or decreased in 15 of 23 patients (disappeared in 9). Pleural effusion disappeared or decreased in 6 of 8 patients (disappeared in 4). Of the 21 patients with poor oral intake at study entry, 15 (71.4%) were able to orally ingest food. Hematologic toxicity of grade 3 or higher comprised leukopenia in 10 patients (21.3%) and neutropenia in 9 (19.1%). Nonhematologic toxicity included anorexia and nausea/vomiting, in 1 patient each (2.1%). The median survival time was 211 days.

CONCLUSION

MFP therapy is useful for the management of diffuse-type inoperable and recurrent gastric cancer, even in patients with conditions such as pleural effusion, ascites, or lymphangitis carcinomatosa who have a poor prognosis or cannot eat solid food.

Prognostic and predictive roles of high-degree microsatellite instability in colon cancer: a National Cancer Institute-National Surgical Adjuvant Breast and Bowel Project Collaborative Study

PURPOSE

The role of high-degree microsatellite instability (MSI-H) as a marker to predict benefit from adjuvant chemotherapy remains unclear.

PATIENTS AND METHODS

To help define its impact, we conducted an analysis of National Surgical Adjuvant Breast and Bowel Project (NSABP) patients who were randomly assigned to a surgery-alone group (untreated cohort) and patients assigned to an adjuvant fluorouracil (FU) -treated group (treated cohort). MSI-H and other potential markers were assessed (TGF-BRII, p53, thymidylate synthase, and Ki67).

RESULTS

In all, 98 (18.1%) of 542 patients exhibited MSI-H, and there was a strong inverse relationship between MSI-H and mutant p53 status (P < .001). The prognostic analyses showed increased recurrence-free survival (RFS) for MSI-H patients versus MSS/MSI-L patients (P = .10), but showed no difference in overall survival (OS; P = .67). There was a potential interaction between MSI-H and mutant p53 in terms of improved RFS (P = .03). In the predictive marker analysis, we observed no interaction between MSI status and treatment for either RFS (P = .68) or OS (P = .62). Hazard ratios (HR) for RFS for MSI-H versus MSS/MSI-L patients were 0.77 (95% CI, 0.40 to 1.48) in the untreated-patients group and 0.60 (95% CI, 0.30 to 1.19) in the treated-patients group. HRs for OS were 0.82 (95% CI, 0.44 to 1.51) and 1.02 (95% CI, 0.56 to 1.85) for the respective groups. There was a trend toward improved RFS in patients with MSI-H and mutant p53.

CONCLUSION

These results do not support the use of MSI-H as a predictive marker of chemotherapy benefit.

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.

Expression of thymidylate synthase and dihydropyrimidine dehydrogenase in oral squamous cell carcinoma: possible markers as predictors of clinical outcome

CONCLUSIONS

Our results suggest that assessment of dihydropyrimidine dehydrogenase (DPD) in oral squamous cell carcinoma (OSCC) may be a useful tool in evaluating clinical outcomes.

OBJECTIVE

The purpose of this study was to estimate the possibility of using thymidylate synthase (TS) and DPD as predictive values of clinical outcomes in OSCC.

MATERIALS AND METHODS

The expression of TS and DPD was examined by immunohistochemistry (IHC) and the real-time reverse transcription-polymerase chain reaction method in 23 patients with OSCC, and the association with clinicopathological factors was determined. Immunohistochemical expression of p53 and P-glycoprotein (P-gp) was also examined.

RESULTS

Neither TS protein nor TS mRNA expression showed any significant correlation to clinicopathological factors. In contrast, the patients with high DPD expression had significantly higher levels of recurrence compared with those with low DPD expression (p = 0.016). Similarly, six of seven patients with relapse had higher DPD mRNA expression values than the median value in the patients examined. On the other hand, no association was observed between TS or DPD and p53 or P-gp expressions.

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.

Pharmacogenetics of colorectal cancer

Colorectal cancer is one of the most common types of cancer in both men and women. Multiple chemotherapy combinations exist; however, there is currently no strategy for individualised therapy selection prior to treatment. Genetic polymorphisms in genes involved in the metabolism, transport or targets for the commonly used chemotherapy drugs (5-fluorouracil, irinotecan and oxaliplatin) have been described. Many require validation in large prospective trials before they can be used as markers for outcome and/or toxicity. This review describes the data available on polymorphisms in key genes that are associated with chemotherapy toxicity and response in colorectal cancer.

Prognostic impact of orotate phosphoribosyl transferase among 5-fluorouracil metabolic enzymes in resectable colorectal cancers treated by oral 5-fluorouracil-based adjuvant chemotherapy

Orotate phosphoribosyl transferase (OPRT) is the main enzyme that involves in phosphoribosylation of 5-fluorouracil (5-FU), an essential step that leads to tumor growth inhibition. In our study, the prognostic relevance of OPRT, thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD) in resectable colorectal cancer (CRC) patients treated by oral 5-FU were compared to further clarify the prognostic value of OPRT. Tumor tissue was collected from 90 CRC patients and the patients were followed for 5.2 years (Median). TS, DPD and OPRT activities in the extract of tumor tissue were determined enzymatically. The cut-off value of OPRT (0.147 nmol/(min mg), TS (0.044 pmol/mg) and DPD (72.10 pmol/(min mg) were determined by maximal chi(2) method. Among these 5-FU metabolic enzymes, only high OPRT group demonstrated significantly better disease-free survival (DFS) (p = 0.0152) and better overall survival (p = 0.0078). In Cox regression analysis, node status (p < 0.0005) and OPRT (p = 0.044) were significant factors for DFS. OPRT activity in tumor tissue was a predictor of prognosis in resectable CRC patients treated by oral 5-FU-based adjuvant chemotherapy, and was useful to pick-up high risk patients independent from known prognosis factors.

Tailor-made chemotherapy for non-small cell lung cancer patients

The selection of the most effective chemotherapy treatment based on evaluation of biomarkers, that is, 'tailor-made chemotherapy', can improve the clinical outcome of non-small cell lung cancer patients, including early-stage tumors with a high metastatic potential and advanced-stage tumors with a low proliferation rate. Therefore, treatment would be chosen according to which drugs would be most effective in combating specific tumors. For example: 5-fluorouracil-derived agents would be used for tumors with a low expression of thymidylate synthase; gefitinib and erlotinib for tumors with epidermal growth factor receptor (EGFR) mutations or increased EGFR gene copy numbers; cisplatin and carboplatin for tumors with a low expression of excision repair cross complementing-1; and gemcitabine for tumors with a low expression of ribonucleotide reductase. The remaining populations of non-small cell lung cancers require chemotherapy using other drugs based on an evaluation of other targeted molecules.

Epidermal growth factor receptor as a prognostic factor in locally advanced rectal-cancer patients treated with preoperative chemoradiation

PURPOSE

We investigated the prognostic value of epidermal growth factor receptor (EGFR) expression in pretreatment biopsy specimens from patients with locally advanced rectal cancer treated with preoperative chemoradiation.

METHODS AND MATERIALS

Pretreatment biopsy specimens from 92 patients with locally advanced rectal cancer were examined for EGFR expression by immunohistochemistry. EGFR expression was assessed by immunoreactive score (IRS). The prognostic value of EGFR expression was evaluated according to the level of EGFR expression.

RESULTS

Epidermal growth factor receptor expression was positive in 65 patients (71%). EGFR expression levels were low (IRS 0 to 5) in 83 patients (90%) and high (IRS 6 to 7) in 9 patients (10%). A high level of EGFR expression was statistically significant for shorter overall survival (p = 0.013), disease-free survival (p = 0.002), and distant metastasis-free survival (p = 0.003), as compared with a low level of expression in univariate analysis. Grouping based on positive or negative EGFR expression did not represent prognostic significance for survival. In multivariate analysis, high EGFR expression was an independent prognostic factor for decreased disease-free survival (relative risk 2.4, p = 0.041) and distant metastasis-free survival (relative risk 2.6, p = 0.04).

CONCLUSIONS

Our results suggest that high level of EGFR expression in a pretreatment biopsy specimen may be a significant adverse prognostic factor for disease-free survival and distant metastasis-free survival.

Does Biomolecular Characterization of Stage II/III Colorectal Cancer Have Any Prognostic Value?

As new improvements in the treatment of colorectal cancer have become available, it has become important to understand the benefits of new therapies or the deleterious effects stemming from the increased risk of toxicity. In particular, a more rational approach to adjuvant chemotherapy for patients with stage II/III disease should be defined by understanding which patients have a higher recurrence risk. Many studies have investigated several molecular markers, but none has been definitively associated with patient outcome. We present a review of studies that have evaluated the immunohistochemical correlation between expression of some biomarkers, such as thymidylate synthase, p53, Ki-67, Bcl-2, and microsatellite instability status expressed by Mut-L homologue 1 and Mut-S homologue 2 proteins, and the prognosis of patients with stage II/III colorectal cancer. We have evaluated studies in which > or = 100 patients were involved in an effort to ensure a representative study group. The only biomarker likely to have a prognostic value is microsatellite instability status, which correlated with a better prognosis.

Thymidylate synthase pharmacogenetics

Thymidylate synthase (TYMS) is an important target for chemotherapy drugs, such as 5-fluorouracil (5FU) and methotrexate. Over-expression of TYMS is linked to resistance to TYMS-targeted chemotherapy drugs. Currently there is no protocol for selecting cancer patients at risk for drug resistance prior to chemotherapy treatment. Three polymorphisms in the 5' and 3' untranslated regions (5'UTR and 3'UTR) of the thymidylate synthase gene have been shown to influence TYMS expression. Preliminary data has suggested a poorer response rate to 5FU or methotrexate is seen in patients with 3 copies of a 28 bp tandem repeat in the 5'UTR enhancer region (TSER polymorphism) and this relationship may be further clarified by the presence of a single nucleotide polymorphism (SNP) with the second repeat of the 3 repeat (TSER(*)3) allele. A 6 bp deletion in the 3'UTR of the TYMS gene has also been shown to affect TYMS RNA expression and has a significant association with poor outcome in 5FU treated patients. Evidence linking all 3 TYMS polymorphisms with TYMS expression and patient response to TYMS-targeted chemotherapy treatment will be highlighted.

Deciphering cellular states of innate tumor drug responses

BACKGROUND

The molecular mechanisms underlying innate tumor drug resistance, a major obstacle to successful cancer therapy, remain poorly understood. In colorectal cancer (CRC), molecular studies have focused on drug-selected tumor cell lines or individual candidate genes using samples derived from patients already treated with drugs, so that very little data are available prior to drug treatment.

RESULTS

Transcriptional profiles of clinical samples collected from CRC patients prior to their exposure to a combined chemotherapy of folinic acid, 5-fluorouracil and irinotecan were established using microarrays. Vigilant experimental design, power simulations and robust statistics were used to restrain the rates of false negative and false positive hybridizations, allowing successful discrimination between drug resistance and sensitivity states with restricted sampling. A list of 679 genes was established that intrinsically differentiates, for the first time prior to drug exposure, subsequently diagnosed chemo-sensitive and resistant patients. Independent biological validation performed through quantitative PCR confirmed the expression pattern on two additional patients. Careful annotation of interconnected functional networks provided a unique representation of the cellular states underlying drug responses.

CONCLUSION

Molecular interaction networks are described that provide a solid foundation on which to anchor working hypotheses about mechanisms underlying in vivo innate tumor drug responses. These broad-spectrum cellular signatures represent a starting point from which by-pass chemotherapy schemes, targeting simultaneously several of the molecular mechanisms involved, may be developed for critical therapeutic intervention in CRC patients. The demonstrated power of this research strategy makes it generally applicable to other physiological and pathological situations.

Intratumoural expression of thymidylate synthase is an independent predictor of prognosis in patients with squamous cell carcinoma of the tongue: results from a retrospective study

The aim of this study was to assess the importance of immunohistochemical thymidylate synthase (TS) expression level as a prognostic marker in tongue cancer patients. In 140 patients with primary squamous cell carcinoma (SCC) of the tongue, intratumoural TS expression was evaluated by immunohistochemistry. The level of TS expression was determined by a semiquantitative scoring system, ranging from 1+ to 3+ according to the ratio of TS-positive cells. Of 140 patients, 64 (45.7%), 49 (35.0%) and 27 (19.3%) were assessed as 1+, 2+ and 3+, respectively. Univariate analyses demonstrated that both disease-free survival (DFS) and overall survival (OS) were significantly lower in patients with a TS 3+ tumour than in those with a TS 1+/2+ tumour (DFS: P = 0.0082, OS: P = 0.0100). In a multivariate analysis using the Cox regression model, cervical lymph-node status and TS expression level were selected as independent factors for DFS and OS. Maintenance adjuvant chemotherapy by oral 5-fluorouracil (5-FU) significantly improved DFS and OS in patients with a TS 1+/2+ tumour (DFS: P = 0.0027, OS: P = 0.0398). These data suggest that the level of immunohistochemical TS expression is an independent prognosticator in patients with tongue SCC, and may be useful in the selection of patients who would benefit from oral 5-FU adjuvant chemotherapy.

A Phase II Trial of Pemetrexed in Advanced Breast Cancer: Clinical Response and Association with Molecular Target Expression

PURPOSE

This phase II trial of pemetrexed explored potential correlations between treatment outcome (antitumor activity) and molecular target expression.

EXPERIMENTAL DESIGN

Chemonaïve patients with advanced breast cancer received up to three cycles of pemetrexed 500 mg/m2 (10-minute i.v. infusion) on day 1 of a 21-day cycle, with folic acid and vitamin B12 supplementation. Tumors were surgically removed after the last cycle of pemetrexed as clinically indicated. Biopsies were taken at baseline, 24 hours after infusion in cycle 1, and after cycle 3.

RESULTS

Sixty-one women (median age, 46 years; range, 32-72 years) were treated and were evaluable for response. Objective response rate was 31%. Simple logistic regression suggested a potential relationship between mRNA expression of thymidylate synthase (TS) and pemetrexed response (P = 0.103). Based on threshold analysis, patients with "low" baseline TS (< or = 71) were more likely to respond to pemetrexed than patients with "high" baseline TS (>71). Expression of baseline dihydrofolate reductase and glycinamide ribonucleotide formyl transferase tended to be higher in responders but this association was not significant (P > 0.311). TS expression increased significantly between baseline and biopsy 2 (P = 0.004) and dropped to near baseline levels at biopsy 3. Conversely, dihydrofolate reductase and glycinamide ribonucleotide formyl transferase decreased after pemetrexed chemotherapy.

CONCLUSIONS

Our results suggest a potential association between "low" pretreatment TS expression levels and response to pemetrexed chemotherapy. Future trials examining expression levels of other genes important to the folate pathway and/or breast cancer may identify a more robust multigene profile that can better predict response to this novel antifolate.

Adjuvant treatment strategies for early colon cancer

Colon cancer remains a major cause of death; however, in the last 3 years a number of trials have been published that have led to changes in the treatment of patients with this disease. Initially, the adjuvant treatment of patients following curative resection was based on their Dukes staging; this is now being refined by consideration of other pathological factors, as well as the investigation of newer prognostic markers such as p53, Ki67 and a number of genes on chromosome 18. Tumours generally develop from the progressive accumulation of genetic events, although some develop through mutation or inactivation of DNA mismatch repair proteins leading to microsatellite instability; this is particularly important in Lynch's syndrome. The loss of gene expression can occur by deletion or mutation of genes or by aberrant methylation of CpG islands. In patients with Dukes C colon cancer the standard of care for adjuvant chemotherapy was previously based on bolus fluorouracil (5-fluorouracil) and folinic acid (leucovorin) administered 5 days per month or weekly for 6 months. Recent studies with a combination of infusional fluorouracil, folinic acid and oxaliplatin have been found to be superior. A further study replacing fluorouracil with oral capecitabine has also demonstrated equivalent disease-free survival. Although some debate remains regarding the benefit of adjuvant treatment for patients with Dukes B colon cancer, the emerging consensus is that, for those patients who are younger and have high-risk features, chemotherapy should be discussed. A number of large vaccine trials have also been conducted in the adjuvant setting and, overall, these have been disappointing. This is a rapidly advancing area of therapy and the results of new trials are awaited to determine whether additional benefits can be achieved with biological therapies such as anti-vascular endothelial growth factor and anti-epithelial growth factor receptor monoclonal antibodies, which have already been shown to be effective in setting of metastatic colon cancer.

Significance of thymidylate synthase gene expression level in patients with adenocarcinoma of the lung

BACKGROUND

Thymidylate synthase (TS) catalyzes the methylation of deoxyuridine monophosphate (dUMP) to deoxythymidine monophosphate (dTMP) and is a key enzyme for DNA synthesis. High expression of TS is thought to be associated with poor prognosis in some kinds of cancers. However, this association has not been clarified for nonsmall cell lung carcinoma. In the current study, the authors investigated the clinicopathologic significance of TS mRNA levels and the correlation with cellular proliferation in patients with lung adenocarcinoma.

METHODS

The expression levels of TS mRNA were measured in 47 lung adenocarcinoma tissues using the Taq-Man real-time reverse transcriptase-polymerase chain reaction (RT-PCR) method and examined the clinicopathologic significance of TS expression. To clarify the correlation between TS expression level and cell proliferation, the Ki-67 labeling index was also examined using immunohistochemical staining.

RESULTS

A positive correlation was observed between the expression levels of TS mRNA and stage of disease, lymph node metastasis, or tumor differentiation (P = .015). The higher expression group of TS mRNA showed a significantly poorer prognosis than the group with lower expression (P = .042). Moreover, there was a strong correlation noted between the expression levels of TS mRNA and the Ki-67 labeling index (P = .009).

CONCLUSIONS

The results of the current study demonstrated that TS may be associated with stage of disease, lymph node metastasis, tumor differentiation, prognosis, and tumor cell proliferation. These results suggest that the expression levels of TS mRNA may be useful for predicting the malignant potential in patients with lung adenocarcinoma.

Expression of thymidylate synthase, dihydropyrimidine dehydrogenase, thymidine phosphorylase, and orotate phosphoribosyl transferase in prostate cancer

The enzymes thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD), thymidine phosphorylase (TP), and orotate phosphoribosyl transferase (OPRT) are involved in the metabolism of the anticancer drug 5-fluorouracil. No reports have examined the expression of these enzymes in prostate cancer (CaP). A total of 25 previously untreated, hormone-sensitive CaP tissue samples and 11 benign prostatic hyperplasia (BPH) specimens were examined. Tissue of CaP and BPH tissue samples were obtained from formalin-fixed, paraffin-embedded sections by laser-captured microdissection, and then RNA was extracted. mRNA expression of TS, DPD, TP, and OPRT was analyzed by quantitative reverse transcriptase-polymerase chain reaction. TS and OPRT expression levels were significantly higher in CaP samples than in BPH. DPD expression level in poorly differentiated CaP was significantly lower than that in CaP with more favorable--well or moderately differentiated--histopathology.

Relationships between promoter polymorphisms in the thymidylate synthase gene and mRNA levels in colorectal cancers

Thymidylate synthase (TS) intratumoural expression may be a prognostic marker and predict outcome of 5-fluorouracil (5-FU)-based chemotherapy in colorectal cancer patients. The TS gene promoter enhancer region contains two different polymorphisms which can influence TS mRNA transcriptional and translational efficiency: a polymorphic tandem repeat sequence (2 or 3 repeats; 2R and 3R) and a single nucleotide polymorphism (SNP), G > C, within the second repeat of the 3R alleles. We studied the relationship between tumoural TS mRNA expression levels and TS gene polymorphisms in the colonic mucosa of 48 colorectal cancer patients. The 3R/3R genotype was characterised by higher TS mRNA levels in the tumour than the 2R/2R-2R/3R genotypes (P = 0.071). Regarding the relationship with the SNP polymorphism, a statistically significant difference in TS gene expression between the 3RG/3RG genotype and 2R/2R-2R/3RC-2R/3RG genotype subset was observed (P = 0.017). No statistically significant correlation was observed between experimental data and baseline clinical-pathological characteristics as well as clinical outcome in the relatively small patient series investigated. This is the first study reporting an association between the TS intra-repeat SNP and gene expression levels in colorectal cancer patients. These results suggest that in 3R/3R patients, the G > C polymorphism may be an important factor in determining TS mRNA expression levels, and warrant further investigation of the role of TS promoter polymorphisms as predictors of sensitivity to 5-FU-based chemotherapy in larger case series.

Prognostic and predictive value of the thymidylate synthase expression in patients with non-metastatic colorectal cancer

AIMS

To assess the value of thymidylate synthase (TS) expression as a predictive factor in the efficacy of adjuvant chemotherapy in colorectal cancer, as well as its independent prognostic value for survival.

METHODS

We studied 114 high risk colorectal carcinoma patients (high risk stage II and stage III), distributed in two treatment groups: surgery alone (61 patients) or surgery followed by 5-FU-based chemotherapy (53 patients). TS protein expression in the tumour tissue was assessed by immunohistochemistry.

RESULTS

In the surgery alone subgroup, overall survival (OS) at 5 years were 77.5% for the patients with low TS expression, against 57.7% for the patients with high TS expression (p=0.006). Among patients with low TS, there was no difference in OS as a result of whether adjuvant chemotherapy was carried out or not (65.8 vs 77.5%, p=0.29). Among the patients with high TS, there was a significant gain in OS in favor of chemotherapy (87.8 vs 57.7%, p=0.04). Analyzing the complete sample, TS expression was not shown as an independent prognostic factor for survival in the multivariate analysis.

CONCLUSIONS

The immunohistochemical TS expression may be used for selecting patients for better adjuvant chemotherapy protocols. In this sample, TS expression was not an independent prognostic factor for survival.

ERbeta isoform expression in colorectal carcinoma: an in vivo and in vitro study of clinicopathological and molecular correlates

Colorectal carcinoma shows several sex-related differences with regard to incidence, response to chemotherapy and microsatellite instability. These differences may relate to differential expression of ERbeta1 (wild-type) as well as the truncated ERbeta2 and ERbeta5 splice variant isoforms, which have recently been detected in normal and malignant colorectal epithelium. This hypothesis was tested through the study of ERbeta isoform protein and/or mRNA expression amongst 91 primary colorectal carcinoma cases and 20 colorectal carcinoma cell lines. Study of the latter showed an absolute correlation between mRNA and protein expressions for ERbeta1 and ERbeta2. ERbeta1 and ERbeta2 protein expression was lost in 22% and 49%, respectively, of the primary colorectal carcinomas. By contrast, ERbeta5 expression was found in all primary colorectal carcinomas and all colorectal carcinoma cell lines studied. Lower ERbeta1 protein expression was associated with poorer differentiation, higher pT stage and absence of microsatellite instability. Higher ERbeta2 protein expression was associated with right-sided location and presence of lymph node metastases. Protein expression of ERbeta1 correlated positively with expression of the oestrogen-responsive protein trefoil factor 1 (TFF1). There was no correlation between ERbeta protein isoform expression and response to 5-fluorouracil therapy, tumour proliferation, or thymidylate synthase expression. These data suggest that ERbeta1 and/or ERbeta2 isoform expression may have prognostic value and may explain sex-related differences in microsatellite instability and colorectal carcinoma. The opposing associations shown by ERbeta1 and/or ERbeta2 in relation to colorectal carcinoma are in keeping with differential activities shown by the two isoforms.

Thymidylate synthase, thymidine phosphorylase, VEGF and p53 protein expression in primary colorectal cancer for predicting response to 5-fluorouracil-based chemotherapy

PURPOSE

In the treatment of advanced metastatic colorectal cancer, several new agents, such as irinotecan and oxaliplatin, have been developed, which have improved both disease free and overall survivals. Among these agents, 5-fluorouracil (5-FU) still remains one of the most active agents, and the selection of patients who can benefit from 5-FU-based chemotherapy is still important, as those unlikely to benefit could be spared the harmful side effects. The expression levels of thymidylate synthase (TS), thymidine phosphorylase (TP) and p53 have been known to be associated with the clinical response to 5-FU-based therapy as well as the prognosis, and that of vascular endothelial growth factor (VEGF) is associated with poor survival.

MATERIALS AND METHODS

The relationship between the expressions of TS, TP, VEGF and p53 in primary tumors, using immunohistochemistry, and the response of 45 metastatic colorectal cancer patients (M:F=25:20, median age 59 yrs) to 5-FU-based chemotherapy were evaluated.

RESULTS

Thirty-seven patients were treated with 5-FU/LV/irinotecan (FOLFIRI) and 8 with 5-FU/LV/oxaplatin (FOLFOX). The overall response rate was 28.9% (13/45). When immunohistochemically analyzed with monoclonal antibodies against TS, TP, VEGF and p53, 55.6% of the patients (25/45) were positive for TS, 48.9% (22/45) for TP, 82.2% (37/45) for VEGF, and 80% (36/45) for p53. There was a significant difference in the intensity of TS expression between the clinical responders and non-responders (p=0.036). In terms of the staining pattern of TS expression, diffuse staining was correlated with a poor response (p=0.012) and poor survival (p=0.045). However, there was no correlation between the expressions of TP, VEGF or P53 and the response to chemotherapy.

CONCLUSION

These results suggest that the expression of TS in primary colorectal cancer might be an important prognostic factor for chemotherapy response and survival, and might be a useful therapeutic marker for the response of chemotherapy.

Pharmacogenetics in Gastrointestinal Tumors

Treatment of gastrointestinal cancers has significantly advanced over the last few years with the introduction of effective chemotherapeutic and targeted drugs. To provide individual treatment with low toxicity on the one hand but maximum benefit on the other hand is still an unsolved problem. Interindividual variation of drug toxicity and efficacy is determined by genetic polymorphisms. The genetic approach based on single-gene (pharmacogenetics) or multi-gene (pharmacogenomics) analyses is developing as a valuable tool to design tailored therapy. This review focuses on clinically significant polymorphisms in genes involved in the metabolism of the major players in the chemotherapy of gastrointestinal cancer: fluoropyrimidines, irinotecan and platinum. In addition, first results of pharmacogenetics in targeted therapy including cetuximab and bevacizumab are discussed. The pharmacogenetic approach to individualize therapy in gastrointestinal cancers is promising, but additional larger and controlled studies are needed to justify changes of treatment strategies.

Detection of Thymidylate Synthase Expression in Lymph Node Metastases of Colorectal Cancer Can Improve the Prognostic Information

Purpose

The level of thymidylate synthase (TS) in primary colorectal cancer (CRC) has been reported as a prognostic marker. The purpose of this study was to determine whether TS expression in lymph node metastases of Dukes' C CRC is a prognostic marker.

Patients and Methods

TS expression in the primary tumor and lymph node metastases from 348 patients with Dukes' C CRC was retrospectively assessed using immunohistochemistry and the monoclonal antibody TS 106. The patients had all been enrolled onto our previous study of 862 CRC patients who were included in Nordic trials that randomly assigned the patients to either surgery alone or surgery plus adjuvant chemotherapy.

Results

TS expression in lymph node metastases was a distinct prognostic marker in the entire study group for overall survival (OS; P = .02) and disease-free survival (DFS; P = .04). A low TS expression in the lymph node metastases correlated with a better clinical outcome. In the subgroup of patients treated with surgery alone, the expression of TS in lymph node metastases also had a prognostic value for OS (P = .04) and DFS (P = .03), but this was not the case for the other subgroup who received adjuvant fluorouracil-based chemotherapy (OS, P = .5; DFS, P = .2). The expression of TS in the primary tumor only had a significant prognostic value among patients who were treated with surgery alone (OS, P = .03; DFS, P = .03) and not among the entire patient population.

Conclusion

These data show that TS expression in lymph node metastases is a prognostic marker for patients with Dukes' C CRC.

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.

Role of Genomic Markers in Colorectal Cancer Treatment

For the last four decades, fluorouracil (FU) has been the main treatment of choice in colorectal cancer (CRC) in both the advanced and adjuvant settings. In the advanced setting, FU monotherapy produces response rates of only 10% to 20%. Furthermore, in resected stage III CRC, FU monotherapy has increased overall survival by only 20%. The combination of FU with newer therapies such as oxaliplatin and irinotecan has significantly improved response rates to 40% to 50%. Despite these improvements, more than half of advanced CRC patients derive no benefit from treatment; this is due to either acquired or inherent drug resistance. This review aims to highlight the current prognostic and predictive markers that have been identified for CRC to date. The limited use of these predictive markers underscores the importance of and need for multiple marker testing in order to improve response rates and decrease toxicity. This review will also focus on high throughput methods to identify panels of predictive markers for CRC, which ultimately aim to tailor treatment according to an individual patient and tumor profile.

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

BACKGROUND

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

METHOD

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

RESULTS

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

CONCLUSIONS

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

[Current status of the prognostic value of molecular markers in patients with colorectal cancer and the prediction of response to adjuvant therapy]

Colorectal cancer is one of the best studied of all malignant diseases in terms of genetics and/or molecular prognostic factors. These factors, and relationships with prognosis, may have important implications especially in the design of surgical and adjuvant chemo-radiotherapy options. However, the true prognostic significance of all known factors has yet to be realised. We have reviewed the literature with specific focus on the role of molecular markers involved in prognosis and the prediction of response to adjuvant treatment.

Prospective clinical trials using a pharmacogenetic/pharmacogenomic approach

The antitumor activity of most anticancer agents is limited by a number of different factors, such as their cellular targets and activating enzymes, while constitutive genetic polymorphisms may limit drug bioavailability and influence either antitumor efficacy or toxic side effects. An example of a drug for which clear predictive parameters have been identified is 5-fluorouracil (5FU): its antitumor activity is limited by either a high activity of the target enzyme thymidylate synthase (TS) and/or a high activity of its degrading enzyme, dihydropyrimidine dehydrogenase (DPD). Retrospective studies showed a clear correlation between a high expression of TS and a poor response, which was stronger when DPD was included in the evaluation (high DPD, poor response). Therefore we initiated a clinical prospective study in which we treated previously untreated patients with advanced colorectal cancer with tailored chemotherapy: at a low TS-mRNA and low DPD-mRNA patients were stratified to receive a standard weekly 5FU-leucovorin regimen. At a high TS and/or DPD, patients were stratified to receive a combination of oxaliplatin and irinotecan. Up to now this proof-of-principle study demonstrated that selection of patients is possible and can clearly improve the clinical outcome. The next step is to develop algorithms to select patients for combination chemotherapy with 5FU-leucovorin and new compounds, such as oxaliplatin or irinotecan, or novel targeted agents such as bevacizumab or cetuximab. For these combination schedules the optimal combination of predictive factors has to be explored.

Predictive factors for response to chemotherapy in colorectal cancer patients

Colorectal cancer represents a major health problem in the western world. A lot of drugs have been employed in treatment of this disease, but only few data are available about predictive factors for response to anticancer treatments in colorectal cancer. Aim of this paper is to review the main data about this investigation field. Using a Medline database search (1966-2003) we reviewed all the relevant papers that investigate clinical and molecular predictors for response to the main drugs used in the treatment of colorectal cancer patients, both in adjuvant and in advanced setting. Moreover we comprehensively reviewed all the data published in abstract form during the most significant international meetings. Our review put in evidence the most important predictive factors for response in colorectal cancer patients treated with anticancer chemotherapy both in adjuvant and in advanced setting. The predictive factors are clustered on the basis of the different anticancer drugs. The results of this review provide the rationale basis for personalizing anticancer treatment in colorectal cancer patients by molecular and clinical features, aiming to improve response rate and reduce toxicities.

Clinical Trial Designs for Predictive Marker Validation in Cancer Treatment Trials

Current staging and risk-stratification methods in oncology, while helpful, fail to adequately predict malignancy aggressiveness and/or response to specific treatment. Increased knowledge of cancer biology is generating promising marker candidates for more accurate diagnosis, prognosis assessment, and therapeutic targeting. To apply these exciting results to maximize patient benefit, a disciplined application of well-designed clinical trials for assessing the utility of markers should be used. In this article, we first review the major issues to consider when designing a clinical trial assessing the usefulness of a predictive marker. We then present two classes of clinical trial designs: the Marker by Treatment Interaction Design and the Marker-Based Strategy Design. In the first design, we assume that the marker splits the population into groups in which the efficacy of a particular treatment will differ. This design can be viewed as a classical randomized clinical trial with upfront stratification for the marker. In the second design, after the marker status is known, each patient is randomly assigned either to have therapy determined by their marker status or to receive therapy independent of marker status. The predictive value of the marker is assessed by comparing the outcome of all patients in the marker-based arm to that of all of the patients in the non–marker-based arm. We present detailed sample size calculations for a specific clinical scenario. We discuss the advantages and disadvantages of the two trial designs and their appropriateness to specific clinical situations to assist investigators seeking to design rigorous, marker-based clinical trials.

Influence of thymidylate synthase and p53 protein expression on clinical outcome in patients with colorectal cancer

AIMS

Thymidylate synthase (TS) and tumor suppressor p53 are two proteins with an influence on tumor resistance to radio-chemotherapy that is well known. For this reason we tested the effect of TS and p53 expression on clinical outcome (tumor recurrence and survival) in patients after curative tumor resection, especially in patients who received adjuvant radio-chemotherapy.

PATIENTS AND METHODS

A total of 120 patients with colorectal cancer were included in the study. A curative resection was possible in 83 patients, and 30 of this group received adjuvant therapy. For the immunohistochemical staining of tumor specimens, monoclonal antibody (mAb) TS 106 against TS and mAb DO-1 against p53 protein were used. TS positivity was defined as a moderate to high staining intensity in the cytoplasma of cells and p53 positivity as nuclear staining of tumor cells in >10% of these cells.

RESULTS

Thymidylate synthase immunoreactivity was found in 59% of all cases and p53 staining in 51%. No relation between clinicopathological features and p53 expression was found in contrast to TS expression, where a highly significant association of TS-positive cases with tumor invasion (pT) was observed. Curatively resected patients with a TS-positive tumor developed tumor recurrence/distant metastases significantly more often than TS negative tumors. The same result was found when comparing p53-positive with p53-negative tumors and TS+/p53+ with TS-/p53- tumors. TS expression was highly significantly associated with poor survival and was the strongest independent prognostic factor in multivariate analysis, followed by lymph node status.

CONCLUSION

Thymidylate synthase expression seems to be an independent prognostic factor and a possible predictor of tumor recurrence in patients with colorectal cancer.

Thymidylate synthase gene polymorphism predicts toxicity in colorectal cancer patients receiving 5-fluorouracil-based chemotherapy

PURPOSE

The target enzyme for 5-fluorouracil (5-FU) is thymidylate synthase (TS). The TYMS gene encoding this enzyme is polymorphic, having either double (2R) or tri-tandem (3R) repeats of a 28-bp sequence in the promoter region and a 6-bp variation in the 3'-untranslated region (3'-UTR). TS expression predicts response to 5-FU-based chemotherapy, and the expression seems to be determined by the TYMS gene promoter. The aim of this study was to investigate the utility of determining these two TYMS gene polymorphisms to predict the toxicity and efficacy of 5-FU treatment in patients with colorectal cancer.

EXPERIMENTAL DESIGN

The determination of TYMS genotypes was performed in tumor and normal tissues by PCR amplification from 90 patients with colorectal cancer who were treated with adjuvant or palliative 5-FU-based chemotherapy. Associations between polymorphisms in the TYMS promoter and in the 3'-UTR gene and clinical outcome of these 90 patients treated with 5-FU based chemotherapy were evaluated individually. The linkage between TYMS promoter and TYMS 3'-UTR region polymorphisms was evaluated and a haplotype analysis was performed.

RESULTS

Individuals who were homozygous for the double repeat in the TYMS promoter region had more severe side effects to 5-FU. Patients with a 2R/2R, a 2R/3R, or a 3R/3R genotype had a grade 3 or 4 toxicity rate of 43, 18, and 3% respectively (P < 0.01). The TYMS promoter and TYMS 3'-UTR polymorphisms were in linkage disequilibrium, and the haplotype 2R/ins 6-bp was significantly associated with a high risk of severe side effects to 5-FU. The TYMS promoter and TYMS 3'-UTR polymorphisms were not associated with a response to 5-FU and survival of patients who received palliative 5-FU-based chemotherapy.

CONCLUSIONS

This study demonstrated that TYMS genotyping could be of help in predicting toxicity to 5-FU-based chemotherapy. TYMS genotyping might make it possible to individualize treatment for patients with colorectal cancer.

Pharmacogenetic influences on treatment response and toxicity in colorectal cancer

Current use of chemotherapeutic and targeted agents for advanced colorectal cancer (CRC) results in high tumor response rates and relatively long overall patient survival. Fluoropyrimidines, irinotecan, and oxaliplatin are highly active in first-line and salvage therapy of colorectal cancer. Targeted therapies, including anti-angiogenesis agents and anti-epidermal growth factor receptor antibodies, have been incorporated with traditional chemotherapy and offer additional options for patients with CRC. However, there is marked variability in response to therapy, as well as frequency and severity of toxicities. Molecular markers and pharmacogenomic profiling may improve prediction of patients who will experience significant benefit or toxicity from currently available agents. Validation of these predictive factors in prospective clinical trials is now necessary to allow for a rational and systematic individualization of cancer therapy.

Intratumoral molecular or genetic markers as predictors of clinical outcome with chemotherapy in colorectal cancer

Identification of molecular markers at either the intragenic, chromosomal, mRNA, or protein level that might predict whether colorectal cancer patients are likely to benefit from adjuvant or palliative therapy is a high priority. The majority of clinical studies addressing this issue, particularly those done in the adjuvant setting, analyzed tumor samples from patients treated in the era when 5-fluorouracil (5-FU) alone or combined with leucovorin or levamisole were the mainstay of therapy. This review highlights some of the intratumoral molecular markers that may have importance as predictors of benefit with 5-FU-based therapy. Although the goal of these investigations is to one day permit selection of therapy for an individual patient based on the tumor phenotype, prospective studies have yet to be conducted that test whether selection of therapy based on molecular markers results in an improved outcome.

Immunohistochemical analysis of thymidylate synthase, p16(INK4a), cyclin-dependent kinase 4 and cyclin D1 in colorectal cancers receiving preoperative chemotherapy: significance of p16(INK4a)-mediated cellular arrest as an indicator of chemosensitivity to 5-fluorouracil

High expression of thymidylate synthase (TS) is allegedly associated with the chemoresistance to 5-fluorouracil (5-FU) in colorectal cancers. However, low TS expression does not necessarily imply chemosensitivity. Inactivation of p16(INK4a) correlates with poor prognosis in various cancers. We immunohistochemically evaluated the relationship between the expression of TS, p16(INK4a), CDK4 and cyclin D1 and the effect of 5-FU-based chemotherapy in colorectal cancers. After antigen retrieval, immunoperoxidase staining was performed on the paraffin-embedded, biopsy and surgical specimens of 37 advanced colorectal cancers preoperatively treated with peroral administration of 5-FU derivatives. As a control group, 31 colorectal cancers without preoperative treatment were analyzed. High TS expression was found in 23 (74%) of 31 tumors resected from histological non-responders and in 19 (61%) of 31 controls but in none of six responders. High p16(INK4a) expression was seen in 83% of the responders, 52% of the non-responders and 32% of the controls. The TS-low/p16(INK4a)-high phenotype was noted in 83% of the responders, but only in 3% of the non-responders (P = 0.0001). Induction of p16(INK4a) expression after chemotherapy was predominantly seen in the responders. Neither CDK4 nor cyclin D1 expression was related to the chemotherapeutic effects. In conclusion, the combination of low expression of TS and induction of p16(INK4a) after chemotherapy can be important indicators of the sensitivity to 5-FU-based chemotherapy in colorectal cancers.

Clinical relevance of thymidylate synthase expression in the signet ring cell histotype component of colorectal carcinoma

Thymidylate Synthase (TS) is the key enzyme for DNA synthesis pathways and is inhibited by 5-fluorouracil (5FU). The aim of this work was to study TS expression and the proliferation rate in the different histological types of colorectal carcinoma (CRC). 50 patients with CRC were included in this study and evaluated immunohistochemically using the monoclonal antibodies, TS106 and Ki67. 20 tumours were of the intestinal type, 15 cases were signet ring cell carcinoma (SRCCs) and 15 cases were "mixed-type", with at least two different histological components. Intestinal and mucinous histotypes were positive for TS and Ki67, while "signet ring cell" samples were negative or showed only weak and focal positivity for both the TS and Ki67 antibodies. Our results show that signet ring cells (that are also often present in intestinal and mucinous carcinomas), are in the post-mitotic phase of the cell cycle and show a low proliferation index and TS expression. As TS is the key enzyme for DNA synthesis pathways and is inhibited by 5-fluorouracil (5FU), we can hypothesise that TS expression levels in the different histotypes of CRC could affect the potential responsiveness of these tumours to fluoropyrimidine chemotherapy, with a low efficacy being expected in signet ring cell areas.

Tailored Chemotherapy for Colorectal Cancer: A New Approach to Therapy

The treatment of colorectal cancer has advanced over the past several years with the introduction of several active agents. Determining which patients to treat with chemotherapy and choosing optimal treatment would allow practioners to maximize the benefit of chemotherapy. Several prognostic and predictive markers have been identified and include oncogenes, tumor suppressor genes, genes involved in angiogenic and apoptotic pathways and cell proliferation, and those encoding targets of chemotherapy. Specifically, prognostic markers include deletion of 18q (DCC), p27 and microsatellite instability. Predictive markers are those that may determine efficacy of drugs used in colorectal cancer such as fluropyrimidines and oxaliplatin. Alterations in gene expression, protein expression and polymorphic variants in genes encoding thymidylate synthase, dihydropyrimidine dehydrogenase, and thymidine phosphorylase and excision repair cross-complementing genes (ERCC1) may be useful as markers for clinical drug response, survival and host toxicity. The integration of these prognostic and predictive markers would allow individualized treatment for patients, maximizing therapeutic effect and minimizing exposure to toxicity.