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

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

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

The Prognostic and Predictive Value of Dihydropyrimidine Dehydrogenase-Related Indicators in Clinical Outcomes of Chemotherapy in Colorectal Cancer Patients: a Systematic Review and Meta-Analysis

Colorectal cancer (CRC) is the third most common cancer worldwide. Predictive biomarkers are needed to predict patients' outcomes and to select a chemotherapy regimen. We assessed whether dihydropyrimidine dehydrogenase (DPD)-related indicators can predict CRC patients' outcomes. We searched the studies in PubMed, EmBase, and the Cochrane Library up to March 4, 2018. We mainly analyzed different CRC patients' outcomes according to specific DPD-related indicators. Twenty-five articles were included in the meta-analysis. The results showed that for disease-free survival (DFS), low DPD expression was significantly superior to high expression (I² = 72%; HR: 1.59; 95%CI: 1.21-2.09; p = 0.001). However, this result had a potential publication bias (Begg's test: p = 0.007; Egger's test: p = 0.004). Among patients treated with chemotherapy, a high thymidylate phosphorylase (TP)/DPD ratio was advantageous for DFS (I² = 63.7%; HR: 0.65; 95%CI: 0.46-0.92; p = 0.015), and this result did not have a publication bias. For overall survival (OS), low DPD expression was superior to high expression (I² = 74.4%; HR: 2.11; 95%CI: 1.48-3.00; p < 0.001), although this result had a publication bias (Egger's test: p = 0.003; Begg's test: p = 0.010). There was no difference in OS according to the TP/DPD ratio (I² = 0%; HR: 0.92; 95%CI: 0.75-1.13; p = 0.420). DFS and OS were better in CRC patients with low DPD expression than in those with high DPD expression. However, because of publication bias, more DPD indicator-related studies, especially with negative results, are still needed. Patients with a high TP/DPD ratio have better DFS but not OS.

Deciphering the potential value of 5-fluorouracil metabolic enzymes in predicting prognosis and treatment response of colorectal cancer patients

Introduction:

5-flourouracil (5-FU) is one of the standard chemotherapeutic drugs used today in the treatment of colorectal cancer patients. Disruption of 5-FU metabolic pathway may contribute to altered effectiveness towards 5-FU-based therapy. Hence, the study of 5-FU metabolizing enzymes might have the potential efficacy to predict survival and response to treatment in colorectal cancer patients.

Materials and methods:

Immunohistochemical localization of 5-FU metabolic enzymes (TS, MTHFR, DPYD, and TP) was evaluated in 143 untreated patients with colorectal cancer; their prognostic and predictive values were also evaluated.

Results:

Immuno-positivity for TS, MTHFR, DPYD, and TP was observed in 77%, 75%, 88%, and 96% of colorectal cancer patients, respectively. Univariate survival analysis in total patients showed that low DPYD expression significantly predicted adverse overall survival ( P=0.042). Moreover, subgroup of colon cancer patients with low TS expression was associated with unfavorable prognosis. TP expression also emerged as a prognosticator in the subgroup of early and advanced stage patients. Additionally, when effect of co-expression of 5-FU metabolic enzymes was evaluated in total patients, low coexpression of all four proteins was predictive of poor overall survival than for individuals expressing high coexpression of these proteins ( P=0.045). In contrast, none of the 5-FU metabolic enzymes—either singly or on coexpression—emerged as a useful biomarker of potential therapeutic value when evaluated in the subgroup of patients treated with 5-FU alone or 5-FU plus oxaliplatin.

Conclusion:

The above findings suggest that coexpression of 5-FU metabolic enzymes possess significant prognostic value and could be useful biomarkers in colorectal cancer patients.

Evaluation of 5-fluorouracil metabolic enzymes as predictors of response to adjuvant chemotherapy outcomes in patients with stage II/III colorectal cancer: a decision-curve analysis

BACKGROUND

The effectiveness of 5-fluorouracil (5-FU)-based adjuvant chemotherapy is reported in patients with colorectal cancer (CRC), but the usefulness of 5-FU metabolic enzymes as predictive biomarkers of the efficacy of this chemotherapy remains unclear.

OBJECTIVE

This study aims to verify whether 5-FU metabolic enzymes are predictive biomarkers in the clinical setting of adjuvant chemotherapy for stage II/III CRC.

METHODS

In total, 179 patients with stage II/III CRC who were treated at our institute between 2000 and 2010 were enrolled. Messenger RNA (mRNA) expression of major 5-FU metabolic enzymes, namely thymidylate synthase, dihydropyrimidine dehydrogenase, thymidine phosphorylase (TP), orotate phosphoribosyl transferase, and β-actin (control) was evaluated using the Danenberg Tumor Profile method. mRNA expression and other clinicopathological data were investigated with regard to CRC relapse.

RESULTS

A total of 78 patients underwent surgery alone, while 101 underwent adjuvant chemotherapy (5-FU plus leucovorin [LV] or tegafur plus uracil /LV) following surgery. Relapse-free survival was longer and risk of recurrence was lower in association with high TP mRNA expression than in association with low TP mRNA expression in the adjuvant chemotherapy group (hazard ratio 0.66; 95 % confidence interval 0.47-0.92; p = 0.016), but not in the surgery alone group. mRNA expression of no other enzymes was associated with relapse in both groups. In decision-curve analyses, the predictive efficiency of TP mRNA expression plus clinicopathological factors was slightly better than that of clinicopathological factors only.

CONCLUSIONS

TP mRNA expression in tumors predicted the effects of adjuvant chemotherapy for stage II/III CRC, although the beneficial effects were marginal.

Expression analysis of genes involved in DNA repair or synthesis in mixed neuroendocrine/nonneuroendocrine carcinomas

BACKGROUND

Mixed neuroendocrine/nonneuroendocrine carcinomas are heterogeneous tumors with poorly defined diagnostic and clinical features and without pathological or molecular markers of prognosis or markers predicting their response to therapy. We aimed at analyzing the pathological features and the expression of genes involved in DNA repair or synthesis in a cohort of patients with mixed carcinomas from different sites as compared to the patients' outcome.

METHODS

Relative cDNA quantification of ribonucleotide reductase, large subunit 1, excision repair cross-complementation group 1, thymidylate synthase and topoisomerase IIa genes was tested using real-time PCR on microdissected neuroendocrine and nonneuroendocrine tumor components of 42 mixed cases (from the lung as well as the gastrointestinal and genitourinary tracts) and on 45 control cases of pure neuroendocrine and nonneuroendocrine carcinomas.

RESULTS

The expression levels of all genes were stable comparing nonneuroendocrine and neuroendocrine components of mixed cases (except for topoisomerase IIa in lung samples) but significantly different as compared to control nonneuroendocrine and neuroendocrine tumors. In the multivariate analysis including all clinical and pathological parameters and gene expression levels available, a predominant nonneuroendocrine component, the administration of additional therapy other than surgery and a high thymidylate synthase expression in nonneuroendocrine tumor tissue were significantly associated with a lower risk of a patient's death.

CONCLUSIONS

Our data show that mixed neuroendocrine/nonneuroendocrine carcinomas are different at the molecular level from their pure neuroendocrine and nonneuroendocrine counterparts, and detailed analyses of their clinical, pathological and molecular features may improve the clinical strategies for the treatment of these rare and underestimated tumors.

Pharmacogenetics research on chemotherapy resistance in colorectal cancer over the last 20 years

During the past two decades the first sequencing of the human genome was performed showing its high degree of inter-individual differentiation, as a result of large international research projects (Human Genome Project, the 1000 Genomes Project International HapMap Project, and Programs for Genomic Applications NHLBI-PGA). This period was also a time of intensive development of molecular biology techniques and enormous knowledge growth in the biology of cancer. For clinical use in the treatment of patients with colorectal cancer (CRC), in addition to fluoropyrimidines, another two new cytostatic drugs were allowed: irinotecan and oxaliplatin. Intensive research into new treatment regimens and a new generation of drugs used in targeted therapy has also been conducted. The last 20 years was a time of numerous in vitro and in vivo studies on the molecular basis of drug resistance. One of the most important factors limiting the effectiveness of chemotherapy is the primary and secondary resistance of cancer cells. Understanding the genetic factors and mechanisms that contribute to the lack of or low sensitivity of tumour tissue to cytostatics is a key element in the currently developing trend of personalized medicine. Scientists hope to increase the percentage of positive treatment response in CRC patients due to practical applications of pharmacogenetics/pharmacogenomics. Over the past 20 years the clinical usability of different predictive markers has been tested among which only a few have been confirmed to have high application potential. This review is a synthetic presentation of drug resistance in the context of CRC patient chemotherapy. The multifactorial nature and volume of the issues involved do not allow the author to present a comprehensive study on this subject in one review.

Predicting chemotherapeutic response and toxicity in colorectal cancer

SUMMARY While treatment for colorectal cancer has evolved significantly over the past 10 years with the introduction of active chemotherapeutic agents and targeted therapies, this has been at the cost of increased toxicity for patients; and significant financial burden for governments and patients. Predicting clinical outcomes, especially given the largely elderly patient population involved, is therefore paramount. This review seeks to summarize existing data regarding the prediction of response and toxicity to chemotherapy agents currently used in the treatment of colorectal cancer.

Multi-microarray identifies lower AQP9 expression in adjuvant chemotherapy nonresponders with stage III colorectal cancer

Approximately 25% of stage III colorectal cancer patients do not benefit from standard adjuvant chemotherapies. To identify biomarkers for nonresponders, fresh-frozen tissues of 19 nonresponders and 16 responders were analyzed with gene expression and microRNA arrays. Fifty-nine genes and 17 miRNAs were differentially expressed by at least two folds. AQP9, SATB2, and WIF1 were simultaneously lower expressed in the nonresponders and modulated by the differentially expressed miRNAs. RT-PCR validated the differential expression of AQP9 (p=0.035). In conclusion, lower AQP9 gene expression is related with non-response to adjuvant chemotherapy, showing potential as predictive marker and therapeutic target.

Clinical management of localized colon cancer with capecitabine

Large randomized trials demonstrated a benefit of adjuvant chemotherapy after resection of the primary colon cancer. It improves overall survival and reduces the risk of death, by 5% in UICC (Union Internationale Contre le Cancer) stage II and approximately 15%-20% in stage III. Fluoropyrimidines have been the standard drugs for the treatment of colon cancer since large randomized controlled trials demonstrated their efficacy and safety in treating patients suffering from this disease. Capecitabine is an orally administered fluoropyrimidine, which is preferably activated in tumor tissue to the active moiety 5-fluorouracil (5FU) and is cytotoxic through inhibition of DNA synthesis. It has proven equivalent efficacy and tolerability despite a changed toxicity profile compared to 5FU with less myelosuppression but more hand-and-foot syndrome. Capecitabine is well tolerated in elderly patients. The oral route of administration avoids frequent clinical visits as well as insertion of central venous catheters. The impact of the particular drug features on daily clinical practice is discussed in this review.

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.

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.

Genetic and epigenetic biomarkers of colorectal cancer

Cancer is a heterogeneous disease caused, in part, by genetic and epigenetic alterations. These changes have been explored in studies of the pathogenesis of colorectal cancer (CRC) and have led to the identification of many biomarkers of disease progression. However, the number of biomarkers that have been incorporated into clinical practice is surprisingly small. We review the genetic and epigenetic mechanisms of colorectal cancer and discuss molecular markers recommended for use in early detection, screening, diagnosis, determination of prognosis, and prediction of treatment outcomes. We also review important areas for future research.

Epigenetics and chemoresistance in colorectal cancer: an opportunity for treatment tailoring and novel therapeutic strategies

Colorectal cancer is the second leading cause of cancer-related deaths in the world. Despite many therapeutic opportunities, prognosis remains dismal for patients with metastatic disease, and a significant portion of early-stage patients develop recurrence after chemotherapy. Epigenetic gene regulation is a major mechanism of cancer initiation and progression, through the inactivation of several tumor suppressor genes. Emerging evidence indicates that epigenetics may also play a key role in the development of chemoresistance. In the present review, we summarize epigenetic mechanisms triggering resistance to three commonly used agents in colorectal cancer: 5-fluorouracil, irinotecan and oxaliplatin. Those epigenetic biomarkers may help stratify colorectal cancer patients and develop a tailored therapeutic approach. In addition, epigenetic modifications are reversible through specific drugs: histone-deacetylase and DNA-methyl-transferase inhibitors. Preclinical studies suggest that these drugs may reverse chemoresistance in colorectal tumors. In conclusion, an epigenetic approach to colorectal cancer chemoresistance may pave the way to personalized treatment and to innovative therapeutic strategies.

Molecular predictors of response to chemotherapy in colorectal cancer

Colorectal cancer (CRC) is one of the leading causes of cancer mortality worldwide. In the last decade, median overall survival has increased significantly with the introduction of new cytotoxics and biologic therapies. Notably, the definition of molecular markers predicting benefit with epidermal growth factor receptor (EGFR)-targeted agents has led to important advances in the personalized treatment of CRC. Data derived from multiple phase III trials have indicated that KRAS mutations can be considered a highly specific negative biomarker of response to anti-EGFR monoclonal antibodies. The predictive value of additional mutations and deregulations of the signaling pathways downstream of the EGFR such as BRAF, NRAS, PIK3CA, or PTEN is under intensive investigation. In addition, status of microsatellite instability and molecular markers related to the metabolism of chemotherapy agents has shown promising ability to select patients with higher chances of response to cytotoxic agents. Although attempts to identify predictive factors for efficacy to antiangiogenic therapies have been disappointing, further research on this field will maximize their therapeutic index. Determination of molecular predictive factors before selection of chemotherapy is rapidly approaching us to the paradigm of individualized treatment of CRC.

5-Fluorouracil pharmacogenomics: still rocking after all these years?

The 5-fluorouracil (5-FU) metabolic pathway is mainly dependent on the activity of several intracellular enzymes. Among them, four in particular; thymidylate synthase, methylenetetrahydrofolate reductase, dihydropyrimidine dehydrogenase and thymidine phosphorylase are considered the key points in determining sensitivity or resistance to this drug. These enzymes are needed to metabolize the drug in its active form (thymidylate phosphorylase) or to drop the concentration of the active drug in the cell (dihydropyrimidine dehydrogenase) or both (thymidylate synthase and methylenetetrahydrofolate reductase). Several different studies have tried to investigate the relationship between the presence of mutations in these enzymes and a reduced/improved activity of treatment based on 5-FU or its derivatives. In this article, we will focus on the often contradictory results of these studies.

TS gene polymorphisms are not good markers of response to 5-FU therapy in stage III colon cancer patients

AIM

Although the predictive and prognostic value of thymidylate synthase (TS) expression and gene polymorphism in colon cancer has been widely studied, the results are inconclusive probably because of methodological differences. With this study, we aimed to elucidate the role of TS gene polymorphisms genotyping in therapy response in stage III colon carcinoma patients treated with 5-FU adjuvant chemotherapy.

PATIENTS AND METHODS

251 patients diagnosed with stage III colon carcinoma treated with surgery followed by 5-FU based adjuvant therapy were selected. The variable number of tandem repeats (VNTR) and the single nucleotide polymorphism (SNP) in the 5'untranslated region of the TS gene were genotyped.

RESULTS

There was a positive association between tumor T stage and the VNTR genotypes (p = 0.05). In both univariate and multivariate survival analysis no effects of the studied polymorphisms on survival were found. However, there was an association between both polymorphisms and age. Among patients younger than 60 years, the patients homozygous for 2R seemed to have a better overall survival, whereas among the patients older than 67 this longer survival was seen by the carriers of other genotypes.

CONCLUSION

We conclude that the TS VNTR and SNP do not predict response to 5-FU therapy in patients with stage III colon carcinoma. However, age appears to modify the effects of TS polymorphisms on survival.

Value of gene polymorphisms as markers of 5-FU therapy response in stage III colon carcinoma: a pilot study

PURPOSE

The role of pharmacogenetics in chemotherapy response in colon carcinoma is controversial. We studied the value of known SNPs in genes involved in 5-FU metabolism as biomarkers of chemotherapy response in patients with stage III colon carcinoma.

METHODS

DNA was isolated from normal colonic tissue of 60 patients with stage III colon carcinoma treated adjuvantly with 5-FU combined with leucovorin. The tested SNPs were validated SNPs on the OPRT, TYMS and DPYD genes and a synonymous SNP on the TYMP gene. Real-time PCR, sequencing and RFLP were used for genotyping.

RESULTS

None of the studied genotypes was associated with any of the tumor or patient characteristics. Moreover, none of the genotypes studied had effect on patient survival.

CONCLUSION

In conclusion, the tested SNPs are not biomarkers of chemotherapy response in our stage III colon cancer patients group.

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.

Predictive diagnostics in colorectal cancer: impact of genetic polymorphisms on individual outcomes and treatment with fluoropyrimidine-based chemotherapy

The 5-fluorouracil (5-FU)-based chemotherapy is a standard treatment for patients with colorectal cancer. However, a relevant number of patients suffer from severe toxic side effects, such as haemotoxicity, while lacking clinical response to adjuvant therapy. The inter-individual variations of drug toxicity and efficacy of the pyrimidine antagonist observed in clinical practice are mainly determined by genetic polymorphisms. The screening of genotypes, such as thymidylate synthase, dihydropyrimidine dehydrogenase, methylene tetrahydrofolate reductase, orotate phosphoribosyltransferase or glutathione S-transferase, could help identifying those patients with colorectal carcinoma who can actually benefit from a 5-FU-based therapy. The current chapter elucidates the roles of the polymorphisms in the enzymes involved in the 5-FU metabolic pathway as prognostic and predictive markers. It reports on the relationship between various genotypes in patients with colorectal carcinoma and their responsiveness to a 5-FU-based chemotherapy, and concludes with an outlook on possible future directions in treatment of colorectal cancer.

Accumulation of thymidine-derived sugars in thymidine phosphorylase overexpressing cells

Thymidine phosphorylase (TP) is often overexpressed in cancer and potentially plays a role in the stimulation of angiogenesis. The exact mechanism of angiogenesis induction is unclear, but is postulated to be related to thymidine-derived sugars. TP catalyzes the conversion of thymidine (TdR) to thymine and deoxyribose-1-phosphate (dR-1-P), which can be converted to dR-5-P, glyceraldehyde-3-phosphate (G3P) or deoxyribose (dR). However, it is unclear which sugar accumulates in this reaction. Therefore, in the TP overexpressing Colo320 TP1 and RT112/TP cells we determined by LC-MS/MS which sugars accumulated, their subcellular localization (using (3)H-TdR) and whether dR was secreted from the cells. In both TP-overexpressing cell lines, dR-1-P and dR-5-P accumulated intracellularly at high levels and dR was secreted extensively by the cells. A specific inhibitor of TP completely blocked TdR conversion, and thus no sugars were formed. To examine whether these sugars may be used for the production of angiogenic factors or other products, we determined with (3)H-TdR in which subcellular location these sugars accumulated. TdR-derived sugars accumulated in the cytoskeleton and to some extent in the cell membrane, while incorporation into the DNA was responsible for trapping in the nucleus. In conclusion, various metabolic routes were entered, of which the TdR-derived sugars accumulated in the cytoskeleton and membrane. Future studies should focus on which exact metabolic pathway is involved in the induction of angiogenesis.

Prognostic and predictive biomarkers in resected colon cancer: current status and future perspectives for integrating genomics into biomarker discovery

The number of agents that are potentially effective in the adjuvant treatment of locally advanced resectable colon cancer is increasing. Consequently, it is important to ascertain which subgroups of patients will benefit from a specific treatment. Despite more than two decades of research into the molecular genetics of colon cancer, there is a lack of prognostic and predictive molecular biomarkers with proven utility in this setting. A secondary objective of the Pan European Trials in Adjuvant Colon Cancer-3 trial, which compared irinotecan in combination with 5-fluorouracil and leucovorin in the postoperative treatment of stage III and stage II colon cancer patients, was to undertake a translational research study to assess a panel of putative prognostic and predictive markers in a large colon cancer patient cohort. The Cancer and Leukemia Group B 89803 trial, in a similar design, also investigated the use of prognostic and predictive biomarkers in this setting. In this article, the authors, who are coinvestigators from these trials and performed similar investigations of biomarker discovery in the adjuvant treatment of colon cancer, review the current status of biomarker research in this field, drawing on their experiences and considering future strategies for biomarker discovery in the postgenomic era.

Clinical biomarkers in oncology: focus on colorectal cancer

Rapidly growing insight into the molecular biology of colorectal cancer has led to high hopes for the identification of molecular markers to be used in optimized and tailored treatment regimens. However, many of the published data on gene-specific biomarkers are contradictory in their findings, and no tests are currently used in clinical practice, with the exception of microsatellite instability (MSI) and guanylyl cyclase C (GCC) testing in the adjuvant setting, and in Europe KRAS mutation testing is used in the setting of epidermal growth factor receptor (EGFR)-targeted therapy for metastatic disease. There are many reasons for the failure of the initial marker hypothesis-driven approach. Although supported by a good biologic rationale, single markers such as tumor protein p53 (TP53) gene mutations, when applied to a complex tumor type containing many synchronous alterations, do not perform well in predicting outcome. Many markers also suffer from technical shortcomings, resulting from the lack of quantitative techniques to capture the impact of the molecular alteration. The impact of markers obtained from microarray expression profiling needs to be further investigated in studies based on much larger cohorts, and cross-validation studies will be essential. Recently, mutations in the KRAS gene were shown to be strong negative predictors of response to EGFR inhibitors in metastatic disease. It has also been suggested that BRAF gene mutations may be predictive of EGFR inhibitor resistance, and there are some conflicting data regarding the role of the PIK3CA gene. Further studies are needed to help integrate the latest findings into clinically useful tools for personalized medicine.

Insulin-like growth factors and insulin-like growth factor-binding proteins in relation to disease status and incidence of hypoglycaemia in patients with a gastrointestinal stromal tumour

OBJECTIVE

Patients with a gastrointestinal stromal tumour (GIST) suffering from non-islet cell tumour-induced hypoglycaemia (NICTH), being associated with increased plasma levels of pro-insulin-like growth factor (IGF)-IIE[68-88], have been reported occasionally. We studied the clinical relevance of pro-IGF-IIE[68-88] and other IGF-related proteins in GIST patients.

PATIENTS AND METHODS

Twenty-four patients were included. Plasma samples were collected before 1 week and median 5 months after start of treatment with imatinib, and levels of IGF-I, total IGF-II, pro-IGF-IIE[68-88], insulin-like growth factor-binding protein (IGFBP)-2, -3 and -6 were determined. GIST specimens from 17 patients and tumour cyst fluid from two patients were analysed for IGF-II and IGFBP-2.

RESULTS

Before treatment and/or during follow-up, 3 of 24 (13%) patients showed increased plasma levels of pro-IGF-IIE[68-88]. All three developed NICTH. Overall, patients with metastatic disease, elevated serum lactate dehydrogenase activity or total tumour size >12 cm had the highest pro-IGF-IIE[68-88] levels. Most patients had increased plasma IGFBP-2 levels and these levels were significantly higher in patients with progressive disease. (Pro-)IGF-II was expressed in 82% of GISTs and IGFBP-2 only in one case.

CONCLUSION

We identified pro-IGF-IIE[68-88] as a marker that may be used in the surveillance of GIST.

Abundant Fas expression by gastrointestinal stromal tumours may serve as a therapeutic target for MegaFasL

Although the tyrosine kinase inhibitor imatinib has been shown to be an active agent in patients with gastrointestinal stromal tumours (GIST), complete remissions are almost never seen and most patients finally experience disease progression during their course of treatment. An alternative therapeutic option is to target death receptors such as Fas. We showed that a panel of imatinib-sensitive (GIST882) and imatinib-resistant (GIST48, GIST430 and GIST430K-) cell lines expressed Fas. MegaFasL, a recently developed hexameric form of soluble Fas ligand (FasL), appeared to be an active apoptosis-inducing agent in these cell lines. Moreover, MegaFasL potentiated the apoptotic effects of imatinib. Immunohistochemical evaluations, in 45 primary GISTs, underscored the relevance of the Fas pathway: Fas was expressed in all GISTs and was expressed strongly in 93%, whereas FasL was expressed at moderate and strong levels in 35 and 53% of GISTs, respectively. Fas and FasL expression were positively correlated in these primary GISTs, but there was no association between Fas or FasL expression and primary site, histological subtype, tumour size, mitotic index, risk classification, and KIT mutation status. The abundant immunohistochemical Fas and FasL expression were corroborated by western blot analysis. In conclusion, our data implicate Fas as a potential therapeutic target in GIST.

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.

ERCC1 and BRCA1 mRNA expression levels in metastatic malignant effusions is associated with chemosensitivity to cisplatin and/or docetaxel

BACKGROUND

One of the major challenges in currently chemotherapeutic theme is lacking effective biomarkers for drug response and sensitivity. Our current study focus on two promising biomarkers, ERCC1 (excision repair cross-complementing group 1) and BRCA1 (breast cancer susceptibility gene 1). To investigate their potential role in serving as biomarkers for drug sensitivity in cancer patients with metastases, we statistically measure the mRNA expression level of ERCC1 and BRCA1 in tumor cells isolated from malignant effusions and correlate them with cisplatin and/or docetaxel chemosensitivity.

METHODS

Real-time quantitative PCR is used to analysis related genes expression in forty-six malignant effusions prospectively collected from non-small cell lung cancer (NSCLC), gastric and gynecology cancer patients. Viable tumor cells obtained from malignant effusions are tested for their sensitivity to cisplatin and docetaxel using ATP-TCA assay.

RESULTS

ERCC1 expression level is negatively correlated with the sensitivity to cisplatin in NSCLC patients (P = 0.001). In NSCLC and gastric group, BRCA1 expression level is negatively correlated with the sensitivity to cisplatin (NSCLC: P = 0.014; gastric: P = 0.002) while positively correlated with sensitivity to docetaxel (NSCLC: P = 0.008; gastric: P = 0.032). A significant interaction is found between ERCC1 and BRCA1 mRNA expressions on sensitivity to cisplatin (P = 0.010, n = 45).

CONCLUSION

Our results demonstrate that ERCC1 and BRCA1 mRNA expression levels are correlated with in vitro chemosensitivity to cisplatin and/or docetaxel in malignant effusions of NSCLC and gastric cancer patients. And combination of ERCC1 and BRCA1 may have a better role on predicting the sensitivity to cisplatin than the single one is considered.

Prognostic significance of thymidylate synthase, dihydropyrimidine dehydrogenase and thymidine phosphorylase protein expression in colorectal cancer patients treated with or without 5-fluorouracil-based chemotherapy

BACKGROUND

Low tumour expression levels of thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD) and thymidine phosphorylase (TP) have been linked with improved outcome for colorectal cancer (CRC) patients treated with 5-fluorouracil (5-FU). It is unclear whether this occurs because such tumours have better prognosis or they are more sensitive to 5-FU treatment.

PATIENTS AND METHODS

Associations between TS, DPD and TP levels, determined by tissue microarrays and immunohistochemistry, and survival was evaluated in 945 CRC patients according to treatment status.

RESULTS

Low TS and DPD expression associated with worse prognosis in stage II [hazard ratio (HR) = 1.69, 95% confidence interval (CI) (1.09-2.63) and HR = 1.92 (95% CI 1.23-2.94), respectively] and stage III CRC patients treated by surgery alone [HR = 1.39 (95% CI 0.92-2.13) and HR = 1.49 (95% CI 1.02-2.17), respectively]. Low TS, DPD and TP associated with trends for better outcome in stage III patients treated with 5-FU [HR = 0.81 (95% CI 0.49-1.33), HR = 0.70 (95% CI 0.42-1.15) and HR = 0.66 (95% CI 0.39-1.12), respectively].

CONCLUSION

Low TS and DPD expression are prognostic for worse outcome in CRC patients treated by surgery alone, whereas low TS, DPD and TP expression are prognostic for better outcome in patients treated with 5-FU chemotherapy. These results provide indirect evidence that low TS, DPD and TP protein expression are predictive of good response to 5-FU chemotherapy.

An in vivo platform for translational drug development in pancreatic cancer

Effective development of targeted anticancer agents includes the definition of the optimal biological dose and biomarkers of drug activity. Currently available preclinical models are not optimal to this end. We aimed at generating a model for translational drug development using pancreatic cancer as a prototype. Resected pancreatic cancers from 14 patients were xenografted and expanded in successive groups of nude mice to develop cohorts of tumor-bearing mice suitable for drug therapy in simulated early clinical trials. The xenografted tumors maintain their fundamental genotypic features despite serial passages and recapitulate the genetic heterogeneity of pancreatic cancer. The in vivo platform is useful for integrating drug screening with biomarker discovery. Passages of tumors in successive cohorts of mice do not change their susceptibility to anticancer agents and represent a perpetual live bank, facilitating the application of new technologies that will result in the creation of an integrated stable database of tumor-drug response data and biomarkers.

Predictive molecular markers for colorectal cancer patients with resected liver metastasis and adjuvant chemotherapy

BACKGROUND & AIMS

The aims of the study were to evaluate the predictive value of 8 candidate molecular markers for colorectal cancer (CRC) patients receiving hepatic arterial infusion (floxuridine [FUDR] and dexamethasone) and systemic irinotecan (CPT11) post resection of liver metastasis.

METHODS

RNA was extracted from microdissected tumor cells of fixed and embedded specimens of resected liver metastases (94 cases) and analyzed by quantitative reverse-transcription polymerase chain reaction (RT-PCR) for thymidine phosphorylase, dihydropyrimidine dehydrogenase, thymidylate synthase, uridine phosphorylase, uridine/cytidine (monophospho)kinase, Bcl-2 related protein, Cyclin-D1, and Survivin expression. Uni- and multivariate statistical analyses and an explorative hierarchical clustering analysis of quantitative RT-PCR data were performed for overall survival and recurrent disease.

RESULTS

After adjustment for multiple clinicopathologic parameters, none of the markers were significantly associated with overall survival (except, marginally, Cyclin-D1; P = .06) or extrahepatic recurrence. However, high Survivin (P = .03) and Cyclin-D1 (P = .05) levels were predictive for hepatic recurrence. Hierarchical cluster analysis identified 7 of 94 patients associated with lower hepatic recurrence (P < .001). This patient group was characterized by low Cyclin-D1 and Survivin messenger RNA levels, both genes also clustering together.

CONCLUSIONS

Cyclin-D1 and Survivin messenger RNA analyzed by standardized, quantitative RT-PCR are predictive markers for CRC patients receiving hepatic arterial infusion (FUDR/dexamethasone) and systemic CPT11 post resection of liver metastasis. Moreover, our exploratory hierarchical cluster analysis of quantitative RT-PCR data supports its potential as an application to define clinically relevant patient subgroups.

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.

Prognostic significance of tumor necrosis factor-related apoptosis-inducing ligand and its receptors in adjuvantly treated stage III colon cancer patients

PURPOSE

In preclinical models, there is synergism between chemotherapy and recombinant human tumor necrosis factor (TNF) -related apoptosis-inducing ligand (TRAIL) on apoptosis induction in tumor cells. Therefore, the prognostic relevance was analyzed of the expression of TRAIL and its death receptors DR4 and DR5 on disease-free survival and overall survival in stage III colon cancer patients treated with adjuvant chemotherapy.

METHODS

Tissue microarrays were constructed of primary tumor tissue from 376 stage III colon cancer patients treated in a randomized adjuvant chemotherapy study (fluorouracil/levamisole v fluorouracil/levamisole/leucovorin) and stained immunohistochemically for TRAIL, DR4, and DR5. Log-rank tests and Cox proportional hazard analysis, with adjustment for treatment arm, sex, age, N stage, microsatellite instability status, and p53 mutation status, were performed.

RESULTS

The majority of tumors showed high expression of TRAIL (83%), DR4 (92%), and DR5 (87%). Median follow-up was 43 months. High DR4 expression was associated with worse disease-free survival (odds ratio [OR] = 2.19; 95% CI, 1.06 to 4.53; P = .03), worse overall survival (OR = 2.22; 95% CI,1.03 to 4.81; P = .04) and shorter time to recurrence (P = .02) compared with those with low DR4 expression. TRAIL or DR5 expression had no prognostic value.

CONCLUSION

High DR4 expression is associated with worse disease-free and overall survival in stage III adjuvant-treated colon cancer patients. Evaluation of DR4 expression in stage III colon cancer patients may identify a subset requiring more aggressive adjuvant treatment.

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.

Drug resistance, predictive markers and pharmacogenomics in colorectal cancer

Resistance to chemotherapy limits the effectiveness of current cancer therapies, including those used to treat colorectal cancer, which is the second most common cause of cancer death in Europe and the United States. 5-Fluorouracil-based chemotherapy regimens are the standard treatment for colorectal cancer in both the adjuvant and advanced disease settings. Drug resistance is thought to cause treatment failure in over 90% of patients with metastatic cancer, while drug resistant micrometastic tumour cells may also reduce the impact of adjuvant chemotherapy treatment. The identification of panels of biomarkers that not only identify those patients most likely to benefit from chemotherapy treatment, but also which chemotherapies to use, would be a major advance. In this review, we describe molecular mechanisms of drug resistance that may be relevant to colorectal cancer. We also describe the results of predictive biomarker studies in this disease. Finally, we discuss how pharmacogenomics and other high through-put technologies may impact on the clinical management of colorectal cancer in the future.