Thymidylate synthase expression in colon carcinomas with microsatellite instability

Targeting Histone Chaperone FACT Complex Overcomes 5-Fluorouracil Resistance in Colon Cancer

Fluorouracil (5-FU) remains a first-line chemotherapeutic agent for colorectal cancer. However, a subset of colorectal cancer patients who have defective mismatch-repair (dMMR) pathway show resistance to 5-FU. Here, we demonstrate that the efficacy of 5-FU in dMMR colorectal cancer cells is largely dependent on the DNA base excision repair (BER) pathway. Downregulation of APE1, a key enzyme in the BER pathway, decreases IC₅₀ of 5-FU in dMMR colorectal cancer cells by 10-fold. Furthermore, we discover that the facilitates chromatin transcription (FACT) complex facilitates 5-FU repair in DNA via promoting the recruitment and acetylation of APE1 (AcAPE1) to damage sites in chromatin. Downregulation of FACT affects 5-FU damage repair in DNA and sensitizes dMMR colorectal cancer cells to 5-FU. Targeting the FACT complex with curaxins, a class of small molecules, significantly improves the 5-FU efficacy in dMMR colorectal cancer in vitro (∼50-fold decrease in IC₅₀) and in vivo xenograft models. We show that primary tumor tissues of colorectal cancer patients have higher FACT and AcAPE1 levels compared with adjacent nontumor tissues. Additionally, there is a strong clinical correlation of FACT and AcAPE1 levels with colorectal cancer patients' response to chemotherapy. Together, our study demonstrates that targeting FACT with curaxins is a promising strategy to overcome 5-FU resistance in dMMR colorectal cancer patients.

The role of microRNAs in 5-FU resistance of colorectal cancer: Possible mechanisms

Colorectal cancer (CRC) is one of the most common cancers globally. Despite recent advances in therapeutic approaches, this cancer continues to have a poor prognosis, particularly when diagnosed late. 5-Fluorouracil (5-FU) has been commonly prescribed for patients with CRC, but resistance to 5-FU is one of the main reasons for failure in the treatment of this condition. Recently, microRNAs (miRNAs) have been established as a means of modifying the signaling pathways involved in initiation and progression of CRC and their role as oncogene or tumor suppressor have been investigated in various studies. Moreover, miRNAs through various mechanisms play an important role in inducing tumor resistance or sensitivity to anticancer drugs. Detecting and targeting these mechanisms may be a new therapeutic approach. This review summarizes the current knowledge about the potential roles of miRNAs in 5-FU resistance, with particular emphasis on molecular mechanism involved.

Adjuvant Chemotherapy for Stage II and III Colon Cancer Following Complete Resection: A Cancer Care Ontario Systematic Review

The objective of this systematic review was to provide current evidence regarding the use of adjuvant systemic chemotherapy for stage II and III colon cancer following curative intent surgery. MEDLINE and EMBASE databases and proceedings of American Society for Clinical Oncology and European Society of Medical Oncology/European Cancer Congress were searched through to August 2015. Systematic reviews (with or without meta-analyses) and randomised controlled trials were included. Patients with completely resected stage III colon cancer have an overall survival benefit from adjuvant chemotherapy. Combination chemotherapy (5-fluorouracil/leucovorin/oxaliplatin or capecitabine/oxaliplatin) provides a larger benefit than monotherapy but with additional toxicity. For stage II colon cancer, a clear overall survival benefit has not been shown. However, based on the subgroup analysis available, patients with high-risk stage II disease may benefit from adjuvant chemotherapy. Patients younger than 70 years of age may derive greater disease-free survival and overall survival benefit from adjuvant chemotherapy (in combination with oxaliplatin) compared with those older than 70 years. Stage II patients with microsatellite instability may have an overall survival detriment if given adjuvant chemotherapy.

Simultaneous, But Not Consecutive, Combination With Folinate Salts Potentiates 5-Fluorouracil Antitumor Activity In Vitro and In Vivo

The combination of folinate salts to 5-fluoruracil (5-FU)-based schedules is an established clinical routine in the landscape of colorectal cancer treatment. The aim of this study was to investigate the pharmacological differences between the sequential administration of folinate salts (1 h before, as in clinical routine) followed by 5-FU and the simultaneous administration of both drugs. Proliferation and apoptotic assays were performed on human colon cancer cells exposed to 5-FU, calcium (CaLV), or disodium (NaLV) levofolinate or their simultaneous and sequential combination for 24 and 72 h. TYMS and SLC19A1 gene expression was performed with real-time PCR. In vivo experiments were performed in xenografted nude mice, which were treated with 5-FU escalating doses and CaLV or NaLV alone or in simultaneous and sequential combination. The simultaneous combination of folinate salts and 5-FU was synergistic (NaLV) or additive (CaLV) in a 24-h treatment in both cell lines. In contrast, the sequential combination of both folinate salts and 5-FU was antagonistic at 24 and 72 h. The simultaneous combination of 5-FU and NaLV or CaLV inhibited TYMS gene expression at 24 h, whereas the sequential combination reduced SLC19A1 gene expression. In vivo experiments confirmed the enhanced antitumor activity of the 5-FU + NaLV simultaneous combination with a good toxicity profile, whereas the sequential combination with CaLV failed to potentiate 5-FU activity. In conclusion, only the simultaneous, but not the consecutive, in vitro and in vivo combination of 5-FU and both folinate salt formulations potentiated the antiproliferative effects of the drugs.

A Study of Thymidylate Synthase Expression as a Biomarker for Resectable Colon Cancer: Alliance (Cancer and Leukemia Group B) 9581 and 89803

Tumor thymidylate synthase (TS) levels were prospectively evaluated in two adjuvant therapy trials for patients with resected stage II or III colon cancer. Results indicated that high tumor TS levels were associated with improved disease‐free survival and overall survival following adjuvant therapy for colon cancer, although tumor TS expression did not predict benefit of 5‐fluorouracil‐based chemotherapy.

Purpose.

Tumor levels of thymidylate synthase (TS), a target of 5‐fluorouracil (5‐FU)‐based chemotherapy for colorectal cancer, have been studied as a predictive or prognostic biomarker with mixed results.

Patients and Methods.

Tumor TS levels were prospectively evaluated in two adjuvant therapy trials for patients with resected stage II or III colon cancer. TS expression was determined by standard immunohistochemistry and by automated quantitative analysis. Tumor mismatch repair deficiency (MMR‐D) and BRAF c.1799T > A (p.V600E) mutation status were also examined. Relationships between tumor TS, MMR‐D, and BRAF mutation status, overall survival (OS), and disease‐free survival (DFS) were investigated in the subset of stage III patients.

Results.

Patients whose tumors demonstrated high TS expression experienced better treatment outcomes, with DFS hazard ratio (HR) = 0.67, 95% confidence interval (CI) = 0.53, 0.84; and OS HR = 0.68, 95% CI = 0.53, 0.88, for high versus low TS expression, respectively. No significant interaction between TS expression and stage was observed (DFS: interaction HR = 0.94; OS: interaction HR = 0.94). Tumors with high TS expression were more likely to demonstrate MMR‐D (22.2% vs. 12.8%; p =  .0003). Patients whose tumors demonstrated both high TS and MMR‐D had a 7‐year DFS of 77%, compared with 58% for those whose tumors had low TS and were non‐MMR‐D (log‐rank p =  .0006). Tumor TS expression did not predict benefit of a particular therapeutic regimen.

Conclusion.

This large prospective analysis showed that high tumor TS levels were associated with improved DFS and OS following adjuvant therapy for colon cancer, although tumor TS expression did not predict benefit of 5‐FU‐based chemotherapy.

Implications for Practice.

This study finds that measurement of tumor levels of thymidylate synthase is not helpful in assigning specific adjuvant treatment for colorectal cancer. It also highlights the importance of using prospective analyses within treatment clinical trials as the optimal method of determining biomarker utility.

Acquired resistance to 5-fluorouracil via HSP90/Src-mediated increase in thymidylate synthase expression in colon cancer

5-fluorouracil (5-FU), one of the first-line chemotherapeutic agents for the treatment of gastrointestinal malignancies, has shown limited efficacy. The expression of thymidylate synthase (TYMS) has been reported to be associated with the resistance to 5-FU. Here, we demonstrate that the enhanced HSP90 function and subsequent activation of Src induce expression of TYMS and acquired resistance to 5-FU in colon cancer. We show that the persistent 5-FU treatment granted 5-FU-sensitive HCT116 colon cancer cells morphologic, molecular, and behavioral characteristic of the epithelial-mesenchymal transition (EMT), contributing to emergence of acquired resistance to 5-FU. HCT116/R, a HCT116 colon cancer cell subline carrying acquired resistance to 5-FU, showed increased expression and activation of HSP90's client proteins and transcriptional up-regulation of TYMS. Forced overexpression of HSP90 or constitutive active Src in HCT116 cells increased TYMS expression. Conversely, pharmacological blockade of HSP90 or Src in HCT116/R cells effectively suppressed the changes involved in 5-FU resistance in vitro and xenograft tumor growth, hematogenous spread, and metastatic tumor development in vivo. This study suggests a novel function of HSP90-Src pathway in regulation of TYMS expression and acquisition of 5-FU resistance. Thus, therapeutics targeting this pathway may be an effective clinical strategy to overcome 5-FU resistance in colon cancer.

Association between mRNA expression of chemotherapy-related genes and clinicopathological features in colorectal cancer: A large-scale population analysis

To establish the individualized treatment of patients with colorectal cancer, factors associated with chemotherapeutic effects should be identified. However, to the best of our knowledge, few studies are available on this topic, although it is known that the prognosis of patients and sensitivity to chemotherapy depend on the location of the tumor and that the tumor location is important for individualized treatment. In this study, primary tumors obtained from 1,129 patients with colorectal cancer were used to measure the mRNA expression levels of the following genes associated with the effects of standard chemotherapy for colorectal cancer: 5-fluorouracil (5-FU)-related thymidylate synthase (TYMS), dihydropyrimidine dehydrogenase (DPYD) and thymidine phosphorylase (TYMP); folate-related dihydrofolate reductase (DHFR), folylpolyglutamate synthase (FPGS) and gamma-glutamyl hydrolase (GGH); irinotecan-related topoisomerase I (TOP1); oxaliplatin-related excision repair cross-complementing 1 (ERCC1); biologic agent-related vascular endothelial growth factor (VEGF) and epidermal growth factor receptor (EGFR). Large-scale population analysis was performed to determine the association of gene expression with the clinicopathological features, in particular, the location of the colorectal cancer. From the results of our analysis of the mRNA expression of these 10 genes, we noted the strongest correlation between DPYD and TYMP, followed by TYMS and DHFR. The location of the colorectal cancer was classified into 4 regions (the right- and left-sided colon, rectosigmoid and rectum) and was compared with gene expression. A significant difference in all genes, apart from VEGF, was noted. Of the remaining 9 genes, the highest expression of TYMS and DPYD was observed in the right-sided colon; the highest expression of GGH and EGFR was noted in the left-sided colon; the highest expression of DHFR, FPGS, TOP1 and ERCC1 was noted in the rectosigmoid, whereas TYMP expression was approximately equivalent in the right-sided colon and rectum, and higher than that in other locations. The data generated from this study may prove to be useful for the development of individualized chemotherapeutic treatments for patients with colorectal cancer, and will mean that the tumor location is taken into account.

Pathologic Factors Associated with Prognosis after Adjuvant Chemotherapy in Stage II/III Microsatellite-Unstable Colorectal Cancers

Background:

Although there are controversies regarding the benefit of fluoropyrimidine-based adjuvant chemotherapy in patients with microsatellite instability–high (MSI-H) colorectal cancer (CRC), the pathologic features affecting postchemotherapeutic prognosis in these patients have not been fully identified yet.

Methods:

A total of 26 histopathologic and immunohistochemical factors were comprehensively evaluated in 125 stage II or III MSI-H CRC patients who underwent curative resection followed by fluoropyrimidine-based adjuvant chemotherapy. We statistically analyzed the associations of these factors with disease-free survival (DFS).

Results:

Using a Kaplan- Meier analysis with log-rank test, we determined that ulceroinfiltrative gross type (p=.003), pT4 (p<.001), pN2 (p=.002), perineural invasion (p=.001), absence of peritumoral lymphoid reaction (p=.041), signet ring cell component (p=.006), and cribriform comedo component (p=.004) were significantly associated with worse DFS in patients receiving oxaliplatin-based adjuvant chemotherapy (n=45). By contrast, pT4 (p<.001) and tumor budding-positivity (p=.032) were significant predictors of poor survival in patients receiving non-oxaliplatin–based adjuvant chemotherapy (n=80). In Cox proportional hazards regression model-based univariate and multivariate analyses, pT category (pT1-3 vs pT4) was the only significant prognostic factor in patients receiving non-oxaliplatin–based adjuvant chemotherapy, whereas pT category, signet ring cell histology and cribriform comedo histology remained independent prognostic factors in patients receiving oxaliplatin-based adjuvant chemotherapy.

Conclusions:

pT4 status is the most significant pathologic determinant of poor outcome after fluoropyrimidine-based adjuvant chemotherapy in patients with stage II/III MSI-H CRC.

Distinct gene expression profiles of proximal and distal colorectal cancer: implications for cytotoxic and targeted therapy

Colorectal cancer (CRC) is a heterogeneous disease with genetic profiles and clinical outcomes dependent on the anatomic location of the primary tumor. How location impacts the molecular makeup of a tumor and how prognostic and predictive biomarkers differ between proximal versus distal colon cancers is not well established. We investigated the associations between tumor location, KRAS and BRAF mutation status, and the mRNA expression of proteins involved in major signaling pathways, including tumor growth (EGFR), angiogenesis (VEGFR2), DNA repair (ERCC1) and fluoropyrimidine metabolism (TS). FFPE tumor specimens from 431 advanced CRC patients were analyzed. The presence of 7 different KRAS base substitutions and the BRAF V600E mutation was determined. ERCC1, TS, EGFR and VEGFR2 mRNA expression levels were detected by RT-PCR. BRAF mutations were significantly more common in the proximal colon (p<0.001), whereas KRAS mutations occurred at similar frequencies throughout the colorectum. Rectal cancers had significantly higher ERCC1 and VEGFR2 mRNA levels compared to distal and proximal colon tumors (p=0.001), and increased TS levels compared to distal colon cancers (p=0.02). Mutant KRAS status was associated with lower ERCC1, TS, EGFR, and VEGFR2 gene expression in multivariate analysis. In a subgroup analysis, this association remained significant for all genes in the proximal colon and for VEGFR2 expression in rectal cancers. The mRNA expression patterns of predictive and prognostic biomarkers as well as associations with KRAS and BRAF mutation status depend on primary tumor location. Prospective studies are warranted to confirm these findings and determine the underlying mechanisms.

Role of topoisomerase I and thymidylate synthase expression in sporadic colorectal cancer: associations with clinicopathological and molecular features

Topoisomerase I (Topo I) and thymidylate synthase (TS) are essential enzymes for the replication, transcription and repair of DNA, and are potential biomarkers in colorectal cancer (CRC). The aim of the study was to correlate the tissue expression of Topo I and TS in sporadic CRCs with relevant pathological and molecular features and patients' outcome. Topo I and TS expression was assessed by immunostaining in 112 consecutive primary CRCs. Increased expression of Topo I was found in 36% of tumors, preferentially rectal (50%) and with not otherwise specified (NOS) histology (44%). Topo I expression was associated with 18q allelic loss (LOH), (p=0.013), microsatellite stable phenotype (p=0.002) and normal expression of mismatch proteins hMLH1 and hMSH2 (p=0.0012 and p=0.02, respectively). High TS expression was found in 60% of tumors, more frequently in distal sites (62%) and with NOS histology (66%); no association with microsatellite instability was observed. Topo I seems to be involved in the chromosomal instability pathway of sporadic CRCs. Conversely, high TS expression is unlikely to affect the clinical behavior of microsatellite unstable CRCs.

The prognostic value of the apoptosis pathway in colorectal cancer: a review of the literature on biomarkers identified by immunohistochemistry

Research towards biomarkers that predict patient outcome in colorectal cancer (CRC) is rapidly expanding. However, none of these biomarkers have been recommended by the American Association of Clinical Oncology or the European Group on Tumor Markers. Current staging criteria result in substantial under-and over-treatment of CRC patients. Evasion of apoptosis, a characteristic feature of tumorigenesis, is known to correlate with patient outcome. We reviewed the literature on immunohistochemistry-based studies between 1998 and 2011 describing biomarkers in this pathway in CRC and identified 26 markers. Most frequently described were p53, Bcl-2, survivin, and the Fas and TRAILR1 receptors and their ligands. None of the studies reviewed provided sufficient support for implementing a single marker into current clinical practice. This is likely due to the complex biology of this pathway. We suggest focusing on the combination of key markers within the apoptosis pathway that together represent an ‘apoptotic tumor profile’, which better reflects the status of this pathway in a tumor.

Molecular markers in colorectal cancer: clinical relevance in stage II colon cancer

SUMMARY Colorectal cancer is the second most common cause of cancer death in developed countries. Adjuvant chemotherapy is standard for stage III colorectal cancer but its use in stage II is controversial. Several clinicopathological factors have been described to define a high-risk group among stage II colon cancers, which can aid the selection of patients who may benefit from chemotherapy. Local tumor invasion (T4), high histological grade, obstruction and perforation at diagnosis, and number of lymph nodes removed are the most widely accepted factors. Several molecular factors have been also investigated as prognostic candidate biomarkers. DNA ploidy, KRAS and TP53 mutations, thymidylate synthase, dihydropyrimidine dehydrogenase, thymidine phosphorylase, loss of heterozygosity on chromosome 18q and microsatellite instability have been widely investigated. The aim of this review is to analyze the current evidence and clinical applications of the classical molecular biomarkers as well as new ones such as BRAF, circulating tumor cells, genome expression signatures and DNA methylation.

A combined analysis of mismatch repair status and thymidylate synthase expression in stage II and III colon cancer

This study in 716 colon cancer patients evaluates if a combined instead of a single marker analysis of mismatch repair (MMR) status and thymidylate synthase (TS) expression could individualize the treatment decision. The results indicate that a combined analysis of MMR status and TS expression can improve prediction of response to adjuvant 5-fluorouracil (5-FU)-based chemotherapy in stage III colon cancer.

BACKGROUND

Colon cancer with mismatch repair deficiency and low TS expression has been associated with an improved prognosis. Data also indicate that MMR proficient colon cancer with high TS expression has a better response to adjuvant 5-FU-based chemotherapy. This study evaluates if a combined analysis of MMR status and TS expression in colon cancer can add prognostic value and better predict response to adjuvant 5-FU-based chemotherapy. The potential relationship between MMR status and TS expression is also investigated.

PATIENTS AND METHODS

This study includes a subgroup of 716 patients with colon cancer out of 2224 stage II and stage III colorectal cancer patients enrolled in Nordic trials randomized to surgery alone or surgery plus adjuvant 5-FU-based chemotherapy. After immunohistochemical analysis of tumor MMR status and TS expression the patients were divided into 4 groups.

RESULTS

There was a nonsignificant difference in overall survival between group 1 (patients with deficient MMR tumors with low TS) and group 4 (patients with proficient MMR tumors expressing high TS). When comparing group 1 and group 4 patients treated with surgery alone a trend to better overall survival was found in group 1, P=.06. In group 4, stage III patients had a significantly improved survival when receiving adjuvant 5-FU-based chemotherapy compared with surgery alone, P=.01. No relationship was found between MMR status and TS expression.

CONCLUSIONS

A combined instead of a single marker analysis of MMR status and TS expression can improve the prediction of response to 5-FU-based chemotherapy in stage III colon cancer.

Factors predicting the response to oral fluoropyrimidine drugs: a phase II trial on the individualization of postoperative adjuvant chemotherapy using oral fluorinated pyrimidines in stage III colorectal cancer treated by curative resection (ACT-01 Study)

We evaluated the predictive relevance of several biomarkers on the survival of patients with stage III colorectal cancer treated with adjuvant chemotherapy of oral fluoropyrimidines. This was a multicenter phase II trial on adult patients with histologically confirmed resected stage III (Dukes' C) colorectal cancer. Patients received oral doxifluridine (800 mg/m2/day) in 3 divided doses, or oral uracil/tegafur (UFT) (400 mg/m2/day) in 2 divided doses for 5 days, every 7 days for 12 months with a 5-year follow-up. Outcome measures were disease-free survival and tissue markers [thymidine phosphorylase (TP), dihydropyrimidine dehydrogenase (DPD) protein levels and TP, DPD, thymidylate synthase (TS) and orotate phosphoribosyltransferase (OPRT) mRNA levels in tumor samples and TS tandem-repeat type in blood samples]. There was a significant association between the intratumoral TP/DPD enzyme ratio and disease-free survival when the model included the drug, the parameter and the interactions between them [hazard ratio (HR)=2.76; P=0.00469]. The 5-year disease-free survival rate was statistically significantly higher in patients with high TP/DPD ratios [median ≥2.63: 71.9%; 95% confidence interval (CI) 61.4-80.0] compared to patients with low TP/DPD ratios (<2.63: 57.0%; 95% CI 46.3-66.3) (log-rank P=0.0277) following adjuvant therapy with oral fluoropyrimidines. No significant association was observed between the intratumoral TP/DPD enzyme ratio (cut-off value 2.0) and the disease-free survival rate in the doxifluridine group; primary endpoint (log-rank P=0.6850). The magnitude of the intratumoral TP/DPD enzyme ratio may be a potential indicator for the individualization of postoperative adjuvant chemotherapy with oral fluoropyrimidines for stage III colorectal cancer.

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

BACKGROUND

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

MATERIALS AND METHOD

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

RESULTS

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

CONCLUSION

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

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.

Prognostic and predictive impact of DNA mismatch repair in the management of colorectal cancer

Colorectal cancers develop via two major pathways that include chromosomal instability and microsatellite instability. Microsatellite instability occurs due to deficient DNA mismatch repair (MMR), which can be caused by epigenetic silencing of the MLH1 MMR gene in sporadic colorectal cancers or germline mutations in MMR genes that result in Lynch syndrome. While the molecular origin of deficient MMR differs, sporadic and Lynch syndrome tumors share similar pathological features and have a more favorable stage-adjusted prognosis compared with MMR-proficient cases. While controversy remains, there is evidence to suggest that deficient MMR may predict a lack of benefit from 5-fluorouracil-based adjuvant chemotherapy. The focus of this article is on the MMR phenotype and its prognostic and predictive implications for the management of patients with colorectal cancer.

Model-based prediction of defective DNA mismatch repair using clinicopathological variables in sporadic colon cancer patients

BACKGROUND

: Colon cancers with defective DNA mismatch repair (MMR) have a favorable prognosis and may lack benefit from 5-fluorouracil-based adjuvant chemotherapy. The authors developed models to predict MMR deficiency in sporadic colon cancer patients using routine clinical and pathological data.

METHODS

: TNM stage II and III colon carcinomas (n = 982) from 6 5-fluorouracil-based adjuvant therapy trials were analyzed for microsatellite instability and/or MMR protein expression. Tumor-infiltrating lymphocytes (TILs) were quantified (n = 326). Logistic regression and a recursive partitioning and amalgamation analysis were used to identify predictive factors for MMR status.

RESULTS

: Defective MMR was detected in 147 (15%) cancers. Tumor site and histologic grade were the most important predictors of MMR status. Distal tumors had a low likelihood of defective MMR (3%; 13 of 468); proximal tumors had a greater likelihood (26%; 130 of 506). By using tumor site, grade, and sex, the logistic regression model showed excellent discrimination (c statistic = 0.81). Proximal site, female sex, and poor differentiation showed a positive predictive value (PPV) of 51% for defective MMR. In a patient subset (n = 326), a model including proximal site, TILs (>2/high-power field), and female sex showed even better discrimination (c statistic = 0.86), with a PPV of 81%.

CONCLUSIONS

: Defective MMR is rare in distal, sporadic colon cancers, which should generally not undergo MMR testing. Proximal site, poor differentiation, and female sex detect 51% of tumors with defective MMR; substituting TILs for grade increases the PPV to 81%. These data can increase the efficiency of MMR testing to assist in clinical decisions. Cancer 2010. (c) 2010 American Cancer Society.

Thymidilate synthase expression predicts longer survival in patients with stage II colon cancer treated with 5-flurouracil independently of microsatellite instability

BACKGROUND

5-Fluorouracil (5-FU) is the most commonly used therapeutic agent for colon cancer treatment. Several studies have evaluated in patients with colon cancer, either the role of genes involved in the 5-FU pathway, such as thymidylate synthase (TS), thymidine phosphorylase (TP) and dihydropyrimidine dehydrogenase (DPD) or the role of microsatellite instability (MSI) as prognostic or predictive markers for adjuvant chemotherapy efficacy, with discordant results. In this study we investigated the combined effect of TS, TP, DPD mRNA expression and MSI status in primary tumors of patients with colon cancer, all treated with 5-FU adjuvant therapy.

METHODS

TS, TP and DPD expression levels were investigated by real-time quantitative RT-PCR on RNA extracts from formalin-fixed and paraffin-embedded tissues of 55 patients with colon adenocarcinoma. In the same case study MSI status was assessed on DNA extracts.

RESULTS

A higher TS expression was significantly associated with a longer survival for patients with cancers of stage II (P < 0.01), but not for those with stage III (P = 0.68). In addition, in multivariate analysis, a higher TS expression was significantly associated with a decreased risk of death (HR 0.13, 95% CI 0.03-0.59, P < 0.01), while the MSI status did not have effects on patients' survival.

CONCLUSIONS

This retrospective investigation suggests that TS gene expression at mRNA level can be a useful marker of better survival in patients (especially of those with cancers of stage II) receiving 5-FU adjuvant chemotherapy, independently of the MSI status.

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.

Prognostic effect of activated EGFR expression in human colon carcinomas: comparison with EGFR status

BACKGROUND

Evidence suggests that epidermal growth factor receptor (EGFR)-activation status may better predict the clinical behaviour of colon cancers than does EGFR expression. However, the prognostic effect of phospho-EGFR in primary colon cancer remains undefined.

METHODS

Phospho-EGFR (Tyr-1173) and EGFR expression were analysed by immunohistochemistry (IHC) in tissue microarrays of TNM stage II and III colon cancers from completed adjuvant therapy trials (n=388). Staining intensity was scored and correlated with clinicopathological variables, DNA mismatch repair (MMR) status, rates of cell proliferation (Ki-67), apoptosis (caspase-3), and patient survival.

RESULTS

Phospho-EGFR expression was detected in 157 of 388 (40%) tumours, whereas EGFR was found in 214 of 361 (59%). Although phospho-EGFR was unrelated to clinicopathological variables, strong EGFR intensity was associated with higher tumour stage (P=0.03). Tumours overexpressing EGFR (P=0.0002) or phospho-EGFR (P=0.015) showed increased Ki-67, but not caspase-3 expression. Phospho-EGFR was not prognostic. EGFR intensity was associated with worse disease-free survival (DFS) (hazard ratio (HR): 1.21 (1.03, 1.41); P=0.019) and overall survival (OS) (HR: 1.19 (1.02, 1.39); P=0.028). Tumours expressing both EGFR and phospho-EGFR had similar survival as EGFR alone. Stage and lymph node number were prognostic for DFS and OS, and histological grade for OS. EGFR was an independent predictor of DFS (P=0.042) after adjustment for stage, histological grade, age, and MMR status.

CONCLUSION

Phospho-EGFR and EGFR expression were associated with tumour cell hyperproliferation. Phospho-EGFR was not prognostic, whereas increased EGFR intensity was independently associated with poor DFS.

Clinical implications of microsatellite instability in sporadic colon cancers

PURPOSE OF REVIEW

To review data demonstrating the prognostic and predictive impact of microsatellite instability (MSI) in human colon carcinomas.

RECENT FINDINGS

MSI is a molecular marker of defective DNA mismatch repair that is detected in approximately 15% of sporadic colon cancers. Most, but not all retrospective studies, have shown that colon cancers with MSI have better stage-adjusted survival rates compared with non-MSI tumors. Furthermore, analyses of colon cancers from participants in randomized adjuvant therapy trials have suggested that MSI tumors do not benefit from treatment with 5-fluorouracil. Recent studies, including a pooled analysis, validate prior data demonstrating the prognostic and predictive impact of MSI status in colon cancer.

SUMMARY

MSI is a molecular marker that can provide valuable prognostic and predictive information in colon cancer patients. In the appropriate clinical setting, MSI data can be used in clinical decision-making. Specifically, the favorable outcome of stage II colon cancers with MSI indicates that such patients should not receive adjuvant chemotherapy. Although data for stage III colon cancers with MSI suggest a lack of benefit from 5-fluorouracil alone, the benefit of the current standard treatment, 5-fluorouracil, leucovorin, and oxaliplatin, in this subgroup remains unknown and awaits further study.

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

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

Does microsatellite instability predict the efficacy of adjuvant chemotherapy in colorectal cancer? A systematic review with meta-analysis

BACKGROUND

Microsatellite instability (MSI) status in predicting the efficacy of adjuvant chemotherapy in colorectal cancer remains controversial.

MATERIALS AND METHODS

Studies were identified through PubMed, Embase and ASCO proceedings with a combination of keywords (colorectal cancer, chemotherapy and MSI).

RESULTS

A MA was performed for treated and non-treated MSI population on seven studies. Statistical calculations were performed on 7 studies representing 3690 patients; mean age: 65.5 years; 810 stage II and 2444 stage III (75%). MSI-high (MSI-H) was found in 454 patients (14% of the global population), and microsatellite stable (MSS) in 2871. A total of 1444 patients received 5-fluorouracil (5FU)-based chemotherapy, whereas 1518 patients did not. For MSI-H patients, there was no statistically significant difference for RFS whether or not they received chemotherapy (5 studies); HR RFS: 0.96 (95% confidence interval (CI): 0.62-1.49); HR OS (6 studies): 0.70 (95% CI: 0.44-1.09; p=0.12). Elsewhere, we found a significant interaction between MSI status (MSI-H or MSS) and therapeutic status suggesting a lesser benefit for MSI-H than for MSS patients (HR interaction RFS: 0.77 (95% CI: 0.67-0.87)).

CONCLUSION

We found similar RFS for treated and untreated MSI-H patients, showing that MSI-H status, in addition to being a good prognostic factor is also a predictive factor of non response.

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

Background

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

Methods

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

Results

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

Conclusion

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

Thymidylate synthase and microsatellite instability in colorectal cancer: implications for disease free survival, treatment response and survival with metastases

BACKGROUND

Colorectal cancer (CRC) cell lines displaying microsatellite instability (MSI) are resistant to 5-fluorouracil (5-FU) in vitro, which can be overcome by restoring DNA mismatch repair (MMR) competence. Thymidylate synthase (TS) is inhibited by 5-FU, being another potential mediator of therapeutic resistance to 5-FU. The clinical relevance of these observations remains unclear.

OBJECTIVE

We examined the expression of TS and two MMR proteins (hMLH1 and hMSH2) in advanced CRC patients, to determine a) their mutual relationship, b) association to therapeutic response and c) impact on disease outcome.

MATERIAL AND METHODS

Tumour samples from 73 patients CRC who were treated in advanced stage with either irinotecan alone or in combination with 5-FU/leucovorin, were analysed for expression of TS, hMLH1 and hMSH2 using immunohistochemistry (IHC).

RESULTS

TS expression was closely correlated with hMLH1 expression (negative-weak/moderate-strong) (p=0.0001). TS-MMR expression was significantly (p=0.029 for whole series; p=0.004 for the 5-FU treated cases) related to response to treatment; tumours with low levels of both TS and MMR responded better (n=14/27, 51.8%) than those with high TS and MMR (n=3/18, 16.6%). Patients with high TS-MMR expression had a significantly longer DFS (47 months vs. 9 months, n=26) than those with low TS-MMR index (p=0.015), while the reverse was true concerning survival with metastases (WMS) (p=0.018) in all the patients (n=73).

CONCLUSIONS

The present data suggest that MSI patients with low TS and deficient MMR demonstrate a significantly shorter DFS and longer WMS than patients with high expression of both markers, and they are also more likely to obtain the greatest benefit from 5-FU based chemotherapy.

Proapoptotic Bad and Bid protein expression predict survival in stages II and III colon cancers

PURPOSE

Proapoptotic BH3-only proteins Bad and Bid initiate apoptosis by binding to regulatory sites on prosurvival Bcl-2 proteins to directly neutralize their function. We determined if expression of these proteins in colon cancers may account for differences in patient survival.

EXPERIMENTAL DESIGN

Tumor-node-metastasis stages II and III primary colon carcinomas from patients treated in 5-fluorouracil-based adjuvant therapy trials were studied. Immunohistochemical analysis of Bad and Bid proteins was done in tumors (n = 379) and adjacent normal mucosa. Expression was correlated with clinicopathologic variables, disease-free survival rates (DFS), and overall survival (OS) rates.

RESULTS

High expression of the Bad protein [hazard ratio (HR), 0.64; 95% confidence interval (95% CI), 0.43-0.96; P = 0.031] in the cytoplasm of tumor cells was significantly associated with more favorable OS in a univariate analysis. The combined Bad and Bid variable was prognostic for DFS (P = 0.027) and OS (P = 0.006). Stage and histologic grade, but not DNA mismatch repair status, were also prognostic for OS. Multivariate Cox analysis showed that high expression of Bad (HR, 0.64; 95% CI, 0.43-0.97; P = 0.027) and Bid (HR, 0.68; 95% CI, 0.49-0.97; P = 0.034) were independent predictors of OS after adjustment for stage, grade, age, treatment, and study. The combined variable of Bad + Bid was independently associated with DFS (P = 0.020) and OS (P = 0.004).

CONCLUSION

Proapoptotic Bad and Bid proteins are independent prognostic variables in colon cancer patients receiving adjuvant treatment. If validated, Bad and Bid expression may assist in risk stratification and selection of patients to receive adjuvant chemotherapy.

Microsatellite instability and the association with plasma homocysteine and thymidylate synthase in colorectal cancer

The possible associations between microsatellite instability, homocysteine and thymidylate synthase were investigated in tumors and plasma from 130 patients with colorectal cancer. Other analyses included thymidylate synthase and 5,10-methylene-tetrahydrofolate reductase gene polymorphisms, carcinoembryonic antigen, vitamin B12, and folate. Microsatellite instability of tumors was associated with higher levels of plasma homocysteine (p = 0.008) and higher protein expression of thymidylate synthase (p < 0.001). Supplemental analyses ruled out that the finding could be explained by the other analyzed factors. CEA was not associated with neither homocysteine nor microsatellite instability. The data suggests that there is a more pronounced methyl unit deficiency in microsatellite instable tumors.

Targeted therapy of cancer: new roles for pathologists in colorectal cancer

Personalized/individualized/tailored therapy for each patient is an important goal for improving the outcome of patients with colorectal adenocarcinoma and includes the intention to maximize efficacy and minimize toxicity of chemotherapeutic agents. Numerous barriers must be overcome to reach this goal because outcome is affected by an unholy trinity of tumor characteristics that include somatic alterations at the DNA, RNA, and protein level; patient characteristics that include germline genetic differences such as polymorphisms in enzymes affecting the metabolism of chemotherapeutic agents; and environmental exposures and factors that include diet and physical activity. At present, evaluation of epidermal growth factor receptor (EGFR) expression by immunohistochemistry in colorectal adenocarcinoma is generally required for treatment with one of the monoclonal antibody therapies directed against that target, despite the absence of evidence for predictive value of the assay, whereas EGFR fluorescent in situ hybridization (FISH) may be predictive. In addition, the Food and Drug Administration of the United States now requires a 'black box' warning on the packaging of irinotecan for evaluation of germline polymorphism in UGT1A1, the gene mutated in Gilbert's syndrome, for potential reduction of drug dosage in patients with the UGT1A1*28 polymorphism. Numerous other potential markers have been identified but have not yet reached levels of evidence that support their routine usage. For example, KRAS gene mutation appears to preclude improved survival after therapy with monoclonal antibody therapy directed at EGFR, and extensive DNA methylation is associated with lack of efficacy of 5-fluorouracil (5-FU)-based chemotherapy. Additional markers will come into routine usage as reports of research studies continue to appear in the literature. Clinical trials driven by molecular targets and agents directed against them, and understanding of the conflicting data on utility of markers reported in the literature, are needed to advance the field.

Colorectal carcinomas with microsatellite instability display increased thymidylate synthase gene expression levels

BACKGROUND

This study investigated whether patients with colorectal cancer (CRC) who have tumors with high microsatellite instability (MSI; MSI-H) had an altered expression of the folate and methyl-group metabolism. The gene expression levels of thymidylate synthase (TS), reduced folate carrier (RFC-1), folylpolyglutamate synthase (FPGS), and methylenetetrahydrofolate reductase (MTHFR) in mucosa and tumor were compared with patients with MSS. Furthermore, the influence of TS polymorphisms on TS gene expression levels and MSI-H was studied.

PATIENTS AND METHODS

The microsatellite status (MSI-H, low instability [MSI-L], or stable [MSS]) and TS polymorphisms were analyzed in genomic DNA from 181 patients with CRC. Gene expression levels of TS, RFC-1, FPGS, and MTHFR in mucosa and tumors were quantified and the difference in TS expression between tumor and mucosa was designated DeltaTS.

RESULTS

Significantly higher gene expression levels of TS (P < .0001) were detected in patients with CRC with MSI-H compared with MSS/MSI-L tumors. Gene expression of TS and FPGS were significantly higher in right-sided MSI-H tumors compared with right-sided MSS/MSI-L tumors (P < .0001, P = .041, respectively). A significant correlation between DeltaTS and the number of unstable markers was found (P < .0001). An inverse association between age and TS expression was found in MSI tumors (r = -0.57; P = .0004) and also in right-sided tumors (r = -0.25, P = .011) regardless of MSI status. No relation was detected between MSI status and the TS polymorphisms or between the TS polymorphisms and TS expression.

CONCLUSION

This study has revealed, for the first time, that age and the frequency of unstable MSI markers were factors that were linked to the variability in TS gene expression in tumors.

5-Fluorouracil is efficiently removed from DNA by the base excision and mismatch repair systems

BACKGROUND & AIMS

5-Fluorouracil (FU) is one of the mainstays of colon cancer chemotherapy. Although developed as an inhibitor of thymidylate synthase, its cytotoxicity has been linked also to its incorporation into RNA. Surprisingly, although FU is incorporated also into DNA, little is known about its metabolism in this nucleic acid.

METHODS

Using extracts of human cells and circular DNA substrates containing a single FU residue either paired with adenine or mispaired with guanine, we studied the enzymology of FU processing.

RESULTS

In nicked circular substrates, FU/G mispairs were efficiently repaired by mismatch repair (MMR). In covalently closed circular DNA, which is refractory to MMR, FU/G repair was initiated by either thymine-DNA glycosylase or uracil-DNA glycosylase, whereas FU/A pairs were processed by UNG. Methylated CpG binding domain 4 protein and single-strand selective monofunctional uracil-DNA glycosylase 1 did not detectably contribute to FU removal; however, because these recombinant enzymes process FU/G and FU/A in oligonucleotide substrates, respectively, they too may be involved in FU metabolism in vivo.

CONCLUSIONS

The functional redundancy of MMR and DNA glycosylases in FU processing should ensure that the drug is efficiently removed from DNA before it can interfere with essential DNA metabolic processes, such as transcription. However, in FU-treated cells, the nucleotide pools are depleted of thymine. The repair synthesis might thus be inhibited and leave cytotoxic gaps or breaks in DNA. Moreover, FU and/or 5-fluorouracil-2'-deoxyuridine-5'-triphosphate removed from DNA will increase the intracellular concentration of the drug and thus exacerbate its cytotoxicity.

Alterations in cell proliferation and apoptosis in colon cancers with microsatellite instability

Colon cancers with microsatellite instability (MSI) demonstrate a host immune response characterized by tumor infiltrating lymphocytes (TILs) that may exert effects upon tumor cell apoptosis and cell proliferation. Accordingly, we compared rates of apoptosis and cell proliferation in colon cancers with defective DNA mismatch repair and their association with phenotypic features and clinical outcome. Primary Astler-Coller stage B2 and C colon carcinomas (n = 329) were analyzed for MSI and for hMLH1 and hMSH2 protein expression. Apoptosis (TUNEL assay) and p53 expression were also analyzed by immunohistochemistry, and TILs were quantified by morphology. DNA ploidy and proliferation (PI: S phase + G(2)M) were evaluated using flow cytometry. MSI-H (n = 58) colon cancers showed increased TILs that were significantly associated with increased apoptosis, higher apoptosis to proliferation (AI/PI) ratios, reduced proliferative indices (PI) and diploid DNA content. Increased TILs (p = 0.036) and reduced PI (p = 0.042), but not AI or AI/PI, were associated with improved disease-free survival. Tumors with MSI-H (p = 0.032) or loss of hMLH1 or hMSH2 proteins (p = 0.040), or diploidy (p = 0.0015), had better adjusted overall survival rates. Interestingly, similar rates of cell turnover and overlapping survival rates were found in diploid MSS/MSI-L tumors and in MSI-H cases. In conclusion, higher apoptosis/proliferation ratios and reduced cell proliferation are phenotypic features of MSI-H tumors that are associated with increased TILs, indicating an activated immune response that may contribute to their favorable survival rates.

Microsatellite instability accounts for tumor site-related differences in clinicopathologic variables and prognosis in human colon cancers

OBJECTIVE

Colon cancers with high frequency microsatellite instability (MSI-H) are preferentially located in the proximal colon. Given that 15-20% of sporadic colon cancers are MSI-H, we determined whether tumor site-specific differences in clinicopathological variables, biomarkers, and prognosis are due to inclusion of MSI-H cases.

METHODS

TNM stage II and III primary colon carcinomas (N = 528) from patients enrolled in 5-fluorouracil-based adjuvant trials were analyzed for MSI using 11 microsatellite markers. Immunostaining for DNA mismatch repair (hMLH1, hMSH2, hMSH6) and p53 proteins was performed. DNA ploidy (diploid vs aneuploid/tetraploid) and proliferative indices (PI: S-phase + G(2)M) were analyzed by flow cytometry.

RESULTS

MSI-H was found in 95 (18%) colon cancers. Proximal tumors (N = 286) were associated with MSI-H, older age (>65 yr), poor differentiation, and diploid DNA content compared with distal tumors (all P< or = 0.016). Nuclear p53 staining was more frequent in distal tumors (P= 0.002); PI was unrelated to tumor site. When MSI-H tumors were excluded, no tumor site-related differences were found except for age, which remained associated with proximal cancers (P= 0.030). Proximal site was associated with improved disease-free survival in all patients (P= 0.042), but not when MSI-H cases were excluded (P= 0.236). MSI-H status or loss of mismatch repair proteins, diploidy, and lower PI were associated with improved survival rates.

CONCLUSIONS

Tumor site-related differences in clinicopathological variables, biomarkers, and prognosis of sporadic colon cancers can be explained by the inclusion of MSI-H cases. Older age, however, is associated with proximal tumor site independent of MSI status.

Advances in chemotherapy for colorectal cancer

Gastroenterologists have a primary role in the management of colorectal cancer patients in that they frequently establish the diagnosis, direct or perform tumor staging evaluations, and initiate referrals for oncologic treatment. Several important advances have been made in the adjuvant treatment of colon and rectal cancers and in therapy of metastatic disease. These advances include the development of more effective combination chemotherapy regimens and molecularly targeted antibodies. These antibodies are directed against regulators of angiogenesis (vascular endothelial growth factor) and tumor cell growth (epidermal growth factor receptor) and have been shown to enhance the efficacy of cytotoxic chemotherapy. In the treatment of localized rectal cancer, the integration of chemotherapy and radiation with surgery has resulted in neoadjuvant approaches that achieve improved tumor control, sphincter preservation, and reduce treatment-related toxicities. This review presents an update of the current approach to colon and rectal cancer treatment, highlighting recent chemotherapeutic advances in the management of these highly prevalent malignancies.