Systematic review of microsatellite instability and colorectal cancer prognosis

Sex differences in epidemiological, clinical and pathological characteristics of colorectal cancer

Sex significantly influences the clinical and pathological characteristics of colorectal cancer (CRC). These include differences in incidence and mortality rates, clinical presentations including age, emergency surgery for complications from CRC, screening participation rates, site, stage and treatment utilization, histopathology and survival. Environmental, behavioral and biological factors contribute to the differential risk. Recent advances in the molecular biology of CRC, specifically in microsatellite status, estrogen hormone and estrogen receptor beta, have led to greater understanding of the effect of estrogen in colorectal carcinogenesis. Estrogen may preferentially protect against microsatellite unstable cancers through its effect on selected molecular targets; however, the exact pathways have not been elucidated. Recognition of important sex disparities in these areas may lead to the implementation of specific measures to diminish these differences and facilitate equitable distribution of health resources. Identifying specific molecular targets on CRC that interact with estrogen may stimulate research to improve the overall outcomes of all patients with CRC.

Olfactomedin 4 (GW112, hGC-1) is an independent prognostic marker for survival in patients with colorectal cancer

Colorectal cancer (CRC) is one of the leading causes of cancer-related deaths worldwide. We previously performed Serial Analysis of Gene Expression (SAGE) on four primary gastric cancer samples and identified several gastric cancer-specific genes. Of these genes, olfactomedin 4 (OLFM4, also known as GW112 or hGC-1) is a candidate gene for cancer-specific expression. In the present study, we examined the expression and distribution of olfactomedin 4 in CRC by immunohistochemistry. Of the 176 CRC cases, 59 (34%) were positive for cytoplasmic staining of olfactomedin 4. Olfactomedin 4-positive CRC cases showed earlier T classification (P=0.0180), N classification (P=0.0149) and stage (P=0.0144) than olfactomedin 4-negative CRC cases. In the 176 CRC patients, those with olfactomedin 4-positive CRC had a better survival rate than patients with olfactomedin 4-negative CRC (P=0.0092). Multivariate analysis indicated that T classification, M classification and negative olfactomedin 4 expression were independent predictors of survival in patients with CRC. In addition to cytoplasmic staining of olfactomedin 4, stromal staining at the invasive front was observed. In total, 29 (16%) of the 176 CRC cases were positive for stromal olfactomedin 4; however, stromal olfactomedin 4 staining was not correlated with any clinicopathologic characteristic or with patient survival. These results indicate that olfactomedin 4 is a valuable marker for long-term survival in patients with CRC.

Prognostic impact of microRNA-related gene polymorphisms on survival of patients with colorectal cancer

PURPOSE

The polymorphisms in microRNA (miRNA) machinery genes and miRNA-containing genomic regions may play an important role in cancer development and prognosis. Accordingly, the present study analyzed the single nucleotide polymorphisms (SNPs) of miRNA-related genes and their impact on the prognosis for patients with colorectal cancer.

METHODS

Four hundred and twenty-six consecutive patients with surgically treated colorectal adenocarcinoma were enrolled. The genomic DNA was extracted from fresh colorectal tissue and 40 polymorphisms of miRNA-related genes determined using a real-time PCR genotyping assay.

RESULTS

In a univariate analysis, the progression-free survival of the patients with the combined mir492 C/G and G/G genotype was significantly worse than that of the patients with the mir492 C/C genotype (rs2289030) (P value = 0.0426), although there was no difference in the overall survival. However, no association was noted between the SNPs of the miRNA-related genes evaluated and survival in a multivariate analysis.

CONCLUSIONS

None of the 40 miRNA-related gene polymorphisms investigated in this study was found to be an independent prognostic marker for Korean patients with surgically resected colorectal cancer. However, further studies are warranted to clarify the role of miRNA-related gene polymorphisms as a prognostic biomarker for colorectal cancer patients.

Clinical impact of microsatellite instability in colon cancer following adjuvant FOLFOX therapy

PURPOSE

Colon cancer with DNA mismatch repair (MMR) defects reveals indistinguishable clinical and pathologic aspects, including better prognosis and reduced response to 5-fluorouracil (5-FU)-based chemotherapy. There has been no consensus for p53 as a prognostic marker in colorectal cancer. This study investigated the clinical implication of MSI-H/MMR-D and p53 expression in R0-resected colon cancer patients who received adjuvant oxaliplatin/5-FU/leucovorin (FOLFOX) therapy.

EXPERIMENTAL DESIGN

We analyzed 135 patients, who had been treated by adjuvant chemotherapy containing 5-FU and oxaliplatin (FOLFOX) after curative resection (R0) for colon adenocarcinoma between May 2004 and November 2007. Tumor expression of the MMR proteins, MLH1 and MSH2, was detected by immunohistochemistry (IHC) in surgically resected tumor specimens. MSI was analyzed by polymerase chain reaction (PCR) amplification using fluorescent dye-labeled primers specific for microsatellite loci. Tumors with MMR defects were defined as those demonstrating loss of MMR protein expression (MMR-D) and/or microsatellite instability high (MSI-H) genotype. Expression patterns of p53 were determined in a semiquantitative manner by light microscopy.

RESULTS

There were 13 (9.6%) patients with stage II, 108 (80%) with stage III, and 14 (10.4%) with stage IV. Fourteen patients with stage IV (10.3%) had metastases to liver only, all of whom underwent complete metastasectomy for liver metastases. In total, 134 tumor specimens were genotyped, 115 specimens were tested by IHC and 113 cases had both genotyping and IHC results available for analysis. Genotyping results demonstrated that 12 (9.0%) cases were MSI-H and 122 (91.0%) were MSI-L/S. By IHC, 11 (9.6%) patients were MMR-D and 104 (90.4%) were MMR-I. The methods were in agreement in 108 patients (94.7%). We assessed 114 patients for p53 expression by immunostaining. MMR status was not significantly associated with DFS (P = 0.56) or OS (P = 0.61) in patients with colon cancer (n = 135) receiving adjuvant FOLFOX. According to p53 status, there was also no significant difference for DFS (P = 0.11) and OS (P = 0.94). For patients with genotyping/IHC agreement (n = 108), there was no difference in DFS (P = 0.57) and OS (P = 0.98) between patients with MSI-H/MMR-D and MSI-L/S/MMR-I tumors.

CONCLUSION

The MMR status or p53 positivity was not significantly associated with outcomes to FOLFOX as adjuvant chemotherapy in colon cancer patients with R0 resection. Adding oxaliplatin in adjuvant chemotherapy may overcome negative impact of 5-FU on colon cancers with MSI-H/MMR-D.

Value of the identification of microsatellite instability in colorectal cancer

OBJECTIVE

Recent studies defend a possible prognostic and therapeutic value of the identification of microsatellite instability (MSI) in colorectal cancer. This work tries to assess the impact that the identification of MSI tumours can have in clinical practice.

MATERIAL AND METHODS

We recovered tumour samples from 92 of the 143 patients operated on for colorectal cancer in our institution between 1995 and 2000. Five MSI markers (BAT 25, BAT 26, D2S123, D5S346 and D17S250) were studied on them. The rate and clinicopathologic characteristics of MSI tumours were investigated along with their impact on the global and disease-free survival as compared with microsatellite stable (MSS) tumours.

RESULTS

All 5 microsatellite markers' status were established in 73 patients (79.3% of the samples). Among them, 7 tumours showed instability in just one marker (low microsatellite instability [MSI-L]) whereas 5 tumours had mutations in 2 or more markers (high microsatellite instability [MSI-H]), for a total 15.4% rate of MSI tumours. All MSI-H tumours were located in the right colon. We could not fi nd any impact from MSI detection on global or disease-free survival.

CONCLUSIONS

MSI determination did not identify groups of patients with a different prognosis. Moreover, with such low incidence its determination can only be justified in those cases that fulfill Bethesda's criteria to identify families with Lynch's syndrome.

Three DNA methylation epigenotypes in human colorectal cancer

PURPOSE

Whereas the CpG island methylator phenotype (CIMP) in colorectal cancer associates with microsatellite instability (MSI)-high and BRAF-mutation(+), the existence of an intermediate-methylation subgroup associated with KRAS-mutation(+) is controversial, and suitable markers for the subgroup have yet to be developed. Our aim is to clarify DNA methylation epigenotypes of colorectal cancer more comprehensively.

EXPERIMENTAL DESIGN

To select new methylation markers on a genome-wide scale, we did methylated DNA immunoprecipitation-on-chip analysis of colorectal cancer cell lines and re-expression array analysis by 5-aza-2'-deoxycytidine/Trichostatin A treatment. Methylation levels were analyzed quantitatively in 149 colorectal cancer samples using matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry. Colorectal cancer was epigenotyped by unsupervised two-way hierarchical clustering method.

RESULTS

Among 1,311 candidate silencing genes, 44 new markers were selected and underwent quantitative methylation analysis in colorectal cancer samples together with 16 previously reported markers. Colorectal cancer was clustered into high-, intermediate-, and low-methylation epigenotypes. Methylation markers were clustered into two major groups: group 1 showing methylation in high-methylation epigenotype, and group 2 showing methylation in high- and intermediate-methylation epigenotypes. A two-step marker panel deciding epigenotypes was developed with 95% accuracy: the 1st panel consisting of three group-1 markers (CACNA1G, LOX, SLC30A10) to extract high-methylation epigenotype, and the 2nd panel consisting of four group-2 markers (ELMO1, FBN2, THBD, HAND1) and SLC30A10 again to divide the remains into intermediate- and low-methylation epigenotypes. The high-methylation epigenotype correlated significantly with MSI-high and BRAF-mutation(+) in concordance with reported CIMP. Intermediate-epigenotype significantly correlated with KRAS-mutation(+). KRAS-mutation(+) colorectal cancer with intermediate-methylation epigenotype showed significantly worse prognosis.

CONCLUSIONS

Three methylation epigenotypes exist in colorectal cancer, and suitable classification markers have been developed. Intermediate-methylation epigenotype with KRAS-mutation(+) correlated with worse prognosis.

The effect of DNA mismatch repair (MMR) status on oxaliplatin-based first-line chemotherapy as in recurrent or metastatic colon cancer

Colon cancer with DNA mismatch repair (MMR) defects reveals distinct clinical and pathologic features, including a better prognosis but reduced response to 5-fluorouracil (5-FU)-based chemotherapy. A current standard treatment for recurrent or metastatic colon cancer uses capecitabine plus oxaliplatin (CAPOX), or continuous-infusion fluorouracil plus oxaliplatin (FOLFOX). This study investigated the effect of MMR status on the treatment outcomes for CAPOX and FOLFOX as first-line combination chemotherapy in recurrent or metastatic colon cancer. We analyzed 171 patients who had been treated with CAPOX or FOLFOX as first-line combination chemotherapy in recurrent or metastatic colon adenocarcinoma between February 2004 and July 2008. Tumor expression of the MMR proteins, MLH1 and MSH2, was detected by immunohistochemistry (IHC) in surgically resected tumor specimens. The microsatellite instability (MSI) was analyzed by polymerase chain reaction (PCR) amplification, using fluorescent dye-labeled primers specific to microsatellite loci. Tumors with MMR defect were defined as those demonstrating a loss of MMR protein expression (MMR-D) and/or a microsatellite instability-high (MSI-H) genotype. In all, 75 patients (44%) received FOLFOX, and 96 patients (56%) received CAPOX as first-line combination chemotherapy. The incidence of colon cancer with MMR defect was 10/171 (6%). Colon cancers with MMR defect (MSI-H and/or MMR-D) are more commonly located in proximal to the splenic flexure (p=0.03). The MMR status did not significantly influence the overall response (p=0.95) to first-line CAPOX or FOLFOX treatment in patients with recurrent or metastatic colon cancer. According to the MMR status, there was no significant difference for PFS (p=0.50) and OS (p=0.47) in patients with recurrent or metastatic colon cancer treated with first-line CAPOX or FOLFOX. In colon cancers with MMR defect, there was no significant difference for PFS (p=0.48) and OS (p=0.56) between CAPOX and FOLFOX as first-line combination chemotherapy. However, in MMR intact, there was significant difference for OS between CAPOX and FOLFOX (p=0.04). OS was significantly better in patients treated with CAPOX when compared to patients with FOLFOX. The MMR status does not predict the effect of oxaliplatin-based combination chemotherapy as 1st line in recurrent or metastatic colon cancers. CAPOX in the first-line treatment of recurrent or metastatic colon cancer with MMR intacts showed a superior OS compared with FOLFOX unlike colon cancer with MMR defects.

Immune infiltration in human tumors: a prognostic factor that should not be ignored

The natural history of a tumor includes phases of 'in situ' growth, invasion, extravasation and metastasis. During these phases, tumor cells interact with their microenvironment and are influenced by signals coming from stromal, endothelial, inflammatory and immune cells. Indeed, tumors are often infiltrated by various numbers of lymphocytes, macrophages or mast cells. It is generally believed that the latter produce factors that maintain chronic inflammation and promote tumor growth, whereas lymphocytes may control cancer outcome, as evidenced in mouse models. In this study, we analyze data from large cohorts of human tumors, clearly establishing that infiltration of the primary tumor by memory T cells, particularly of the Th1 and cytotoxic types, is the strongest prognostic factor in terms of freedom from disease and overall survival at all stages of clinical disease. We review data suggesting that tertiary lymphoid structures adjacent to tumors and composed of mature dendritic cells (T and B cells organized as germinal centers) may be the site of an antitumor reaction. We propose an immune scoring based on the type, density and location of lymphocyte infiltrates as a novel prognostic factor for use in addition to tumor node metastasis staging to predict disease-free survival and to aid in decisions regarding adjuvant therapies in early stage human cancers.

A review on the molecular diagnostics of Lynch syndrome: a central role for the pathology laboratory

Lynch syndrome (LS) is caused by mutations in mismatch repair genes and is characterized by a high cumulative risk for the development of mainly colorectal carcinoma and endometrial carcinoma. Early detection of LS is important since surveillance can reduce morbidity and mortality. However, the diagnosis of LS is complicated by the absence of a pre-morbid phenotype and germline mutation analysis is expensive and time consuming. Therefore it is standard practice to precede germline mutation analysis by a molecular diagnostic work-up of tumours, guided by clinical and pathological criteria, to select patients for germline mutation analysis. In this review we address these molecular analyses, the central role for the pathologist in the selection of patients for germline diagnostics of LS, as well as the molecular basis of LS.

Locally advanced rectal cancer: from molecular profiling to clinical practice. A literature review: Part 2

Colorectal cancer is the third most common cause of cancer deaths worldwide. The management of rectal cancer has undergone, and continues to undergo, significant evolutions. In the last two decades, new multimodality strategies have been developed. The ability to predict tumor response before treatment could significantly impact the selection of patients for preoperative combined-modality therapy, as well as potentially modify postoperative treatment plans. The present review analyzes the new molecular targets that could be involved in predicting response and prognosis.

Colorectal cancer due to deficiency in DNA mismatch repair function: a review

Lynch syndrome (LS) is an autosomal dominant cancer predisposition syndrome attributable to deleterious germline mutations in mismatch repair (MMR) genes. The syndrome is typified by early-onset, frequently right-sided colorectal cancers (CRCs) with characteristic histologic features and tendency for multiplicity and an increased risk for extracolonic tumors at particular sites; it accounts for 1% to 5% of CRC. Deficient mismatch repair (dMMR) function manifests as immunohistochemically detectable absence of one or more MMR proteins and microsatellite instability (MSI). Approximately 15% of sporadic, noninherited CRC are characterized by high-level MSI, nearly always owing to transcriptional silencing of MLH1; these sporadic and LS cases exhibit considerable phenotypic overlap. Identification of CRC with dMMR is desirable to identify LS and because MSI status is prognostic and potentially predictive. This review will discuss the history of LS, the principles of MMR and MSI, the clinicopathologic features of LS-associated and sporadic high-level MSI CRC, the fundamentals of clinical testing for dMMR CRC, and the results of the Columbus-area Lynch syndrome study. We conclude with our approach to population-based LS screening based on institutional experience with nearly 2000 cases.

A prospective cohort study shows unique epigenetic, genetic, and prognostic features of synchronous colorectal cancers

BACKGROUND & AIMS

Synchronous colorectal neoplasias (2 or more primary carcinomas identified in the same patient) are caused by common genetic and environmental factors and can be used to study the field effect. Synchronous colon cancers have not been compared with control solitary cancers in a prospective study.

METHODS

We analyzed data collected from 47 patients with synchronous colorectal cancers and 2021 solitary colorectal cancers (controls) in 2 prospective cohort studies. Tumors samples were analyzed for methylation in LINE-1 and 16 CpG islands (CACNA1G, CDKN2A [p16], CRABP1, IGF2, MLH1, NEUROG1, RUNX3, SOCS1, CHFR, HIC1, IGFBP3, MGMT, MINT1, MINT31, p14 [ARF], and WRN); microsatellite instability (MSI); the CpG island methylator phenotype (CIMP); 18q loss of heterozygosity; KRAS, BRAF, and PIK3CA mutations; and expression of beta-catenin, p53, p21, p27, cyclin D1, fatty acid synthase, and cyclooxygenase-2.

RESULTS

Compared with patients with solitary colorectal cancer, synchronous colorectal cancer patients had reduced overall survival time (log-rank, P = .0048; hazard ratio [HR], 1.71; 95% confidence interval [CI]: 1.17-2.50; P = .0053; multivariate HR, 1.47; 95% CI: 1.00-2.17; P = .049). Compared with solitary tumors, synchronous tumors more frequently contained BRAF mutations (P = .0041), CIMP-high (P = .013), and MSI-high (P = .037). Methylation levels of LINE-1 (Spearman r = 0.82; P = .0072) and CpG island methylation (P < .0001) correlated between synchronous cancer pairs from the same individuals.

CONCLUSIONS

Synchronous colorectal cancers had more frequent mutations in BRAF, were more frequently CIMP- and MSI-high, and had a worse prognosis than solitary colorectal cancers. Similar epigenomic and epigenetic events were frequently observed within a synchronous cancer pair, suggesting the presence of a field defect.

Lymphocytic reaction to colorectal cancer is associated with longer survival, independent of lymph node count, microsatellite instability, and CpG island methylator phenotype

PURPOSE

Host immune response to tumor may be an important prognostic factor for colon cancer patients. However, little is known on prognostic significance of histopathologic lymphoid reaction to tumor, independent of the number of lymph nodes examined and tumoral molecular alterations, including microsatellite instability (MSI) and the CpG island methylator phenotype (CIMP), both of which are associated with lymphocytic reaction and clinical outcome.

EXPERIMENTAL DESIGN

Using 843 colorectal cancer patients in two independent prospective cohorts, we examined patient prognosis in relation to four components of lymphocytic reaction (i.e., Crohn's-like reaction, peritumoral reaction, intratumoral periglandular reaction, and tumor-infiltrating lymphocytes) and overall lymphocytic score (0-12). CIMP was determined using eight markers including CACNA1G, CDKN2A (p16), CRABP1, IGF2, MLH1, NEUROG1, RUNX3, and SOCS1. Cox proportional hazard models computed hazard ratio for mortality, adjusted for covariates including tumor stage, body mass index, lymph node count, KRAS, BRAF, p53, cyclooxygenase-2 (PTGS2), MSI, CIMP, and LINE-1 methylation.

RESULTS

Increasing overall lymphocytic reaction score including tumor-infiltrating lymphocytes was associated with a significant improvement in colorectal cancer-specific and overall survival (log-rank P < 0.003). These findings remained significant (adjusted hazard ratio estimates, 0.49-0.71; P(trend) < 0.009) in multivariate models that adjusted for covariates, including body mass index, MSI, CIMP, LINE-1 hypomethylation, and cyclooxygenase-2. The beneficial effect of tumoral lymphocytic reaction was consistent across strata of clinical, pathologic, and molecular characteristics.

CONCLUSIONS

Lymphocytic reactions to tumor were associated with improved prognosis among colorectal cancer patients, independent of lymph node count and other clinical, pathologic, and molecular characteristics.

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.

Intraepithelial effector (CD3+)/regulatory (FoxP3+) T-cell ratio predicts a clinical outcome of human colon carcinoma

BACKGROUND & AIMS

Regulatory T cells (Tregs) express the forkhead box transcription factor (FoxP3) and suppress the antitumor immune response. We investigated whether the intratumoral densities of FoxP3(+) and effector CD3(+) lymphocytes are associated with prognosis of patients with colon cancer.

METHODS

FoxP3 and CD3 expression and location were determined in stage II and III colon carcinomas (n = 160) and normal mucosa (n = 25) by immunohistochemistry; CD4 and FoxP3 were localized by dual immunofluorescence microscopy. T-cell markers were compared with pathological variables, DNA mismatch repair status, and patient survival using Cox proportional hazards models.

RESULTS

FoxP3(+) and CD3(+) T-cell densities were increased in carcinomas compared with autologous normal mucosa (P < .0001). An increase in intraepithelial FoxP3(+) cells was associated with poor tumor differentiation (P = .038), female sex (P = .028), and advanced patient age (P = .042). FoxP3(+) cell density was not prognostic, yet patients with tumors with reduced intraepithelial CD3(+) T-cell densities had reduced disease-free survival (DFS) rates (hazard ratio [HR], 1.87 [95% confidence interval, 1.10-3.16]; P = .018). A low intraepithelial CD3(+)/FoxP3(+) cell ratio predicted reduced DFS (46.2% vs 66.7% survival at 5 years; HR, 2.17 [95% confidence interval, 1.11-4.23]; P = .0205). The prognostic impact of these markers was maintained when tumors were stratified by mismatch repair status. By multivariate analysis, a low CD3(+)/FoxP3(+) cell ratio (P= .0318) and low numbers of CD3(+) T cells (P = .0397) predicted shorter DFS times and were stronger prognostic variables than tumor stage or number of lymph node metastases.

CONCLUSIONS

A low intraepithelial CD3(+)/FoxP3(+) cell ratio and reduced numbers of CD3(+) T cells were associated with shorter patient survival time, indicating the importance of an effector to Treg cell ratio in colon cancer prognosis.

Aurora A is differentially expressed and regulated in chromosomal and microsatellite instable sporadic colorectal cancers

The centrosome-associated kinase aurora A has been shown to be involved in genetic instability and to be (over)expressed in several human carcinomas. This study investigated aurora A gene copy numbers, mRNA and protein expression as well as tumour cell proliferation and aneuploidy in chromosomal and microsatellite instable sporadic colorectal cancers. Case-matched tissues of normal (n=71) and dysplastic (n=49) colorectal epithelium and invasive carcinomas (n=71) were included in this study. PCR-based microsatellite analysis classified 14/71 (20%) of carcinomas as microsatellite instable. A stepwise increase of aurora A mRNA expression (P<0.0001; quantitative RT-PCR) and aurora A protein expressing tumour cells (P=0.0141; immunohistochemistry) occurred in the adenoma-carcinoma sequence. Within invasive carcinomas, aurora A mRNA levels (P=0.0259) and aurora A positive tumour cells (P<0.0001) were closely associated with tumour cell proliferation (Ki-67 specific immunohistochemistry). Compared with chromosomal instable carcinomas, microsatellite instable carcinomas had significantly more aurora A positive tumour cells (P=0.0043) and a higher tumour cell proliferation (P=0.0335). In contrast, only chromosomal instable carcinomas exhibited marked tumour cell aneuploidy (P=0.0004, fluorescence in situ hybridization) and significantly higher aurora A gene copy numbers (P=0.0206) as compared with microsatellite instable carcinomas. This study further supports a role of aurora A in the carcinogenesis of sporadic colorectal cancers. Moreover, it demonstrates that in a minority of predominantly microsatellite instable carcinomas the presence of aurora A positive tumour cells is merely reflecting tumour cell proliferation. In contrast, the large majority of chromosomal instable carcinomas shows additional (de)regulation of aurora A by gene amplification and concomitant tumour cell aneuploidy. Thus, sporadic colorectal cancers exhibit different mechanisms of aurora A regulation and this may impact the efficacy of aurora-targeted therapies.

IVS10+12A>G polymorphism in hMSH2 gene associated with prognosis for patients with colorectal cancer

BACKGROUND

The polymorphisms in DNA repair genes may contribute to a variation in the DNA repair capacity, thereby affecting the risk of carcinogenesis and prognosis of colorectal cancer. Accordingly, the present study analyzed 14 polymorphisms in DNA repair genes and their impact on the prognosis for patients with colorectal cancer.

MATERIALS AND METHODS

Three hundred and ninety-seven consecutive patients with curatively resected colorectal adenocarcinoma were enrolled in the present study. The genomic DNA was extracted from fresh colorectal tissue and 14 polymorphisms of DNA repair genes determined using a real-time PCR genotyping assay.

RESULTS

The median age of the patients was 63 years, and 218 (54.9%) patients had colon cancer, while 179 (45.1%) patients had rectal cancer. A multivariate survival analysis, including age, differentiation, carcinoembryonic antigen level, and stage, revealed a better survival for the patients with the combined IVS10+12AG and GG genotype than for the patients with the IVS10+12AA genotype [disease-free survival: hazard ratio (HR) 0.47, 95% confidence interval (CI) 0.30-0.75, P = 0.002; overall survival: HR 0.50, 95% CI 0.26-0.98, P = 0.042]. None of the other polymorphisms was associated with survival.

CONCLUSION

The IVS10+12A>G polymorphism in the hMSH2 gene was found to be an independent prognostic marker for patients with colorectal cancer.

Clinical implications of microsatellite instability and MLH1 gene inactivation in sporadic insulinomas

CONTEXT

The molecular pathogenesis of sporadic insulinomas is unknown. There is a lack of biomarker to distinguish benign and malignant form of insulinoma.

OBJECTIVE

Our objective was to confirm the occurrence of microsatellite instability (MSI) in insulinomas, to identify alterations of mismatch repair (MMR) genes in the tumors, and to evaluate the possibility to distinguish benign and malignant insulinoma or to predict the clinical outcome of patients with these alterations.

DESIGN AND PATIENTS

We detected MSI and inactivation of MLH1 gene in 55 sporadic insulinomas by PCR, immunohistochemical staining, allelic typing, analysis of promoter methylation, and exon mutations. Their correlations with clinicopathological characteristics were analyzed with univariate and multivariate statistic analysis.

RESULTS

A high rate of MSI (MSI-H) was found in 33% of sporadic insulinomas. Reduced expression of mutL homolog 1 (MLH1) protein was observed in 36% of insulinomas and correlated with MSI-H (P = 0.008). Promoter methylation and loss of heterozygosity of MLH1 gene was found in 31 and 49% of insulinomas, respectively. Reduced expression of MLH1 and MSI-H were significantly associated with both tumor malignancy (P = 0.033 and P = 4.8 x 10(-6), respectively) and incurable disease (P = 0.006 and P = 0.001, respectively).

CONCLUSION

High frequency of MSI occurred in sporadic insulinomas. The silencing of MLH1 gene may partially contribute to the MSI-H in the tumors. Assessing MSI-H and expressions of MLH1 could be used to distinguish benign and malignant insulinomas and to predict the outcome of patients.

p21 expression in colon cancer and modifying effects of patient age and body mass index on prognosis

p21 (Cyclin-dependent kinase inhibitor-1A, CDKN1A or CIP1) plays a role in regulating cell cycle, and its expression is lost in most colorectal cancers. p21 Is related with energy balance status, cellular senescence, and stem cell aging. Thus, the influence of p21 loss on tumor behavior and clinical outcome may be modified by patient age and body mass index (BMI). Using 647 colon cancers in two independent prospective cohorts, p21 loss was observed in 509 (79%) tumors by immunohistochemistry. Cox proportional hazard models computed hazard ratio (HR) for death, adjusted for potential confounders, including p53, cyclin D1, KRAS, BRAF, PIK3CA, LINE-1 hypomethylation, CpG island methylator phenotype (CIMP), and microsatellite instability (MSI). p21 Loss was independently associated with low colon cancer-specific mortality [HR, 0.58; 95% confidence interval (95% CI), 0.38-0.89; adjusted for the covariates including MSI, CIMP, and LINE-1 methylation]. The prognostic effect of p21 loss differed significantly by age at diagnosis (P(interaction) < 0.0001) and BMI (P(interaction) = 0.002). The adjusted HR for cancer-specific mortality (p21 loss versus p21 expression) was 4.09 (95% CI, 1.13-14.9) among patients <60 year old and 0.37 (95% CI, 0.24-0.59) among patients >or=60 year old. The adverse prognostic effect of obesity was limited to p21-expressing cases (adjusted HR, 5.85; 95% CI, 2.28-15.0; BMI, >or=30 versus <30 kg/m(2)), but no such effect was observed among p21-lost cases. In conclusion, p21 loss in colon cancer is associated with longer survival among patients >or=60 year old, whereas it is associated with shorter survival among patients <60 year old. Patient BMI also differentially influences prognosis according to p21 CDKN1A status. Our data suggest host-tumor interactions influencing tumor aggressiveness.

Prognostic significance and molecular associations of 18q loss of heterozygosity: a cohort study of microsatellite stable colorectal cancers

PURPOSE

Loss of heterozygosity (LOH) at chromosome 18q frequently occurs late during colon cancer development and is inversely associated with microsatellite instability (MSI). 18q LOH has been reported to predict shorter survival in patients with colorectal cancer, whereas MSI-high status has been associated with superior prognosis. However, it is unclear whether 18q LOH in colorectal cancer has any prognostic implication independent of MSI status and other potential predictors of clinical outcome.

PATIENTS AND METHODS

Among 555 non-MSI-high colorectal cancers (stage I to IV) in two independent prospective cohort studies, we examined 18q LOH in relation to other molecular events and patient survival. Cox proportional hazard models computed hazard ratio of death, adjusted for clinical and tumoral characteristics, including KRAS, BRAF, PIK3CA, beta-catenin, p53, CpG island methylator phenotype, LINE-1 methylation, and John Cunningham (JC) virus T antigen.

RESULTS

In multivariate logistic regression, 18q LOH was independently associated with JC virus T antigen (odds ratio [OR] = 1.93; P = .0077), body mass index > or = 30 kg/m(2) (obesity; OR = 2.01; P = .014), high tumor grade (OR = 0.40; P = .018), KRAS mutation (OR = 0.66; P = .40), and LINE-1 hypomethylation (for a 30% decrease; OR = 1.92; P = .045). Five-year colorectal cancer-specific survival was 75% among patients with 18q LOH-positive tumors and 74% among those with 18q LOH-negative tumors (log-rank P = .80). Five-year overall survival was 70% among patients with 18q LOH-positive tumors and 68% among those with 18q LOH-negative tumors (log-rank P = .54). Multivariate analysis did not show prognostic significance of 18q LOH.

CONCLUSION

In our large prospective study of patients with non-MSI-high colorectal cancer, 18q LOH or allelic imbalance was not associated with patient survival.

CD3+ cells at the invasive margin of deeply invading (pT3-T4) colorectal cancer and risk of post-surgical metastasis: a longitudinal study

BACKGROUND

The density of tumour-infiltrating lymphocytes (TIL) has been proposed as an independent predictor of outcome in patients with colorectal cancer. However, the relative roles of TIL density, nodal status, and microsatellite instability (MSI) in predicting tumour progression to metachronous metastasis remain to be elucidated. The aim of this study was to assess the relationship between the density of CD3+ TIL and the postsurgical occurrence of distant-organ metastases in a large series of patients with deeply invading and MSI-typed colorectal cancer.

METHODS

Per cent areas of immunoreactivity due to CD3+ TIL at the invasive margin of the tumour (CD3+ TIL(IM)) were measured by computer-assisted image analysis in 286 tissue specimens from pT3 or pT4 MSI-tested colorectal cancer. Tissue samples were taken from consecutive patients who underwent resection at the IRCCS Istituto Clinico Humanitas, Rozzano, Milan, Italy, from January, 1997, to November, 2004, for colorectal cancer with no evidence of metastasis at diagnosis. Occurrence of metachronous metastasis, disease-specific survival (DSS), and disease-free survival (DFS), were assessed retrospectively in relation to per cent immunoreactivity.

FINDINGS

CD3+ TIL(IM) density was higher in MSI colorectal cancer than in mismatch repair-system-proficient tumours (6.53%vs 2.19%; p<0.0001). At Cox analysis, higher CD3+ TIL(IM) densities, colonic site, and absence of nodal involvement were significantly associated with a lower risk of metachronous metastasis, but only the interaction between CD3+ TIL(IM) density and N-stage was significant on multivariate analysis (p=0.002). On separate analysis of node-negative colorectal cancer, increasing percentage of CD3+ immunoreactive area progressively reduced the risk of metachronous metastasis (<1%, reference; 1-5%, HR 0.28, 95% CI 0.10-0.81, p=0.02; >5%, 0.06, 0.01-0.48, p=0.008). Conversely, no significant association was seen between CD3+ immunoreactive area and risk of metachronous metastasis in node-positive colorectal cancer. Accordingly, CD3+ TIL(IM) density was associated with a better DSS (p=0.01) and DFS (p=0.006) only in patients with node-negative colorectal cancer. In primary tumours that had progressed to metachronous metastasis, stage III tumours had higher CD3+ TIL(IM) densities than stage II tumours (p=0.0004).

INTERPRETATION

Metachronous metastases are unlikely to arise from node-negative colorectal cancers with a high-density CD3+ TIL(IM), whereas high densities of CD3+ TIL(IM) are not associated with the absence of postsurgical metastasis in patients with node-positive colorectal cancer. Our data suggest that densities of CD3+ TIL(IM) cannot be used as an independent predictor of clinical outcome in patients with stage III colorectal cancer and, at least for now, the tumour-node-metastasis classification should remain the preferred prognostic system. Our findings are consistent with a relationship between nodal involvement and tumour immunoevasion.

FUNDING

MIUR (Ministero dell'Istruzione, dell'Università e della Ricerca), Target Project Oncologia 2006, and Alleanza Contro il Cancro.

A cohort study of STMN1 expression in colorectal cancer: body mass index and prognosis

OBJECTIVES

STMN1 (stathmin or oncoprotein-18) destabilizes microtubules and reorganizes cytoskeleton, and functions in cell cycle progression and cell migration. STMN1 activity is influenced by p53, p27, and the PI3K/AKT pathway. However, its prognostic significance in colon cancer is uncertain.

METHODS

Utilizing 546 colorectal cancers (stage I-IV) from two independent prospective cohort studies (the Nurses' Health Study and Health Professionals Follow-up Study), STMN1 expression was detected in 297 (54%) tumors by immunohistochemistry. Cox proportional hazard models computed hazard ratios (HRs) of mortality, adjusted for clinical and tumoral features, including microsatellite instability (MSI), CpG island methylation phenotype (CIMP), LINE-1 hypomethylation, KRAS, BRAF, PIK3CA, p53, p21, p27, cyclin D1, beta-catenin, fatty acid synthase, FASN, and COX-2.

RESULTS

Five-year colorectal cancer-specific survival was 78% in STMN1-positive patients and 76% in STMN1-negative patients (log-rank P=0.30). STMN1-positivity was not significantly associated with cancer-specific survival in univariate analysis with HR of 0.82 (95% confidence interval (CI), 0.59-1.14), which became significant in multivariate analysis (adjusted HR=0.60; 95% CI, 0.41-0.87; P=0.0078). Notably, the prognostic effect of obesity (body mass index, BMI> or =30 kg/m2) significantly differed by STMN1 (P(interaction)=0.005). Obesity was associated with high cancer-specific mortality among STMN1-positive patients (adjusted HR=2.36; 95% CI, 1.18-4.69), whereas obesity was not associated with high mortality among STMN1-negative patients (adjusted HR=0.51; 95% CI, 0.24-1.07).

CONCLUSIONS

STMN1 overexpression in colorectal cancer is independently associated with improved survival. The adverse prognostic effect of obesity was limited to patients with STMN1-positive tumors. Our findings suggest the presence of a tumor (STMN1)-host (BMI) interaction that potentially determines clinical outcome.

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.

Prognostic and predictive value of common mutations for treatment response and survival in patients with metastatic colorectal cancer

BACKGROUND

We address the prognostic and predictive value of KRAS, PIK3CA and BRAF mutations for clinical outcomes in response to active agents in the treatment of metastatic colorectal cancer (mCRC).

METHODS

We determined KRAS, BRAF and PIK3CA mutations in tumours from 168 patients treated for mCRC at two institutions. All patients received 5-FU-based first-line chemotherapy and treatment outcome was analysed retrospectively.

RESULTS

KRAS, BRAF and PIK3CA mutations were present in 62 (37%), 13 (8%) and 26 (15%) cases, respectively. Multivariate analysis uncovered BRAF mutation as an independent prognostic factor for decreased survival (hazard ratio (HR) 4.0, 95% confidence interval (CI) 2.1-7.6). In addition, patients with BRAF-mutant tumours had significantly lower progression-free survival (PFS: HR 4.0, 95% CI 2.2-7.4) than those whose tumors that carried wild-type BRAF. Among 92 patients treated using chemotherapy and cetuximab as salvage therapy, KRAS mutation was associated with lack of response (P=0.002) and shorter PFS (P=0.09). BRAF (P=0.0005) and PIK3CA (P=0.01) mutations also predicted reduced PFS in response to cetuximab salvage therapy.

CONCLUSIONS

These results underscore the potential of mutational profiling to identify CRCs with different natural histories or treatment responses. The adverse significance of BRAF mutation should inform patient selection and stratification in clinical trials.

Genetic prognostic and predictive markers in colorectal cancer

Despite many studies of the likely survival outcome of individual patients with colorectal cancer, our knowledge of this subject remains poor. Until recently, we had virtually no understanding of individual responses to therapy, but the discovery of the KRAS mutation as a marker of probable failure of epidermal growth factor receptor (EGFR)-targeted therapy is a first step in the tailoring of treatment to the individual. With the application of molecular analyses, as well as the ability to perform high-throughput screens, there has been an explosive increase in the number of markers thought to be associated with prognosis and treatment outcome in this disease. In this Review, we attempt to summarize the sometimes confusing findings, and critically assess those markers already in the public domain.

A cohort study of cyclin D1 expression and prognosis in 602 colon cancer cases

PURPOSE

Cyclin D1 and cyclin-dependent kinases (CDK) are commonly activated in colorectal cancer. The activity of cyclin D1 can be blocked by CDK inhibitors, including p27 (CDKN1B) and p21 (CDKN1A, which is induced by p53). However, prognostic significance of tumoral cyclin D1 remains uncertain, and no previous study has considered potential confounding effect of p53, p21, p27, and related molecular events [microsatellite instability (MSI), CpG island methylator phenotype, and LINE-1 hypomethylation].

EXPERIMENTAL DESIGN

Among 602 colon cancer patients (stage I-IV) in two prospective cohort studies, cyclin D1 overexpression was detected in 330 (55%) tumors by immunohistochemistry. Cox proportional hazard models computed hazard ratios (HR) of colon cancer-specific and overall mortalities, adjusted for patient characteristics and tumoral molecular features, including p53, p21, p27, cyclooxygenase-2, fatty acid synthase, LINE-1 methylation, CpG island methylator phenotype, MSI, BMI, KRAS, and BRAF.

RESULTS

Cyclin D1 overexpression was associated with a low cancer-specific mortality in Kaplan-Meier analysis (P = 0.006), and in both univariate Cox regression [unadjusted HR, 0.64; 95% confidence interval (CI), 0.47-0.88; P = 0.0063] and multivariate analyses (adjusted HR, 0.57; 95% CI, 0.39-0.84; P = 0.0048). Similar findings were observed for an overall mortality (adjusted HR, 0.74; 95% CI, 0.57-0.98; P = 0.036). Notably, the effect of cyclin D1 on survival might differ by MSI status (P(interaction) = 0.008). Compared with tumors that were both cyclin D1-negative and MSI-low/microsatellite stable, the presence of either cyclin D1 or MSI-high or both seemed to confer better clinical outcome (adjusted HR point estimates, 0.10-0.65).

CONCLUSIONS

Cyclin D1 overexpression is associated with longer survival in colon cancer.

Prognostic implications of BAX protein expression and microsatellite instability in all non-metastatic stages of primary colon cancer treated by surgery alone

PURPOSE

This study examined whether the apoptosis-related protein, BAX, or the microsatellite-instability phenotype provide prognostic information in patients with resected colon cancer.

METHODS

A total of 371 stage I-III patients that previously underwent radical surgery were included (mean follow-up 51.8 months). BAX expression was examined by immunohistochemical staining; high-frequency microsatellite instability (MSI+) was determined by assessing the specific marker, BAT26, using single-strand conformation polymorphism (SSCP)-based analysis.

RESULTS

High BAX expression was found in 66.4% of patients. MSI+ tumors were observed in 14.8% of 344 patients. Univariate analysis showed that unlike MSI, low BAX expression was significantly correlated with poor disease-specific overall survival (OS) in stages I-III (p = 0.04). Multivariate subgroup analyses revealed that unlike MSI, low BAX was an independent predictor for OS in stage II (p = 0.009); however, in stages I or III, BAX or MSI were not independent predictors of OS.

CONCLUSIONS

In stage II colon cancer treated with surgery alone, BAX protein expression may be a predictor for prognosis.

Pharmacogenomics and -genetics in colorectal cancer

Despite recent progress in our knowledge about the development and therapy of colorectal cancer (CRC), it still remains one of the major cancer related deaths throughout the world. With the introduction of new cytotoxic and targeting agents a significant improvement in progression-free and overall survival has been achieved. However, a significant percentage (40-50%) of patients do not experience beneficial effects and suffer from severe toxicities. It will be critical to identify molecular markers, which may help to assess therapeutic response and outcome in CRC. Validation of predictive and prognostic molecular markers will enable oncologists to tailor patient specific treatment strategies for the individual patient according to the molecular profile of both the patient and their tumor. Individualized therapy will help to improve therapeutic efficacy and to minimize toxicities and therapeutic expenses.

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.

Methylation of helicase-like transcription factor in serum of patients with colorectal cancer is an independent predictor of disease recurrence

BACKGROUND

CpG island hypermethylation is a common epigenetic event in colorectal cancer. The presence of simultaneous methylation of multiple genes is associated with poor prognosis in many types of tumours including colorectal cancer. We have shown earlier that the hypermethylation of the genes HLTF and HPP1/TPEF are independent prognostic serum markers in colorectal cancer identifying patients with increased risk of death. The purpose of this study was to analyse whether these factors also identify patients at risk of disease recurrence after curative surgery.

METHODS

Pretherapeutic sera of 106 patients curatively resected for colorectal cancer with known 5-year follow-ups were analysed for the presence of methylation of the genes HLTF and HPP1/TPEF.

RESULTS

HLTF serum methylation was associated with an increased risk of disease recurrence by a factor of 2.7 (95% confidence interval: 1.2-6.0; P=0.014). Multivariate analysis showed methylated HLTF serum DNA to be independently associated with poor outcome and a relative risk of disease recurrence of 2.5 (95% confidence interval: 1.1-5.6; P=0.023).

CONCLUSION

Here, we show for the first time that a DNA methylation-based surrogate marker can serve as a predictor of disease recurrence in colorectal cancer.

Utility of p16 immunohistochemistry for the identification of Lynch syndrome

PURPOSE

Immunohistochemistry for mismatch repair proteins has shown utility in the identification of Lynch syndrome, but majority of tumors with loss of MLH1 expression are due to sporadic hypermethylation of the MLH1 promoter. These tumors can also show epigenetic silencing of other genes, such as p16. The aim of our study is to evaluate the utility of p16 immunohistochemistry in the prediction of MLH1 germline mutations.

EXPERIMENTAL DESIGN

p16 immunohistochemistry was appropriately evaluated in 79 colorectal cancers with loss of MLH1 expression. Methylation of MLH1 and p16 were quantitatively studied using real-time PCR assay Methylight. BRAF V600E mutation in tumor tissue was also investigated. Genetic testing for germline mutation of MLH1 was made on 52 patients.

RESULTS

Loss of p16 expression was seen in 21 of 79 samples (26.6%). There was found statistically significant association between p16 expression and p16 methylation (P < 0.001), MLH1 methylation (P < 0.001), and BRAF mutation (P < 0.005). All tumors with loss of p16 expression showed hypermethylation of p16 (21 of 21), 95.2% (20 of 21) showed MLH1 methylation, and 71.4% (15 of 21) were mutated for BRAF V600E. Mutational analysis showed pathogenic germline mutations in 8 of the patients, harboring 10 tumors. All 10 of these tumors showed normal staining of p16 in the immunochemical analysis.

CONCLUSIONS

p16 immunohistochemistry is a good surrogate marker for p16 and MLH1 epigenetic silencing due to hypermethylation, and is useful as screening tool in the selection of patients for genetic testing in Lynch syndrome.

Gene expression patterns in mismatch repair-deficient colorectal cancers highlight the potential therapeutic role of inhibitors of the phosphatidylinositol 3-kinase-AKT-mammalian target of rapamycin pathway

PURPOSE

High-frequency microsatellite-instable (MSI-H) tumors account for approximately 15% of colorectal cancers. Therapeutic decisions for colorectal cancer are empirically based and currently do not emphasize molecular subclassification despite an increasing collection of gene expression information. Our objective was to identify low molecular weight compounds with preferential activity against MSI colorectal cancers using combined gene expression data sets.

EXPERIMENTAL DESIGN

Three expression/query signatures (discovery data set) characterizing MSI-H colorectal cancer were matched with information derived from changes induced in cell lines by 164 compounds using the systems biology tool "Connectivity Map." A series of sequential filtering and ranking algorithms were used to select the candidate compounds. Compounds were validated using two additional expression/query signatures (validation data set). Cytotoxic, cell cycle, and apoptosis effects of validated compounds were evaluated in a panel of cell lines.

RESULTS

Fourteen of the 164 compounds were validated as targeting MSI-H cell lines using the bioinformatics approach; rapamycin, LY-294002, 17-(allylamino)-17-demethoxygeldanamycin, and trichostatin A were the most robust candidate compounds. In vitro results showed that MSI-H cell lines due to hypermethylation of MLH1 are preferentially targeted by rapamycin (18.3 versus 4.4 mumol/L; P = 0.0824) and LY-294002 (15.02 versus 10.37 mumol/L; P = 0.0385) when compared with microsatellite-stable cells. Preferential activity was also observed in MSH2 and MSH6 mutant cells.

CONCLUSION

Our study shows that the phosphatidylinositol 3-kinase-AKT-mammalian target of rapamycin pathway is of special relevance in mismatch repair-deficient colorectal cancer. In addition, we show that amalgamation of gene expression information across studies provides a robust approach for selection of potential therapies corresponding to specific groups of patients.

Colorectal cancer expression of peroxisome proliferator-activated receptor gamma (PPARG, PPARgamma) is associated with good prognosis

BACKGROUND & AIMS

The peroxisome proliferator-activated receptor gamma (PPARG, PPARgamma) is a nuclear receptor that regulates expression of mediators of lipid metabolism and the inflammatory response. There is controversy over the pro-oncogenic or antioncogenic effects of PPARG, and little is known about its prognostic significance in colon cancer.

METHODS

Among 470 patients with colorectal cancer (stages I-IV) identified in 2 independent prospective cohorts, PPARG expression was detected in 102 tumors (22%) by immunohistochemistry. Cox proportional hazards models were used to compute hazard ratios (HRs) of colorectal cancer-specific and overall mortalities, adjusted for patient characteristics and molecular features including cyclooxygenase 2, fatty acid synthase, KRAS, BRAF, PIK3CA, p53, p21, beta-catenin, LINE-1 hypomethylation, microsatellite instability (MSI), and the CpG island methylation phenotype (CIMP).

RESULTS

Compared with patients with PPARG-negative tumors, patients with PPARG-positive tumors had significantly lower overall mortality, determined by Kaplan-Meier analysis (P=.0047), univariate Cox regression (HR, 0.55; 95% confidence interval [CI], 0.37-0.84; P=.0053), and multivariate analysis (adjusted HR, 0.43; 95% CI, 0.27-0.69; P=.0004). Patients with PPARG-positive tumors experienced lower colorectal cancer-specific mortality (adjusted HR, 0.44; 95% CI, 0.25-0.79; P=.0054). The relationship between PPARG and lower mortality did not appear to be significantly modified by MSI, CIMP, LINE-1, or the other clinical and molecular variables examined (all P(interaction)>.05).

CONCLUSIONS

Tumor expression of PPARG is independently associated with longer survival of patients. PPARG expression appears to mark an indolent subset of colorectal cancers.

p27Kip1 in stage III colon cancer: implications for outcome following adjuvant chemotherapy in cancer and leukemia group B protocol 89803

BACKGROUND

In retrospective studies, loss of p27(Kip1) (p27), a cyclin-dependent kinase inhibitor, has been associated with poor prognosis following colorectal cancer treatment. In a prospective study, we validated this relationship in patients enrolled on a trial of adjuvant chemotherapy for stage III colon cancer.

METHODS

Cancer and Leukemia Group B protocol 89803 randomized 1,264 stage III colon cancer patients to receive weekly bolus 5-fluorouracil/leucovorin or weekly bolus irinotecan, 5-fluorouracil, and leucovorin (IFL). The primary endpoint was overall survival (OS); disease-free survival was a secondary endpoint. Expression of p27 and DNA mismatch repair proteins were determined by immunohistochemistry in primary tumor and normal tissue from paraffin blocks. Data were analyzed using log-rank test.

RESULTS

Of 601 tumors analyzed, 207 (34.4%) showed p27 loss, 377 (62.8%) retained p27, and 17 (2.8%) were indeterminate. Patients with p27-negative tumors showed reduced OS [5-year OS 66%: 95% confidence interval (95% CI), 0.59-0.72 versus 75%: 95% CI, 0.70-0.79; log-rank P = 0.021]. This relationship was not influenced by treatment arm. Combination of p27 status with mismatch repair status, however, identified a small subset of patients that may benefit from IFL (n = 36; 5-year disease-free survival 81%: 95% CI, 0.64-0.98 versus 47%: 95% CI, 0.21-0.72; log-rank P = 0.042; 5-year OS 81%: 95% CI, 0.64-0.98 versus 60%: 95% CI, 0.35-0.85; log-rank P = 0.128).

CONCLUSIONS

Loss of p27 is associated with reduced survival in stage III colon cancer but by itself does not indicate a significant difference in outcome between patients treated IFL or 5-fluorouracil/leucovorin.

The impact of microRNAs on colorectal cancer

MicroRNAs are small RNAs that regulate gene expression at the post-transcriptional level. After their discovery 15 years ago, a new layer of gene regulation was introduced into every field of human biology and medicine. Considering the strong association between genetic alterations and neoplastic diseases, it is not surprising that there is a special focus on miRNAs and cancer. A multitude of experimental studies on colorectal cancer, the most common cancer site and furthermore the second most common cause of death due to cancer, deliver insight into miRNA-mediated, regulatory links to well-known oncogenic and tumour suppressor signalling pathways. Furthermore, several investigations have described the ability of microRNA expression patterns to predict prognosis in colon cancer and support diagnosis of poorly differentiated tumours. In this short review, we give a comprehensive overview focussed on miRNAs in colorectal cancer research.

Deficient mismatch repair system in patients with sporadic advanced colorectal cancer

A deficient mismatch repair system (dMMR) is present in 10–20% of patients with sporadic colorectal cancer (CRC) and is associated with a favourable prognosis in early stage disease. Data on patients with advanced disease are scarce. Our aim was to investigate the incidence and outcome of sporadic dMMR in advanced CRC. Data were collected from a phase III study in 820 advanced CRC patients. Expression of mismatch repair proteins was examined by immunohistochemistry. In addition microsatellite instability analysis was performed and the methylation status of the MLH1 promoter was assessed. We then correlated MMR status to clinical outcome. Deficient mismatch repair was found in only 18 (3.5%) out of 515 evaluable patients, of which 13 were caused by hypermethylation of the MLH1 promoter. The median overall survival in proficient MMR (pMMR), dMMR caused by hypermethylation of the MLH1 promoter and total dMMR was 17.9 months (95% confidence interval 16.2–18.8), 7.4 months (95% CI 3.7–16.9) and 10.2 months (95% CI 5.9–19.8), respectively. The disease control rate in pMMR and dMMR patients was 83% (95% CI 79–86%) and 56% (30–80%), respectively. We conclude that dMMR is rare in patients with sporadic advanced CRC. This supports the hypothesis that dMMR tumours have a reduced metastatic potential, as is observed in dMMR patients with early stage disease. The low incidence of dMMR does not allow drawing meaningful conclusions about the outcome of treatment in these patients.

Microsatellite instability predicts improved response to adjuvant therapy with irinotecan, fluorouracil, and leucovorin in stage III colon cancer: Cancer and Leukemia Group B Protocol 89803

PURPOSE

Colon cancers exhibiting DNA mismatch repair (MMR) defects demonstrate distinct clinical and pathologic features, including better prognosis and reduced response to fluorouracil (FU) -based chemotherapy. This prospective study investigated adjuvant chemotherapy containing FU and irinotecan in patients with MMR deficient (MMR-D) colon cancers.

PATIENTS AND METHODS

Cancer and Leukemia Group B 89803 randomly assigned 1,264 patients with stage III colon cancer to postoperative weekly bolus FU/leucovorin (LV) or weekly bolus irinotecan, FU, and LV (IFL). The primary end point was overall survival; disease-free survival (DFS) was a secondary end point. Tumor expression of the MMR proteins, MLH1 and MSH2, was determined by immunohistochemistry (IHC). DNA microsatellite instability was also assessed using a panel of mono- and dinucleotide markers. Tumors with MMR defects were those demonstrating loss of MMR protein expression (MMR-D) and/or microsatellite instability high (MSI-H) genotype.

RESULTS

Of 723 tumor cases examined by genotyping and IHC, 96 (13.3%) were MMR-D/MSI-H. Genotyping results were consistent with IHC in 702 cases (97.1%). IFL-treated patients with MMR-D/MSI-H tumors showed improved 5-year DFS as compared with those with mismatch repair intact tumors (0.76; 95% CI, 0.64 to 0.88 v 0.59; 95% CI, 0.53 to 0.64; P = .03). This relationship was not observed among patients treated with FU/LV. A trend toward longer DFS was observed in IFL-treated patients with MMR-D/MSI-H tumors as compared with those receiving FU/LV (0.57; 95% CI, 0.42 to 0.71 v 0.76; 95% CI, 0.64 to 0.88; P = .07; hazard ratio interaction between tumor status and treatment, 0.51; likelihood ratio P = .117).

CONCLUSION

Loss of tumor MMR function may predict improved outcome in patients treated with the IFL regimen as compared with those receiving FU/LV.

Pharmacoepigenomics in colorectal cancer: a step forward in predicting prognosis and treatment response

Despite therapeutic innovations and increasing education on lifestyle to prevent colorectal cancer, it is still one of the most common cancer types, and for men the second cause of cancer-related death. Lately, much attention has been given to identify molecular markers involved in colorectal cancer prognosis and treatment with the aim to develop a more accurate classification system based on (epi)genetic alterations and, in addition, find markers that could potentially enhance management of colorectal cancer by predicting treatment response in advance. Although many genetic markers have been claimed to have prognostic or predictive influence, results are often inconclusive and, with some exception, they are not used in standard practice. Epigenetic alterations have received less attention although they are probably even more interesting as they can potentially be reversed through drug treatment. This review describes the current knowledge on the prognostic and predictive value of epigenetic markers in colorectal cancer.

Mucinous histology predicts for poor response rate and overall survival of patients with colorectal cancer and treated with first-line oxaliplatin- and/or irinotecan-based chemotherapy

The objective of this study was to investigate the efficacy of first-line chemotherapy containing irinotecan and/or oxaliplatin in patients with advanced mucinous colorectal cancer. Prognostic factors associated with response rate and survival were identified using univariate and multivariate logistic and/or Cox proportional hazards analyses. The population included 255 patients, of whom 49 (19%) had mucinous and 206 (81%) had non-mucinous colorectal cancer. The overall response rates for mucinous and non-mucinous tumours were 18.4 (95% CI, 7.5–29.2%) and 49% (95% CI, 42.2–55.8%), respectively (P=0.0002). After a median follow-up of 45 months, median overall survival for the mucinous patients was 14.0 months compared with 23.4 months for the non-mucinous group (hazard ratio (HR), 1.74; CI 95%, 1.27–3.31; P=0.0034). After adjustment for significant features by multivariate Cox regression analysis, mucinous histology was associated with poor overall survival (HR, 1.593, 95% CI, 1.05–2.40; P=0.0267), together with performance status ECOG 2, number of metastatic sites ⩾2, and peritoneal metastases. This retrospective analysis shows that patients with mucinous colorectal cancer have poor responsiveness to oxaliplatin/irinotecan-based first-line combination chemotherapy and an unfavourable prognosis compared with non-mucinous colorectal cancer patients.

Participation of DNA repair in the response to 5-fluorouracil

The anti-metabolite 5-fluorouracil (5-FU) is employed clinically to manage solid tumors including colorectal and breast cancer. Intracellular metabolites of 5-FU can exert cytotoxic effects via inhibition of thymidylate synthetase, or through incorporation into RNA and DNA, events that ultimately activate apoptosis. In this review, we cover the current data implicating DNA repair processes in cellular responsiveness to 5-FU treatment. Evidence points to roles for base excision repair (BER) and mismatch repair (MMR). However, mechanistic details remain unexplained, and other pathways have not been exhaustively interrogated. Homologous recombination is of particular interest, because it resolves unrepaired DNA intermediates not properly dealt with by BER or MMR. Furthermore, crosstalk among DNA repair pathways and S-phase checkpoint signaling has not been examined. Ongoing efforts aim to design approaches and reagents that (i) approximate repair capacity and (ii) mediate strategic regulation of DNA repair in order to improve the efficacy of current anticancer treatments.