Kirsten ras mutations in patients with colorectal cancer: the 'RASCAL II' study

Clinical usefulness of KRAS, BRAF, and PIK3CA mutations as predictive markers of cetuximab efficacy in irinotecan- and oxaliplatin-refractory Japanese patients with metastatic colorectal cancer

BACKGROUND

Anti-epidermal growth factor receptor (EGFR) antibodies, cetuximab, and panitumumab are established as a new treatment option for metastatic colorectal cancer (mCRC). Among activating mutations downstream of EGFR, the KRAS mutation, which is present in 30-45 % of CRC patients, has shown to be a predictive biomarker of resistance to anti-EGFR antibody therapy based on Caucasian studies.

METHODS

Forty-three chemotherapy-refractory Japanese patients with mCRC were treated with cetuximab monotherapy or cetuximab plus irinotecan. KRAS, BRAF, and PIK3CA mutational status of tumors was assessed. The association between mutational status and treatment outcome was evaluated.

RESULTS

Of 43 tumors, KRAS, BRAF, and PIK3CA mutations were identified in 12 (27.9 %), 2 (4.7 %), and 2 (4.7 %) tumors, respectively. The wild-type KRAS subgroup showed better clinical outcomes than the mutant KRAS subgroup in terms of response rate (RR) (31.3 % vs. 0 %, P = 0.034) and progression-free survival (PFS) (5.1 vs. 3.0 months, P = 0.017). No responder to treatment was shown in 16 (37.2 %) patients with tumors harboring mutations in any one of the three genes (KRAS, BRAF, and PIK3CA). The wild-type subgroup without any mutations in KRAS, BRAF, and PIK3CA had a better RR (37.0 %) and PFS (6.4 months) than did the wild-type KRAS subgroup.

CONCLUSION

Our data indicated that KRAS status is predictive of cetuximab response in the Japanese population. The additional analysis of BRAF and PIK3CA genes in wild-type KRAS patients could improve selection of patients who are most likely to benefit from anti-EGFR antibody therapy.

Prognostic value of different CT measurements in early therapy response evaluation in patients with metastatic colorectal cancer

Objectives: Patients with advanced stage colorectal carcinoma (CRC) display hepatic metastases on initial staging in up to 20% of cases. The effectiveness of chemotherapy is generally evaluated by computed tomography (CT) imaging using standardized criteria (RECIST). However, RECIST is not always optimal, and other criteria have been shown to correlate with pathologic response and overall survival. The aim of this study was to evaluate the prognostic value of different CT measurement for response assessment after initiation of chemotherapy in patients with synchronous colorectal cancer liver metastases. Methods: Fifty-five patients with CRC and synchronous hepatic metastases were evaluated retrospectively at 2 academic centers. Different size, volume, ratio and attenuation parameters were determined at baseline and after 3 cycles of chemotherapy. The prognostic value of baseline measurements and of the change between baseline and second measurements was analyzed using Kaplan–Meier estimates. Results: Median time to progression was 279 days, median overall survival was 704 days. In this selective patient population, neither a significant prognostic value of initial baseline CT parameters nor a prognostic value of the change between the first and the second CT measurements was found. Conclusion: Initial morphological response assessment using different CT measurements has no prognostic value concerning time to progression or overall survival in patients with synchronous colorectal liver metastases.

Predictive role of multiple gene alterations in response to cetuximab in metastatic colorectal cancer: a single center study

Background

KRAS mutations negatively affect outcome after treatment with cetuximab in metastatic colorectal cancer (mCRC) patients. As only 20% of KRAS wild type (WT) patients respond to cetuximab it is possible that other mutations, constitutively activating the EGFR pathway, are present in the non-responding KRAS WT patients. We retrospectively analyzed objective tumor response rate, (ORR) progression-free (PFS) and overall survival (OS) with respect to the mutational status of KRAS, BRAF, PIK3CA and PTEN expression in mCRC patients treated with a cetuximab-based regimen.

Methods

67 mCRC patients were enrolled onto the study. DNA was extracted from paraffin-embedded sections derived from primary or metastatic lesions. Exon 2 of KRAS and exon 15 of BRAF were analyzed by direct sequencing, PIK3CA was evaluated by pyrosequencing and PTEN expression by immunohistochemistry.

Results

BRAF and PIK3CA mutations were independently associated with worse PFS (p = 0.006 and p = 0.028, respectively) and OS (p = 0.008 and p = 0.029, respectively). No differences in clinical outcome were found between patients who were positive or negative for PTEN expression. Conversely, patients negative for KRAS, BRAF and PIK3CA mutations were characterized by significantly better ORR, PFS and OS than patients with at least one of these mutations.

Conclusions

BRAF and PIK3CA mutations would seem to be independent predictors of anti-EGFR therapy effectiveness and could be taken into consideration during treatment decision making.

Mutant allele-specific imbalance modulates prognostic impact of KRAS mutations in colorectal adenocarcinoma and is associated with worse overall survival

The prognostic impact of distinct KRAS mutations in colorectal carcinomas is not fully characterized. We hypothesized that the prognostic impact of KRAS mutations is modulated by KRAS mutant allele-specific imbalance (MASI). KRAS MASI was assessed by sequencing electropherograms in KRAS-mutated colorectal carcinomas (N = 394, prospectively tested). The mechanism of KRAS MASI was studied by fluorescence in situ hybridization (FISH; N = 50). FISH showed that KRAS MASI developed by chromosome 12 hyperploidy (9/18, 50%) or KRAS amplification (1/18, 5.5%). KRAS MASI was more common in tumors with KRAS codon 13 than with codon 12 mutations [24/81, 30% vs. 54/313, 17%; odds ratio (OR), 2.0, 95% confidence interval (CI), 1.2-3.5; p = 0.01]. KRAS MASI was correlated with overall survival (N = 358, median follow-up = 21 months). In a multivariate analysis, KRAS codon 13 MASI was an independent adverse prognostic factor (compared to codon 13 mutants without MASI combined with all codon 12 mutants; adjusted hazard ratio, 2.2, 95% CI: 1.2-3.9; p = 0.01). KRAS MASI arises through chromosome 12 hyperploidy or KRAS amplification and, when affects KRAS codon 13, is associated with worse overall survival.

Clinical characterization of patients with metastatic colorectal cancer depending on the KRAS status

This retrospective study investigated the clinical characteristics of patients with metastatic colorectal cancer (mCRC) depending on the KRAS status, thereby differentiating KRAS exon 2 mutations in codon 12 versus codon 13. In total, 273 patients with mCRC receiving first-line therapy were analyzed. One hundred patients were treated within the FIRE-3 trial (FOLFIRI plus cetuximab or bevacizumab), 147 patients within the AIO KRK-0104 trial (cetuximab plus CAPIRI or CAPOX), and further 26 patients received therapy outside the study. Thirty-eight tumors with KRAS mutation in codon 13, 140 tumors with mutation in codon 12, and 95 tumors with KRAS wild type as a comparison were included in this analysis. Bivariate analyses demonstrated significant differences between KRAS wild-type, codon 12-mutated, and codon 13-mutated tumors with regard to synchronous lymph node metastasis (P=0.018), organ metastasis (76.8% vs. 65.9% vs. 89.5%, P=0.009), liver metastasis (89.5% vs. 78.2% vs. 92.1%, P=0.025), lung metastasis (29.5% vs. 42.9% vs. 50%, P=0.041), liver-only metastasis (48.4% vs. 28.8% vs. 28.9%, P=0.006), and metastases in two or more organs (49.5, 61.4, 71.1, P=0.047). Regression models indicated a significant impact of KRAS mutations in codon 12 versus codon 13 for synchronous organ and nodal metastasis (P=0.01, 0.03). This pooled analysis indicates that mCRC is a heterogeneous disease, which seems to be defined by KRAS mutations of the tumor. Compared with KRAS codon 12 mutations, codon 13-mutated mCRC presents as a more aggressive disease frequently associated with local and distant metastases at first diagnosis.

Are KRAS/BRAF mutations potent prognostic and/or predictive biomarkers in colorectal cancers?

KRAS and BRAF mutations lead to the constitutive activation of EGFR signaling through the oncogenic Ras/Raf/Mek/Erk pathway. Currently, KRAS is the only potential biomarker for predicting the efficacy of anti-EGFR monoclonal antibodies (mAb) in colorectal cancer (CRC). However, a recent report suggested that the use of cetuximab was associated with survival benefit among patients with p.G13D-mutated tumors. Furthermore, although the presence of mutated BRAF is one of the most powerful prognostic factors for advanced and recurrent CRC, it remains unknown whether patients with BRAF-mutated tumors experience a survival benefit from treatment with anti-EGFR mAb. Thus, the prognostic or predictive relevance of the KRAS and BRAF genotype in CRC remains controversial despite several investigations. Routine KRAS/BRAF screening of pathological specimens is required to promote the appropriate clinical use of anti-EGFR mAb and to determine malignant phenotypes in CRC. The significance of KRAS/BRAF mutations as predictive or prognostic biomarkers should be taken into consideration when selecting a KRAS/BRAF screening assay. This article will review the spectrum of KRAS/BRAF genotype and the impact of KRAS/BRAF mutations on the clinicopathological features and prognosis of patients with CRC, particularly when differentiating between the mutations at KRAS codons 12 and 13. Furthermore, the predictive role of KRAS/BRAF mutations in treatments with anti-EGFR mAb will be verified, focusing on KRAS p.G13D and BRAF mutations.

RAS signalling in the colorectum in health and disease

RAS proteins act as molecular switches between several homeostatic inputs and signal transduction pathways that regulate important cellular processes including cell growth, differentiation and survival. Activating mutations change the function of normal proto-oncogenic RAS proteins to oncogenic RAS proteins that trigger a wide range of downstream effectors altering expression of transcription factors that together stimulate cell proliferation and modulate apoptosis and differentiation. RAS genes are amongst the most frequently mutated genes in human cancers, in particular KRAS is mutated in 40-50% of colorectal cancers. Mutation of this gene has a significant impact on treatment management and patients' survival, particularly in relation to anti-EGFR therapy, which is only effective in KRAS wild-type cases. Here, we discuss the regulation of KRAS signalling in the colorectum, some of the post-transcriptional and post-translational modifications that control its activity, the mutations and other DNA alterations that are found in this tumour type and the implications that they have for disease progression and current drug treatments.

Review of biomarkers in colorectal cancer

AIM

Advances in molecular technology have resulted in the discovery of many putative biomarkers relevant to colorectal cancer (CRC).

METHOD

Literature searches were performed on PubMed and EMBASE using the words 'colorectal cancer', AND 'biomarkers OR markers'. Biomarkers that are either currently in clinical use or have potential clinical use were identified.

RESULTS

Most potential markers are in the discovery phase waiting to undergo clinical validation. Hypermethylation of the plasma septin-9 gene shows promise as a nonstool-based screening tool. Hypermethylation of the DYPD gene (encodes the enzyme dihydropyrimidine dehydrogenase) and variation of the uridine diphosphate-glucuronosyltransferase 1A (UGT1A1) gene have predictive value for side effects and the efficacy of 5-fluoruracil and irinotecan, respectively. Mismatch repair protein immunohistochemistry is able to predict response to 5-fluorouracil, and the KRAS (Kirsten rat sarcoma viral oncogene) and B-RAF (v-RAF murine sarcoma viral oncogene homolog B1) somatic gene mutation status can predict the response to anti-epidermal growth factor receptor therapy.

CONCLUSION

Recent advances indicate that the widespread use of biomarkers may herald the next major advance in the diagnosis and management of CRC.

K-ras mutations are correlated to lymph node metastasis and tumor stage, but not to the growth pattern of colon carcinoma

In colorectal carcinoma, pathological assessment of tumors is essential for determining therapy and prognosis of the disease. Molecular associations of tumor complexity index and genetic alternations can be helpful to understand the tumor progression mechanism. Oncogenic K-ras is one of the major colorectal cancer associated genes, and is mutated in up to 50% of colorectal cancers. In this current study, we correlated tumor complexity index with mutations in K-ras codon 12, 13, and 61 in association with different clinicopathological parameters such as TNM stage, localization, sex, and age. Formalin-fixed paraffin embedded tissue blocks from colon cancer samples was selected from 88 patients diagnosed with adenocarcinoma. Mutations in the K-ras gene were detected using pyrosequencing technique. Tumor complexity index was calculated using immunohistochemically stained images of the tumor outline of the specimens and then analyzing these pictures using Photoshop CS, Fovea Pro, and Image J computer programs. Statistical analysis was performed with SPSS. K-ras mutations were detected in 17 (19.3%) colon cancer samples. Most of the samples were at a lower complexity index. No correlation was observed between K-ras mutations and complexity index. However, K-ras mutations were correlated with regional lymph node metastasis and tumor stages and complexity index with tumor wall penetration. In conclusion, complexity index and K-ras mutations are independent events; however, both correlate with tumor progression and are important in the biologic development of colon carcinoma.

Analytical performance of a PCR assay for the detection of KRAS mutations (codons 12/13 and 61) in formalin-fixed paraffin-embedded tissue samples of colorectal carcinoma

KRAS mutation testing is mandatory before prescribing anti-epidermal growth factor monoclonal antibodies in the treatment of advanced colorectal cancer. We describe the performance of a TaqMelt polymerase chain reaction (PCR) assay—the cobas® KRAS Mutation Test—designed to detect 19 mutations in codons 12, 13, and 61. The limit of detection was determined using DNA blends from cell lines, plasmids, and formalin-fixed paraffin-embedded tissue specimens. Assay performance was compared to Sanger sequencing using a panel of 188 specimens. Discordant specimens were subjected to next generation pyrosequencing (454). Assay repeatability was assessed using a panel of six specimens. A >95% correct mutation call rate was obtained in all specimen types with ~5% mutant alleles at DNA inputs of 0.8–6.3 ng per PCR reaction; 100% detection rate was observed at the recommended DNA input of 50 ng. The positive percent agreement with Sanger was 97.5% (79/81) for codons 12/13 and 85.7% (6/7) for codon 61. Negative percent agreement was 94.4% (101/107) for codon 12/13 and 99.4% (180/181) for codon 61. Nine of 10 discordant specimens yielded 454 results consistent with the cobas® results. With repeated testing, the assay showed a correct call rate of 100% (192/192) for all operators, instruments, reagent lots, and days tested. The cobas® test detects KRAS mutations in codons 12, 13, and 61 at a limit of detection of <5%. The PCR assay was more sensitive and specific than Sanger sequencing, and performance was highly reproducible. Test performance was not influenced by various endogenous interfering substances or common gut microbes.

Regulation of homeostasis and oncogenesis in the intestinal epithelium by Ras

Much of our current state of knowledge pertaining to the mechanisms controlling intestinal epithelial homeostasis derives from epidemiological, molecular genetic, cell biological, and biochemical studies of signaling pathways that are dysregulated during the process of colorectal tumorigenesis. Activating mutations in members of the RAS oncoprotein family play an important role in the progression of colorectal cancer (CRC) and, by extension, intestinal epithelial homeostasis. Mutations in K-RAS account for 90% of the RAS mutations found in CRC. As such, the study of RAS protein function in the intestinal epithelium is largely encompassed by the study of K-RAS function in CRC. In this review, we summarize the data available from genetically defined in vitro and in vivo models of CRC that aim to characterize the oncogenic properties of mutationally activated K-RAS. These studies paint a complex picture of a multi-functional oncoprotein that engages an array of downstream signaling pathways to influence cellular behaviors that are both pro- and anti-tumorigenic. While the complexity of K-RAS biology has thus far prevented a comprehensive understanding of its oncogenic properties, the work to date lays a foundation for the development of new therapeutic strategies to treat K-RAS mutant CRC.

Neuroendocrine and squamous colonic composite carcinoma: Case report with molecular analysis

Composite colorectal carcinomas are rare. There are a modest number of cases in the medical literature, with even fewer cases describing composite carcinoma with neuroendocrine and squamous components. There are to our knowledge no reports of composite carcinoma molecular alterations. We present a case of composite carcinoma of the splenic flexure in a 33 year-old Caucasian male to investigate the presence and prognostic significance of molecular alterations in rare colonic carcinoma subtypes. Formalin-fixed paraffin-embedded (FFPE) tissue was hematoxylin and eosin- and mucicarmine-stained according to protocol, and immuno-stained with cytokeratin (CK)7, CK20, CDX2, AE1/AE3, chromogranin-A and synaptophysin. DNA was extracted from FFPE tissues and molecular analyses were performed according to lab-developed methods, followed by capillary electrophoresis. Hematoxylin and eosin staining showed admixed neuroendocrine and keratinized squamous cells. Positive nuclear CDX2 expression confirmed intestinal derivation. CK7 and CK20 were negative. Neuroendocrine cells stained positively for synaptophysin and AE1/AE3 and negatively for chromogranin and mucicarmine. Hepatic metastases showed a similar immunohistochemical profile. Molecular analysis revealed a G13D KRAS mutation. BRAF mutational testing was negative and microsatellite instability was not detected. The patient had rapid disease progression on chemotherapy and died 60 d after presentation. Although the G13D KRAS mutation normally predicts an intermediate outcome, the aggressive tumor behavior suggests other modifying factors in rare types of colonic carcinomas.

Prognostic significance of glucose transporter-1 (GLUT1) gene expression in rectal cancer after preoperative chemoradiotherapy

PURPOSE

Most cancer cells exhibit increased glycolysis. The elevated glucose transporter 1 (GLUT1) expression has been reported to be associated with resistance to therapeutic agents and a poor prognosis. We wondered whether GLUT1 expression was associated with the clinical outcome in rectal cancer after preoperative chemoradiotherapy (CRT), and whether glycolysis inhibition could represent a novel anticancer treatment.

METHODS

We obtained total RNA from residual cancer cells using microdissection from a total of 52 rectal cancer specimens from patients who underwent preoperative CRT. We performed transcriptional analyzes, and studied the association of the GLUT1 gene expression levels with the clinical outcomes. In addition, we examined each proliferative response of three selected colorectal cancer cell lines to a glycolysis inhibitor, 3-bromopyruvic acid (3-BrPA), with regard to their expression of the GLUT1 gene.

RESULTS

An elevated GLUT1 gene expression was associated with a high postoperative stage, the presence of lymph node metastasis, and distant recurrence. Moreover, elevated GLUT1 gene expression independently predicted both the recurrence-free and overall survival. In the in vitro studies, we observed that 3-BrPA significantly suppressed the proliferation of colon cancer cells with high GLUT1 gene expression, compared with those with low expression.

CONCLUSION

An elevated GLUT1 expression may be a useful predictor of distant recurrence and poor prognosis in rectal cancer patients after preoperative CRT.

Beyond KRAS: perspectives on new potential markers of intrinsic and acquired resistance to epidermal growth factor receptor inhibitors in metastatic colorectal cancer

The monoclonal antibodies cetuximab and panitumumab, directed against the epidermal growth factor receptor (EGFR), are licensed for the treatment of KRAS wild-type metastatic colorectal cancer (mCRC). Such 'molecular restriction' derived from post-hoc analyses of randomized trials and from other retrospective series all indicate how tumors bearing KRAS (v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog) mutations are resistant to EGFR inhibition. Even if highly sensitive for nonresponse, KRAS testing is not very specific. In fact, a limited but still considerable proportion of KRAS wild-type patients rapidly progress on treatment with an EGFR inhibitor. New potential molecular determinants of benefit from such treatment are under investigation and may further refine the selection of patients. Pharmacogenomic analyses and translational studies are also ongoing for exploring the field of acquired resistance to anti-EGFRs, since all patients eventually progress. New biological data are awaited for optimizing the use of molecular agents in colorectal cancer and for identifying promising targets that could allow to better understand and, potentially, overcome mechanisms of primary or secondary resistance to EGFR inhibitors.

Validation study of a quantitative multigene reverse transcriptase-polymerase chain reaction assay for assessment of recurrence risk in patients with stage II colon cancer

PURPOSE

We developed quantitative gene expression assays to assess recurrence risk and benefits from chemotherapy in patients with stage II colon cancer.

PATIENTS AND METHODS

We sought validation by using RNA extracted from fixed paraffin-embedded primary colon tumor blocks from 1,436 patients with stage II colon cancer in the QUASAR (Quick and Simple and Reliable) study of adjuvant fluoropyrimidine chemotherapy versus surgery alone. A recurrence score (RS) and a treatment score (TS) were calculated from gene expression levels of 13 cancer-related genes (n = 7 recurrence genes and n = 6 treatment benefit genes) and from five reference genes with prespecified algorithms. Cox proportional hazards regression models and log-rank methods were used to analyze the relationship between the RS and risk of recurrence in patients treated with surgery alone and between TS and benefits of chemotherapy.

RESULTS

Risk of recurrence was significantly associated with RS (hazard ratio [HR] per interquartile range, 1.38; 95% CI, 1.11 to 1.74; P = .004). Recurrence risks at 3 years were 12%, 18%, and 22% for predefined low, intermediate, and high recurrence risk groups, respectively. T stage (HR, 1.94; P < .001) and mismatch repair (MMR) status (HR, 0.31; P < .001) were the strongest histopathologic prognostic factors. The continuous RS was associated with risk of recurrence (P = .006) beyond these and other covariates. There was no trend for increased benefit from chemotherapy at higher TS (P = .95).

CONCLUSION

The continuous 12-gene RS has been validated in a prospective study for assessment of recurrence risk in patients with stage II colon cancer after surgery and provides prognostic value that complements T stage and MMR. The TS was not predictive of chemotherapy benefit.

Mutations in BRAF correlate with poor survival of colorectal cancers in Chinese population

PURPOSE

Mutations in KRAS and BRAF genes were associated with treatment failure from EGF receptor inhibitors in colorectal cancer (CRC) patients. However, whether these mutations were associated with survival in patients not treated with EGF receptor inhibitors remained controversial. Moreover, few data were available in Chinese. Therefore, we aimed to evaluate the impact of KRAS and BRAF mutations on the survival of Chinese CRC patients.

METHODS

CRC patients who underwent surgery between October 2003 and April 2006 were included in this study. They were observed until June 30, 2010 or when death was ascertained by the National Death Registration System. Prospectively collected fresh frozen tumor tissues were used for detection of mutations at codons 12, 13, and 61 of the KRAS gene and exons 11 and 15 of BRAF gene by PCR amplification followed by direct sequencing.

RESULTS

Among the 314 patients, KRAS and BRAF mutations were detected in 65 (20.7%) and 12 (3.8%) patients, respectively. KRAS mutations appeared to occur more frequently in females than males (p = 0.039) and in non-smokers (p = 0.039). KRAS and BRAF mutations were significantly associated with the proximal location of cancer (p = 0.017 and 0.001, respectively). In the univariate analysis, KRAS and BRAF mutations were not associated with survival. However, BRAF mutations were associated with a significantly worse overall survival (hazard ratio = 3.91, 95% confidence interval 1.31 to 11.66, p = 0.014) in the multivariate Cox proportional hazard model after adjustment for all direct clincopathological variables.

CONCLUSION

BRAF mutations, but not KRAS mutations, were associated with a worse outcome in Chinese CRC patients.

What can the molecular pathologist offer for optimal decision making?

As a consequence of new innovative therapies and therapeutic combinations, the treatment of advanced colorectal cancer is becoming increasingly complex. Validated molecular biomarkers could contribute to patient management, but until recently, none has been routinely used. With the recognition that activating mutations of the KRAS oncogene can predict resistance to anti-epidermal growth factor receptor agents, the clinical value of biomarkers in advanced colorectal cancer has been brought to the fore. Prognostic and predictive biomarkers that reflect the molecular and therapeutic complexities of advanced colorectal cancer may provide valuable information regarding likely clinical outcome and therapeutic response and thus may improve patient management and therapeutic agent selection. Such biomarkers are discussed herein.

Sensitive quantification of somatic mutations using molecular inversion probes

Somatic mutations in DNA can serve as cancer specific biomarkers and are increasingly being used to direct treatment. However, they can be difficult to detect in tissue biopsies because there is often only a minimal amount of sample and the mutations are often masked by the presence of wild type alleles from nontumor material in the sample. To facilitate the sensitive and specific analysis of DNA mutations in tissues, a multiplex assay capable of detecting nucleotide changes in less than 150 cells was developed. The assay extends the application of molecular inversion probes to enable sensitive discrimination and quantification of nucleotide mutations that are present in less than 0.1% of a cell population. The assay was characterized by detecting selected mutations in the KRAS gene, which has been implicated in up to 25% of all cancers. These mutations were detected in a single multiplex assay by incorporating the rapid flow cytometric readout of multiplexable DNA biosensors.

Multiple mutations in the Kras gene in colorectal cancer: review of the literature with two case reports

PURPOSE

Kras mutations are negative predictors of anti-EGFR therapy, occurring in 40% of colorectal carcinomas (CRCs). Point substitutions in codon 12 or 13 are the most frequent mutations in Kras, but multiple mutations (MMs) in other codons can also develop. Few data exist on MMs with regard to their frequency and the codons and amino acids that are affected. We report two cases of Kras double mutations in codons 12 and 13 and review Kras MMs in primary CRC in PubMed databases.

CASE REPORT

A 53-year-old woman and a 70-year-old man presented with deep, invasive, moderately differentiated CRC at an advanced clinical stage. The former had regional lymph node involvement and vaginal wall neoplastic implantation, and the latter had liver metastasis. Primary tumors were examined for Kras mutations by pyrosequencing, which were confirmed by direct sequencing. Both tumors had a mutation in codons 12 and 13, wherein codon 12 was mutated to GAT, and codon 13 became GAC.

CONCLUSIONS

We identified 69 reported cases of Kras MMs and reported two other cases, representing 2.1% of all mutated tumors; the incidence of such mutations is 1.0% in CRC patients. In most cases (59%), MMs develop in a single codon, usually codon 12. Codons 12 and 13 are affected simultaneously in only 27% of cases. These findings add information about the impact of specific amino acid changes in the Kras gene.

Predictive molecular classifiers in colorectal cancer

The introduction of predictive molecular markers has radically enhanced the identification of which patients may benefit from a given treatment. Despite recent controversies, KRAS mutation is currently the most recognized molecular predictive marker in colorectal cancer (CRC), predicting efficacy of anti-epidermal growth factor receptor (anti-EGFR) antibodies. However, other relevant markers have been reported and claimed to identify patients that will benefit from anti-EGFR therapies. This group of markers includes BRAF mutations, PI3KCA mutations, and loss of PTEN expression. Similarly, molecular markers for cytotoxic agents' efficacy also may predict outcome in patients with CRC. This review aims to summarize the most important predictive molecular classifiers in patients with CRC and further discuss any inconsistent or conflicting findings for these molecular classifiers.

Panitumumab in combination with cytotoxic chemotherapy for the treatment of metastatic colorectal carcinoma

The fully human anti-epidermal growth factor receptor (EGFR) monoclonal antibody panitumumab has been shown to improve progression-free survival when administered as a monotherapy for patients with chemotherapy-refractory metastatic colorectal cancer (mCRC) and is approved in this setting. Two large randomized clinical trials have investigated panitumumab in combination with 5-fluorouracil, leucovorin, and oxaliplatin (FOLFOX) as a first-line therapy for mCRC and 5-fluorouracil, leucovorin, and irinotecan (FOLFIRI) as a second-line therapy for mCRC. In these studies, the combination of panitumumab with FOLFOX or FOLFIRI resulted in improved progression-free survival compared with FOLFOX or FOLFIRI alone. Improved tumor response was also observed with the addition of panitumumab to FOLFIRI. As in monotherapy trials, the clinical benefits associated with panitumumab treatment were confined to patients with wild-type KRAS tumors, further showing the validity of KRAS mutational status as a predictive biomarker in mCRC. In addition to KRAS mutational status, a number of other potential predictive biomarkers are currently being investigated in mCRC and may eventually help identify patients who are likely to benefit from treatment with anti-EGFR monoclonal antibodies. Toxicities observed during treatment with panitumumab combined with FOLFOX or FOLFIRI were generally manageable and commonly included skin toxicities and gastrointestinal toxicities. Because it can lead to dose delays, dose reductions, and discontinuation, physicians and patients should carefully manage skin toxicity. Overall, the results of these two studies show that panitumumab improves outcomes when added to FOLFOX or FOLFIRI among patients with mCRC with wild-type KRAS.

Molecular differences in the KRAS gene mutation between a primary tumor and related metastatic sites - case report and a literature review

In recent years the the set of diagnostic tools in colorectal cancers has been extended by the assessment of the KRAS gene status. Currently it is a necessary step in order to qualify patients for the targeted therapy. The results of the analysis of several studies revealed a high rate of compliance of the KRAS gene mutational status in primary and metastatic tumors. In this paper we present a rare case of incompatibility of the KRAS mutations in the primary tumor located in the colon and metastatic changes in the liver.

Predictive and prognostic markers in colorectal cancer

Colorectal cancer (CRC) has a complex pathogenesis involving multiple sequential steps with accumulation of genetic alterations including mutations, gene amplification, and epigenetic changes. Treatment of CRC has undergone a paradigm shift over the past decade due in part to a better understanding of the biology of the disease and development of newer drugs including biologic agents. In the era of personalized medicine, it is attractive to investigate the molecular pathways leading to colorectal cancer tumorigenesis, thus raising the possibility of identifying novel therapeutic targets. It has intuitive appeal to hypothesize that biomarkers that have prognostic and/or predictive value are those that are intimately connected to the pathogenesis of CRC. In this article, we focus on prognostic and predictive markers in CRC that have a substantial body of data in support of their potential role in routine clinical practice.

Metastatic colorectal cancer KRAS genotyping in routine practice: results and pitfalls

KRAS genotyping is mandatory before anti-epidermal growth factor receptor monoclonal antibody therapy in metastatic colorectal cancer, which is the second leading cause of cancer-related death in the United States and in Europe. Thus, large-scale KRAS mutation screening is needed for efficient patient management and in the future metastatic colorectal cancer genotyping might also include the detection of the BRAF V600E mutation, which is a very strong negative prognostic factor in colorectal cancer. We report our experience of routine KRAS/BRAF mutation screening practice performed on 1130 formalin-fixed paraffin-embedded tumor samples from 992 colorectal cancer patients. DNA was extracted from macrodissected tumor areas highlighted by a pathologist, KRAS codons 12/13 and BRAF V600E mutations were assessed in a single SNaPshot® multiplex assay and each mutation was confirmed by an independent analysis. KRAS and BRAF mutations were, respectively, present in 41.8 and 6.5% of the tumor samples. If KRAS and BRAF mutations were mutually exclusive, four samples presented two concomitant KRAS mutations. Genotyping of paired primary tumors and metastases from 44 patients indicated that 5 patients (11.4%) presented discordant KRAS mutational status. KRAS genotype heterogeneity was also observed within primary tumor sites in seven cases. Non-reproducible KRAS artefactual mutations were detected in 53 samples (4.7%). We found that the prominent mechanism leading to these artefactual mutations was the fragmentation of DNA occurring during tissue processing. Routine KRAS genotyping performed on formalin-fixed paraffin-embedded tissues requires, therefore, the development of quality control scheme for molecular pathology, especially because of DNA damages induced by formalin fixation. The tumor heterogeneity observed in some patients indicates that it should be more appropriate to perform KRAS genotyping on metastases if sample is available.

Clinically important molecular features of Peruvian colorectal tumours: high prevalence of DNA mismatch repair deficiency and low incidence of KRAS mutations

BACKGROUND

The incidence of colorectal cancer (CRC) in Peru has been increasing, and no data have been published on the molecular features. We explored the most relevant genetic events involved in colorectal carcinogenesis, with clinical implications.

METHODS

Using immunohistochemistry for mismatch-repair (MMR) proteins (MLH1, MSH2, MSH6, and PMS2) and microsatellite instability analysis, we evaluated the status of 90 non-selected CRC Peruvian patients followed in a nationwide reference hospital for cancer (INEN, Lima). Tumours with loss of hMLH1 were evaluated further for hMLH1 promoter hypermethylation and all cases were evaluated for the presence of KRAS and BRAF-V600E mutations.

RESULTS

MMR deficiency was found in 35 (38.8%) patients. We identified an unexpected association between MMR deficiency and older age. Among the 14 cases with loss of MLH1, 10 samples exhibited hypermethylation. Of the 90 cases evaluated, 15 (16.7%) carried KRAS mutations; we found one previously unreported mutation (G13R).

CONCLUSIONS

Peruvian CRC tumours exhibited the highest prevalence of MMR deficiency reported to date. The expected hereditary component was also high. The age of onset of these MMR deficient tumours was greater than that observed for non-MMR deficient cases, suggesting the ineffectiveness of the Bethesda criteria for Lynch syndrome screening in Peru. Prospective studies are warranted to define the molecular characteristics of CRC in this population.

Adjuvant Chemotherapy for Stage II Colon Cancer: The Role of Molecular Markers in Choosing Therapy

The optimal adjuvant treatment for stage II colon cancer remains controversial. While chemotherapy is often recommended for high-risk stage II disease, many low-grade tumors with similar histopathologic features will recur and ultimately cause cancer-associated mortality. The development of molecular markers that predict clinical outcome or response to therapy in stage II colon cancer is an important tool that could give clinicians added information in discussions regarding the role of adjuvant chemotherapy. While many potential molecular biomarkers have been investigated, to date none have been validated in prospective clinical trials. Among the most promising molecular markers to be studied are microsatellite instability and 18q and 17p loss of heterozygosity, both of which are currently being evaluated as prognostic indicators in a large prospective clinical trial (Eastern Cooperative Oncology Group 5202). This review focuses on potential molecular biomarkers being evaluated for their prognostic value in stage II colon cancer and their potential role in clinical decision-making regarding the use of adjuvant chemotherapy.

Pyrosequencing-based methods reveal marked inter-individual differences in oncogene mutation burden in human colorectal tumours

BACKGROUND

The epidermal growth factor receptor-targeted monoclonal antibody cetuximab (Erbitux) was recently introduced for the treatment of metastatic colorectal cancer. Treatment response is dependent on Kirsten-Ras (K-Ras) mutation status, in which the majority of patients with tumour-specific K-Ras mutations fail to respond to treatment. Mutations in the oncogenes B-Raf and PIK3CA (phosphoinositide-3-kinase) may also influence cetuximab response, highlighting the need for a sensitive, accurate and quantitative assessment of tumour mutation burden.

METHODS

Mutations in K-Ras, B-Raf and PIK3CA were identified by both dideoxy and quantitative pyrosequencing-based methods in a cohort of unselected colorectal tumours (n=102), and pyrosequencing-based mutation calls correlated with various clinico-pathological parameters.

RESULTS

The use of quantitative pyrosequencing-based methods allowed us to report a 13.7% increase in mutation burden, and to identify low-frequency (<30% mutation burden) mutations not routinely detected by dideoxy sequencing. K-Ras and B-Raf mutations were mutually exclusive and independently associated with a more advanced tumour phenotype.

CONCLUSION

Pyrosequencing-based methods facilitate the identification of low-frequency tumour mutations and allow more accurate assessment of tumour mutation burden. Quantitative assessment of mutation burden may permit a more detailed evaluation of the role of specific tumour mutations in the pathogenesis and progression of colorectal cancer and may improve future patient selection for targeted drug therapies.

RASOnD-a comprehensive resource and search tool for RAS superfamily oncogenes from various species

Background

The Ras superfamily plays an important role in the control of cell signalling and division. Mutations in the Ras genes convert them into active oncogenes. The Ras oncogenes form a major thrust of global cancer research as they are involved in the development and progression of tumors. This has resulted in the exponential growth of data on Ras superfamily across different public databases and in literature. However, no dedicated public resource is currently available for data mining and analysis on this family. The present database was developed to facilitate straightforward accession, retrieval and analysis of information available on Ras oncogenes from one particular site.

Description

We have developed the RAS Oncogene Database (RASOnD) as a comprehensive knowledgebase that provides integrated and curated information on a single platform for oncogenes of Ras superfamily. RASOnD encompasses exhaustive genomics and proteomics data existing across diverse publicly accessible databases. This resource presently includes overall 199,046 entries from 101 different species. It provides a search tool to generate information about their nucleotide and amino acid sequences, single nucleotide polymorphisms, chromosome positions, orthologies, motifs, structures, related pathways and associated diseases. We have implemented a number of user-friendly search interfaces and sequence analysis tools. At present the user can (i) browse the data (ii) search any field through a simple or advance search interface and (iii) perform a BLAST search and subsequently CLUSTALW multiple sequence alignment by selecting sequences of Ras oncogenes. The Generic gene browser, GBrowse, JMOL for structural visualization and TREEVIEW for phylograms have been integrated for clear perception of retrieved data. External links to related databases have been included in RASOnD.

Conclusions

This database is a resource and search tool dedicated to Ras oncogenes. It has utility to cancer biologists and cell molecular biologists as it is a ready source for research, identification and elucidation of the role of these oncogenes. The data generated can be used for understanding the relationship between the Ras oncogenes and their association with cancer. The database updated monthly is freely accessible online at http://202.141.47.181/rasond/ and http://www.aiims.edu/RAS.html.

Review of histopathological and molecular prognostic features in colorectal cancer

Prediction of prognosis in colorectal cancer is vital for the choice of therapeutic options. Histopathological factors remain paramount in this respect. Factors such as tumor size, histological type and subtype, presence of signet ring morphology and the degree of differentiation as well as the presence of lymphovascular invasion and lymph node involvement are well known factors that influence outcome. Our understanding of these factors has improved in the past few years with factors such as tumor budding, lymphocytic infiltration being recognized as important. Likewise the prognostic significance of resection margins, particularly circumferential margins has been appreciated in the last two decades. A number of molecular and genetic markers such as KRAS, BRAF and microsatellite instability are also important and correlate with histological features in some patients. This review summarizes our current understanding of the main histopathological factors that affect prognosis of colorectal cancer.

Impact of KRAS and BRAF Gene Mutation Status on Outcomes From the Phase III AGITG MAX Trial of Capecitabine Alone or in Combination With Bevacizumab and Mitomycin in Advanced Colorectal Cancer

PURPOSE

Mutations affecting the KRAS gene are established predictive markers of outcome with anti-epithelial growth factor receptor (EGFR) antibodies in advanced colorectal cancer (CRC). The relevance of these markers for anti-vascular endothelial growth factor (VEGF) therapy is controversial. This analysis was performed to assess the predictive and prognostic impact of KRAS and BRAF gene mutation status in patients receiving capecitabine with bevacizumab (CG) or capecitabine without bevacizumab in the phase III AGITG MAX (Australasian Gastrointestinal Trials Group MAX) study.

PATIENTS AND METHODS

Mutation status was determined for 315 (66.9%) of the original 471 patients. Mutation status was correlated with efficacy outcomes (response rate, progression-free survival [PFS], and overall survival [OS]), and a predictive analyses was undertaken.

RESULTS

Mutations in KRAS and BRAF genes were observed in 28.8% and 10.6% of patients, respectively. KRAS gene mutation status (wild type [WT] v mutated [MT]) had no prognostic impact for PFS (hazard ratio [HR], 0.89; CI, 0.69 to 1.14) or OS (HR, 0.97; CI, 0.73 to 1.28). BRAF mutation status (WT v MT) was not prognostic for PFS (HR, 0.80; CI, 0.54 to 1.18) but was prognostic for OS (HR, 0.49; CI, 0.33 to 0.73; P = .001). By using the comparison of capecitabine versus capecitabine and bevacizumab (CB) and CB plus mitomycin (CBM), KRAS gene mutation status was not predictive of the effectiveness of bevacizumab for PFS or OS (test for interaction P = .95 and 0.43, respectively). Similarly, BRAF gene mutation status was not predictive of the effectiveness of bevacizumab for PFS or OS (test for interaction P = .46 and 0.32, respectively).

CONCLUSION

KRAS gene mutation status was neither prognostic for OS nor predictive of bevacizumab outcome in patients with advanced CRC. BRAF gene mutation status was prognostic for OS but was not predictive of outcome with bevacizumab.

Molecular diagnosis of response to neoadjuvant chemoradiation therapy in patients with locally advanced rectal cancer

BACKGROUND

Pathologic complete response (pCR) to neoadjuvant chemoradiation (CRT) is an important prognostic factor in locally advanced rectal cancer. However, it is uncertain if histopathological techniques accurately detect pCR. We tested a novel molecular approach for detecting pCR and compared it with current histopathological approaches.

STUDY DESIGN

Pretreatment tumor biopsies and surgical specimens were collected from 96 patients with locally advanced rectal cancer treated with neoadjuvant CRT and surgery. Tumor response was categorized by tumor regression grade. Tumor DNA from pre-CRT tumor biopsies was screened for K-ras and p53 mutations. DNA from paired surgical specimens was then screened for the same mutations using highly sensitive polymerase chain reaction-based techniques.

RESULTS

Sixty-eight of 96 (71%) pretreatment biopsies harbored K-ras and/or p53 mutation; 36 (38%) had K-ras mutations, 52 (54%) had p53 mutations, and 20 (21%) carried both mutations. Of 70 patients with tumor regression grades 1 to 3, sixty-six (94%) had a concordant K-ras and p53 mutation profile in pre- and post-treatment tissues. Of 26 patients with tumor regression grade 0 (pCR), 12 had K-ras or p53 mutations in pretreatment biopsies. Of these, 2 (17%) patients had the same K-ras (n = 1) or p53 (n = 1) mutation detected in post-treatment tissue.

CONCLUSIONS

Sensitive molecular techniques detect K-ras and p53 mutations in post-CRT surgical specimens in some patients with a pCR. This suggests histopathological techniques might not be completely accurate, and some patients diagnosed with a pCR to CRT might have occult cancers cells in their surgical specimens.

Molecular Prognostic and Predictive Markers in Colorectal Cancer: Current Status

In parallel with our growing understanding of the molecular pathways underlying colorectal neoplasia, significant advances have been made in the treatment of colorectal cancer (CRC). For the past few decades, 5-fluorouracil-based therapy has been the cornerstone of adjuvant therapy. More recently, additional cytotoxic drugs and molecular-targeted therapies have provided additional clinical benefit in certain patient populations. Unfortunately, overall survival remains about 45%. Notably, our understanding of why certain patients do or do not respond to treatment remains limited. Thus, as therapeutic options for CRC continue to expand, there is now an even greater imperative to identify reliable biomarkers that have the potential to predict prognosis as well as response to chemotherapy. In this review, we will summarize the current status of such molecular prognostic and predictive biomarkers in CRC and assess their usefulness in tailoring therapeutic options.

Accumulation of K-Ras codon 12 mutations in the F344 rat distal colon following azoxymethane exposure

Azoxymethane (AOM) administration to F344 male rats is a widely used model of human colon carcinogenesis. The current study investigates quantitatively the accumulation of K-Ras codon 12 mutations following AOM exposure. Male, 6-week-old F344 rats were treated subcutaneously with 30 mg/kg body weight of AOM, and colon tissue was collected at 1, 8, 24, and 32 weeks after treatment. The K-Ras codon 12 GGT to GAT and GGT to GTT mutant fractions (MFs) were measured using allele-specific competitive blocker polymerase chain reaction (ACB-PCR). Between 1 and 32 weeks after AOM treatment, the K-Ras codon 12 GGT to GAT geometric mean MF in the rat colon increased significantly from 12.9 × 10(-5) to 145 × 10(-5) , and the GGT to GTT geometric mean MF increased significantly from 5.26 × 10(-5) to 180 × 10(-5) . K-Ras codon 12 GGT to GAT MF also increased significantly in AOM-treated rat colon tissue at 1 week compared to controls (4.44 × 10(-5) ). The accumulation of the GGT to GAT MF long after the DNA adduct repair phase suggests that a portion of cells containing this mutation have a proliferative advantage, allowing them to accumulate as nascent tumors progress. Also, the GGT to GAT background MF increased in untreated rats, indicating that there is accumulation with age. The ACB-PCR assay generates quantitative data of cancer-related mutations and thus provides insight into pathological processes following carcinogen exposure.

Integration of biologic agents with cytotoxic chemotherapy in metastatic colorectal cancer

Colorectal cancer (CRC) remains a leading cause of cancer death in the developed world. Metastatic disease eventually develops in nearly 50% of patients with CRC. Chemotherapy is the mainstay of treatment in metastatic CRC (mCRC); however the majority of patients remain incurable with current therapeutic options. Progress made in the field of surgery, locoregional treatment for low-volume metastatic disease, and systemic chemotherapy has created new treatment paradigms and improved survival in mCRC. Development of new cytotoxic drugs and the advent of targeted agents over the past decade have seen the median overall survival (OS) for mCRC increase from 9 months to > 2 years. Data from trials integrating targeted therapies appear to indicate that not all have efficacy as single agents and the choice of chemotherapy used in combination with these agents may impact results. Ongoing research is leading to identification of new biomarkers of response, further defining the subpopulations who achieve greatest benefit. Hence optimizing treatment for this group of patients has become increasingly complex, requiring a multidisciplinary approach not only to identify those who are curable with resectable disease but also to determine when it is best to incorporate targeted drugs, with which chemotherapy, and in whom. Currently bevacizumab, cetuximab, and panitumumab are the only approved biologic agents for use in mCRC. In this article we discuss the evidence supporting the use of biologic agents with chemotherapy and suggested strategies for their integration into the treatment armamentarium of mCRC.

Genetic-based biomarkers and next-generation sequencing: the future of personalized care in colorectal cancer

The past 5 years have witnessed extraordinary advances in the field of DNA sequencing technology. What once took years to accomplish with Sanger sequencing can now be accomplished in a matter of days with next-generation sequencing (NGS) technology. This has allowed researchers to sequence individual genomes and match combinations of mutations with specific diseases. As cancer is inherently a disease of the genome, it is not surprising to see NGS technology already being applied to cancer research with promises of greater understanding of carcinogenesis. While the task of deciphering the cancer genomic code remains ongoing, we are already beginning to see the application of genetic-based testing in the area of colorectal cancer. In this article we will provide an overview of current colorectal cancer genetic-based biomarkers, namely mutations and other genetic alterations in cancer genome DNA, discuss recent advances in NGS technology and speculate on future directions for the application of NGS technology to colorectal cancer diagnosis and treatment.

Differential gene expression signatures between colorectal cancers with and without KRAS mutations: crosstalk between the KRAS pathway and other signalling pathways

PURPOSE

KRAS mutation is an important predictive marker in determining resistance to anti-Epidermal Growth Factor Receptor (EGFR) antibody therapies. In order to clarify whether not only KRAS related signalling pathways but also other signalling pathways are altered in patients with colorectal cancers (CRCs) with KRAS mutations, we examined the differences in the gene expression signatures between CRCs with and without KRAS mutation.

PATIENTS AND METHODS

One-hundred and thirteen patients who underwent a surgical resection of a primary CRC were examined. KRAS mutational status was determined using the Peptide Nucleic Acid (PNA)-clamp real-time polymerase chain reaction (PCR) TaqMan assay. Gene expression profiles were compared between CRCs with and without KRAS mutation using the Human Genome GeneChip array U133.

RESULTS

Among 113 CRCs, KRAS mutations were present in 35 tumours (31%). We identified 30 genes (probes) that were differentially expressed between CRCs with and without KRAS mutation (False Discovery Rate (FDR), p<0.01), by which we were able to predict the KRAS status with an accuracy of 90.3%. Thirty discriminating genes included TC21, paired-like homeodomain 1 (PITX1), Sprouty-2, dickkopf homologue 4 (DKK-4), SET and MYND domain containing 3 (SMYD3), mitogen-activated protein kinase kinase kinase 14 (MAP3K14) and c-mer Proto-oncogene tyrosine kinase (MerTK). These genes were related to not only KRAS related signalling pathway but also to other signalling pathways, such as the Wnt-signalling pathway, the NF-kappa B activation pathway and the TGF-beta signalling pathway.

CONCLUSIONS

KRAS mutant CRCs exhibited a distinct gene expression signature different from wild-type KRAS CRCs. Using human CRC samples, we were able to show that there is crosstalk between the KRAS-mediated pathway and other signalling pathways. These results are necessary to be taken into account in establishing chemotherapeutic strategies for patients with anti-EGFR-refractory KRAS mutant CRCs.

Prognostic value of colorectal cancer biomarkers

Despite the large amount of data in cancer biology and many studies into the likely survival of colorectal cancer (CRC) patients, knowledge regarding the issue of CRC prognostic biomarkers remains poor. The Tumor-Node-Metastasis (TNM) staging system continues to be the most powerful and reliable predictor of the clinical outcome of CRC patients. The exponential increase of knowledge in the field of molecular genetics has lead to the identification of specific alterations involved in the malignant progression. Many of these genetic alterations were proposed as biomarkers which could be used in clinical practice to estimate CRC prognosis. Recently there has been an explosive increase in the number of putative biomarkers able to predict the response to specific adjuvant treatment. In this review we explore and summarize data concerning prognostic and predictive biomarkers and we attempt to shed light on recent research that could lead to the emergence of new biomarkers in CRC.

Biomarkers in advanced colorectal cancer: challenges in translating clinical research into practice

The growing number of therapeutic agents and known molecular targets in oncology makes the study and clinical use of biomarkers imperative for improving response and survival, reducing toxicity and ensuring economic sustainability. Colorectal cancer, among others, is at the forefront of development of predictive and prognostic biomarkers; however, the difficulty lies in translating potential biomarkers garnered from retrospective analyses in small numbers of patients to generalizable and affordable biomarkers used worldwide. This review outlines the progress made in prognostic and predictive biomarkers in advanced colorectal cancer (ACRC) from the early use of carcinoembryonic antigen (CEA) to the KRAS mutation and beyond. Future challenges are to incorporate standardized and validated methods preferentially during early phases of drug development linked with sophisticated biostatistical support. New trial designs focusing on biomarkers will be essential not only for better understanding of mechanisms of action, but also to make confident 'go or no-go' decisions.

Predictive and prognostic factors in colorectal cancer: a personalized approach

It is an exciting time for all those engaged in the treatment of colorectal cancer. The advent of new therapies presents the opportunity for a personalized approach to the patient. This approach considers the complex genetic mechanisms involved in tumorigenesis in addition to classical clinicopathological staging. The potential predictive and prognostic biomarkers which have stemmed from the study of the genetic basis of colorectal cancer and therapeutics are discussed with a focus on mismatch repair status, KRAS, BRAF, 18qLOH, CIMP and TGF-β.

Increased expression of annexin A1 is correlated with K-ras mutation in colorectal cancer

The activation of K-ras gene and expression of annexin A1 play an important role in colorectal tumorigenesis. We initiated this study to analyze the possible relationship between the annexin A1 expression and the K-ras mutation status in colorectal cancer. K-ras mutations are present in one fourth to one half of colorectal cancers. Annexin A1, a 37-kDa calcium- and phospholipid-binding protein, is over-expressed in colorectal cancers and may be involved in invasive tumor growth and metastasis. Here, we examined twenty paired specimens of colorectal cancer and adjacent normal tissues for K-ras mutations and annexin A1 expression. Sequencing analysis of codons 12 and 13 of K-ras revealed the presence of K-ras mutations in six colorectal cancer tissue specimens (30%). RT-PCR and immunoblotting studies further found that the expression levels of annexin A1 mRNA and protein were increased (2.9-fold and 1.7-fold, respectively) in colorectal cancers harboring K-ras codon 12 or codon 13 mutation compared with adjacent normal tissues (P < 0.05). In colorectal cancer tissues with wild-type K-ras, 12 (85.7%) specimens showed reduced expression of annexin A1 (0.48-fold and 0.81-fold, respectively). No significant association was found between K-ras mutations or annexin A1 over-expression and demographic or other clinicopathological parameters such as gender, differentiation or metastasis. However, a significant and positive correlation was identified between K-ras mutations and annexin A1 over-expression. Our findings indicate that annexin A1 could be implicated in colorectal cancer development and progression and could be of potential use as a predictive marker for guiding targeted therapy for colorectal cancer.

Value of mismatch repair, KRAS, and BRAF mutations in predicting recurrence and benefits from chemotherapy in colorectal cancer

PURPOSE

It is uncertain whether modest benefits from adjuvant chemotherapy in stage II colorectal cancer justify the toxicity, cost, and inconvenience. We investigated the usefulness of defective mismatch repair (dMMR), BRAF, and KRAS mutations in predicting tumor recurrence and sensitivity to chemotherapy.

PATIENTS AND METHODS

Immunohistochemistry for dMMR and pyrosequencing for KRAS/BRAF were performed for 1,913 patients randomly assigned between fluorouracil and folinic acid chemotherapy and no chemotherapy in the Quick and Simple and Reliable (QUASAR) trial.

RESULTS

Twenty-six percent of 695 right-sided colon, 3% of 685 left-sided colon, and 1% of 407 rectal tumors were dMMR. Similarly, 17% of right colon, 2% of left colon, and 2% of rectal tumors were BRAF mutant. KRAS mutant tumors were more evenly distributed: 40% right colon, 28% left colon, and 36% rectal tumors. Recurrence rate for dMMR tumors was half that for MMR-proficient tumors (11% [25 of 218] v 26% [438 of 1,695] recurred; risk ratio [RR], 0.53; 95% CI, 0.40 to 0.70; P < .001). Risk of recurrence was also significantly higher for KRAS mutant than KRAS wild-type tumors (28% [150 of 542] v 21% [219 of 1,041]; RR, 1.40; 95% CI, 1.12 to 1.74; P = .002) but did not differ significantly between BRAF mutant and wild-type tumors (P = .36). No marker predicted benefit from chemotherapy with efficacy not differing significantly by MMR, KRAS, or BRAF status. The prognostic value of MMR and KRAS was similar in the presence and absence of chemotherapy.

CONCLUSION

MMR assays identify patients with a low risk of recurrence. KRAS mutational analysis provides useful additional risk stratification to guide use of chemotherapy.

Prognostic significance of preoperative bowel obstruction in stage III colorectal cancer

BACKGROUND

Previous studies have suggested a detrimental prognostic effect of preoperative obstruction proximal to colorectal cancer (CRC). If such a detrimental effect is preserved in each stage of advanced (stage II or III) CRC, we can identify high-risk patients.

METHODS

We enrolled 641 patients with pathologically confirmed advanced CRC (stage II, n = 207; stage III, n = 434) who had undergone curative resection of the primary lesion. The association of preoperative obstruction with clinicopathologic parameters was evaluated. Kaplan-Meier analysis and Cox proportional hazard models were used to estimate the effect of preoperative obstruction on disease-free survival in each stage.

RESULTS

Preoperative obstruction was seen in 63 patients (9.8%) (stage II, n = 16; stage III, n = 47). Multivariable analysis showed that preoperative obstruction was significantly associated with preoperative elevation of carcinoembryonic antigen level in patients with colon cancer (odds ratio = 3.59; P < 0.001), while it was correlated with poor differentiation in patients with rectal cancer (odds ratio = 3.99; P = 0.016). Preoperative obstruction was a significant prognostic factor in stage III CRC (P < 0.001), but not in stage II disease. Multivariable prognostic analysis showed that preoperative obstruction was a remnant independent prognostic factor in stage III CRC. This finding was confirmed by separate analyses of colon and rectal cancer. Preoperative obstruction was associated with systemic recurrence (P = 0.003) rather than peritoneal or local recurrence.

CONCLUSIONS

These findings suggest that preoperative obstruction may predict worse long-term prognosis in patients with stage III CRC and may be a potential clinical marker to identify patients with high-risk stage III CRC.

Analysis of K-ras, BRAF, and PIK3CA mutations in laterally-spreading tumors of the colorectum

BACKGROUND AND AIMS

Laterally-spreading tumors (LST) are a newly-recognized category of colorectal neoplasia, and are defined as lesions larger than 10 mm in diameter and extending circumferentially rather than vertically. However, genetic features of this new category of tumors are not fully elucidated. The aim of this study was to evaluate genetic alterations in LST.

METHODS

We examined K-ras, BRAF, and phosphoinositide-3-kinase catalytic-α polypeptide (PIK3CA) mutations in 101 LST, including 68 LST-granular type (LST-G) and 33 LST-non-granular type by direct sequencing. As controls, we examined these gene mutations in 66 protruded colon adenomas (10 mm or larger) and 44 advanced colon cancers.

RESULTS

K-ras, BRAF, and PIK3CA mutations were observed in 59 (58%), zero (0%), and three (3%) LST, respectively. LST-G morphology in the right-sided colon was significantly correlated with the existence of K-ras mutations, whereas a size of 20 mm or larger was the only predictor of mutations in the left-sided colorectum. The frequency of K-ras mutations in LST was particularly marked in the left-sided colorectum compared to protruded adenomas or advanced cancers (LST vs protruded adenomas, P < 0.001; LST vs advanced cancers, P = 0.002), whereas in the right-sided colon, K-ras mutations were equally frequent. PIK3CA mutations were not familiar in either LST (3%) or advanced cancers (9%).

CONCLUSIONS

K-ras mutations were involved in colorectal LST in different manners according to tumor location.