Correlation of K-ras codon 12 mutations in human feces and ages of patients with colorectal cancer (CRC)

Impact of microsatellite status on chemotherapy for colorectal cancer patients with KRAS or BRAF mutation

KRAS and BRAF mutations are frequently detected in cases of colorectal cancer (CRC). The microsatellite status of patients with CRC and mutated KRAS/BRAF is important when determining cancer therapy. In the present study, the microsatellite status and genetic polymorphisms of KRAS (codons 12 and 13) and BRAF (V600E) were characterized in CRC tissue. The mismatch repair activity and oncogenic potential of KRAS were assessed by immunoblots from two KRAS-mutated CRC cell lines, SW480 and HCT116, with different microsatellite statuses, following treatment with 5-fluorouracil (5-FU) and oxaliplatin. Of all the 205 patients with CRC enrolled in the present study, 31.2% (64 of 205) had a KRAS or BRAF mutation, and 79.7% (51 of 64) of these patients with a KRAS/BRAF mutation exhibited microsatellite stability (MSS), indicating that microsatellite status is correlated with KRAS/BRAF mutation (P=0.027). A higher proportion (39.0%, 41 of 105) of elderly patients (≥62.6 years) had mutated KRAS or BRAF than younger patients (<62.6 years; 23.0%, 23 of 100; P=0.013). In the subgroup of 154 patients with MSS, patients without the KRAS or BRAF mutation (n=110) had longer disease-specific survival rates (58.8±9.4%) than patients with KRAS or BRAF mutations (n=44; 50.6±11.0%; P=0.043). Cytoplasmic KRAS levels decreased whereas nuclear MutS protein homolog 2 (MSH2) levels increased slightly in CRC HCT116 cells that were microsatellite instable, following treatment with 76.9 µM 5-FU for 2 days. In microsatellite stable SW480 cells, MSH2 levels markedly increased in the nucleus following 150 µM oxaliplatin treatment for 3 days. However, no significant change was observed regarding KRAS distribution in these cells. The results of the present study suggest that it is important to identify patients with CRC who may benefit from adjuvant chemotherapy with 5-FU or oxaliplatin, particularly CRC patients with MSS and mutated KRAS or BRAF, who have poorer overall survival rates than patients with microsatellite instability. Knowledge of the microsatellite status of patients and whether they harbor KRAS or BRAF mutations may enable more effective therapeutic strategies to be developed. Further prospective studies are required to validate the findings of the current study.

Cell-free nucleic acids as noninvasive biomarkers for colorectal cancer detection

Cell-free nucleic acids (CFNA) have been reported by several authors in blood, stool, and urine of patients with colorectal cancer (CRC). These genetic biomarkers can be an indication of neoplastic colorectal epithelial cells, and can thus potentially be used as noninvasive tests for the detection of the disease in CRC patients and monitor their staging, without the need to use heavier and invasive tools. In a number of test-trials, these genetic tests have shown the advantage of non-invasiveness, making them well accepted by most of the patients, without major side effects. They have also shown a promising sensitivity and specificity in the detection of malignant and premalignant neoplasms. Moreover, costs for performing such tests are very low. Several studies reported and confirmed the proof of the principle for these genetic tests for screening, diagnosis, and prognosis; the main challenge of translating this approach from research to clinical laboratory is the validation from large and long-term randomized trials to prove sustainable high sensitivity and specificity. In this paper, we present a review on the noninvasive genetics biomarkers for CRC detection described in the literature and the challenges that can be encountered for validation processes.

An oligonucleotide-tagged microarray for routine diagnostics of colon cancer by genotyping KRAS mutations

Colorectal cancer (CRC) is one of the most prevalent types of cancer, causing significant morbidity and mortality worldwide. CRC is curable if diagnosed at an early stage. Mutations in the oncogene KRAS play a critical role in early development of CRC. Detection of activated KRAS is of diagnostic and therapeutic importance. In this study, KRAS gene fragments containing mutations in codon 12 were amplified by multiplex PCR using a 5'-Cy5-labeled reverse primer in combination with 3'-mutation-specific forward primers that were linked with four unique nucleotide-sequence tags at the 5'-end. The Cy5-labeled reverse primer was extended under PCR amplification to the 5'-end of the mutation-specific forward primers and thus included the complimentary sequence of the tag. PCR products were hybridized to tag-probes immobilized on various substrates and detected by a scanner. Our results indicate that all mutations at codon 12 of KRAS derived from cancer cells and clinical samples could be unambiguously detected. KRAS mutations were accurately detected when the mutant DNA was present only in 10% of the starting mixed materials including wild-type genomic DNA, which was isolated from either cancer cells or spiked fecal samples. The immobilized tag-probes were stable under multiple thermal cycling treatments, allowing re-use of the tag-microarray and further optimization to solid PCR. Our results demonstrated that a novel oligonucleotide-tagged microarray system has been developed which would be suitable to be used for detection of KRAS mutations and clinical diagnosis of CRC.

Ribosomal protein S27-like in colorectal cancer: a candidate for predicting prognoses

Background

The development and progression of colorectal cancer (CRC) involve a complex process of multiple genetic changes. Tumor suppressor p53 is capable of determining the fate of CRC cells. However, the role of a p53-inducible modulator, ribosomal protein S27-like (RPS27L), in CRC is unknown.

Methods

Here, the differential expression of RPS27L was examined in the feces and colonic tissues of CRC patients, to explore its possible correlation with patient survival and to investigate the cellular mechanisms underlying their clinical outcomes. Eighty intermediate-stage CRC patients (42 at stage II and 38 at stage III) were divided into two groups according to their fecal RPS27L mRNA levels. The survival probabilities of the groups were estimated using the Kaplan–Meier method. The RPS27L protein in the colonic tissues of stage III patients with different prognoses was further examined immunohistochemically. RPS27L expression in LoVo cells was manipulated to examine the possible cellular responses in vitro.

Results

Elevated RPS27L expression, in either feces or tissues, was related to a better prognosis. In vitro, RPS27L-expressing LoVo cells ceased DNA synthesis and apoptotic activity while the expression of their DNA repair molecules was upregulated.

Conclusions

Elevated RPS27L may improve the prognoses of certain CRC patients by enhancing the DNA repair capacity of their colonic cells, and can be determined in feces. By integrating clinical, molecular, and cellular data, our study demonstrates that fecal RPS27L may be a useful index for predicting prognoses and guiding personalized therapeutic strategies, especially in patients with intermediate-stage CRC.

Molecular biomarkers in esophageal, gastric, and colorectal adenocarcinoma

Cancers of the esophagus, stomach and colon contribute to a major health burden worldwide and over 20% of all cancer deaths. Biomarkers that should indicate pathogenic process and are measureable in an objective manner for these tumors are rare and not established in the clinical setting. In general biomarkers can be very useful for cancer management as they can improve clinical decision-making regarding diagnosis, surveillance, and therapy. Biomarkers can be different types of molecular entities (such as DNA, RNA or proteins), which can be detected, in different tissues or body fluids. However, more important is the type of biomarker itself, which allows diagnostic, prognostic or predictive analyses for different clinical problems. This review aims to systematically summarize the recent findings of genetic and epigenetic markers for gastrointestinal tumors within the last decade. While many biomarkers seem to be very promising, especially if used as panels, further development is urgently needed to address practical considerations of biomarkers in cancer treatment.

Noninvasive screening tests for colorectal cancer

BACKGROUND

Identifying an accurate, reliable, affordable, and acceptable noninvasive screening test for colorectal cancer (CRC) would greatly facilitate population screening.

METHODS

Published literature from 2000 through February 2012 on noninvasive CRC screening tests was identified, reviewed, and summarized.

RESULTS

The highest quality evidence for noninvasive screening exists for guaiac-based fecal occult blood tests (gFOBTs), for which the CRC-specific incidence and mortality reductions are modest. Fecal immunochemical tests (FITs) offer better sensitivity and comparable specificity. Cross-sectional studies comparing gFOBTs and FITs suggest that FITs provide higher detection of advanced neoplasia. Modeling studies favor FITs over gFOBTs with respect to effectiveness and cost-effectiveness. A myriad of studies report the performance of fecal-based and blood-based genetic and protein-based biomarkers; the studies differ in patient population assembled, marker selection, and assay methods. Several markers and panels of markers are promising, although nearly all studies focus on new markers and/or assay methods on small sets of referred patients rather than validating markers using optimal assays in a screening setting.

CONCLUSION

In the absence of long-term randomized trials, adoption of the noninvasive tests will require cross-sectional data on test characteristics obtained from the screening setting, where CRC prevalence is low and the full spectrum of colorectal findings exists, along with estimates of cumulative risks, benefits, and cost-effectiveness. Test adoption will ultimately depend on test characteristics, availability, affordability, and user appeal. There is no noninvasive substitute for the currently recommended screening tests. FITs should replace gFOBTs wherever gFOBTs are used for screening.

Clinical Implementation of KRAS Testing in Metastatic Colorectal Carcinoma: The Pathologist's Perspective

Context.—Mutation status of the KRAS gene identifies a distinct disease subtype of metastatic colorectal carcinoma that does not respond to antibody therapeutics targeting the epidermal growth factor receptor. This is currently the only validated marker in metastatic colorectal carcinoma with a clear implication in treatment selection. KRAS testing is widely accepted in clinical practice to guide metastatic colorectal carcinoma therapeutic decisions, and there are many commercially available platforms to perform the test.

Objective.—To evaluate the critical role of pathologists in the full implementation of KRAS testing by optimizing tumor tissue collection and fixation procedures and by choosing testing technologies and reliable Clinical Laboratory Improvement Amendments of 1988–certified laboratories to perform the tests.

Data Sources.—Prospective clinical trials, retrospective studies, and quality assessment and survey reports were identified in the following databases: PubMed, American Society of Clinical Oncology Proceedings (American Society of Clinical Oncology Annual Meeting and Gastrointestinal Cancer Symposium) and European Society for Medical Oncology Proceedings (Annals of Oncology European Society for Medical Oncology Congress and Annals of Oncology World Congress on Gastrointestinal Cancers).

Conclusions.—More bona fide standards are needed to address the variety of available test methods, which have different performance characteristics including speed, sensitivity to detect rare mutations, and technical requirements. Refined standards addressing timing of KRAS testing, laboratory performance and accuracy, quality assurance and control, proper tissue collection, and appropriate result reporting would also be greatly beneficial. Pathologists should be aware that the amount of information they need to manage will increase, because future trends and technological advances will enhance the predictive power of diagnostic tests or the scope of the biomarker panels tested routinely across tumor types.

Fecal molecular markers for colorectal cancer screening

Despite multiple screening techniques, including colonoscopy, flexible sigmoidoscopy, radiological imaging, and fecal occult blood testing, colorectal cancer remains a leading cause of death. As these techniques improve, their sensitivity to detect malignant lesions is increasing; however, detection of precursor lesions remains problematic and has generated a lack of general acceptance for their widespread usage. Early detection by an accurate, noninvasive, cost-effective, simple-to-use screening technique is central to decreasing the incidence and mortality of this disease. Recent advances in the development of molecular markers in faecal specimens are encouraging for its use as a screening tool. Genetic mutations and epigenetic alterations that result from the carcinogenetic process can be detected by coprocytobiology in the colonocytes exfoliated from the lesion into the fecal matter. These markers have shown promising sensitivity and specificity in the detection of both malignant and premalignant lesions and are gaining popularity as a noninvasive technique that is representative of the entire colon. In this paper, we summarize the genetic and epigenetic fecal molecular markers that have been identified as potential targets in the screening of colorectal cancer.

Molecular tests for colorectal cancer screening

Detecting and removing high-risk adenomas and early colorectal cancer (CRC) can reduce mortality of this disease. The noninvasive fecal occult blood test (FOBT; guaiac-based or immunochemical) is widely used in screening programs and although effective, it leaves room for improvement in terms of test accuracy. Molecular tests are expected to be more sensitive, specific and informative than current detection tests, and are promising future tools for CRC screening. This review provides an overview of the performances of DNA, RNA, and protein markers for CRC detection in stool and blood. Most emphasis currently is on DNA and protein markers. Among DNA markers there is trend to move away from mutation markers in favor of methylation markers. The recent boost in proteomics research leads to many new candidate protein markers. Usually in small series, some markers show better performance than the present FOBT. Evaluation in large well-controlled randomized trials is the next step needed to take molecular markers for CRC screening to the next level and warrant implementation in a screening setting.

KRAS mutation screening in colorectal cancer: From paper to practice

The identification of KRAS mutation status as a predictive biomarker for the activity of epidermal growth factor receptor (EGFR) inhibitors in metastatic colorectal cancer has marked a turning point in the use of these agents in the clinic. A wealth of data indicates that patients with wild-type KRAS derive meaningful clinical benefit from cetuximab in first- and second-line settings and beyond, both in combination and as a single agent, and from panitumumab as a single agent in the refractory setting. Patients with KRAS-mutant tumors do not benefit from EGFR inhibition and should not be treated with these agents. KRAS mutation testing should be part of routine standard practice, preferably at the time of diagnosis or early in the course of management. Immediate knowledge of the KRAS mutation status of a tumor allows for the optimal incorporation of anti-EGFR monoclonal antibody (MoAb) therapy where it may be most beneficial for the patient, such as in downstaging regimens outside of the refractory setting where anti-EGFR MoAb therapy is otherwise typically indicated. Available technologies make this test relatively easy to implement; archival paraffin-embedded samples from primary or metastatic sites can be used indistinctly without compromising reliability and without the need for repeated biopsies. Several diagnostic laboratories provide KRAS testing services. This powerful selection tool reduces unnecessary toxicities and costs and should be part of the standard diagnostic workup of any patient.

Sensitive and specific KRAS somatic mutation analysis on whole-genome amplified DNA from archival tissues

Kirsten RAS (KRAS) is a small GTPase that plays a key role in Ras/mitogen-activated protein kinase signaling; somatic mutations in KRAS are frequently found in many cancers. The most common KRAS mutations result in a constitutively active protein. Accurate detection of KRAS mutations is pivotal to the molecular diagnosis of cancer and may guide proper treatment selection. Here, we describe a two-step KRAS mutation screening protocol that combines whole-genome amplification (WGA), high-resolution melting analysis (HRM) as a prescreen method for mutation carrying samples, and direct Sanger sequencing of DNA from formalin-fixed, paraffin-embedded (FFPE) tissue, from which limited amounts of DNA are available. We developed target-specific primers, thereby avoiding amplification of homologous KRAS sequences. The addition of herring sperm DNA facilitated WGA in DNA samples isolated from as few as 100 cells. KRAS mutation screening using high-resolution melting analysis on wgaDNA from formalin-fixed, paraffin-embedded tissue is highly sensitive and specific; additionally, this method is feasible for screening of clinical specimens, as illustrated by our analysis of pancreatic cancers. Furthermore, PCR on wgaDNA does not introduce genotypic changes, as opposed to unamplified genomic DNA. This method can, after validation, be applied to virtually any potentially mutated region in the genome.

Stool DNA and occult blood testing for screen detection of colorectal neoplasia

BACKGROUND

Stool DNA testing is a new approach to colorectal cancer detection. Few data are available from the screening setting.

OBJECTIVE

To compare stool DNA and fecal blood testing for detection of screen-relevant neoplasia (curable-stage cancer, high-grade dysplasia, or adenomas >1 cm).

DESIGN

Blinded, multicenter, cross-sectional study.

SETTING

Communities surrounding 22 participating academic and regional health care systems in the United States.

PARTICIPANTS

4482 average-risk adults.

MEASUREMENTS

Fecal blood and DNA markers. Participants collected 3 stools, smeared fecal blood test cards and used same-day shipment to a central facility. Fecal blood cards (Hemoccult and HemoccultSensa, Beckman Coulter, Fullerton, California) were tested on 3 stools and DNA assays on 1 stool per patient. Stool DNA test 1 (SDT-1) was a precommercial 23-marker assay, and a novel test (SDT-2) targeted 3 broadly informative markers. The criterion standard was colonoscopy.

RESULTS

Sensitivity for screen-relevant neoplasms was 20% by SDT-1, 11% by Hemoccult (P = 0.020), 21% by HemoccultSensa (P = 0.80); sensitivity for cancer plus high-grade dysplasia did not differ among tests. Specificity was 96% by SDT-1, compared with 98% by Hemoccult (P < 0.001) and 97% by HemoccultSensa (P = 0.20). Stool DNA test 2 detected 46% of screen-relevant neoplasms, compared with 16% by Hemoccult (P < 0.001) and 24% by HemoccultSensa (P < 0.001). Stool DNA test 2 detected 46% of adenomas 1 cm or larger, compared with 10% by Hemoccult (P < 0.001) and 17% by HemoccultSensa (P < 0.001). Among colonoscopically normal patients, the positivity rate was 16% with SDT-2, compared with 4% with Hemoccult (P = 0.010) and 5% with HemoccultSensa (P = 0.030).

LIMITATIONS

Stool DNA test 2 was not performed on all subsets of patients without screen-relevant neoplasms. Stools were collected without preservative, which reduced detection of some DNA markers.

CONCLUSION

Stool DNA test 1 provides no improvement over HemoccultSensa for detection of screen-relevant neoplasms. Stool DNA test 2 detects significantly more neoplasms than does Hemoccult or HemoccultSensa, but with more positive results in colonoscopically normal patients. Higher sensitivity of SDT-2 was particularly apparent for adenomas.

Faecal ribosomal protein L19 is a genetic prognostic factor for survival in colorectal cancer

Ribosomal proteins are encoded by a gene family, members of which are overexpressed in human cancers. Many of them have been found, using oligonucleotide microarray hybridization, to be differentially expressed in the faeces of patients with various stages of col-orectal cancer (CRC). The gene encoding ribosomal protein L19 (RPL19), a prognostic marker for human prostate cancer, is differentially expressed in CRC patients. Measurement of faecal RPL19 mRNA might improve prognostic prediction for CRC patients. Using quantitative real-time reverse transcription PCR, levels of RPL19 mRNA were detected in samples of colonic tissues from 44 CRC patients, in the faeces of 54 CRC patients and 15 controls, and in 11 colonic cell lines. Seven of 24 patients with late-stage CRC (Dukes' stages C and D) expressed over 2-fold more RPL19 in colonic tumour tissues than in corresponding normal tissues (P= 0.038). The mean faecal RPL19 mRNA levels of late-staged patients were higher than those of controls (P= 0.003) and early-staged patients (P= 0.008). Patients with both high serum levels of carcinoembryonic antigen (CEA; >5 ng/mL) and high-faecal RPL19 mRNA (≥0.0069) had higher risk (odds ratio, 8.0; P= 0.015) and lower overall 48-month survival (33.8 ± 13.7%, P= 0.013). Oligonucleotide microarray hybridization analysis of faecal molecules identified gene transcripts differentially present in faeces. In conclusion, faecal RPL19 expression is associated with advanced tumour stages and addictive to serum CEA in predicting prognosis of CRC patients.