KRAS mutation detection and prognostic potential in sporadic colorectal cancer using high-resolution melting analysis

Prevalence of KRAS G12C Mutation and Co-mutations and Associated Clinical Outcomes in Patients With Colorectal Cancer: A Systematic Literature Review

PURPOSE

A systematic literature review was conducted to estimate the global prevalence of Kirsten rat sarcoma virus gene (KRAS) mutations, with an emphasis on the clinically significant KRAS G12C mutation, and to estimate the prognostic significance of these mutations in patients with colorectal cancer (CRC).

DESIGN

Relevant English-language publications in the Embase, MEDLINE, and the Cochrane Library databases (from 2009 to 2021) and congress presentations (from 2016 to 2021) were reviewed. Eligible studies were those that reported the prevalence and clinical outcomes of the KRAS G12C mutation in patients with CRC.

RESULTS

A total of 137 studies (interventional [n = 8], post hoc analyses of randomized clinical trials [n = 6], observational [n = 122], and longitudinal [n =1]) were reviewed. Sixty-eight studies reported the prevalence of KRAS mutations (KRASm) in 42 810 patients with CRC. The median global prevalence of KRASm was 38% (range, 13.3%-58.9%) and that of the KRAS G12C mutation (KRAS G12C) 3.1% (range, 0.7%-14%). Available evidence suggests that KRASm are possibly more common in tumors that develop on the right side of the colon. Limited evidence suggests a lower objective response rate and inferior disease-free/relapse-free survival in patients with KRAS G12C compared with patients with KRASwt or other KRASm.

CONCLUSION

Our analysis reveals that KRAS G12C is prevalent in 3% of patients with CRC. Available evidence suggests a poor prognosis for patients with KRAS G12C. Right-sided tumors were more likely to harbor KRASm; however, their role in determining clinical outcomes needs to be investigated further.

Prognostic and Predictive Cross-Roads of Microsatellite Instability and Immune Response to Colon Cancer

Understanding molecular features of colon cancer has shed light on its pathogenesis and progression. Over time, some of these features acquired clinical dignity and were incorporated in decision making. Namely, microsatellite instability (MSI) due to mismatch repair of defects, which primarily was adopted for the diagnosis of Lynch syndrome, became recognized as the biomarker of a different disease type, showing a less aggressive behavior. MSI tumors harbor high amounts of tumor infiltrating lymphocytes (TILs) due to their peculiar load in neoantigens. However, microsatellite stable colon cancer may also show high amounts of TILs, and this feature is as well associated with better outcomes. High TIL loads are in general associated with a favorable prognosis, especially in stage II colon cancer, and therein identifies a patient subset with the lowest probability of relapse. With respect to post-surgical adjuvant treatment, particularly in stage III, TILs predictive ability seems to weaken along with the progression of the disease, being less evident in high risk patients. Moving from cohort studies to the analysis of a series from clinical trials contributed to increase the robustness of TILs as a biomarker. The employment of high TIL densities as an indicator of good prognosis in early-stage colon cancers is strongly advisable, while in late-stage colon cancers the employment as an indicator of good responsiveness to post-surgical therapy requires refinement. It remains to be clarified whether TILs could help in identifying those patients with node-positive cancers to whom adjuvant treatment could be spared, at least in low-risk groups as defined by the TNM staging system.

Prognostic Value of BRAF and KRAS Mutation in Relation to Colorectal Cancer Survival in Iranian Patients: Correlated to Microsatellite Instability

PURPOSE

To evaluate the prognostic role of BRAF and KRAS mutations after adjustment for microsatellite instability (MSI) in Iranian colorectal cancer (CRC) patients.

METHODS

BRAF and KRAS mutations and MSI status were assessed in 258 Iranian subjects with CRC. Two hundred fifty-eight consecutive stages I-IV CRC patients, who underwent surgical resection of adenocarcinoma from 2012 to 2016, were enrolled in the research. Pyrosequencing and Cast-PCR methods were used to the detection of KRAS and BRAF mutations. Kaplan-Meier and Cox regression were employed to estimate hazard ratios (HR) for the association between BRAF and KRAS mutation and overall survival (OS).

RESULTS

KRAS and BRAF mutations were detected in 36 (14%) and 15 (5.8%) cases of 258 patients with CRC, respectively. BRAF mutations that all comprised V600E and KRAS mutations was found in codon 12 and 13 (80.6% and 19.4%), respectively. KRAS mutations were detected in 19 (15.4%) patients of 123 microsatellite stable (MSS) CRC and it is significantly associated with tumor location and metastasis. BRAF and KRAS mutant vs. wild type of BRAF and KRAS, 5-year OS was 73.3% vs. 82.3% and 83.3% vs. 81.5% (long-rank P > 0.05), respectively. KRAS mutant vs. KRAS-wild-type tumors in MSS/MSI-L status CRC patients, 5-year OS was 78.9% vs. 90.4% (long-rank p = 0.046).

CONCLUSION

The present study revealed that BRAF and KRAS mutations were not related to the worse overall survival, while KRAS mutation can be a prognostic factor for overall survival in sporadic microsatellite-stable (MSS) status in Iranian CRC patients.

Formation of mammalian preribosomes proceeds from intermediate to composed state during ribosome maturation

In eukaryotes, ribosome assembly is a rate-limiting step in ribosomal biogenesis that takes place in a distinctive subnuclear organelle, the nucleolus. How ribosomes get assembled at the nucleolar site by forming initial preribosomal complexes remains poorly characterized. In this study, using several human and murine cell lines, we developed a method for isolation of native mammalian preribosomal complexes by lysing cell nuclei through mild sonication. A sucrose gradient fractionation of the nuclear lysate resolved several ribonucleoprotein (RNP) complexes containing rRNAs and ribosomal proteins. Characterization of the RNP complexes with MS-based protein identification and Northern blotting-based rRNA detection approaches identified two types of preribosomes we named here as intermediate preribosomes (IPRibs) and composed preribosome (CPRib). IPRib complexes comprised large preribosomes (105S to 125S in size) containing the rRNA modification factors and premature rRNAs. We further observed that a distinctive CPRib complex consists of an 85S preribosome assembled with mature rRNAs and a ribosomal biogenesis factor, Ly1 antibody-reactive (LYAR), that does not associate with premature rRNAs and rRNA modification factors. rRNA-labeling experiments uncovered that IPRib assembly precedes CPRib complex formation. We also found that formation of the preribosomal complexes is nutrient-dependent because the abundances of IPRib and CPRib decreased substantially when cells were either deprived of amino acids or exposed to an mTOR kinase inhibitor. These findings indicate that preribosomes form via dynamic and nutrient-dependent processing events and progress from an intermediate to a composed state during ribosome maturation.

Combined assessment of the TNM stage and BRAF mutational status at diagnosis in sporadic colorectal cancer patients

The prognostic impact of KRAS mutations and other KRAS-related and non-related genes such as BRAF, NRAS and TP53, on sporadic colorectal cancer (sCRC) remain controversial and/or have not been fully established. Here we investigated the frequency of such mutations in primary sCRC tumors and their impact on patient progression-free survival (PFS) and overall survival (OS). Primary tumor tissues from 87 sCRC patients were analysed using a custom-built next generation sequencing (NGS) panel to assess the hotspot mutated regions of KRAS/NRAS (exons 2, 3 and 4), BRAF (exon 15) and TP53 (all exons). Overall, mutations in these genes were detected in 46/87 sCRC tumors analyzed (53%) with the following frequencies per gene: TP53, 33%; KRAS, 28%; BRAF, 7%; and NRAS, 1%. A significant association was found between KRAS mutations and right side colon tumor location (p=0.05), well-differentiated tumors (p=0.04) and absence of lymphovascular invasion (p=0.05). In turn, BRAF-mutated tumors frequently corresponded to poorly- or moderately-differentiated sCRC (p=0.02) and showed a higher frequency of peritoneal carcinomatosis (p=0.006) and microsatellite instability (p=0.007). From the prognostic point of view, the BRAF mutational status together with the TNM stage were the only variables that showed an independent adverse impact on patient outcome in the multivariate analyses for both PFS and OS. Based on these results a scoring system was built and patients were classified into three prognostic subgroups with different PFS rates at 2 years: 91% vs. 77% vs. 0%, respectively (p<0.0001). Additional prospective studies in larger series of sCRC patients where mutations in genes other than those investigated here are required to validate the utility of the proposed predictive model.

Evolving notions on immune response in colorectal cancer and their implications for biomarker development

INTRODUCTION

Colorectal cancer (CRC) still represents the third most commonly diagnosed type of cancer in men and women worldwide. CRC is acknowledged as a heterogeneous disease that develops through a multi-step sequence of events driven by clonal selections; this observation is sustained by the fact that histologically similar tumors may have completely different outcomes, including a varied response to therapy.

METHODS

In "early" and "intermediate" stage of CRC (stages II and III, respectively) there is a compelling need for new biomarkers fit to assess the metastatic potential of their disease, selecting patients with aggressive disease that might benefit from adjuvant and targeted therapies. Therefore, we review the actual notions on immune response in colorectal cancer and their implications for biomarker development.

RESULTS

The recognition of the key role of immune cells in human cancer progression has recently drawn attention on the tumor immune microenvironment, as a source of new indicators of tumor outcome and response to therapy. Thus, beside consolidated histopathological biomarkers, immune endpoints are now emerging as potential biomarkers.

CONCLUSIONS

The introduction of immune signatures and cellular and molecular components of the immune system as biomarkers is particularly important considering the increasing use of immune-based cancer therapies as therapeutic strategies for cancer patients.

Prognostic and Predictive Value of RAS Gene Mutations in Colorectal Cancer: Moving Beyond KRAS Exon 2

The advent of anti-EGFR (epidermal growth factor receptor) therapy resulted in significant progress in the treatment of metastatic colorectal cancer patients. However, many patients do not respond to this therapy or develop acquired resistance within a few months after the start of treatment. Since 2008, anti-EGFR therapy is restricted to KRAS wild-type patients as it has been shown that KRAS exon 2-mutated patients do not respond to this therapy. Still, up to 60 % of KRAS exon 2 wild-type patients show primary resistance to this treatment. Recently, several studies investigating the predictive and prognostic role of RAS mutations other than in KRAS exon 2 demonstrated that patients with these mutations are not responding to therapy. However, the role of these mutations has long been questioned as The National Comprehensive Cancer Network Guidelines in Oncology and the European Medicines Agency indications had already been changed in order to restrict anti-EGFR therapy to all RAS wild-type colorectal cancer patients, while the Food and Drug Administration guidelines remained unchanged. Recently, the Food and Drug Administration guidelines have also been changed, which implies the importance of RAS mutations beyond KRAS exon 2 in colorectal cancer. In this review, we discuss the most important studies regarding the predictive and prognostic role of RAS mutations other than in KRAS exon 2 in order to demonstrate the importance of these RAS mutations in patients with metastatic colorectal cancer treated with anti-EGFR therapy.

Expression of ITGB1 predicts prognosis in colorectal cancer: a large prospective study based on tissue microarray

BACKGROUND

ITGB1 is a heterodimeric cell-surface receptor involved in cell functions such as proliferation, migration, invasion and survival. The aim of this study was to assess ITGB1 expression in colorectal cancer and correlate it with clinicopathological features, as well as to evaluate its potential prognostic significance.

MATERIALS AND METHODS

In this study, we examined the expression of ITGB1 using tissue microarrays containing analyzed specimens by immunohistochemistry. ITGB1 expression was further correlated with clinicopathological and prognostic data. The prognostic significance was assessed using Kaplan-Meier survival estimates and log-rank tests. A multivariate study with the Cox's proportional hazard model was used to evaluate the prognostic aspects.

RESULTS

ITGB1 expression was present in 88.5% of the analyzed specimens. Significant differences in ITGB1 expression were found between normal mucosa and carcinomas (P<0.001). High ITGB1 expression was associated with poor prognosis, and it independently correlated with shortened overall survival and disease-free survival in colorectal cancer patients (P<0.001). More so, ITGB1 expression, bowel wall invasion, lymph node metastasis and distant metastasis were independent prognostic factors for overall survival. Additionally, significant differences in ITGB1 expression were observed in adenomas and tumors from patients with familial adenomatous polyposis compared to normal colon mucosa (P<0.05) CONCLUSION: The results of this study indicate that ITGB1 overexpression in colorectal tumors is associated with poor prognosis, as well as aggressive clinicopathological features. Therefore, ITGB1 expression could be used as potential prognostic predictor in colorectal cancer patients.

BRAF-mutated colorectal cancer: clinical implications for a distinct subset of the disease

SUMMARY 

Colorectal cancer (CRC) is many diseases, with each case defined by the underlying genetic and molecular changes of that particular tumor. The heterogeneity of CRC emphasizes the need to understand this disease within the context of genetic subsets. BRAF mutations mark a subpopulation that arises through the serrated pathway to carcinogenesis. This subset of cancers is associated with unique clinical and histopathologic characteristics. BRAF-mutated CRCs have a worse prognosis compared with their wild-type counterparts, and may not be as responsive to chemotherapy. Target therapies specifically against BRAF and its related signaling pathways are under both scientific and clinical investigation. This article highlights the clinical relevance of the subset of BRAF-mutated CRCs.

Comparison of genetic and epigenetic alterations of primary tumors and matched plasma samples in patients with colorectal cancer

Background

Although recent advances in circulating DNA analysis allow the prediction of tumor genomes by noninvasive means, some challenges remain, which limit the widespread introduction of cfDNA in cancer diagnostics. We analyzed the status of the two best characterized colorectal cancer (CRC) genetic and epigenetic alterations in a cohort of CRC patients, and then compared the degree to which the two patterns move from tissue to plasma in order to improve our understanding of biology modulating the concordance between tissues and plasma methylation and mutation profiles.

Methods

Plasma and tumor tissues were collected from 85 patients (69±14 years, 56 males). KRAS and SEPT9 status was assessed by allele refractory mutation system quantitative PCR and quantitative methylation-specific PCR, respectively. Six of the most common point mutations at codon 12 and 13 were investigated for KRAS analysis.

Results

KRAS mutations and SEPT9 promoter methylation were present in 34% (29/85) and in 82% (70/85) of primary tumor tissue samples. Both genetic and epigenetic analyses of cfDNA revealed a high overall concordance and specificity compared with tumor-tissue analyses. Patients presenting with both genetic and epigenetic alterations in tissue specimens (31.8%, 27/85) were considered for further analyses. The median methylation rates in tumour tissues and plasma samples were 64.5% (12.2–99.8%) and 14.5% (0–45.5%), respectively. The median KRAS mutation load (for matched mutations) was 33.6% (1.8–86.3%) in tissues and 2.9% (0–17.3) in plasma samples. The plasma/tissue (p/t) ratio of SEPT9 methylation rate was significantly higher than the p/t ratio of KRAS mutation load, especially in early stage cancers (p=0.0108).

Conclusion

The results of this study show a discrepant rate of epigenetic vs. genetic alterations moving from tissue to plasma. Many factors could affect mutation cfDNA analysis, including both presence of tumor clonal heterogeneity and strict compartmentalization of KRAS mutation profile. The present study highlights the importance of considering the nature of the alteration when analyzing tumor-derived cfDNA.

Mutation analysis of genes in the EGFR pathway in Head and Neck cancer patients: implications for anti-EGFR treatment response

Background

Targeted therapy against the Epidermal Growth Factor Receptor (EGFR) is among the most promising molecular therapeutics for Head and Neck Squamous Cell Carcinoma (HNSCC). However, drug resistance limits the clinical efficacy of anti-EGFR monoclonal antibodies and no predictive biomarker has entered the clinic yet.

Methods

A retrospective clinical study was performed utilizing pathological specimens from 52 newly diagnosed HNSCC patients. These patients were screened for mutations in EGFR and KRAS. Tyrosine kinase mutations in EGFR and KRAS mutations were evaluated by high resolution melting analysis (HRMA), whereas EGFRvIII was determined using one-step real-time PCR. Finally, patient samples were screened for HPV-DNA by GP5+/6+ PCR. Survival analysis was performed using Kaplan-Meier analysis and significance was calculated using log-rank statistic.

Results

In our study population no EGFRvIII mutations were present. However, two silent mutations were found; T785T in exon 20 and R836R in exon 21 of the EGFR gene. Additionally, HRMA revealed an abnormal KRAS melting pattern in 7.0% of the samples. However, the KRAS StripAssay could confirm only one sample with a G12S mutation and none of these samples could be confirmed by direct sequencing. HPV DNA was present in 3/25 larynx and 9/27 oropharynx tumors.

Conclusion

The low rate of EGFR and KRAS mutations in this Belgian HNSCC population suggests that these genes will probably not play a major role in predicting response to anti-EGFR therapy in HNSCC. Hence, other predictive markers need to be discovered in order to optimize EGFR targeting therapy.

Deep sequencing reveals complex mechanisms of microRNA deregulation in colorectal cancer

Deregulated microRNAs (miRNAs) have been reported to be of functional relevance for tumor biology. In this study, we analyzed the small RNA transcriptomes of 10 paired colorectal cancer samples using SOLiD next-generation sequencing, and generated a total of >15141000 reads. miRNA expression profiles obtained by SOLiD sequencing correlated well with quantitative PCR results. The results showed that the expression of 36 miRNAs was significantly different between the two groups of samples. Additionally, we explored the global miRNA-mRNA interactions using a statistical model. In-depth analysis reveals a diagram of extensive post-transcriptional miRNA regulations. Signaling pathways associated with the miRNA altered expression signature were identified using gene enrichment analysis. The results suggest that these microRNAs, in the aggregate, regulate signaling pathways, such as MAPK, Wnt and p53 pathways in cancer, which are known to be involved in the transformation of colorectal cancer. This evidence demonstrates that miRNAs can cooperatively regulate a given pathway and play a subtle role by regulating their target genes.

KRAS mutations: analytical considerations

Colorectal cancer (CRC) is the third most common cancer and the second most common cause of cancer death globally. Significant improvements in survival have been made in patients with metastasis by new therapies. For example, Cetuximab and Panitumumab are monoclonal antibodies that inhibit the epidermal growth receptor (EGFR). KRAS mutations in codon 12 and 13 are the recognized biomarkers that are analyzed in clinics before the administration of anti-EGFR therapy. Genetic analyses have revealed that mutations in KRAS predict a lack of response to Panitumumab and Cetuximab in patients with metastatic CRC (mCRC). Notably, it is estimated that 35-45% of CRC patients harbor KRAS mutations. Therefore, KRAS mutation testing should be performed in all individuals with the advanced CRC in order to identify the patients who will not respond to the monoclonal EGFR antibody inhibitors. New techniques for KRAS testing have arisen rapidly, and each technique has advantages and disadvantages. Herein, we review the latest published literature specific to KRAS mutation testing techniques. Since reliability and feasibility are important issues in clinical analyses. Therefore, this review also summarizes the effectiveness and limitations of numerous KRAS mutation testing techniques.

MACC1 mRNA levels predict cancer recurrence after resection of colorectal cancer liver metastases

OBJECTIVE

Upon colon cancer metastasis resection in liver, disease outcome is heterogeneous, ranging from indolent to very aggressive, with early recurrence. The aim of this study is to investigate the capability of metastasis associated in colon cancer 1 (MACC1) levels measured in liver metastasis specimens to predict further recurrence of the disease.

METHODS

Gene expression and gene dosage of MACC1, hepatocyte growth factor (HGF), and hepatocyte growth factor receptor (MET) were assessed using quantitative realtime polymerase chain reaction on a cohort of 64 liver metastasis samples from patients with complete follow-up of 36 months and detailed clinical annotation. The most relevant mutations associated to prognosis in colorectal cancer, KRAS, and PIK3CA were assessed on the same specimens with Sanger sequencing.

RESULTS

Receiver operating characteristic (ROC) analysis revealed that MACC1 mRNA abundance is a good indicator of metastatic recurrence (AUC = 0.65, P < 0.05), whereas no such results were obtained with MET and HGF, nor with gene dosage. Generation of MACC1-based risk classes was capable of successfully separating patients into poor and good prognosis subgroups [hazard ratio (HR) = 5.236, 95% confidence interval (CI) = 1.2068-22.715, P < 0.05]. Also KRAS mutation was significantly associated with higher risk of recurrence (HR = 2.07, 95% CI = 1.048-4.09, P < 0.05). Cox regression multivariate analysis supported the independence of MACC1, but not KRAS, from known prognostic clinical information (Node Size HR = 3.155, 95% CI = 1.4418-6.905, P < 0.001, Preoperative carcinoembryonic antigen HR = 2.359, 95% CI = 1.0203-5.452, P < 0.05, MACC1 HR = 7.2739, 95% CI = 1.6584-31.905, P < 0.01).

CONCLUSIONS

MACC1, a new easily detectable biomarker in cancer, is an independent prognostic factor of recurrence after liver resection of colorectal cancer metastasis.

Anti-epidermal growth factor receptor therapy in head and neck squamous cell carcinoma: focus on potential molecular mechanisms of drug resistance

Targeted therapy against the epidermal growth factor receptor (EGFR) is one of the most promising molecular therapeutics for head and neck squamous cell carcinoma (HNSCC). EGFR is overexpressed in a wide range of malignancies, including HNSCC, and initiates important signal transduction pathways in HNSCC carcinogenesis. However, primary and acquired resistance are serious problems and are responsible for low single-agent response rate and tumor recurrence. Therefore, an improved understanding of the molecular mechanisms of resistance to EGFR inhibitors may provide valuable indications to identify biomarkers that can be used clinically to predict response to EGFR blockade and to establish new treatment options to overcome resistance. To date, no predictive biomarker for HNSCC is available in the clinic. Therapeutic resistance to anti-EGFR therapy may arise from mechanisms that can compensate for reduced EGFR signaling and/or mechanisms that can modulate EGFR-dependent signaling. In this review, we will summarize some of these molecular mechanisms and describe strategies to overcome that resistance.

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

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

Circulating tumor-derived mutant mitochondrial DNA: a predictive biomarker of clinical prognosis in human squamous cell carcinoma

While circulating tumor-derived molecules have been identified in a variety of malignant tumors, it is sometimes difficult to detect the molecular targets due to the lower serum concentration. We report that evaluation of circulating tumor-derived mitochondrial DNA (mtDNA) seems to have novel efficiency for detecting tumoral micrometastasis. In murine xenografting human oral cancer cells, human mtDNAs could be quantitatively detected from multiple organs and blood samples whereas human nucleic DNAs could not. We also determined if this mtDNA blood test was relevant for patients with oral cancer with no histologic evidence of tumoral cells in their surgical margins. For this, mtDNA from normal and tumorous tissues and serum mtDNA obtained pre and postoperatively was examined at three different regions including the displacement loop, 12S-rRNA, and 16S-rRNA. All recurring patients had significantly higher amounts of mutant mtDNAs in the tumoral tissues compared with the non-recurring group. More importantly, on the blood test with the cut-off point by receiver operating characteristic (ROC) curve analysis, while the vast majority of serum mtDNA samples obtained postoperatively in the recurring cases maintained significantly higher amounts of mutant mtDNAs, the non-recurring cases did not, and they showed good prognosis. This is the first report of this approach for managing patients after resection of oral tumors, and may have substantial diagnostic potential for other tumoral types.

The KRAS StripAssay for detection of KRAS mutation in Egyptian patients with colorectal cancer (CRC): a pilot study

BACKGROUND

Epidermal growth factor receptor (EGFR) and its downstream factors KRAS and BRAF are mutated in several types of cancer, affecting the clinical response to EGFR inhibitors. Mutations in the EGFR kinase domain predict sensitivity to the tyrosine kinase inhibitors gefitinib and erlotinib in lung adenocarcinoma, while activating point mutations in KRAS and BRAF confer resistance to the anti-EGFR monoclonal antibody cetuximab in colorectal cancer. The development of new generation methods for systematic mutation screening of these genes will allow more appropriate therapeutic choices.

PURPOSE

Detection of KRAS mutation in Egyptian colorectal cancer (CRC) patients by the KRAS StripAssay.

METHODS

Examination of 20 colorectal cancer (CRC) patients is done to detect KRAS mutations by KRAS StripAssay. For the StripAssay, a mutant-enriched PCR was followed by hybridization to KRAS-specific probes bound to a nitrocellulose strip.

RESULTS

Among 20 patients, KRAS mutations were identified in 80% of patients by the KRAS StripAssay.

CONCLUSIONS

Our preliminary results suggest that KRAS StripAssay is an alternative to protocols currently in use for KRAS mutation detection.

KRAS Testing: A Tool for the Implementation of Personalized Medicine

Activating point mutations in codons 12, 13, and 61 of the KRAS proto-oncogene are common in colorectal, non-small cell lung, pancreatic, and thyroid cancers. Constitutively activated KRAS mutations are strongly associated with a resistance to anti-epidermal growth factor receptor (EGFR) therapies, such as panitumumab and cetuximab used for treating metastatic colorectal carcinoma and EGFR tyrosine inhibitors used for advanced non-small cell lung cancers. Since anti-EGFR therapies are costly and may exert deleterious effects on individuals without activating mutations, KRAS mutation testing is recommended prior to the initiation of anti-EGFR therapy for these malignancies. The goal of this review is to summarize the KRAS mutation testing methods. Testing is now routinely requested in the clinical practice to provide data to assign the most appropriate anticancer chemotherapy for each given patient. Review of the most relevant literature was performed. Several areas were considered: ordering of the test, selection of the sample to be tested, and review of the testing methodologies. We found that several different methods are used for clinical KRAS mutation testing. Each of the methodologies is described, and information is provided about their performance, cost, turnaround times, detection limits, sensitivities, and specificities. We also provided "tips" for the appropriate selection and preparation of the sample to be tested. This is an important aspect of KRAS testing for clinical use, as the results of the test will affect clinical decisions with consequences for the patient.

Prognostic relevance of KRAS and BRAF mutations in Japanese patients with colorectal cancer

BACKGROUND

Mutations of the KRAS or BRAF genes are now recognized as prognostic markers for colorectal cancer (CRC). They are also important predictive markers for resistance to the monoclonal antibodies that target the epidermal growth factor receptor.

METHODS

In this retrospective study, KRAS and BRAF mutations were analyzed using a direct sequence method in 254 Japanese CRC patients, and the associations between KRAS or BRAF mutations and clinicopathological characteristics or outcome were evaluated.

RESULTS

KRAS and BRAF mutations were detected in 33.5 and 6.7 % of all patients, respectively. Consistent with previous reports, BRAF mutations were significantly correlated with the anatomical site of the tumor (P < 0.001), tumor grade (P = 0.001) and high frequency of microsatellite instability (P < 0.001). BRAF mutations were correlated with poor overall survival in the full patient cohort (P = 0.009). KRAS mutations were significantly correlated with poor recurrence-free survival (P = 0.03), particularly in patients with stage II CRC (P = 0.007). Cox regression analysis showed that KRAS mutations were a negative predictor of recurrence-free survival in patients with stage II CRC.

CONCLUSION

KRAS mutation status could be a novel biomarker for predicting disease recurrence in Japanese patients with stage II CRC.

Mutant KRAS codon 12 and 13 alleles in patients with metastatic colorectal cancer: assessment as prognostic and predictive biomarkers of response to panitumumab

PURPOSE

Panitumumab, a fully human monoclonal antibody targeting the epidermal growth factor receptor (EGFR), has demonstrated significant improvements in progression-free survival (PFS) in patients with wild-type KRAS metastatic colorectal cancer (mCRC) in studies 20050203 (first line), 20050181 (second line), and 20020408 (monotherapy). Mutations in KRAS codons 12 and 13 are recognized biomarkers that predict lack of response to anti-EGFR antibody therapies. This retrospective analysis of three randomized phase III studies assessed the prognostic and predictive impact of individual mutant KRAS codon 12 and 13 alleles.

PATIENTS AND METHODS

Patients were randomly assigned 1:1 to FOLFOX4 (infusional fluorouracil, leucovorin, and oxaliplatin) in study 20050203, FOLFIRI (fluorouracil, leucovorin, and irinotecan) in study 20050181, or best supportive care in study 20020408 with or without panitumumab 6.0 mg/kg once every 2 weeks. In all, 441 (20050203), 486 (20050181), and 126 (20020408) patients with mutant KRAS codon 12 or 13 alleles were included in the analysis.

RESULTS

No mutant KRAS allele in patients treated on the control arm emerged as a consistent prognostic factor for PFS or overall survival (OS). In addition, no mutant KRAS allele was consistently identified as a predictive factor for PFS or OS in patients receiving panitumumab treatment. Significant interactions for individual mutant KRAS alleles were observed only in study 20050203 with G13D negatively and G12V positively associated with OS in the panitumumab-containing arm. Pooled analysis indicated that only G12A was associated with a negative predictive effect on OS.

CONCLUSION

In this retrospective analysis, results across three treatment regimens suggest that patients with mutant KRAS codon 12 or 13 mCRC tumors are unlikely to benefit from panitumumab therapy. Currently, panitumumab therapy should be limited to patients with wild-type KRAS mCRC.

Retrospective analysis of KRAS status in metastatic colorectal cancer patients: a single-center feasibility study

Background:

The occurrence of KRAS mutations and their association with prognosis in metastatic colorectal cancer patients is not well documented in population-based studies.

Objectives:

To examine the feasibility of identifying archived colorectal cancer specimens, and through linkage with nationwide Danish population-based databases to investigate the prevalence of KRAS mutations and their association with colorectal cancer survival.

Methods:

We used the Danish Pathology Database to identify the physical location of primary (or in some cases secondary) tumor specimens from selected metastatic colorectal cancer patients referred to our hospital for palliative chemotherapy between November 1, 2008 and September 30, 2009. Routinely stored paraffin tissue blocks were obtained from the pathology archives of the originating hospital. KRAS mutation tumor status was assessed for each patient using the commercialized TheraScreen KRAS Mutation Kit. Using the unique identifier number, we linked the patients to the Danish National Registry of Patients and the Danish Civil Registration System to obtain data on date of first colorectal cancer diagnosis and follow-up status. We estimated prevalence of KRAS mutations and the 1-, 2-, and 5-year survival after colorectal cancer diagnosis using the Kaplan–Meier technique.

Results:

We identified 106 metastatic colorectal cancer patients (64% males). All were successfully linked to the registries, and archived tumor-tissue samples were obtained and analyzed in each case. The overall prevalence of KRAS mutations was 55%, and 1-, 2-, and 5-year overall survival after colorectal cancer diagnosis was 91%, 68%, and 25%, respectively.

Conclusion:

It is feasible to use Danish population-based registries to obtain archived tissue samples from metastatic colorectal cancer patients, and to estimate prevalence of KRAS mutation and subsequently evaluate the association with colorectal cancer survival.

Involvement of KRAS G12A mutation in the IL-2-independent growth of a human T-LGL leukemia cell line, PLT-2

Cytokine-dependent cell lines have been used to analyze the cytokine-induced cellular signaling and the mechanism of oncogenesis. In the current study, we analyzed MOTN-1 and PLT-2 cell lines established from different stages of a T-cell large granular lymphocyte leukemia patient (Daibata et al. 2004). MOTN-1 is IL-2-dependent derived from the chronic phase, whereas IL-2-independent PLT-2 is from the aggressive and terminal stage. They shared considerable chromosome abnormalities and the pattern of T-cell receptor rearrangement, presuming that the cytokine independence of PLT-2 was due to the additive genetic abnormality. Besides IL-2, IL-15 supported MOTN-1 cell growth, because these receptors share beta- and gamma-subunits. IL-2 activated ERK, AKT and STAT pathway of MOTN-1. STAT3 pathway of PLT-2 was also activated by IL-2, suggesting intact IL-2 induces signal transduction of PLT-2. However, ERK1/2 but not AKT, was continuously activated in PLT-2, consistent with the increased Ras-activity of PLT-2. Sequence analysis revealed KRAS G12A mutation but not NRAS and HRAS mutation of PLT-2 but not MOTN-1. Another signaling molecule affecting Ras-signaling pathway, SHP2, which has been frequently mutated in juvenile myelomonocytic leukemia (JMML), did not show mutation. Moreover, MEK inhibitor, PD98059, as well as farnesylation inhibitor inhibited PLT-2 cell growth. Using NIH3T3 and MOTN-1, ERK activation, increased cell proliferation and survival by KRAS G12A were shown, suggesting the important role of KRAS G12A in IL-2-independent growth of PLT-2. Taken together, KRAS G12A is important for IL-2-independent growth of PLT-2 cells and suggests the possibility of involvement of KRAS mutation with disease progression.

KRAS mutation detection by high-resolution melting analysis significantly predicts clinical benefit of cetuximab in metastatic colorectal cancer

Background:

Anti-epidermal growth factor receptor (EGFR) monoclonal antibodies are restricted to KRAS wild-type (WT) metastatic colorectal cancers (mCRCs), usually identified by direct sequencing, that may yield false negative results because of genetic heterogeneity within the tumour. We evaluated the efficiency of high-resolution melting analysis (HRMA) in identifying KRAS-mutant (MUT) tumours.

Methods:

We considered 50 mCRC patients scored as KRAS-WT by direct sequencing and treated with cetuximab-containing chemotherapy, and tested the correlations between HRMA findings and response rate (RR), progression-free (PFS) and overall survival (OS).

Results:

Aberrant melting curves were detected in four (8%) cases; gene cloning confirmed these mutations. Response rate (RR) of HRMA KRAS-WT patients was 28.3%. There was no response in HRMA KRAS-MUT patients. Disease control rate (responsive plus stable disease) was 58.7% in HRMA KRAS-WT patients and 25% in HRMA KRAS-MUT patients. There was no correlation between HRMA KRAS status and RR (P=0.287) or disease control (P=0.219). Median PFS (4.8 vs 2.3 months; hazard ratio (HR)=0.29, P=0.02) and OS (11.0 vs 2.7 months; HR=0.11, P=0.03) were significantly longer for the HRMA KRAS-WT than for HRMA KRAS-MUT patients.

Conclusions:

High-resolution melting analysis identified 8% more KRAS-MUT patients not responding to cetuximab-containing regimens, suggesting that HRMA may be more effective than direct sequencing in selecting patients for anti-EGFR antibodies.

Involvement of K-RAS mutations and amino acid substitutions in the survival of metastatic colorectal cancer patients

The efficacy of epidermal growth factor-targeting therapies has been found to be limited in tumors with the wild-type K-RAS gene, suggesting a predictive value of K-RAS gene analysis in tumoral response. However, the prognostic value of K-RAS is controversial. This study included patients diagnosed with metastatic colorectal cancer. The presence of K-RAS mutations was analyzed, and the tumors positive for a K-RAS mutation were further analyzed to identify the mutation type. Similarly, the following clinical and pathological variables were also collected. The study was composed of 53.3 % of patients with wild-type K-RAS and 46.7 % of patients with mutated K-RAS (mutated codon 12 was the most frequent). With a mean follow-up of 15 months (range, 1-45), the median survival of patients with wild-type K-RAS was 31.6 months. The median survival was 24.8 months for patients with K-RAS mutated in codon 12 and 17.8 months for patients with mutated codon 13 (p = 0.37). In a univariate analysis, K-RAS was associated with stage IV at diagnosis (p < 0.005). When K-RAS was mutated, a lower overall survival was observed in cases of G → A transition compared with G → T transversion (19.5 vs. 24.2 months, respectively; p = 0.47). When the amino acid change resulted in an acidic substitution, survival was lower, but it increased when the substitution resulted in a polar or nonpolar amino acid (19.5 vs. 23.2 vs. 24.4 months, p = 0.79). The type of K-RAS mutation or amino acid changes may have prognostic implications in metastatic colon cancer patients. Further research is needed in patients treated in prospective controlled trials.

KRAS mutational status of endoscopic biopsies matches resection specimens

Aims

This study was performed to determine systematically whether KRAS mutational analysis in biopsy tissue is a reliable indicator of KRAS status in subsequent corresponding resection specimens.

Methods

30 colorectal cancer (CRC) patients with biopsy and corresponding subsequent surgical resection specimens were studied. KRAS mutational analysis was performed on each biopsy sample as well as two separate samples from each resection specimen by PCR and Sanger sequencing.

Results

Overall, KRAS mutations were identified in 12/30 (40%) of the tumours. There was 100% correlation between biopsy and resection specimens regarding the presence or absence of KRAS mutations. In fact, the same point mutation was identified in both biopsy and corresponding resection specimens in 12/12 (100%) cases. In addition, in two cases, there were two different point mutations detected within the same biopsy specimen.

Conclusion

This study shows perfect correlation between KRAS mutation status in biopsy and resection specimens from an individual patient, and suggests that biopsy material is adequate for KRAS mutational analysis in CRC patients.

Ras in cancer and developmental diseases

Somatic, gain-of-function mutations in ras genes were the first specific genetic alterations identified in human cancer about 3 decades ago. Studies during the last quarter century have characterized the Ras proteins as essential components of signaling networks controlling cellular proliferation, differentiation, or survival. The oncogenic mutations of the H-ras, N-ras, or K-ras genes frequently found in human tumors are known to throw off balance the normal outcome of those signaling pathways, thus leading to tumor development. Oncogenic mutations in a number of other upstream or downstream components of Ras signaling pathways (including membrane RTKs or cytosolic kinases) have been detected more recently in association with a variety of cancers. Interestingly, the oncogenic Ras mutations and the mutations in other components of Ras/MAPK signaling pathways appear to be mutually exclusive events in most tumors, indicating that deregulation of Ras-dependent signaling is the essential requirement for tumorigenesis. In contrast to sporadic tumors, separate studies have identified germline mutations in Ras and various other components of Ras signaling pathways that occur in specific association with a number of different familial, developmental syndromes frequently sharing common phenotypic cardiofaciocutaneous features. Finally, even without being a causative force, defective Ras signaling has been cited as a contributing factor to many other human illnesses, including diabetes and immunological and inflammatory disorders. We aim this review at summarizing and updating current knowledge on the contribution of Ras mutations and altered Ras signaling to development of various tumoral and nontumoral pathologies.