Ultra-deep sequencing confirms immunohistochemistry as a highly sensitive and specific method for detecting BRAF V600E mutations in colorectal carcinoma

The rapidly changing field of predictive biomarkers of non-small cell lung cancer

Lung cancer is a leading cause of cancer-related death worldwide in both men and women, however mortality in the US and EU are recently declining in parallel with the gradual cut of smoking prevalence. Consequently, the relative frequency of adenocarcinoma increased while that of squamous and small cell carcinomas declined. During the last two decades a plethora of targeted drug therapies have appeared for the treatment of metastasizing non-small cell lung carcinomas (NSCLC). Personalized oncology aims to precisely match patients to treatments with the highest potential of success. Extensive research is done to introduce biomarkers which can predict the effectiveness of a specific targeted therapeutic approach. The EGFR signaling pathway includes several sufficient targets for the treatment of human cancers including NSCLC. Lung adenocarcinoma may harbor both activating and resistance mutations of the EGFR gene, and further, mutations of KRAS and BRAF oncogenes. Less frequent but targetable genetic alterations include ALK, ROS1, RET gene rearrangements, and various alterations of MET proto-oncogene. In addition, the importance of anti-tumor immunity and of tumor microenvironment has become evident recently. Accumulation of mutations generally trigger tumor specific immune defense, but immune protection may be upregulated as an aggressive feature. The blockade of immune checkpoints results in potential reactivation of tumor cell killing and induces significant tumor regression in various tumor types, such as lung carcinoma. Therapeutic responses to anti PD1-PD-L1 treatment may correlate with the expression of PD-L1 by tumor cells. Due to the wide range of diagnostic and predictive features in lung cancer a plenty of tests are required from a single small biopsy or cytology specimen, which is challenged by major issues of sample quantity and quality. Thus, the efficacy of biomarker testing should be warranted by standardized policy and optimal material usage. In this review we aim to discuss major targeted therapy-related biomarkers in NSCLC and testing possibilities comprehensively.

Comparative efficiency of differential diagnostic methods for the identification of BRAF V600E gene mutation in papillary thyroid cancer (Review)

V-Raf murine sarcoma viral oncogene homolog B1 (BRAF) encodes a serine-threonine kinase. The V600E point mutation in the BRAF gene is the most common mutation, predominantly occurring in melanoma, and colorectal, thyroid and non-small cell lung cancer. Particularly in the context of thyroid cancer research, it is routinely employed as a molecular biomarker to assist in diagnosing and predicting the prognosis of papillary thyroid cancer (PTC), and to formulate targeted therapeutic strategies. Currently, several methods are utilized in clinical settings to detect BRAF V600E mutations in patients with PTC. However, the sensitivity and specificity of various detection techniques vary significantly, resulting in diverse detection outcomes. The present review highlights the advantages and disadvantages of the methods currently employed in medical practice, with the aim of guiding clinicians and researchers in selecting the most suitable detection approach for its high sensitivity, reproducibility and potential to develop targeted therapeutic regimens for patients with BRAF gene mutation-associated PTC.

BRAFV600E immunohistochemistry can reliably substitute BRAF molecular testing in the Lynch syndrome screening algorithm in colorectal cancer

AIMS

The Lynch syndrome (LS) screening algorithm requires BRAF testing as a fundamental step to distinguish sporadic from LS-associated colorectal carcinomas (CRC). BRAF testing by immunohistochemistry (IHC) has shown variable results in the literature. Our aim was to analyse concordance between BRAFV600E IHC and BRAF molecular analysis in a large, mono-institutional CRC whole-slide, case series with laboratory validation.

METHODS AND RESULTS

MisMatch repair (MMR) protein (hMLH1, hPMS2, hMSH2, and hMSH6) and BRAFV600E IHC were performed on all unselected cases of surgically resected CRCs (2018-2023). An in-house validation study for BRAFV600E IHC was performed in order to obtain optimal IHC stains. BRAFVV600E IHC was considered negative (score 0), positive (scores 2-3), and equivocal (score 1). Interobserver differences in BRAFV600E IHC scoring were noted in the first 150 cases prospectively collected. Nine-hundred and ninety CRCs cases (830 proficient (p)MMR/160 deficient (d)MMR) were included and all cases performed BRAFV600E IHC (BRAFV600E IHC-positive 13.5% of all series; 66.3% dMMR cases; 3.4% pMMR cases), while 333 also went to BRAF mutation analysis. Optimal agreement in IHC scoring between pathologists (P < 0.0001) was seen; concordance between BRAFV600E IHC and BRAF molecular analysis was extremely high (sensitivity 99.1%, specificity 99.5%; PPV 99.1%, and NPV 99.5%). Discordant cases were reevaluated; 1 score 3 + IHC/wildtype case was an interpretation error and one score 0 IHC/mutated case was related to heterogenous BRAFV600E IHC expression. Among the 12 IHC-equivocal score 1+ cases (which require BRAF molecular analysis), three were BRAF-mutated and nine BRAF-wildtype.

CONCLUSION

BRAFV600E IHC can be used as a reliable surrogate of molecular testing after stringent in-house validation.

Prognostic Value of BRAF, Programmed Cell Death 1 (PD1), and PD Ligand 1 (PDL1) Protein Expression in Colon Adenocarcinoma

Patients with colorectal cancer in different stages show variable outcomes/therapeutic responses due to their distinct tumoral biomarkers and biological features. In this sense, this study aimed to explore the prognostic utility of BRAF, programmed death-1 (PD1), and its ligand (PDL1) protein signatures in colon adenocarcinoma. The selected protein markers were explored in 64 archived primary colon adenocarcinomas in relation to clinicopathological features. BRAF overexpression was found in 39% of the cases and was significantly associated with grade 3, N1, advanced Dukes stage, presence of relapse, and shorter overall survival (OS). PD1 expression in the infiltrating immune cells (IICs) exhibited significant association with T2/T3, N0/M0, early Dukes stage, and absence of relapse. PDL1 expression in IICs is significantly associated with advanced nodal stage/distant metastasis, advanced Dukes stage, and shorter OS. Meanwhile, PDL1 expression in neoplastic cells (NC) was associated with the advanced lymph node/Dukes stage. A positive combined expression pattern of PDL1 in NC/IICs was associated with poor prognostic indices. Tumor PDL1 expression can be an independent predictor of OS and DFS. The multivariate analyses revealed that short OS was independently associated with the RT side location of the tumor, PD1 expression in stromal IICs, and PDL1 expression in NC. In conclusion, overexpression of BRAF in colon adenocarcinoma is considered a poor prognostic pathological marker. In addition, PDL1 expression in NC is considered an independent prognostic factor for DFS/OS. Combined immunohistochemical assessment for BRAF and PD1/PDL1 protein expressions in colon adenocarcinoma might be beneficial for selecting patients for future targeted therapy.

BRAF-mutated colorectal adenocarcinomas: pathological heterogeneity and clinical implications

Advances in molecular biology have markedly increased our understanding of the heterogeneous molecular landscape of colorectal cancer (CRC). Up to 15% of CRCs harbor the BRAF p.V600E somatic mutation (BRAFmt), a well-established negative prognostic marker in patients with metastatic CRC (mCRC). The BEACON CRC trial set a new standard of care in patients with progressive BRAFmt cancers, consisting of the combination of encorafenib and cetuximab. On these bases, BRAF mutational testing is now recommended in patients with mCRC. However, efforts are needed to further stratify patients carrying this mutation. Here, we discuss the heterogeneous pathologic and molecular landscape of BRAFmt CRCs, focusing on the promises and pitfalls of molecular diagnostics, on novel biomarkers to improve patients' stratification and on the current diagnostic scenario for CRC. We believe that a better stratification based on histopathological features and novel molecular biomarkers should be performed to optimize patient management and therapeutic decision-making.

Preliminary Study on the Identification of BRAFV600E Mutation in Colorectal Cancer by Near-Infrared Spectroscopy

Introduction

In metastatic colorectal cancer (mCRC), the B-type Raf kinase (BRAF)^V600E mutation is a molecular biomarker of poor prognosis and is of great importance to drug target. Currently, the commonly used methods for detecting BRAF^V600E mutation include immunohistochemistry (IHC) and gene sequencing, but both present certain limitations. Near-infrared (NIR) spectroscopy is a spectroscopy technology that takes advantage of the electromagnetic wavelength between visible light and mid-infrared light.

Methods

IHC was used to detect the expression of BRAF^V600E protein with the BRAF^V600E (VE1) antibody in 42 cases of paraffin-embedded (FFPE) mCRC tissue sections. The NIR-discriminant analysis model (NIRS-DA) was established using 6 cases of wild-type and 6 cases of mutant-type BRAF specimens.

Results

IHC detection results revealed 13 cases of weakly positive (+), 1 case of moderately positive (++), and 28 cases of negative (-) CRC. Compared with the next-generation sequencing (NGS) results, the positive rate was 66.7%. The classification accuracy of calibration (CAC) was 100% compared with the results of NGS, demonstrating that the BRAF^V600E mutant NIRS-DA model, verified by 2 cases of wild-type and 2 cases of mutant-type CRC samples was established. The NIRS-DA model was used to predict gene mutation in the CRC samples, 7 cases were positive (+), and 35 cases were negative (-), and the classification accuracy of prediction (CAP) was 83.3% (35/42).

Discussion

The NIRS-DA model-predicted results were in high agreement with the detection results of NGS, and the difference in IHC is not statistically significant (P>0.05). However, this study is a preliminary discussion on a methodology due to its small sample size.

Mismatch repair deficiency assessment by immunohistochemistry: for Lynch syndrome screening and beyond

While mismatch repair (MMR) deficiency has been studied extensively, the assessment of MMR status in colorectal and other cancers remains highly relevant, particularly in light of recent data demonstrating that MMR deficiency is a strong predictor for treatment benefit with immune checkpoint inhibitors across multiple tumor types. In colorectal cancer, there is a growing consensus in support of routine MMR testing for Lynch syndrome screening, to inform prognosis and adjuvant chemotherapy use in early stage disease, and to predict response to immunotherapy in advanced disease. Here, we provide a review of the Ventana MMR Immunohistochemistry Panel, which was recently approved by the US FDA for use in Lynch syndrome screening.

Immunohistochemistry with Anti-BRAF V600E (VE1) Mouse Monoclonal Antibody is a Sensitive Method for Detection of the BRAF V600E Mutation in Colon Cancer: Evaluation of 120 Cases with and without KRAS Mutation and Literature Review

The major aim of this study was to evaluate the performance of anti-BRAF V600E (VE1) antibody in colorectal tumors with and without KRAS mutation. KRAS and BRAF are two major oncogenic drivers of colorectal cancer (CRC) that have been frequently described as mutually exclusive, thus the BRAF V600E mutation is not expected to be present in the cases with KRAS mutation. In addition, a review of 25 studies comparing immunohistochemistry (IHC) using the anti-BRAF V600E (VE1) antibody with BRAF V600E molecular testing in 4041 patient samples was included. One-hundred and twenty cases with/without KRAS or BRAF mutations were acquired. The tissue were immunostained with anti-BRAF V600E (VE1) antibody with OptiView DAB IHC detection kit. The KRAS mutated cases with equivocal immunostaining were further evaluated by Sanger sequencing for BRAF V600E mutation. Thirty cases with BRAF V600E mutation showed unequivocal, diffuse, uniform, positive cytoplasmic staining and 30 cases with wild-type KRAS and BRAF showed negative staining with anti-BRAF V600E (VE1) antibody. Out of 60 cases with KRAS mutation, 56 cases (93.3%) were negative for BRAF V600E mutation by IHC. Four cases showed weak, equivocal, heterogeneous, cytoplasmic staining along with nuclear staining in 25-90% of tumor cells. These cases were confirmed to be negative for BRAF V600E mutation by Sanger sequencing. Overall, IHC with anti-BRAF V600E (VE1) antibody using recommended protocol with OptiView detection is optimal for detection of BRAF V600E mutation in CRC. Our data are consistent with previous reports indicating that KRAS and BRAF V600E mutation are mutually exclusive.

The current value of determining the mismatch repair status of colorectal cancer: A rationale for routine testing

Colorectal Cancer (CRC) is the third most prevalent cancer in men and women. Up to 15% of CRCs display microsatellite instability (MSI). MSI is reflective of a deficient mismatch repair (MMR) system and is most commonly caused by hypermethylation of the MLH1 promoter. However, it may also be due to autosomal dominant constitutional mutations in DNA MMR, termed Lynch Syndrome. MSI may be diagnosed via polymerase chain reaction (PCR) or alternatively, immunohistochemistry (IHC) can identify MMR deficiency (dMMR). Many institutions now advocate universal tumor screening of CRC via either PCR for MSI or IHC for dMMR to guide Lynch Syndrome testing. The association of sporadic MSI with methylation of the MLH1 promoter and an activating BRAF mutation may offer further exclusion criteria for genetic testing. Aside from screening for Lynch syndrome, MMR testing is important because of its prognostic and therapeutic implications. Several studies have shown MSI CRCs exhibit different clinicopathological features and prognosis compared to microsatellite-stable (MSS) CRCs. For example, response to conventional chemotherapy has been reported to be less in MSI tumours. More recently, MSI tumours have been shown to be responsive to immune-checkpoint inhibition providing a novel therapeutic strategy. This provides a rationale for routine testing for MSI or dMMR in CRC.

SP174, NRAS Q61R Mutant-Specific Antibody, Cross-Reacts With KRAS Q61R Mutant Protein in Colorectal Carcinoma

CONTEXT

- NRAS is a member of the RAS family oncoproteins implicated in cancer. Gain-of-function NRAS mutations were reported in a subset of colorectal cancers. These mutations occur at codons 12, 13, and 61 and are detected by molecular genetic testing. Recently, an antibody (clone SP174) became available to immunohistochemically pinpoint NRAS Q61R mutant protein. In malignant melanoma, NRAS Q61R mutant-specific immunohistochemistry was shown to be a valuable supplement to traditional genetic testing.

OBJECTIVE

- To evaluate the significance of NRAS Q61R mutant-specific immunohistochemistry in a cohort of colorectal carcinomas.

DESIGN

- A total of 1185 colorectal carcinomas were immunohistochemically evaluated with SP174 antibody. NRAS Q61R mutant-specific immunohistochemistry was validated by molecular genetic testing including Sanger sequencing, quantitative polymerase chain reaction (qPCR), and next-generation sequencing.

RESULTS

- Twelve tumors showed strong SP174 immunoreactivity. Sanger sequencing detected an identical c.182A>G substitution, causing NRAS Q61R mutation at the protein level, only in 8 SP174-positive cases. These results were confirmed by qPCR study. Subsequently, NRAS wild-type tumors with strong SP174 staining were evaluated by next-generation sequencing and revealed KRAS c.182A>G substitutions predicted to cause KRAS Q61R mutation. Review of colorectal carcinomas with known KRAS and NRAS genotype revealed that none of 62 wild-type tumors or 47 mutants other than Q61R were SP174 positive.

CONCLUSION

- SP174 immunohistochemistry allows sensitive detection of NRAS and KRAS Q61R mutants. However, molecular genetic testing is necessary to determine specifically which RAS gene is mutated.

Analysis of Pre-Analytic Factors Affecting the Success of Clinical Next-Generation Sequencing of Solid Organ Malignancies

Application of next-generation sequencing (NGS) technology to routine clinical practice has enabled characterization of personalized cancer genomes to identify patients likely to have a response to targeted therapy. The proper selection of tumor sample for downstream NGS based mutational analysis is critical to generate accurate results and to guide therapeutic intervention. However, multiple pre-analytic factors come into play in determining the success of NGS testing. In this review, we discuss pre-analytic requirements for AmpliSeq PCR-based sequencing using Ion Torrent Personal Genome Machine (PGM) (Life Technologies), a NGS sequencing platform that is often used by clinical laboratories for sequencing solid tumors because of its low input DNA requirement from formalin fixed and paraffin embedded tissue. The success of NGS mutational analysis is affected not only by the input DNA quantity but also by several other factors, including the specimen type, the DNA quality, and the tumor cellularity. Here, we review tissue requirements for solid tumor NGS based mutational analysis, including procedure types, tissue types, tumor volume and fraction, decalcification, and treatment effects.

NRAS (Q61R), BRAF (V600E) immunohistochemistry: a concomitant tool for mutation screening in melanomas

Background

The determination of NRAS and BRAF mutation status is a major requirement in the treatment of patients with metastatic melanoma. Mutation specific antibodies against NRAS^Q61R and BRAF^V600E proteins could offer additional data on tumor heterogeneity. The specificity and sensitivity of NRAS^Q61R immunohistochemistry have recently been reported excellent. We aimed to determine the utility of immunohistochemistry using SP174 anti-NRAS^Q61R and VE1 anti-BRAF^V600E antibodies in the theranostic mutation screening of melanomas.

Methods

142 formalin-fixed paraffin-embedded melanoma samples from 79 patients were analyzed using pyrosequencing and immunohistochemistry.

Results

23 and 26 patients were concluded to have a NRAS-mutated or a BRAF-mutated melanoma respectively. The 23 NRAS^Q61R and 23 BRAF^V600E-mutant samples with pyrosequencing were all positive in immunohistochemistry with SP174 antibody and VE1 antibody respectively, without any false negative. Proportions and intensities of staining were varied. Other NRAS^Q61L, NRAS^Q61K, BRAF^V600K and BRAF^V600R mutants were negative in immunohistochemistry. 6 single cases were immunostained but identified as wild-type using pyrosequencing (1 with SP174 and 5 with VE1). 4/38 patients with multiple samples presented molecular discordant data. Technical limitations are discussed to explain those discrepancies. Anyway we could not rule out real tumor heterogeneity.

Conclusions

In our study, we showed that combining immunohistochemistry analysis targeting NRAS^Q61R and BRAF^V600E proteins with molecular analysis was a reliable theranostic tool to face challenging samples of melanoma.

Electronic supplementary material

The online version of this article (doi:10.1186/s13000-015-0359-0) contains supplementary material, which is available to authorized users.

The IL-33/ST2 pathway contributes to intestinal tumorigenesis in humans and mice

Colorectal cancer (CRC) develops through a multistep process and is modulated by inflammation. However, the inflammatory pathways that support intestinal tumors at different stages remain incompletely understood. Interleukin (IL)-33 signaling plays a role in intestinal inflammation, yet its contribution to the pathogenesis of CRC is unknown. Using immunohistochemistry on 713 resected human CRC specimens, we show here that IL-33 and its receptor ST2 are expressed in low-grade and early-stage human CRCs, and to a lesser extent in higher-grade and more advanced-stage tumors. In a mouse model of CRC, ST2-deficiency protects from tumor development. Moreover, bone marrow (BM) chimera studies indicate that engagement of the IL-33/ST2 pathway on both the radio-resistant and radio-sensitive compartment is essential for CRC development. Mechanistically, activation of IL-33/ST2 signaling compromises the integrity of the intestinal barrier and triggers the production of pro-tumorigenic IL-6 by immune cells. Together, this data reveals a tumor-promoting role of IL-33/ST2 signaling in CRC.

The Wnt signalling cascade and the adherens junction complex in craniopharyngioma tumorigenesis

Craniopharyngiomas are epithelial, sellar tumours with adamantinomatous (aCP) and papillary (pCP) subtypes. The aCP type usually occurs during childhood and pCP in middle-aged adults; aCPs often contain mutations in CTNNB1, encoding β-catenin, a component of the adherens junction and a mediator of Wnt signalling. No such mutational event has been associated with pCPs, where the BRAF gene appears to be more important. In a large series of 95 craniopharyngiomas, we show that the aCP subtype harbours mutations in CTNNB1 in 52 % of cases, while the pCP subtype does not, with agreement between immunohistochemistry and sequencing methods in the majority of cases. When present, the CTNNB1 mutation is found throughout the aCP tumour, while translocation of β-catenin from membrane to cytosol and nucleus is restricted to small cell clusters near the invading tumour front. We observed translocated β-catenin in 100 % of aCPs, occurring not only in cell clusters but also in individual cells scattered throughout the tumour. We characterised the adherens junction involving α-catenin, β-catenin, γ-catenin, p120 and E-cadherin (cytosolic and membranous components). Although suggested to be important in other sellar mass tumourigenesis pathways, there was no disruption of the adherens junction in these tumours, indicating that a loss of junctional integrity is not associated with β-catenin translocation or mutation. We conclude that mutations in CTNNB1 underlie tumourigenesis in the majority of aCPs, which are distinct morphologically and at the molecular level from pCPs.

BRAF V600E mutation-specific antibody: A review

The significance of BRAF mutations in neoplasia was first recognized in 2002 when mutations were discovered in a broad range of cancers. Numerous subsequent studies expanded our understanding of BRAF V600E as a critical diagnostic, prognostic, and predictive biomarker in many cancers. Additionally, the advent of small-molecule inhibitors of BRAF V600E rendered assessment of BRAF mutation status essential in tumors such as melanoma. In clinical practice, evaluation of BRAF mutation status has routinely been performed by DNA-based assays utilizing polymerase chain reaction (PCR). However, molecular testing is not available at many hospitals since it is time-consuming, expensive, and requires expertise in molecular techniques. The first BRAF V600E-specific antibody was reported in 2011 (clone VE1). A purified version of this antibody as well as a second monoclonal antibody targeted to BRAF V600E is now commercially available. In this review, clinicopathologic characteristics associated with BRAF-mutant tumors will be highlighted, and the prognostic and predictive implications of a BRAF V600E mutation will be discussed with a focus on melanoma, thyroid carcinoma and colorectal carcinoma. Additionally, we will review the correlation between immunohistochemistry and molecular results and deliberate how BRAF immunohistochemistry might be utilized in the evaluation of these tumors.

BRAF V600E immunohistochemistry is reliable in primary and metastatic colorectal carcinoma regardless of treatment status and shows high intratumoral homogeneity

In colorectal carcinoma the evaluation of BRAF mutation status is increasingly being performed given its utility as a prognostic and predictive biomarker. However, there are conflicting reports of the sensitivity and specificity of BRAF V600E immunohistochemistry (IHC), and little is known about its reliability in tissues collected from metastatic sites or after chemotherapy, radiation therapy and/or targeted therapy. The degree of intratumoral staining heterogeneity is also not well established. We performed IHC for BRAF V600E (VE1) on 204 cases of colorectal carcinoma including 59 with the BRAF V600E mutation. These included primary (n=147) and metastatic/recurrent (n=57) tumors, collected before (n=133) or after (n=71) chemotherapy, radiation therapy and/or targeted therapy. Evaluation of a test cohort (39 cases) with knowledge of mutation status established a specific staining pattern for the mutation: diffuse cytoplasmic staining of near-uniform intensity, regardless of strength of staining. Using this pattern, pathologists at 3 levels of training independently performed blinded evaluation of the remaining cases. BRAF V600E staining was 96.3% sensitive and 98.5% specific for the mutation, including both pretreatment and posttreatment specimens. Fleiss κ for interobserver agreement was 0.96. Staining of whole sections of the BRAF mutants showed diffuse staining in all cases and uniform or near-uniform intensity in 91%. In 20 cases with both pretreatment and posttreatment specimens, there was 100% accuracy and agreement in staining between samples. We conclude that BRAF V600E IHC is reliable for the evaluation of mutational status in colorectal carcinoma regardless of site or prior treatment history, and staining shows a high degree of intratumoral homogeneity.

Performance comparison of three BRAF V600E detection methods in malignant melanoma and colorectal cancer specimens

Personalized cancer care requires reliable biomarkers. While the BRAF V600E mutation is implemented in the clinic, no method for its detection has so far been established as reference. We aimed to perform a comprehensive comparison of three methods currently being used for V600E detection in clinical samples. We analysed genomic DNA from 127 malignant melanomas (77 patients) and 389 tumours from 141 colorectal cancer patients (383 liver metastases and 6 primary tumours) by Sanger sequencing and a single probe-based high-resolution melting assay (LightMix). Formalin-fixed paraffin-embedded (FFPE) tissue from a subset of these lesions (n = 77 and 304, respectively) was analysed by immunohistochemistry (IHC) using the V600E-specific antibody VE1. In a dilution series of V600E-mutated DNA in wild-type DNA, the detection limit for the LightMix assay was 1:1000 mutated alleles while it was 1:10 for Sanger sequencing. In line with this, we detected 15 additional mutated melanoma samples and two additional mutated metastatic colorectal cancer samples by the LightMix assay compared to Sanger sequencing. For the melanoma samples, we observed high concordance between DNA-based methods and analysis by IHC. However, in colorectal samples, IHC performed poorly with 12 samples being scored as V600E positive exclusively by IHC and nine samples being scored as V600E negative exclusively by IHC. In conclusion, the VE1 antibody is not recommendable for clinical tests of colorectal cancer samples. For melanoma samples, IHC may be useful as a screening tool guiding further analytical approaches.

Detection of the BRAF V600E mutation in colon carcinoma: critical evaluation of the imunohistochemical approach

Recently BRAF V600E mutant-specific antibody (clone VE1) became available to immunohistochemically pinpoint the occurrence of these BRAF-mutant proteins in different tumors, such as colon carcinoma. Detection of BRAF mutations is important for the accurate application of targeted therapy against BRAF serine-threonine kinase activation. In this study, we evaluated 113 colon carcinomas including 95 primary and 27 metastatic tumors with the VE1 antibody using Leica Bond-Max automated immunohistochemistry. To ensure comprehensive BRAF V600E mutation detection, all cases were evaluated using 4 molecular methods (Sanger sequencing, the Cobas 4800 BRAF V600 Mutation Test, BRAF V600 allele-specific polymerase chain reaction, and BRAF V600 quantitative polymerase chain reaction) with nearly 100% concordance. Molecular and immunohistochemical studies were blinded. Furthermore, all cases were evaluated for KRAS and NRAS mutations as parameters mutually exclusive with BRAF mutations offering parallel evidence for BRAF mutation status. Strong to moderate VE1 positivity was seen in 34 tumors. Twelve colon carcinomas showed weak VE1 immunohistochemical staining, and 67 were entirely negative. An identical c.1799T>A single nucleotide substitution leading to the BRAF V600E mutation was identified in 27 of 113 (24%) colon carcinomas. A majority of BRAF-mutant tumors were located in the right side of the colon and had mismatch-repair deficiency. V600E mutation-negative carcinomas were more often sigmoid tumors and usually showed intact mismatch-repair proteins and KRAS or NRAS mutations. The sensitivity and specificity of positive results (strong to moderate staining) of VE1 immunohistochemistry were 85% and 68%, respectively. If any positivity would be considered, then the specificity declined to 51% with no significant improvement of sensitivity. Therefore, only strong positivity should be considered when using the VE1 antibody and Leica Bond-Max automated immunohistochemistry with these parameters. Although VE1 antibody can be useful in the screening of colon carcinomas for BRAF V600E-mutant proteins, molecular genetic confirmation is always necessary for mutation diagnosis.

A further investigation of combined mismatch repair and BRAFV600E mutation specific immunohistochemistry as a predictor of overall survival in colorectal carcinoma

Mutation specific immunohistochemistry (IHC) is a promising new technique to detect the presence of the BRAFV600E mutation in colorectal carcinoma (CRC). When performed in conjunction with mismatch repair (MMR) IHC, BRAFV600E IHC can help to further triage genetic testing for Lynch Syndrome. In a cohort of 1426 patients undergoing surgery from 2004 to 2009 we recently demonstrated that the combination of MMR and BRAFV600E IHC holds promise as a prognostic marker in CRC, particularly because of its ability to identify the poor prognosis MMR proficient (MMRp) BRAFV600E mutant subgroup. We attempted to validate combined MMR and BRAFV600E IHC as a prognostic indicator in a separate cohort comprising consecutive CRC patients undergoing surgery from 1998 to 2003. IHC was performed on a tissue microarray containing tissue from 1109 patients with CRC. The 5 year survivals stratified by staining patterns were: MMRd/BRAFwt 64%, MMRd/BRAFV600E 64%, MMRp/BRAFwt 60% and MMRp/BRAFV600E 53%. Using the poor prognosis MMRp/BRAFV600E phenotype as baseline, univariate Cox regression modelling demonstrated the following hazard ratios for death: MMRd/BRAFwt HR = 0.71 (95%CI = 0.40–1.27), p = 0.31; MMRd/BRAFV600E HR = 0.74 (95%CI = 0.51–1.07), p = 0.11 and MMRp/BRAFwt HR = 0.79 (95%CI = 0.60–1.04), p = 0.09. Although the findings did not reach statistical significance, this study supports the potential role of combined MMR and BRAF IHC as prognostic markers in CRC.