How the BRAF V600E Mutation Defines a Distinct Subgroup of Colorectal Cancer: Molecular and Clinical Implications. Gastroenterol Res Pract. 2018;2018:9250757. [PMID: 30598662 PMCID: PMC6287148 DOI: 10.1155/2018/9250757]

Cellular and molecular events in colorectal cancer: biological mechanisms, cell death pathways, drug resistance and signalling network interactions

Colorectal cancer (CRC) is a leading cause of cancer-related deaths worldwide, affecting millions each year. It emerges from the colon or rectum, parts of the digestive system, and is closely linked to both genetic and environmental factors. In CRC, genetic mutations such as APC, KRAS, and TP53, along with epigenetic changes like DNA methylation and histone modifications, play crucial roles in tumor development and treatment responses. This paper delves into the complex biological underpinnings of CRC, highlighting the pivotal roles of genetic alterations, cell death pathways, and the intricate network of signaling interactions that contribute to the disease's progression. It explores the dysregulation of apoptosis, autophagy, and other cell death mechanisms, underscoring the aberrant activation of these pathways in CRC. Additionally, the paper examines how mutations in key molecular pathways, including Wnt, EGFR/MAPK, and PI3K, fuel CRC development, and how these alterations can serve as both diagnostic and prognostic markers. The dual function of autophagy in CRC, acting as a tumor suppressor or promoter depending on the context, is also scrutinized. Through a comprehensive analysis of cellular and molecular events, this research aims to deepen our understanding of CRC and pave the way for more effective diagnostics, prognostics, and therapeutic strategies.

Deciphering the Role of BRAFV600E Immunohistochemistry in Breast Lesions: A Comprehensive Review

The BRAFV600E mutation has been extensively studied in various cancers, but its role in breast lesions remains less understood. Immunohistochemistry (IHC) has emerged as a valuable tool for detecting BRAFV600E expression in breast tissue, aiding in diagnosis and prognosis. This comprehensive review examines the significance of BRAFV600E IHC in breast lesions, encompassing its frequency, association with clinicopathological features, and potential clinical implications. We summarize key findings, emphasizing their utility in diagnosis, prognosis prediction, and treatment response assessment. Additionally, we discuss implications for clinical practice, highlighting the need for integrating BRAFV600E IHC into diagnostic algorithms. Recommendations for future research include larger-scale studies to validate findings, optimize detection techniques, and explore therapeutic interventions targeting BRAFV600E in breast cancer. This review contributes to understanding the molecular landscape of breast lesions and informs clinical decision-making in their management.

The role of heavy metals in the development of colorectal cancer

OBJECTIVE

To investigate the relationship among 18 heavy metals, microsatellite instability (MSI) status, ERCC1, XRCC1 (rs25487), BRAF V600E and 5 tumor markers and their role in the development of colorectal cancer (CRC).

METHODS

A total of 101 CRC patients and 60 healthy controls were recruited in the present study. The levels of 18 heavy metals were measured by ICP-MS. MSI status and the genetic polymorphism were determined by PCR (FP205-02, Tiangen Biochemical Technology Co., Ltd., Beijing, China) and Sanger sequencing. Spearman's rank correlation was used to analyze the relationship among various factors.

RESULTS

The level of selenium (Se) was lower in the CRC group compared with the control group (p < 0.01), while vanadium (V), arsenic (As), tin (Sn), barium (Ba) and lead (Pb) were higher (p < 0.05), chromium (Cr) and copper (Cu) were significantly higher (p < 0.0001) in the CRC group than those in the control group. Multivariate logistic regression analysis indicated that Cr, Cu, As and Ba were the risk factors for CRC. In addition, CRC was positively correlated with V, Cr, Cu, As, Sn, Ba and Pb, but negatively correlated with Se. MSI was positively correlated with BRAF V600E, but negatively correlated with ERCC1. BRAF V600E was positively correlated with antimony (Sb), thallium (Tl), CA19-9, NSE, AFP and CK19. XRCC1 (rs25487) was found to be positively correlated with Se but negatively correlated with Co. The levels of Sb and Tl were significantly higher in the BRAF V600E positive group compared to the negative group. The mRNA expression level of ERCC1 was significantly higher (P = 0.035) in MSS compared to MSI. And there was a significant correlation between XRCC1 (rs25487) polymorphism and MSI status (P<0.05).

CONCLUSION

The results showed that low level of Se and high levels of V, As, Sn, Ba, Pb, Cr, and Cu increased the risk of CRC. Sb and Tl may cause BRAF V600E mutations, leading to MSI. XRCC1 (rs25487) was positively correlated with Se but negatively correlated with Co. The expression of ERCC1 may be related to MSS, while the XRCC1 (rs25487) polymorphism is related to MSI.

Nursing care and management of adverse events for patients with BRAFV600E-mutant metastatic colorectal cancer receiving encorafenib in combination with cetuximab: a review

Encorafenib is a B-Raf proto-oncogene serine/threonine-protein kinase (BRAF) inhibitor, approved in the EU and USA, in combination with the epidermal growth factor receptor (EGFR) inhibitor cetuximab, for the treatment of patients with BRAF^V600E-mutant metastatic colorectal cancer (mCRC). In the pivotal BEACON CRC trial, patients achieved longer survival with encorafenib in combination with cetuximab vs. conventional chemotherapy. This targeted therapy regimen is also generally better tolerated than cytotoxic treatments. However, patients may present with adverse events unique to the regimen and characteristic of BRAF and EGFR inhibitors, which produce their own set of challenges. Nurses play an essential role in navigating the care of patients with BRAF^V600E-mutant mCRC and managing adverse events that patients may experience. This includes early and efficient identification of treatment-related adverse events, subsequent management of adverse events and education of patients and their caregivers around key adverse events. This manuscript aims to provide support to nurses managing patients with BRAF^V600E-mutant mCRC receiving encorafenib in combination with cetuximab, by summarising potential adverse events and providing guidance on how to manage them. Special attention will be paid to the presentation of key adverse events, dose modifications that may be required, practical recommendations and supportive care measures.

Analysis of KRAS, NRAS, and BRAF Mutations, Microsatellite Instability, and Relevant Prognosis Effects in Patients With Early Colorectal Cancer: A Cohort Study in East Asia

Background

Early colorectal cancer (ECRC) refers to any size of colorectal cancer (CRC) whose depth of invasion is limited to the mucosa and submucosa. About 10% of patients with ECRC die from cancer after surgery. KRAS, NRAS, and BRAF mutations and microsatellite instability (MSI) are considered diagnostic and prognostic markers in CRC. However, their characteristics in ECRC and whether postoperative chemotherapy based on them will benefit ECRC patients or not remain unknown.

Patients and Methods

Patients with ECRC and 298 patients with advanced colorectal cancer (ACRC) were collected in our hospital from January 2013 to December 2015. The Amplification Refractory Mutation System (ARMS)-PCR was used to perform the KRAS, NRAS, and BRAF mutant tests.

Results

In ECRC patients, 43 cases of KRAS mutation were found, accounting for 69.35%. Interestingly, among KRAS mutations, there were 10 KRAS multi-site mutation patients (16.13% in 62 ECRC patients). Moreover, the NRAS mutation rate was 3.23% but no BRAF mutation was found and only 1 case of MSI-High was detected. KRAS mutation was only related to the depth of tumor invasion whereas KRAS multi-site mutations were related to mucus components and tumor size. As far as NRAS is concerned, mutations were associated with elevated CEA, mucus components, and the depth of tumor invasion. Notably, compared with 2.35% KRAS multi-site mutation in ACRC, the rate of KRAS multi-site mutation in ECRC was much higher. Furthermore, Cox regression analysis revealed that KRAS mutation could be an independent prognostic factor of ECRC in patients who have undergone endoscopic resection or surgery.

Conclusion

Patients with ECRC might benefit from KRAS mutation testing but not from postoperative chemotherapy.

Systematic review of randomised clinical trials and observational studies for patients with RAS wild-type or BRAFV600E-mutant metastatic and/or unresectable colorectal cancer

Approximately 8-10% of metastatic colorectal cancer (mCRC) tumours harbour BRAF^V600E mutations. Eleven randomised controlled trials (RCTs) and 24 non-RCTs were identified. Seven studies evaluated BRAF inhibitors. Single-agent BRAF inhibitors had minimal efficacy, whereas BRAF inhibitor plus anti-EGFR therapy improved outcomes. In BEACON CRC, overall survival (OS) was significantly longer for patients receiving encorafenib plus cetuximab ± binimetinib when compared with irinotecan/FOLFIRI plus cetuximab as second- and third-line therapy. Seven prospective non-RCTs reported worse OS and progression-free survival (PFS) for patients with BRAF^V600E-mutant vs BRAF wild-type mCRC. Eight RCTs reported that PFS and OS were generally shorter for patients with BRAF^V600E-mutant mCRC vs those with KRAS or RAS wild-type mCRC. Patients with BRAF^V600E-mutant mCRC have worse outcomes with conventional therapy vs patients with BRAF wild-type tumours. BRAF inhibitors in conjunction with anti-EGFR therapy improves outcomes for patients with BRAF^V600E-mutant mCRC vs conventional therapy or a BRAF inhibitor alone.

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.

Diagnostic and therapeutic biomarkers in colorectal cancer: a review

Colorectal cancer (CRC) is a public health concern and the second most common type of cancer among men and women causing a significant mortality. Biomarkers closely linked to the disease morbidity could holds potential as diagnostic and/or prognostic biomarker for the disease. This review provides an overview of recent advances in the search for colorectal cancer biomarkers through genomics and proteomics according to clinical function and application. Specifically, a number of biomarkers were identified and discussed. Emphasis was placed on their clinical applications relative to the diagnosis and prognosis of CRC. The discovery of more sensitive and specific markers for CRC is an urgent need, and the study of molecular targets is extremely important in this process, as they will allow for a better understanding of colorectal carcinogenesis, identification and validation of potential genetic signatures.

Dramatic Therapeutic Response to Dabrafenib Plus Trametinib in BRAF V600E Mutated Papillary Craniopharyngiomas: A Case Report and Literature Review

Background

Craniopharyngioma is a rare intracranial tumor, with a high morbidity rate due to its common refractiveness to conventional treatments. BRAF V600E mutation has recently been identified as the principal oncogenic molecular driver of papillary craniopharyngiomas (PCP), one of the two main variants of craniopharyngioma.

Case Presentation

A 49-year-old man with recurrent craniopharyngioma, harboring BRAF V600E mutation, has been treated with targeted therapy based on a combination of a BRAF-inhibitor, dabrafenib (150 mg, orally two times daily), and a MEK-inhibitor, trametinib (2 mg, orally two times daily). Before starting treatment, the patient was symptomatic: he lamented confusion, dysphasia, and intense fatigue, that did not allow him to work normally. After just one cycle of treatment, the patient showed an important clinical improvement, reporting a progressive regression of the basal symptoms, hinting at a rapid and dramatic response, which was confirmed at the first radiological assessment. Thus, treatment was continued and at the time of writing, the treatment is still ongoing (total duration of treatment: 14 months) and it is well tolerated, with very good quality of life: the patient has no limitations in daily activities and he has even been able to restart to work.

Conclusion

The use of targeted therapies—as a clinical practice or in clinical trials—represents an important therapeutic alternative and a great evolution for patients' prognosis vs. the standard of care, historically represented by unselected chemotherapies. The discovery of the BRAF V600E mutation in patients with PCP is very rare, resulting in a lack of data on the efficacy of the combination of dabrafenib and trametinib.

Survey of germline variants in cancer-associated genes in young adults with colorectal cancer

Colorectal cancer (CRC) incidence in young adults is rising. Identifying genetic risk factors is fundamental for the clinical management of patients and their families. This study aimed to identify clinically significant germline variants among young adults with CRC. Whole-exome sequencing data of blood-derived DNA from 133 unrelated young CRC patients (<55 years of age) underwent a comprehensive analysis of 133 cancer-predisposition/implicated genes. All patient tumors were evaluated for mismatch repair deficiency (dMMR). Among 133 patients (aged 16-54 years), 15% (20/133) had clinically actionable pathogenic or likely pathogenic (P/LP) variants in at least 1 well established cancer-predisposing gene: dMMR genes (6), MUTYH [bi-allelic (2), mono-allelic (3)], RNF43 (1), BMPR1A (1), BRCA2 (4), ATM (1), RAD51C (1), and BRIP1 (1). Five patients (4%) had variants in genes implicated in cancer but where the significance of germline variants in CRC risk is uncertain: GATA2 (1), ERCC2 (mono-allelic) (1), ERCC4 (mono-allelic) (1), CFTR (2). Fourteen (11%) had dMMR tumors. Eighteen (14%) reported a first-degree relative with CRC, but only three of these carried P/LP variants. Three patients with variants in polyposis-associated genes showed no polyposis (one each in MUTYH [bi-allelic], RNF43, and BMPR1A). Approximately one in five young adults in our series carried at least one P/LP variant in a cancer-predisposing/implicated gene; 80% of these variants are currently considered clinically actionable in a familial cancer setting. Family history and phenotype have limitations for genetic risk prediction; therefore multigene panel testing and genetic counseling are warranted for all young adults with CRC regardless of those two factors.

Association of BRAF V600E mutations with vasoactive intestinal peptide syndrome in MYCN-amplified neuroblastoma

Very rarely, vasoactive intestinal peptide-related diarrhea (VIP-D) is observed in patients with high-risk neuroblastoma (HR-NB) where the associated fluid and electrolyte abnormalities can pose a major clinical challenge for administering the required aggressive multimodality treatment. Two patients with HR-NB developed VIP-D during induction and were found to have a somatic BRAF V600E mutation. Serum VIP levels and diarrhea promptly resolved in both patients after initiating treatment with BRAF and MEK inhibitors. This illustrates an association of VIP-D with BRAF V600E mutations and demonstrates a therapeutic strategy in the specific context of VIP-D and BRAF V600E mutations in HR-NB patients. The addition of BRAF and MEK inhibitors allows continued conventional tumor-directed treatment by decreasing the severity of symptoms caused by this life-threatening complication.

Unbiased Proteomic and Phosphoproteomic Analysis Identifies Response Signatures and Novel Susceptibilities After Combined MEK and mTOR Inhibition in BRAFV600E Mutant Glioma

The mitogen-activated protein kinase pathway is one of the most frequently altered pathways in cancer. It is involved in the control of cell proliferation, invasion, and metabolism, and can cause resistance to therapy. A number of aggressive malignancies, including melanoma, colon cancer, and glioma, are driven by a constitutively activating missense mutation (V600E) in the v-Raf murine sarcoma viral oncogene homolog B (BRAF) component of the pathway. Mitogen-activated protein kinase kinase (MEK) inhibition is initially effective in targeting these cancers, but reflexive activation of mammalian target of rapamycin (mTOR) signaling contributes to frequent therapy resistance. We have previously demonstrated that combination treatment with the MEK inhibitor trametinib and the dual mammalian target of rapamycin complex 1/2 inhibitor TAK228 improves survival and decreases vascularization in a BRAFV600E mutant glioma model. To elucidate the mechanism of action of this combination therapy and understand the ensuing tumor response, we performed comprehensive unbiased proteomic and phosphoproteomic characterization of BRAFV600E mutant glioma xenografts after short-course treatment with trametinib and TAK228. We identified 13,313 proteins and 30,928 localized phosphosites, of which 12,526 proteins and 17,444 phosphosites were quantified across all samples (data available via ProteomeXchange; identifier PXD022329). We identified distinct response signatures for each monotherapy and combination therapy and validated that combination treatment inhibited activation of the mitogen-activated protein kinase and mTOR pathways. Combination therapy also increased apoptotic signaling, suppressed angiogenesis signaling, and broadly suppressed the activity of the cyclin-dependent kinases. In response to combination therapy, both epidermal growth factor receptor and class 1 histone deacetylase proteins were activated. This study reports a detailed (phospho)proteomic analysis of the response of BRAFV600E mutant glioma to combined MEK and mTOR pathway inhibition and identifies new targets for the development of rational combination therapies for BRAF-driven tumors.

Immunohistochemistry features and molecular pathology of appendiceal neoplasms

Primary appendiceal neoplasms (ANs) comprise a heterogeneous group of tumors. The pathology and classification of ANs have been controversial, and thus, a new classification of these neoplasms was published in the World Health Organization (WHO) classification of tumors (5th edition, 2019). However, immunohistochemistry (IHC) features of epithelial ANs are not explained in this edition and the limited data on the molecular pathology of these tumors shows inconsistent findings in various studies. It would be useful to identify biomarkers appropriate for each subtype to better aid in treatment selection. Therefore, we reviewed the literature to investigate what is known of the molecular pathology and IHC features of the most frequently diagnosed pathological subtypes of epithelial ANs based on the recent classification. The inconsistencies in research findings regarding the IHC features and molecular pathology of ANs could be due to differences in the number of samples and their collection and preparation as well as to the lack of a universally accepted classification system for these neoplasms. However, the literature shows that epithelial ANs typically stain positive for MUC2, CK20, and CDX2 and that the expression of SATB2 protein could be used as a biomarker for appendix tumor origin. Low-grade appendiceal mucinous neoplasms tend to have mutations in KRAS and GNAS but are usually wild-type for BRAF, APC, and P53. Conversely, appendiceal adenocarcinomas are frequently found with mutations in KRAS, GNAS, P53, PIK3CA, and APC, and have significant nuclear expression of β-catenin, loss of nuclear or nuclear and cytoplasmic expression of SMAD4, and loss of cytoplasmic membranous expression of E-cadherin. Goblet cell carcinomas (GCCs) typically stain positive for keratin and mucin markers and are frequently mutated in P53 and chromatin-modifier genes, but they tend to be wild-type for KRAS, GNAS, APC, and PIK3CA. The expression of CK7 and SATB2 proteins is usually negative in appendiceal neuroendocrine neoplasms and they lack the mutations in common cancer-associated genes including APC, BRAF, SMAD4, and PIK3C. The available data suggest that GCCs have distinct molecular and immunohistochemical features and that they have characteristics more in common with adenocarcinoma than classical neuroendocrine tumors. In addition, MSI does not seem to have a role in the pathogenesis of epithelial ANs because they are rarely detected in these tumors. Finally, hereditary predisposition may have a role in the development of ANs because heterozygous CTNNβ1, NOTCH1, and NOTCH4 germline mutations have recently been identified in low and high grades ANs.

New advances in the clinical management of RAS and BRAF mutant colorectal cancer patients

INTRODUCTION

In colorectal carcinogenesis, genetic alterations in RAS and BRAF oncogenes play an important role for cancer initiation and/or progression and represent a key focus in the search for targeted therapies. Despite many years of research and a great amount of studies, until very recently this pathway was considered extremely hard to downregulate to obtain a significant clinical impact in colorectal cancer patients. But better times are coming with the advent of new promising drugs and combinations strategies.

AREAS COVERED

In this review, we go over the biological characteristics of the MAPK pathway in colorectal tumors, while illustrating the clinical correlation of RAS and BRAF mutations, particularly its prognostic and predictive value. We also present newly data about recent improvements in the treatment strategy for patients harboring these types of tumors.

EXPERT COMMENTARY

With great advances in the knowledge of molecular basis of RAS and BRAF mutant colorectal cancer in conjunction with biotechnology development and the constant effort for improvement, in the near future many new therapeutic options would be available for the management of this group of patient with dismal prognosis.

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.

Precision Approaches in the Management of Colorectal Cancer: Current Evidence and Latest Advancements Towards Individualizing the Treatment

The genetic and molecular underpinnings of metastatic colorectal cancer have been studied for decades, and the applicability of these findings in clinical decision making continues to evolve. Advancements in translating molecular studies have provided a basis for tailoring chemotherapeutic regimens in metastatic colorectal cancer (mCRC) treatment, which have informed multiple practice guidelines. Various genetic and molecular pathways have been identified as clinically significant in the pathogenesis of metastatic colorectal cancer. These include rat sarcoma (RAS), epithelial growth factor receptor (EGFR), vascular endothelial growth factor VEGF, microsatellite instability, mismatch repair, and v-raf murine sarcoma viral oncogene homolog b1 (BRAF) with established clinical implications. RAS mutations and deficiencies in the mismatch repair pathway guide decisions regarding the administration of anti-EGFR-based therapies and immunotherapy, respectively. Furthermore, there are several emerging pathways and therapeutic modalities that have not entered mainstream use in mCRC treatment and are ripe for further investigation. The well-established data in the arena of targeted therapies provide evidence-based support for the use or avoidance of various therapeutic regimens in mCRC treatment, while the emerging pathways and platforms offer a glimpse into the future of transforming a precision approach into a personalized treatment.

What could microRNA expression tell us more about colorectal serrated pathway carcinogenesis?

In the last two decades, the vision of a unique carcinogenesis model for colorectal carcinoma (CRC) has completely changed. In addition to the adenoma to carcinoma transition, colorectal carcinogenesis can also occur via the serrated pathway. Small non-coding RNA, known as microRNAs (miRNAs), were also shown to be involved in progression towards malignancy. Furthermore, increased expression of certain miRNAs in premalignant sessile serrated lesions (SSLs) was found, emphasizing their role in the serrated pathway progression towards colon cancer. Since miRNAs function as post-transcriptional gene regulators, they have enormous potential to be used as useful biomarkers for CRC and screening in patients with SSLs particularly. In this review, we have summarized the most relevant information about the specific role of miRNAs and their relevant signaling pathways among different serrated lesions and polyps as well as in serrated adenocarcinoma. Additional focus is put on the correlation between gut immunity and miRNA expression in the serrated pathway, which remains unstudied.

BRAF Mutation in Colorectal Cancers: From Prognostic Marker to Targetable Mutation

Simple Summary

Colorectal cancer with a mutation in an oncogene BRAF has paid much attention, as it comprises a population with dismal prognosis since two decades ago. A series of research since then has successfully changed this malignancy to be treatable with specific treatment. Here we thoroughly overviewed the basic, translational and clinical studies on colorectal cancer with BRAF mutation from a physician’s viewpoint. Accumulating lines of evidence suggest that intervention of the trunk cellular growth signal transduction pathway, namely EGFR-RAS-RAF-MEK-ERK pathway, is a clue to controlling this disease. However, it is not so straightforward. Recent studies unveil the diverse and plastic nature of this signal transduction pathway. We will introduce our endeavor to conquer this condition, based on newly arriving datasets, and discuss how we could open the door to future development of CRC treatment.

Abstract

The Raf murine sarcoma viral oncogene homolog B (BRAF) mutation is detected in 8–12% of metastatic colorectal cancers (mCRCs) and is strongly correlated with poor prognosis. The recent success of the BEACON CRC study and the development of targeted therapy have led to the determination of BRAF-mutated mCRCs as an independent category. For nearly two decades, a growing body of evidence has established the significance of the BRAF mutation in the development of CRC. Herein, we overview both basic and clinical data relevant to BRAF-mutated CRC, mainly focusing on the development of treatment strategies. This review is organized into eight sections, including clinicopathological features, molecular features, prognosis, the predictive value of anti-epidermal growth factor receptor (EGFR) therapy, resistant mechanisms for BRAF-targeting treatment, the heterogeneity of the BRAF mutation, future perspectives, and conclusions. A characterization of the canonical mitogen-activated protein kinase (MAPK) pathway is essential for controlling this malignancy, and the optimal combination of multiple interventions for treatments remains a point of debate.

Targeted next generation sequencing of MLH1-deficient, MLH1 promoter hypermethylated, and BRAF/RAS-wild-type colorectal adenocarcinomas is effective in detecting tumors with actionable oncogenic gene fusions

Oncogenic gene fusions represent attractive targets for therapy of cancer. However, the frequency of actionable genomic rearrangements in colorectal cancer (CRC) is very low, and universal screening for these alterations seems to be impractical and costly. To address this problem, several large scale studies retrospectivelly showed that CRC with gene fusions are highly enriched in groups of tumors defined by MLH1 DNA mismatch repair protein deficiency (MLH1d), and hypermethylation of MLH1 promoter (MLH1ph), and/or the presence of microsatellite instability, and BRAF/KRAS wild-type status (BRAFwt/KRASwt). In this study, we used targeted next generation sequencing (NGS) to explore the occurence of potentially therapeutically targetable gene fusions in an unselected series of BRAFwt/KRASwt CRC cases that displayed MLH1d/MLH1ph. From the initially identified group of 173 MLH1d CRC cases, 141 cases (81.5%) displayed MLH1ph. BRAFwt/RASwt genotype was confirmed in 23 of 141 (~16%) of MLH1d/MLH1ph cases. Targeted NGS of these 23 cases identified oncogenic gene fusions in nine patients (39.1%; CI95: 20.5%-61.2%). Detected fusions involved NTRK (four cases), ALK (two cases), and BRAF genes (three cases). As a secondary outcome of NGS testing, we identified PIK3K-AKT-mTOR pathway alterations in two CRC cases, which displayed PIK3CA mutation. Altogether, 11 of 23 (~48%) MLH1d/MLH1ph/BRAFwt/RASwt tumors showed genetic alterations that could induce resistance to anti-EGFR therapy. Our study confirms that targeted NGS of MLH1d/MLH1ph and BRAFwt/RASwt CRCs could be a cost-effective strategy in detecting patients with potentially druggable oncogenic kinase fusions.

Implications of Hereditary Origin on the Immune Phenotype of Mismatch Repair-Deficient Cancers: Systematic Literature Review

Microsatellite instability (MSI) represents one of the major types of genomic instability in human cancers and is most common in colorectal cancer (CRC) and endometrial cancer (EC). MSI develops as a consequence of DNA mismatch repair (MMR) deficiency, which can occur sporadically or in the context of Lynch syndrome (LS), the most common inherited tumor syndrome. MMR deficiency triggers the accumulation of high numbers of somatic mutations in the affected cells, mostly indel mutations at microsatellite sequences. MSI tumors are among the most immunogenic human tumors and are often characterized by pronounced local immune responses. However, so far, little is known about immunological differences between sporadic and hereditary MSI tumors. Therefore, a systematic literature search was conducted to comprehensively collect data on the differences in local T cell infiltration and immune evasion mechanisms between sporadic and LS-associated MSI tumors. The vast majority of collected studies were focusing on CRC and EC. Generally, more pronounced T cell infiltration and a higher frequency of B2M mutations were reported for LS-associated compared to sporadic MSI tumors. In addition, phenotypic features associated with enhanced lymphocyte recruitment were reported to be specifically associated with hereditary MSI CRCs. The quantitative and qualitative differences clearly indicate a distinct biology of sporadic and hereditary MSI tumors. Clinically, these findings underline the need for differentiating sporadic and hereditary tumors in basic science studies and clinical trials, including trials evaluating immune checkpoint blockade therapy in MSI tumors.

Mouse models of colorectal cancer: Past, present and future perspectives

Colorectal cancer (CRC) is the third most common diagnosed malignancy among both sexes in the United States as well as in the European Union. While the incidence and mortality rates in western, high developed countries are declining, reflecting the success of screening programs and improved treatment regimen, a rise of the overall global CRC burden can be observed due to lifestyle changes paralleling an increasing human development index. Despite a growing insight into the biology of CRC and many therapeutic improvements in the recent decades, preclinical in vivo models are still indispensable for the development of new treatment approaches. Since the development of carcinogen-induced rodent models for CRC more than 80 years ago, a plethora of animal models has been established to study colon cancer biology. Despite tenuous invasiveness and metastatic behavior, these models are useful for chemoprevention studies and to evaluate colitis-related carcinogenesis. Genetically engineered mouse models (GEMM) mirror the pathogenesis of sporadic as well as inherited CRC depending on the specific molecular pathways activated or inhibited. Although the vast majority of CRC GEMM lack invasiveness, metastasis and tumor heterogeneity, they still have proven useful for examination of the tumor microenvironment as well as systemic immune responses; thus, supporting development of new therapeutic avenues. Induction of metastatic disease by orthotopic injection of CRC cell lines is possible, but the so generated models lack genetic diversity and the number of suited cell lines is very limited. Patient-derived xenografts, in contrast, maintain the pathological and molecular characteristics of the individual patient’s CRC after subcutaneous implantation into immunodeficient mice and are therefore most reliable for preclinical drug development – even in comparison to GEMM or cell line-based analyses. However, subcutaneous patient-derived xenograft models are less suitable for studying most aspects of the tumor microenvironment and anti-tumoral immune responses. The authors review the distinct mouse models of CRC with an emphasis on their clinical relevance and shed light on the latest developments in the field of preclinical CRC models.

Personalized Medicine-Current and Emerging Predictive and Prognostic Biomarkers in Colorectal Cancer

Colorectal cancer (CRC) is the third most common cancer diagnosed worldwide and is heterogeneous both morphologically and molecularly. In an era of personalized medicine, the greatest challenge is to predict individual response to therapy and distinguish patients likely to be cured with surgical resection of tumors and systemic therapy from those resistant or non-responsive to treatment. Patients would avoid futile treatments, including clinical trial regimes and ultimately this would prevent under- and over-treatment and reduce unnecessary adverse side effects. In this review, the potential of specific biomarkers will be explored to address two key questions—1) Can the prognosis of patients that will fare well or poorly be determined beyond currently recognized prognostic indicators? and 2) Can an individual patient’s response to therapy be predicted and those who will most likely benefit from treatment/s be identified? Identifying and validating key prognostic and predictive biomarkers and an understanding of the underlying mechanisms of drug resistance and toxicity in CRC are important steps in order to personalize treatment. This review addresses recent data on biological prognostic and predictive biomarkers in CRC. In addition, patient cohorts most likely to benefit from currently available systemic treatments and/or targeted therapies are discussed in this review.

Postmenopausal hormone replacement therapy and colorectal cancer risk by molecular subtypes and pathways

Postmenopausal hormone replacement therapy (HRT) was found to be associated with lower risk of colorectal cancer (CRC). However, little is known regarding associations with molecular subtypes of CRC. The current study includes female participants of a large German population-based case-control study (922 CRC cases and 1,183 controls). Tumor tissue samples were analyzed for microsatellite instability (MSI), CpG island methylator phenotype (CIMP), BRAF and KRAS mutation status. Multivariable logistic regression models were used to assess the association of HRT use with molecular subtypes and pathways. Postmenopausal HRT use was overall associated with reduced risk of CRC (adjusted odds ratio (aOR) 0.62, 95% confidence interval (CI) 0.50-0.76) and no major differences were observed for molecular subtypes or for tumor marker combinations representing molecular pathways. When stratified by median age (≤/>71 years) potentially stronger risk reductions were observed in the older group for subtypes showing MSI (OR = 0.36, 95% CI 0.17-0.76), BRAF mutation (OR = 0.40, 95% CI 0.30-0.83) and CIMP-high (OR = 0.40, 95% CI 0.21-0.73) and for CRC suggestive of the sessile serrated pathway (OR = 0.45, 95% CI 0.20-1.01). In conclusion, postmenopausal use of HRT was similarly associated with risk reduction of major molecular tumor subtypes and pathways of CRC. Potentially stronger risk reductions with CRC subtypes diagnosed at higher ages require confirmation and clarification from other studies. The current study extends the limited understanding of the mechanisms of HRT in CRC prevention.

MSI status is associated with distinct clinicopathological features in BRAF mutation colorectal cancer: A systematic review and meta-analysis

BACKGROUND

Microsatellite stable (MSS) BRAF p.V600E mutation colorectal cancer (BRAF-CRC) has a poor prognosis, whereas microsatellite instability (MSI) in BRAF-CRC is associated with a favorable prognosis. Although usually considered a single clinical entity, the MSI BRAF-CRC subtype shows some distinct characteristics in comparison with the MSS BRAF-CRC subtype.

METHODS

We conducted a meta-analysis to investigate the influence of clinicopathological features on MSI status in BRAF-CRC. We searched publications up to March 2019 from PubMed, Embase, and the Cochrane Library. The effect of MSI status on outcome parameters was assessed using odds ratios (ORs) with 95% confidence intervals (CIs) and fixed- or random-effects models according to the heterogeneity.

RESULTS

After reviewing 2839 reports, 16 eligible studies including 1381 patients with BRAF-CRC met the criteria. The MSI BRAF-CRC subtype was associated with older age, female sex (OR = 1.70; 95% CI = 1.35-2.14; P < 0.00001), proximal tumor location (OR = 5.10; 95% CI = 3.70-7.03; P < 0.00001), early TNM stage (OR = 5.28; 95% CI = 3.93-7.09; P < 0.00001), and poor differentiation (OR = 2.29; 95% CI = 1.60-3.28; P < 0.00001).

CONCLUSIONS

MSI was significantly correlated with distinct favorable clinicopathological characteristics in BRAF-CRC. These results suggest that MSI status should be considered as a stratification factor for better management of the BRAF-CRC.

BRAF Mutation in Colorectal Rhabdoid and Poorly Differentiated Medullary Carcinomas

Colorectal rhabdoid carcinomas (CRbCs) are very rare and aggressive cancers. The BRAF mutation and CpG island methylator phenotype have been reported to be common features of CRbCs. This study reviews the literature about CRbCs and analyzes the clinicopathological and molecular profiles of seven CRbCs characterized by large discohesive cells with abundant eosinophilic cytoplasm, showing hyaline inclusions and large rounded to bean-shaped nuclei. For comparison, we included four poorly differentiated medullary carcinomas (PDMCs) with focal aspects mimicking rhabdoid features. Overall survival was poor in both subsets, with 78% of patients dying of disease within 2–11 months. The main features of CRbCs were: Loss of/reduced SMARCB1/INI expression, intense vimentin immunostaining, and dense neutrophilic infiltration. The PDMCs were positive for pancytokeratin but negative for vimentin and showed moderate peritumoral/intratumoral CD8+ lymphocytes. All PDMCs showed SMARCB1(INI-1) expression. The coexistence of BRAF and TP53 mutations was observed in 80% of CRbCs and PDMCs. PDMCs always showed microsatellite instability and CpG island methylator phenotype (CIMP), while CRbCs were CIMP negative and exhibited microsatellite instability (MSI) in two out of seven cases. CRbCs are characterized by BRAF and TP53 mutations. Loss/reduced expression of nuclear SMARCB1/INI, intense vimentin immunostaining, dense neutrophilic infiltration, and low frequency of CIMP are useful markers to recognize these rare aggressive tumors.

The Molecular Hallmarks of the Serrated Pathway in Colorectal Cancer

Colorectal cancer (CRC) is a leading cause of cancer death worldwide. It includes different subtypes that differ in their clinical and prognostic features. In the past decade, in addition to the conventional adenoma-carcinoma model, an alternative multistep mechanism of carcinogenesis, namely the “serrated pathway”, has been described. Approximately, 15 to 30% of all CRCs arise from neoplastic serrated polyps, a heterogeneous group of lesions that are histologically classified into three morphologic categories: hyperplastic polyps, sessile serrated adenomas/polyps, and the traditional serrated adenomas/polyps. Serrated polyps are characterized by genetic (BRAF or KRAS mutations) and epigenetic (CpG island methylator phenotype (CIMP)) alterations that cooperate to initiate and drive malignant transformation from normal colon mucosa to polyps, and then to CRC. The high heterogeneity of the serrated lesions renders their diagnostic and pathological interpretation difficult. Hence, novel genetic and epigenetic biomarkers are required for better classification and management of CRCs. To date, several molecular alterations have been associated with the serrated polyp-CRC sequence. In addition, the gut microbiota is emerging as a contributor to/modulator of the serrated pathway. This review summarizes the state of the art of the genetic, epigenetic and microbiota signatures associated with serrated CRCs, together with their clinical implications.

Rigidification Dramatically Improves Inhibitor Selectivity for RAF Kinases

One effective means to achieve inhibitor specificity for RAF kinases, an important family of cancer drug targets, has been to target the monomeric inactive state conformation of the kinase domain, which, unlike most other kinases, can accommodate sulfonamide-containing drugs such as vemurafenib and dabrafenib because of the presence of a unique pocket specific to inactive RAF kinases. We previously reported an alternate strategy whereby rigidification of a nonselective pyrazolo[3,4-d]pyrimidine-based inhibitor through ring closure afforded moderate but appreciable increases in selectivity for RAF kinases. Here, we show that a further application of the rigidification strategy to a different pyrazolopyrimidine-based scaffold dramatically improved selectivity for RAF kinases. Crystal structure analysis confirmed our inhibitor design hypothesis revealing that 2l engages an active-like state conformation of BRAF normally associated with poorly discriminating inhibitors. When screened against a panel of distinct cancer cell lines, the optimized inhibitor 2l primarily inhibited the proliferation of the expected BRAF^V600E-harboring cell lines consistent with its kinome selectivity profile. These results suggest that rigidification could be a general and powerful strategy for enhancing inhibitor selectivity against protein kinases, which may open up therapeutic opportunities not afforded by other approaches.

Mutation status and surgical selection

Current evidence cannot support denying metastasectomy in otherwise resectable patients solely based on their overall KRAS or BRAF mutational status. The combination of KRAS or BRAF mutational status with certain clinicopathologic characteristics has defined groups of patients who may not derive benefit from metastasectomy, but external validation is needed. The effect of certain KRAS or BRAF variants on survival may be more pronounced and therefore future studies should consider them for surgical selection.