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Background Colorectal cancer (CRC) harboring BRAF V600E mutation exhibits low response to conventional therapy and poorest prognosis. Due to the emerging correlation between gut microbiota and CRC carcinogenesis, we investigated in serrated BRAF V600E cases the existence of a peculiar fecal microbial fingerprint and specific bacterial markers, which might represent a tool for the development of more effective clinical strategies. Methods By injecting human CRC stem-like cells isolated from BRAF V600E patients in immunocompromised mice, we described a new xenogeneic model of this subtype of CRC. By performing bacterial 16S rRNA sequencing, the fecal microbiota profile was then investigated either in CRC-carrying mice or in a cohort of human CRC subjects. The microbial communities’ functional profile was also predicted. Data were compared with Mann-Whitney U, Welch’s t-test for unequal variances and Kruskal-Wallis test with Benjamini–Hochberg false discovery rate (FDR) correction, extracted as potential BRAF class biomarkers and selected as model features. The obtained mean test prediction scores were subjected to Receiver Operating characteristic (ROC) analysis. To discriminate the BRAF status, a Random Forest classifier (RF) was employed. Results A specific microbial signature distinctive for BRAF status emerged, being the BRAF -mutated cases closer to healthy controls than BRAF wild-type counterpart. In agreement, a considerable score of correlation was also pointed out between bacteria abundance from BRAF -mutated cases and the level of markers distinctive of BRAF V600E pathway, including those involved in inflammation, innate immune response and epithelial-mesenchymal transition. We provide evidence that two candidate bacterial markers, Prevotella enoeca and Ruthenibacterium lactatiformans , more abundant in BRAF V600E and BRAF wild-type subjects respectively, emerged as single factors with the best performance in distinguishing BRAF status (AUROC = 0.72 and 0.74, respectively, 95% confidence interval). Furthermore, the combination of the 10 differentially represented microorganisms between the two groups improved performance in discriminating serrated CRC driven by BRAF mutation from BRAF wild-type CRC cases (AUROC = 0.85, 95% confidence interval, 0.69–1.01). Conclusion Overall, our results suggest that BRAF V600E mutation itself drives a distinctive gut microbiota signature and provide predictive CRC-associated bacterial biomarkers able to discriminate BRAF status in CRC patients and, thus, useful to devise non-invasive patient-selective diagnostic strategies and patient-tailored optimized therapies.

The BRAF V600E mutation occurs in approximately 10% of patients with metastatic colorectal cancer (CRC) and constitutes a distinct subtype of the disease with extremely poor prognosis. To address this refractory disease, we investigated the unique metabolic gene profile of BRAF V600E‐mutated tumors via in silico analysis using a large‐scale clinical database. We found that BRAF V600E‐mutated tumors exhibited a specific metabolic gene expression signature, including some genes that are associated with poor prognosis in CRC. We discovered that BRAF V600E‐mutated tumors expressed high levels of glycolytic enzyme enolase 2 (ENO2), which is mainly expressed in neuronal tissues under physiological conditions. In vitro experiments using CRC cells demonstrated that BRAF V600E‐mutated cells exhibited enhanced dependency on ENO2 compared to BRAF wild‐type cancer cells and that knockdown of ENO2 led to the inhibition of proliferation and migration of BRAF V600E‐mutated cancer cells. Moreover, inhibition of ENO2 resulted in enhanced sensitivity to vemurafenib, a selective inhibitor of BRAF V600E. We identified AP‐1 transcription factor subunit (FOSL1) as being involved in the transcription of ENO2 in CRC cells. In addition, both MAPK and PI3K/Akt signaling were suppressed upon inhibition of ENO2, implying an additional oncogenic role of ENO2. These results suggest the crucial role of ENO2 in the progression of BRAF V600E‐mutated CRC and indicate the therapeutic implications of targeting this gene. There was no significant difference in the expression of ENO1 in BRAF V600E‐mutated CRC and other types of CRC, but ENO2 levels were significantly higher in BRAF V600E‐mutated CRC.

BRAF V600E‐mutant colorectal cancer (CRC) represents a distinct molecular subtype with considerable heterogeneity in tumor biology and therapeutic response. Although gene expression‐based classifications (BM1/BM2 subtypes) provide valuable insights into underlying molecular and immune features, their clinical application is limited by the need for high‐throughput sequencing. This study aims to establish an immunohistochemistry (IHC)‐based classification system to enable practical subtype stratification and aid prognostic and therapeutic evaluation. Using two independent cohorts (public dataset, n = 218; institutional cohort, n = 122), we performed differential expression analysis, machine learning modeling, and clinical feasibility evaluation. Fourteen candidate markers were identified, and a decision tree algorithm selected CD8 and ARHGEF17 as optimal classifiers. Based on these markers, two IHC‐based subtypes were established: iBM1 (CD8+/ARHGEF17−) and iBM2 (CD8− with any ARHGEF17 expression or CD8+/ARHGEF17+). The IHC‐based subtypes showed concordance with transcriptomic BM subtypes (training: 82.69%, κ = 0.55; validation: 72.22%, κ = 0.44; prospective: 83.33%, κ = 0.57). Transcriptomic profiling revealed enrichment of immune activation and epithelial–mesenchymal transition in iBM1, and cell cycle‐related pathways in iBM2. In clinical validation, iBM1 was associated with poorer survival but greater sensitivity to immune checkpoint inhibitors. This IHC‐based classification provides a practical and accessible approach for BM subtype stratification, reflecting underlying molecular and immune characteristics, and may support prognostic assessment and therapeutic decision‐making in BRAF V600E‐mutant CRC. This study develops an immunohistochemistry (IHC)‐based classification system for BRAF V600E‐mutant colorectal cancer, enabling practical stratification into iBM1 and iBM2 subtypes using CD8 and ARHGEF17 markers. The IHC‐defined subtypes demonstrated concordance with transcriptomic BM1/BM2 classifications and reflected distinct molecular and immune features, with iBM1 associated with poorer prognosis but enhanced responsiveness to immune checkpoint blockade.

The RAS/RAF/MEK/ERK (MAPK) signaling cascade is essential for cell inter- and intra-cellular communication, which regulates fundamental cell functions such as growth, survival, and differentiation. The MAPK pathway also integrates signals from complex intracellular networks in performing cellular functions. Despite the initial discovery of the core elements of the MAPK pathways nearly four decades ago, additional findings continue to make a thorough understanding of the molecular mechanisms involved in the regulation of this pathway challenging. Considerable effort has been focused on the regulation of RAF, especially after the discovery of drug resistance and paradoxical activation upon inhibitor binding to the kinase. RAF activity is regulated by phosphorylation and conformation-dependent regulation, including auto-inhibition and dimerization. In this review, we summarize the recent major findings in the study of the RAS/RAF/MEK/ERK signaling cascade, particularly with respect to the impact on clinical cancer therapy.

The dimerisation of Raf kinases involves a central cluster within the kinase domain, the dimer interface (DIF). Yet, the importance of the DIF for the signalling potential of wild‐type B‐Raf (B‐Raf wt ) and its oncogenic counterparts remains unknown. Here, we show that the DIF plays a pivotal role for the activity of B‐Raf wt and several of its gain‐of‐function (g‐o‐f) mutants. In contrast, the B‐Raf V600E , B‐Raf insT and B‐Raf G469A oncoproteins are remarkably resistant to mutations in the DIF. However, compared with B‐Raf wt , B‐Raf V600E displays extended protomer contacts, increased homodimerisation and incorporation into larger protein complexes. In contrast, B‐Raf wt and Raf‐1 wt mediated signalling triggered by oncogenic Ras as well as the paradoxical activation of Raf‐1 by kinase‐inactivated B‐Raf require an intact DIF. Surprisingly, the B‐Raf DIF is not required for dimerisation between Raf‐1 and B‐Raf, which was inactivated by the D594A mutation, sorafenib or PLX4720. This suggests that paradoxical MEK/ERK activation represents a two‐step mechanism consisting of dimerisation and DIF‐dependent transactivation. Our data further implicate the Raf DIF as a potential target against Ras‐driven Raf‐mediated (paradoxical) ERK activation. An intact dimer interface (DIF) is required for both signalling and dimerisation in wild‐type Raf, but surprisingly for neither in certain oncogenic Raf versions. Paradoxical Raf activation reveals an additional layer of complexity, with the DIF now dispensable for dimerisation but required for signalling.

Background: Metastatic colorectal cancer (mCRC) that harbours a BRAF V600E mutation ( BRAF MT) is associated with poorer outcomes. However, whether this mutation is predictive of treatment benefit from anti-epidermal growth factor receptor (EGFR) monoclonal antibodies (mAbs) is uncertain. Methods: We conducted a systematic review and meta-analysis of randomised controlled trials (RCTs) published up to July 2014 that evaluated the effect of BRAF MT on the treatment benefit from anti-EGFR mAbs for mCRC. Results: Seven RCTs met the inclusion criteria for assessment of overall survival (OS), whereas eight RCTs met the inclusion criteria for assessment of progression-free survival (PFS). For RAS WT/ BRAF MT tumours, the hazard ratio for OS benefit with anti-EGFR mAbs was 0.97 (95% CI; 0.67–1.41), whereas the hazard ratio was 0.81 (95% CI; 0.70–0.95) for RAS WT/ BRAF WT tumours. However, the test of interaction ( P =0.43) was not statistically significant, highlighting that the observed differences in the effect of anti-EGFR mAbs on OS according to the BRAF mutation status may be due to chance alone. Regarding PFS benefit with anti-EGFR mAbs, the hazard ratio was 0.86 (95% CI; 0.61–1.21) for RAS WT/ BRAF MT tumours as compared with 0.62 (95% CI; 0.50–0.77) for RAS WT/ BRAF WT tumours (test of interaction, P =0.07). Interpretation: This meta-analysis demonstrates that there is insufficient evidence to definitively state that RAS WT/ BRAF MT individuals attain a different treatment benefit from anti-EGFR mAbs for mCRC compared with RAS WT/ BRAF WT individuals. As such, there are insufficient data to justify the exclusion of anti-EGFR mAb therapy for patients with RAS WT/ BRAF MT mCRC.

Background: Next-generation sequencing (NGS) is an approved test to select patients for BRAF V600E targeted therapy in Korea. However, the high cost, long turnaround times, and the need for sophisticated equipment and skilled personnel limit the use of NGS in daily practice. Immunohistochemistry (IHC) is a rapid and relatively inexpensive assay available in most laboratories. Therefore, in this study, we evaluate the usefulness of BRAF VE1 IHC in terms of predictive value and interobserver agreement in non–small cell lung cancers (NSCLCs). Methods: A total of 30 cases with known BRAF mutation status were selected, including 20 cases of lung adenocarcinomas, six cases of colorectal adenocarcinomas, and four cases of papillary thyroid carcinomas. IHC for BRAF V600E was carried out using the VE1 antibody. Fifteen pathologists independently scored both the staining intensity and the percentage of tumor cell staining on whole slide images. Results: In the lung adenocarcinoma subset, interobserver agreement for the percentage of tumor cell staining and staining intensity was good (percentage of tumor cell staining, intraclass correlation coefficient = 0.869; staining intensity, kappa = 0.849). The interobserver agreement for the interpretation using the cutoff of 40% was almost perfect in the entire study group and the lung adenocarcinoma subset (kappa = 0.815). Sensitivity, specificity, positive predictive value, and negative predictive value of BRAF VE1 IHC were 80.0%, 90.0%, 88.9%, and 81.8%, respectively. Conclusions: BRAF VE1 IHC could be a screening test for the detection of BRAF V600E mutation in NSCLC. However, further studies are needed to optimize the protocol and to establish and validate interpretation criteria for BRAF VE1 IHC.

MITF (microphthalmia-associated transcription factor) represents a melanocytic lineage-specific transcription factor whose role is profoundly extended in malignant melanoma. Over the last few years, the function of MITF has been tightly connected to plasticity of melanoma cells. MITF participates in executing diverse melanoma phenotypes defined by distinct gene expression profiles. Mutation-dependent alterations in MITF expression and activity have been found in a relatively small subset of melanomas. MITF activity is rather modulated by its upstream activators and suppressors operating on transcriptional, post-transcriptional and post-translational levels. These regulatory mechanisms also include epigenetic and microenvironmental signals. Several transcription factors and signaling pathways involved in the regulation of MITF expression and/or activity such as the Wnt/β-catenin pathway are broadly utilized by various types of tumors, whereas others, e.g., BRAFⱽ⁶⁰⁰ᴱ/ERK1/2 are more specific for melanoma. Furthermore, the MITF activity can be affected by the availability of transcriptional co-partners that are often redirected by MITF from their own canonical signaling pathways. In this review, we discuss the complexity of a multilevel regulation of MITF expression and activity that underlies distinct context-related phenotypes of melanoma and might explain diverse responses of melanoma patients to currently used therapeutics.

BRAF mutations have been identified as targetable, oncogenic mutations in many cancers. Given the paucity of treatments for primary brain tumors and the poor prognosis associated with high-grade gliomas, BRAF mutations in glioma are of considerable interest. In this review, we present the spectrum of BRAF mutations and fusion alterations present in each class of primary brain tumor based on publicly available databases and publications. We also summarize clinical experience with RAF and MEK inhibitors in patients with primary brain tumors and describe ongoing clinical trials of RAF inhibitors in glioma. Sensitivity to RAF and MEK inhibitors varies among BRAF mutations and between tumor types as only class I BRAF V600 mutations are sensitive to clinically available RAF inhibitors. While class II and III BRAF mutations are found in primary brain tumors, further research is necessary to determine their sensitivity to third-generation RAF inhibitors and/or MEK inhibitors. We recommend that the neuro-oncologist consider using these drugs primarily in the setting of a clinical trial for patients with BRAF-altered glioma in order to advance our knowledge of their efficacy in this patient population.