BRAF Mutant Tumors Research Articles

Antitumor activity of KIN-2787, a next-generation pan-RAF inhibitor, in combination with MEK inhibition in preclinical models of human NRAS mutant melanoma.

e15099 Background: NRAS mutations which activate MAPK signaling represent oncogenic driver alterations in approximately 20% melanoma cases in the US. NRAS mutant melanomas are uniquely dependent upon CRAF rather than BRAF for activation of downstream MEK/ERK signaling. In BRAF mutant melanoma, approved RAF-targeted therapies are commonly used in combination with a MEK inhibitor which provides clinical benefit by inhibition of two targets within the oncogenic MAPK signaling pathway. Emerging data with pan-RAF inhibitors in early clinical development suggests benefit with and without combined MEK inhibition, yet no approved targeted therapy exists for NRAS mutant melanoma patients. KIN-2787 is a novel, orally available pan-RAF inhibitor designed to be effective in RAF-dependent cancers, regardless of isoform. Methods: Kinome profiling was evaluated by radiometric enzyme assay at Reaction Biology across 688 kinases (including wild type, atypical, and mutant). Cellular activity was assessed by suppression of downstream MAPK pathway signaling and cell growth inhibition in human tumor cell lines. Combination cell growth inhibition studies were performed in 9x5 dose matrices with KIN-2787 and binimetinib, respectively. Extended cell growth inhibition effects were assessed by Incucyte imaging. In vivo KIN-2787 and combination efficacy was evaluated in NRAS mutant xenograft models. Results: Kinome profiling of KIN-2787 revealed exquisite selectivity with only 2 of 669 non-RAF family kinases inhibited > 75% at 1 M KIN-2787 and retained ̃10x and 70x selectivity window against those two kinases, DDR1 and p38b, respectively, relative to RAF kinases. We previously reported KIN-2787 activity across BRAF, NRAS, and KRAS mutant tumor cell lines with greatest sensitivity in Class II and III dimer-driven BRAF models. Here, we evaluated NRAS mutant, BRAF WT melanoma for combination potential with binimetinib. Melanoma tumor cell lines bearing NRAS hotspot mutations demonstrated synergistic benefit with KIN-2787 combined with binimetinib. Daily KIN-2787 plus binimetinib treatment in NRAS mutant melanoma xenograft models resulted in significant tumor growth inhibition benefit relative to either agent alone and was associated with added MAPK pathway biomarker suppression. Conclusions: KIN-2787 is a highly selective, potent, next-generation, pan-RAF inhibitor with activity across BRAF and RAS mutant human tumor cell models. Preclinical in vitro and in vivo studies using KIN-2787 in combination with binimetinib demonstrated significant combination benefit in NRAS mutant melanoma models. Taken together with its unique selectively, these data support use of KIN-2787 in combination therapy in this patient segment. A Phase 1/1b dose escalation and expansion clinical trial evaluating the safety and efficacy of KIN-2787 is ongoing (NCT04913285).

Abemaciclib in metastatic or locally advanced anaplastic thyroid cancer.

TPS6112 Background: Anaplastic thyroid cancer (ATC) is a rare and lethal tumor of thyroid epithelium, with disease-specific mortality approaching 100%. ATC accounts for > 50% of the 1200 annual deaths attributable to thyroid cancer. In the pre-molecular era, treatment options were largely ineffective, reflected in a median overall survival of 3-4 months following diagnosis. Outcomes have improved in BRAF V600E-mutated ATC with the FDA approval of dabrafenib and trametinib (Subbiah et al. JCO, 2018). However, a significant need exists for patients with BRAF wild-type tumors and patients with BRAF-mutated tumors who progress following treatment with BRAF-directed therapies. Abemaciclib is a CDK4/6 inhibitor currently FDA-approved in combination with endocrine therapy for hormone-positive breast cancer. Genomic analyses of ATC have indicated the presence of an intact Rb (Retinoblastoma) expression as well as the existence of CDKN2A (the gene encoding human p16) mutations in up to 32% of patients with ATC (Khan et al., Head Neck, 2019). Moreover, Lee et al. in 2008 reported undetectable p16 levels in 24 out of 27 (89%) patients with ATC. Low p16 levels would be expected to result in accelerated S phase entry, leading to uncontrolled ATC growth. Finally, studies in mouse xenograft models have demonstrated that ribociclib (a CDK4/6 inhibitor) slows proliferation and induces apoptosis of ATC cells (Lee et al., Cancer Letters, 2018). These molecular alterations and pre-clinical data provide a mechanistic rationale by which to evaluate CDK4/6 inhibitors in ATC and, to date, no CDK4/6 inhibitors have been evaluated in thyroid cancer. Methods: This multicenter, single-arm Phase 2 study will evaluate the safety and efficacy of treatment with abemaciclib in patients with histologically confirmed unresectable or metastatic ATC, using an optimal Simon two-stage design. Patients with BRAF V600E+ ATC must have progressed on or have an intolerance to dabrafenib and trametinib. The study intervention is abemaciclib 200 mg orally twice daily. The primary endpoint is overall response rate at eight weeks from the start of treatment. Secondary endpoints include progression-free survival and overall survival. Currently, 6 patients have been enrolled. Planned genomic analysis will be conducted to identify potential predictive biomarkers. Clinical trial information: NCT04552769.

Pan-cancer analysis of BRAF alterations and tumor-specific mechanisms of activation.

e17005 Background: BRAF is a proto-oncogene that is altered in various cancers and is a druggable target. Particularly, the selective BRAF kinase inhibitors Dabrafenib and Vemurafenib are FDA approved for melanoma and thyroid cancer that harbor the activating BRAF V600 hotspot mutations. In pre-clinical studies, activated BRAF promotes tumor cell function across many additional cancer types in which therapeutics have not been considered. We propose that identifying BRAF-activated cancers will guide future pre-clinical investigations and potentially expand the usage of existing BRAF-targeting therapeutics. Methods: We utilized bioinformatics to investigate the molecular profiles of pan-cancer cohorts from two platforms based on distinct sequencing technology. This included a custom curated dataset (whole exome, 6 studies, 39 cancer types, n = 12,019) and GENIE9.1 (targeted gene panel, 62 cancer types, n = 78,619). Studies were included based on genomic modalities (copy number alterations, mutations, gene fusions). We cataloged the frequency and all types of BRAF genomic alterations pan-cancer. We also examined other genomic features, including tumor mutational burden (TMB) and fraction of the genome altered (FGA), and their association with types of BRAF alterations across cancer types. Results: In both platforms, we found that BRAF alterations were observed across over 80% of cancer types. Melanoma, thyroid, and colorectal tumors exhibited the greatest rates of mutations. Regarding gene body rearrangements, we noted endocrine-driven cancers including ovarian and metastatic prostate tumors (mPC) exhibited relative robust rates of amplification. In addition, thyroid carcinoma and mPC harbored recurrent BRAF gene fusion events. In mPC, we found that the BRAF gene fusions often included an N-terminus gene fragment from known androgen-target genes (TMPRSS2 and SND1). These fusion events represented a dysregulated hormone-driven mechanism of BRAF activation. We also found that hotspot missense mutations were cancer-type specific, including K601 hotspots in mPC, G469 hotspots in non-small cell lung cancers, and G466 hotspots in ovarian cancers. Lastly, BRAF-amplified endocrine tumors harbored a 1.5-fold increase in FGA medians, whereas BRAF-mutated lung and colorectal tumors exhibited a 1.6-fold increase in TMB medians. Conclusions: Our molecular analysis revealed that cancers accrued activated BRAF through cancer-type-specific and divergent genomic mechanisms. These molecular features provide genomic evidence to expand the application of BRAF-targeted therapies in additional cancer lineages, including mPC. BRAF mutations were also associated with genomic biomarkers, such as TMB, which may predict response to immune therapies. This suggests that BRAF alterations can be considered as an additional feature to aid therapy selection.

A pilot study of trametinib in combination with paclitaxel in the treatment of anaplastic thyroid cancer.

6088 Background: Anaplastic Thyroid Cancer (ATC) is a rare and highly aggressive tumor with extremely poor prognosis. Outside of the recent approval of dabrafenib/trametinib for BRAF mutant tumors, there are no other standard treatment available for metastatic ATC. The majority of ATC is driven through the MAPK pathway. Data in lung cancer suggested synergy with trametinib, a MEK inhibitor, and taxanes. Methods: In this pilot study we used Trametinib (2 mg) daily with Paclitaxel (80 mg/m2) administered weekly for the first 3 weeks out the 4 week-cycle. Restaging imaging was performed every 6-8 weeks (1.5-2 cycles). Eligible patients had ATC with baseline ECOG performance status ≤ 1 and were enrolled at Memorial Sloan Kettering Cancer Center. Prior treatment allowed. Prior brain metastases were allowed if treated and stable off of steroids. Primary objective was PFS at 6 months with the target of > 2 subjects out of 12 at the time point. Results: 12 patients (6 men and 6 women) were enrolled between 11/2017 and 10/2021. Seven (58%) had prior radiation to the neck; 4 (33%) had prior treatment (not including with radiation) for ATC; 1 (8%) had prior brain metastases. Three (25%) partial responses were reported, and five (41.67%) reported stable disease. Subjects with partial responses had a BRAF V600E mutation (1), BRAF fusion gene (1), and a RAS mutation (1). Median time on treatment was 10.5 weeks (3-47+ weeks). Median overall survival was 26 weeks (3-59+). Six-month progression free survival (PFS) was achieved in 3 patient (25%), one of whom remains on study. 2 patients discontinued treatment due to unacceptable toxicity. The most frequent adverse events observed (all grades) were anemia (75%), increased AST, diarrhea and leukopenia (all 50%). Grade 3/4 AEs included neutropenia (25%), with anemia, AST increased, febrile neutropenia, and lymphopenia, all 16.67%. Grade 4 reactions included lymphopenia (n = 2) and leukopenia (n = 1). Conclusions: Our target progression-free survival (PFS) at 6 months was observed on this study. The combination of trametinib and paclitaxel should be evaluated in a larger cohort of patients in the future. Clinical trial information: NCT03085056.

Impact of Grade on Survival in Pleomorphic Xanthoastrocytoma and Low Prevalence of BRAF V600E Mutation

The prevalence of BRAFV600E mutations in pleomorphic xanthoastrocytoma (PXA) World Health Organization (WHO) Grade 2 and PXA WHO Grade 3 reported varies from 60% to 80%, yet the prognostic implications remain unclear. We reviewed the demographic and clinicoradiologic data of 20 PXAs WHO Grade 2 and 13 PXAs WHO Grade 3, operated between 2007 and 2020, to ascertain extent of excision, recurrence, progression-free survival (PFS), and overall survival (OS). PXAs WHO Grade 3 were defined by the presence of >5 mitoses/high-power field. PXAs WHO Grade 3 received adjuvant radiation therapy and chemotherapy whereas PXAs received radiation therapy if subtotally excised. All samples were analyzed for the presence of BRAFV600E mutation using DNA obtained from paraffin blocks using droplet-digital polymerase chain reaction. The median patient age at diagnosis was 22 years with a male preponderance. BRAFV600E mutations were noted in 30% of tumors; 8 PXAs WHO Grade 2 and 2 PXAs WHO Grade 3. Recurrence occurred in 6 of 13 PXA WHO Grade 3 (55%) and 1 of 20 PXAs WHO Grade 2 (5%). At median follow-up of 45 months, the OS was 54 months and 33 months in the PXA WHO Grade 2 and PXA WHO Grade 3 groups, respectively (P= 0.02). OS and PFS did not differ between BRAF-mutated and BRAF-negative tumors. BRAFV600E mutations are less frequent in our population than reported in the literature. The BRAF mutation does not significantly impact OS and PFS. PXAs WHO Grade 3 are a distinct clinical entity, associated with worse PFS and OS than PXAs WHO Grade2.

Immune Profile of BRAF-Mutated Metastatic Colorectal Tumors with Good Prognosis after Palliative Chemotherapy.

Simple SummaryThe present study demonstrated that the distinct subgroup of BRAF-MT CRC showed a good response after palliative chemotherapy. Based on the immune profile analysis, higher PD-L1 expression and CD8-positive cell infiltration were shown in this study population. Furthermore, the assessment of the immune profile of BRAF-MT tumors can be helpful to better understand tumor biology and the different clinical outcomes of BRAF-MT CRC. Background: BRAF-mutated colorectal cancers (BRAF-MT CRCs) are known to have poor prognoses. BRAF-MT CRC was reported to be possibly related to the immune-activated phenotype. Objectives: This study aimed to investigate the association between the immune microenvironment and prognosis of BRAF-MT CRC. Methods: We evaluated clinical outcomes and investigated the immune profile of the BRAF-MT CRC tumors using the multiplex immunohistochemistry of immune-related markers: cytokeratin, programmed death ligand-1 (PD-L1), programmed cell death protein-1 (PD-1), and a cluster of differentiation 8 (CD8). Results: Out of 2313 tumors, 123 were BRAF-MT tumors. Among them, 86 tumors with available tissue were included. Out of 86 patients, 75 patients were non-good responders (GR), whereas 11 patients were GR. Median progression-free survival after first-line chemotherapy (4.6 vs. 12.4 months, p = 0.008) and overall survival (11.8 vs. 45.0 months) were longer in the GR group (p < 0.001). Median CD8+ T cell (254.29 vs. 656.0, p = 0.092), PD-L1+ tumor cell (0.95 vs.15.56, p = 0.050), PD-L1+ stromal cell (3.17 vs. 72.38, p = 0.025), PD-L1+ tumor and stromal cell (5.08 vs. 74.92, p = 0.032), and PD-1+ stromal cell (45.08 vs. 325.40, p = 0.046) counts were greater in the GR group. Conclusion: The clinical outcomes of unselected patients with BRAF-MT CRC were generally similar to those in previous studies. Based on the immune profile analysis, higher PD-L1 expression and CD8-positive cell infiltration were observed in BRAF-MT tumors with a good prognosis.

Close proximity of immune and tumor cells underlies response to BRAF/MEK-targeted therapies in metastatic melanoma patients

Abstract Acquired resistance to BRAF/MEK-targeted therapy occurs in the majority of melanoma patients that harbor BRAF-mutated tumors, leading to relapse or progression and the underlying mechanism is unclear in many cases. The tumoral spatial heterogeneity is a potential key to the understanding of the therapy-response relationships, but they also bring challenges of proper parameterization and model validation. In this study, we developed a workflow to detect immune and tumor cells using multiplex immunohistochemistry and spatial imaging analysis from whole-tumor imaging data. Simultaneous characterization of CD11c+, CD8+, CD40+, CD80+ and SOX10+ cells using multispectral imaging was performed on paired tumor sections from eleven melanoma patients prior to BRAF/MEK-targeted therapy and when disease progressed on therapy. We observed a significant increase of tumor cellularity in the progressed tumors, and the close association of SOX10+ melanoma cells with CD8+ cytotoxic T cells (Tc) negatively correlated with patient’s progression-free survival, which may indicate a potential mechanism for acquired resistance to BRAF/MEK-targeted therapy. Using preclinical mouse model of YUMM3.3 BRAF-mutated tumors, we showed the detrimental role of PD-L1:PD-1 axis between melanoma-cell:Tc-cell in melanoma. In TCGA-melanoma dataset (n=445), SOX10hi is associated with a significant reduction of IFNG and GZMB, as well as poor overall survival (OS) in melanoma. Tumor cellularity (SOX10 and MLANA expression) exhibited additive prognostic value in the immune score signature to predict OS in patients with early-stage melanoma and prognoses OS independent of immune score in patients with late-stage melanoma. This work was supported by a VA Merit Award (I01BX002301) and SRCS award to AR and by R01-CA116021 (AR).

Characterization of the treatment-naive immune microenvironment in melanoma with BRAF mutation

BackgroundPatients with BRAF-mutant and wild-type melanoma have different response rates to immune checkpoint blockade therapy. However, the reasons for this remain unknown. To address this issue, we investigated the precise...

Role of Furin in Colon Cancer Stem Cells Malignant Phenotype and Expression of LGR5 and NANOG in KRAS and BRAF-Mutated Colon Tumors.

Simple SummaryColorectal cancer (CRC) is one of the most common malignancies in the digestive system. We have previously shown that the proprotein convertase Furin is involved in calcium regulation in cancer cells. In this study, we revealed that the malignant phenotype of colon cancer stem cells is repressed by Furin inhibition that is associated with reduced expression of LGR5 and Nanog and dysregulated expression of several calcium regulators involved in colon cancer. Our data support the idea that targeting Furin in colorectal cancer stem cells may constitute a potential therapeutic approach.Proprotein convertases or PCs are known to regulate the malignant phenotype of colon cancer cells by different mechanisms, but their effects on cancer stem cells (CSCs) have been less widely investigated. Here, we report that PCs expression is altered in colon CSCs, and the inhibition of their activity reduced colon CSCs growth, survival, and invasion in three-dimensional spheroid cultures. In vivo, repression of PCs activity by the general PC inhibitors α1-PDX, Spn4A, or decanoyl-RVKR-chloromethylketone (CMK) significantly reduced tumor expression levels of the stem cell markers LGR5 and NANOG that are associated with reduced tumor xenografts. Further analysis revealed that reduced tumor growth mediated by specific silencing of the convertase Furin in KRAS or BRAF mutated-induced colon tumors was associated with reduced expression of LGR5 and NANOG compared to wild-type KRAS and BRAF tumors. Analysis of various calcium regulator molecules revealed that while the calcium-transporting ATPase 4 (ATP2B4) is downregulated in all the Furin-silenced colon cancer cells, the Ca2+-mobilizing P2Y receptors, was specifically repressed in BRAF mutated cells and ORAI1 and CACNA1H in KRAS mutated cells. Taken together, our findings indicate that PCs play an important role in the malignant phenotype of colon CSCs and stem cell markers’ expression and highlight PCs repression, particularly of Furin, to target colon tumors with KRAS or BRAF mutation.

Investigating the prognostic value of TP53 and PIK3CA mutations in metastatic colorectal cancer (mCRC): Applying Structured Query Language (SQL) algorithms to real-world data from a high-volume U.K. tertiary cancer center.

57 Background: Real world data is a valuable research resource but manual data collection is time consuming and labour intensive. As there is no consensus on the prognostic role of TP53 and PIK3CA mutations in mCRC, we assessed the feasibility of using SQL, a programming language, to derive data from routine electronic clinical notes to investigate the prognostic impact of TP53 and PIK3CA mutations in mCRC. Methods: A cohort of patients (pts) diagnosed with metastatic or recurrent colorectal cancer as per ICD-10 classification from January 2015 to December 2017 and managed at the Royal Marsden Hospital were identified using SQL algorithms developed in-house. Baseline demographics, histopathological and molecular characteristics and death dates were derived from the Electronic Patient Record and extracted in a structured format for statistical analysis. Mutational analysis of TP53 and PIK3CA were performed with standard of care KRAS, NRAS and BRAF testing using next generation sequencing. Overall survival (OS) according to TP53 or PIK3CA mutational status was estimated using the Kaplan-Meier method. Uni- and multivariate Cox regression included KRAS, NRAS, BRAF, sidedness and mismatch repair (MMR) status. Association between TP53 or PIK3CA and MMR status was tested by the Chi squared test. Results: A total of 367 mCRC pts were identified; 10 were excluded due to ineligibility or inadequate data availability. Based on a final dataset of 357 pts, 342 and 354 pts had TP53 and PIK3CA results available. The incidence of TP53 mutations was 75% (n = 257/342) and PIK3CA 16% (n = 55/354). Co-mutations with KRAS, NRAS and BRAF were seen (Table). The overall median follow-up was 42.3 and 42.7 months for TP53 and PIK3CA respectively. There was no difference in OS between TP53 mutant (MT) and wild type (WT) pts (22.0 vs. 22.8 months, p = 0.96) and between PIK3CA MT and WT pts (21.7 vs. 22.4 months, p = 0.49). Right sided and BRAF MT tumours were associated with poorer survival than left sided and BRAF WT tumours when all other factors were constant for TP53 (p&lt;0.001 &amp; p=0.033 respectively) and PIK3CA (both p&lt;0.001) OS on multivariate analysis. MMR deficient tumours were significantly more frequent in TP53 WT compared to TP53 MT tumours (15% vs. 4%, p=0.001) while they were significantly more frequent in PIK3CA MT compared to PIK3CA WT tumours (20% vs. 5%, p &lt; 0.001). Conclusions: Bespoke SQL algorithms enables large-scale data extraction to facilitate research. Based on this dataset, we have shown that TP53 and PIK3CA mutations have no prognostic impact in mCRC. [Table: see text]

Nuclear PD-L1 promotes cell cycle progression of BRAF-mutated colorectal cancer by inhibiting THRAP3

Colorectal cancers (CRCs) with the BRAF V600E mutation exhibit upregulation of programmed death ligand 1 (PD-L1) but fail to respond to immunotherapy targeting programmed cell death protein 1 (PD-1)/PD-L1. Recent studies have explored the intracellular functions of PD-L1. Here, we demonstrate that PD-L1 was highly expressed in both the cytoplasm and nucleus of BRAF-mutated CRC tumor cells and tissues. Nuclear PD-L1 (nPD-L1) promoted the growth of tumor cells both in vitro and in vivo. Mechanistic investigations revealed that PD-L1 translocation into the nucleus was facilitated by the binding of p-ERK. Further, nPD-L1 upregulated the expression of cell cycle regulator BUB1 via interactions with thyroid hormone receptor-associated protein 3 (THRAP3), thereby accelerating cell cycle progression and promoting cell proliferation. Moreover, BRAF V600E-mutated CRC cells exhibited upregulation of PD-L1 expression via the transcription factor LEF-1. These findings reveal a novel role of nPD-L1, which promotes cell cycle progression in an immune-independent manner in BRAF V600E-mutated CRC. Our study provides novel insight into the mechanisms underlying BRAF V600E-mutated CRC progression.

Seriniquinones as Therapeutic Leads for Treatment of BRAF and NRAS Mutant Melanomas.

Isolated from the marine bacteria Serinicoccus sp., seriniquinone (SQ1) has been characterized by its selective activity in melanoma cell lines marked by its modulation of human dermcidin and induction of autophagy and apoptosis. While an active lead, the lack of solubility of SQ1 in both organic and aqueous media has complicated its preclinical evaluation. In response, our team turned its effort to explore analogues with the goal of returning synthetically accessible materials with comparable selectivity and activity. The analogue SQ2 showed improved solubility and reached a 30–40-fold greater selectivity for melanoma cells. Here, we report a detailed comparison of the activity of SQ1 and SQ2 in SK-MEL-28 and SK-MEL-147 cell lines, carrying the top melanoma-associated mutations, BRAFV600E and NRASQ61R, respectively. These studies provide a definitive report on the activity, viability, clonogenicity, dermcidin expression, autophagy, and apoptosis induction following exposure to SQ1 or SQ2. Overall, these studies showed that SQ1 and SQ2 demonstrated comparable activity and modulation of dermcidin expression. These studies are further supported through the evaluation of a panel of basal expression of key-genes related to autophagy and apoptosis, providing further insight into the role of these mutations. To explore this rather as a survival or death mechanism, autophagy inhibition sensibilized BRAF mutants to SQ1 and SQ2, whereas the opposite happened to NRAS mutants. These data suggest that the seriniquinones remain active, independently of the melanoma mutation, and suggest the future combination of their application with inhibitors of autophagy to treat BRAF-mutated tumors.

Characterization of Subtypes of BRAF-Mutant Papillary Thyroid Cancer Defined by Their Thyroid Differentiation Score.

The BRAFV600E mutation has been associated with more advanced clinical stage in papillary thyroid cancer (PTC) and decreased responsiveness to radioiodine (RAI). However, some BRAF mutant PTCs respond to RAI and have an indolent clinical behavior suggesting the presence of different subtypes of BRAF mutant tumors with distinct prognosis. To characterize the molecular and clinical features of 2 subtypes of BRAF-mutant PTCs defined by their degree of expression of iodine metabolism genes. 227 BRAF-mutant PTCs from the Cancer Genome Atlas Thyroid Cancer study were divided into 2 subgroups based on their thyroid differentiation score (TDS): BRAF-TDShi and BRAF-TDSlo. Demographic, clinico-pathological, and molecular characteristics of the 2 subgroups were compared. Compared to BRAF-TDShi tumors (17%), BRAF-TDSlo tumors (83%) were more frequent in blacks and Hispanics (6% vs 0%, P = 0.035 and 12% vs 0%, P = 0.05, respectively), they were larger (2.95 ± 1.7 vs 2.03 ± 1.5, P = 0.002), with more tumor-involved lymph nodes (3.9 ± 5.8 vs 2.0 ± 4.2, P = 0.042), and a higher frequency of distant metastases (3% vs 0%, P = 0.043). Gene set enrichment analysis showed positive enrichment for RAS signatures in the BRAF-TDShi cohort, with corresponding reciprocal changes in the BRAF-TDSlo group. Several microRNAs (miRs) targeting nodes in the transforming growth factor β (TGFβ)-SMAD pathway, miR-204, miR-205, and miR-144, were overexpressed in the BRAF-TDShi group. In the subset with follow-up data, BRAF-TDShi tumors had higher complete responses to therapy (94% vs 57%, P < 0.01) than BRAF-TDSlo tumors. Enrichment for RAS signatures, key genes involved in cell polarity and specific miRs targeting the TGFβ-SMAD pathway define 2 subtypes of BRAF-mutant PTCs with distinct clinical characteristics and prognosis.

MAPK Inhibition Requires Active RAC1 Signaling to Effectively Improve Iodide Uptake by Thyroid Follicular Cells

Simple SummaryThe Sodium/Iodide Simulator (NIS) is responsible for the uptake of iodide in the thyroid follicular cells. NIS is present in most differentiated thyroid carcinomas (DTC), allowing radioactive iodine (RAI) to be used to destroy malignant cells. However, a significant proportion of DTCs stop picking up iodide and become resistant to RAI therapy. This is mainly due to the symporter no longer being produced or not being placed correctly at the cell’s membrane. This has been associated with mechanisms linked to malignant transformation, namely the overactivation of the so-called MAPK pathway. Thus, several drugs have been developed to inhibit this pathway, attempting to increase NIS levels and iodide uptake. However, MAPK inhibitors have had only partial success in restoring NIS expression. We found that the activity of another protein, the small GTPase RAC1, has an important role in this process, determining the outcome of MAPK inhibitors. Thus, our findings open new opportunities to find effective therapeutic alternatives for DTC resistant to RAI.The Sodium/Iodide Symporter (NIS) is responsible for the active transport of iodide into thyroid follicular cells. Differentiated thyroid carcinomas (DTCs) usually preserve the functional expression of NIS, allowing the use of radioactive iodine (RAI) as the treatment of choice for metastatic disease. However, a significant proportion of patients with advanced forms of TC become refractory to RAI therapy and no effective therapeutic alternatives are available. Impaired iodide uptake is mainly caused by the defective functional expression of NIS, and this has been associated with several pathways linked to malignant transformation. MAPK signaling has emerged as one of the main pathways implicated in thyroid tumorigenesis, and its overactivation has been associated with the downregulation of NIS expression. Thus, several strategies have been developed to target the MAPK pathway attempting to increase iodide uptake in refractory DTC. However, MAPK inhibitors have had only partial success in restoring NIS expression and, in most cases, it remained insufficient to allow effective treatment with RAI. In a previous work, we have shown that the activity of the small GTPase RAC1 has a positive impact on TSH-induced NIS expression and iodide uptake in thyroid cells. RAC1 is a downstream effector of NRAS, but not of BRAF. Therefore, we hypothesized that the positive regulation induced by RAC1 on NIS could be a relevant signaling cue in the mechanism underlying the differential response to MEK inhibitors, observed between NRAS- and BRAF-mutant tumors. In the present study, we found that the recovery of NIS expression induced through MAPK pathway inhibition can be enhanced by potentiating RAC1 activity in thyroid cell systems. The negative impact on NIS expression induced by the MAPK-activating alterations, NRAS Q61R and BRAF V600E, was partially reversed by the presence of the MEK 1/2 inhibitors AZD6244 and CH5126766. Notably, the inhibition of RAC1 signaling partially blocked the positive impact of MEK inhibition on NIS expression in NRAS Q61R cells. Conversely, the presence of active RAC1 considerably improved the rescue of NIS expression in BRAF V600E thyroid cells treated with MEK inhibitors. Overall, our data support an important role for RAC1 signaling in enhancing MAPK inhibition in the context of RAI therapy in DTC, opening new opportunities for therapeutic intervention.

Preclinical Characterization of a Next-Generation Brain Permeable, Paradox Breaker BRAF Inhibitor.

Disease progression in BRAF V600E/K positive melanomas to approved BRAF/MEK inhibitor therapies is associated with the development of resistance mediated by RAF dimer inducing mechanisms. Moreover, progressing disease after BRAFi/MEKi frequently involves brain metastasis. Here we present the development of a novel BRAF inhibitor (Compound Ia) designed to address the limitations of available BRAFi/MEKi. The novel, brain penetrant, paradox breaker BRAFi is comprehensively characterized in vitro, ex vivo, and in several preclinical in vivo models of melanoma mimicking peripheral disease, brain metastatic disease, and acquired resistance to first-generation BRAFi. Compound Ia manifested elevated potency and selectivity, which triggered cytotoxic activity restricted to BRAF-mutated models and did not induce RAF paradoxical activation. In comparison to approved BRAFi at clinical relevant doses, this novel agent showed a substantially improved activity in a number of diverse BRAF V600E models. In addition, as a single agent, it outperformed a currently approved BRAFi/MEKi combination in a model of acquired resistance to clinically available BRAFi. Compound Ia presents high central nervous system (CNS) penetration and triggered evident superiority over approved BRAFi in a macro-metastatic and in a disseminated micro-metastatic brain model. Potent inhibition of MAPK by Compound Ia was also demonstrated in patient-derived tumor samples. The novel BRAFi demonstrates preclinically the potential to outperform available targeted therapies for the treatment of BRAF-mutant tumors, thus supporting its clinical investigation.

Precision medicine in aggressive thyroid cancer: Moving beyond multitargeted tyrosine kinase inhibitors

Precision medicine in aggressive thyroid cancer: Moving beyond multitargeted tyrosine kinase inhibitors

BRAF mutations in thyroid cancer.

Activating mutations in the mitogen-activated protein kinase (MAPK) pathway play an important role in papillary (PTC) and anaplastic (ATC) thyroid cancer. The aim of this review is to discuss the impact of BRAF mutations on clinical features and treatment of patients with thyroid cancer. Despite the unfavorable course associated with PTCs harboring BRAF V600E mutation, its prognostic role remains debated. BRAF V600E-driven tumors exhibit high Extracellular signal-regulated kinase phosphorylation, leading to unregulated cell proliferation and inhibition of the required genes for radioiodine responsiveness in thyroid cancer. The mechanism associated with the variable BRAF-mutant tumor aggressiveness remains unclear and other pathways are likely to co-operate to promote cancer progression. Overexpression of the Notch signaling and loss of individual switch/ sucrose non-fermentable chromatin-remodeling complexes subunits might be involved. The combination of the BRAF inhibitor dabrafenib and the mitogen-activated protein kinase kinase inhibitor trametinib has shown remarkable results in clinical trials of patients with BRAF-mutated ATCs. The impact of BRAF mutations on the clinical outcomes of PTC remains debatable. In ATCs, in turn, BRAF mutations identify patients eligible for targeted therapy, which is now considered in two settings: as neoadjuvant for unresectable tumors and as a treatment for metastatic or unresectable disease.

BRAF mutations may identify a clinically distinct subset of glioblastoma

Glioblastoma (GBM) is the most common primary malignant brain tumor in adults. Prior studies examining the mutational landscape of GBM revealed recurrent alterations in genes that regulate the same growth control pathways. To this regard, ~ 40% of GBM harbor EGFR alterations, whereas BRAF variants are rare. Existing data suggests that gain-of-function mutations in these genes are mutually exclusive. This study was designed to explore the clinical, pathological, and molecular differences between EGFR- and BRAF-mutated GBM. We reviewed retrospective clinical data from 89 GBM patients referred for molecular testing between November 2012 and December 2015. Differences in tumor mutational profile, location, histology, and survival outcomes were compared in patients with EGFR- versus BRAF-mutated tumors, and microarray data from The Cancer Genome Atlas was used to assess differential gene expression between the groups. Individuals with BRAF-mutant tumors were typically younger and survived longer relative to those with EGFR-mutant tumors, even in the absence of targeted treatments. BRAF-mutant tumors lacked distinct histomorphology but exhibited unique localization in the brain, typically arising adjacent to the lateral ventricles. Compared to EGFR- and IDH1-mutant tumors, BRAF-mutant tumors showed increased expression of genes related to a trophoblast-like phenotype, specifically HLA-G and pregnancy specific glycoproteins, that have been implicated in invasion and immune evasion. Taken together, these observations suggest a distinct clinical presentation, brain location, and gene expression profile for BRAF-mutant tumors. Pending further study, this may prove useful in the stratification and management of GBM.

Pyrexia in patients treated with dabrafenib plus trametinib across clinical trials in BRAF-mutant cancers

BackgroundDabrafenib plus trametinib has demonstrated clinical benefit across multiple BRAF-mutant tumours, leading to approval for resected stage III and metastatic melanoma, non–small-cell lung cancer (NSCLC) and anaplastic thyroid cancer. Pyrexia is a common adverse event in patients treated with dabrafenib plus trametinib. Here, we characterise the incidence, patterns and management of pyrexia in patients receiving dabrafenib plus trametinib in clinical trials. MethodsPatients (N = 1076) included in the analysis received dabrafenib plus trametinib in the following clinical trials: phase II registration trial in advanced NSCLC (N = 82), phase III COMBI-AD study in resectable stage III melanoma (N = 435) and phase III COMBI-d and COMBI-v studies in unresectable or metastatic melanoma (N = 209 and N = 350, respectively). ResultsAmong the 1076 patients enrolled in the clinical trials, 61.3% developed pyrexia, 5.7% developed grade 3/4 pyrexia and 15.6% developed a protocol-defined serious pyrexia event. Among the 660 patients with pyrexia, 33.0% had 1 occurrence, 19.8% had 2 occurrences and 47.1% had ≥3 occurrences. The incidence of pyrexia was highest early in treatment and decreased with time on treatment. Temporary dose interruption of dabrafenib or trametinib was the most common and effective management strategy. ConclusionsPyrexia is the most common adverse event associated with dabrafenib plus trametinib but is manageable with dose interruption. Trial registrationClinicalTrials.gov (Phase II NSCLC, NCT01336634; COMBI-AD, NCT01682083; COMBI-d, NCT01584648; COMBI-v, NCT01597908).

A kinome-centered CRISPR-Cas9 screen identifies activated BRAF to modulate enzalutamide resistance with potential therapeutic implications in BRAF-mutated prostate cancer

Resistance to drugs targeting the androgen receptor (AR) signaling axis remains an important challenge in the treatment of prostate cancer patients. Activation of alternative growth pathways is one mechanism used by cancer cells to proliferate despite treatment, conferring drug resistance. Through a kinome-centered CRISPR-Cas9 screen in CWR-R1 prostate cancer cells, we identified activated BRAF signaling as a determinant for enzalutamide resistance. Combined pharmaceutical targeting of AR and MAPK signaling resulted in strong synergistic inhibition of cell proliferation. The association between BRAF activation and enzalutamide resistance was confirmed in two metastatic prostate cancer patients harboring activating mutations in the BRAF gene, as both patients were unresponsive to enzalutamide. Our findings suggest that co-targeting of the MAPK and AR pathways may be effective in patients with an activated MAPK pathway, particularly in patients harboring oncogenic BRAF mutations. These results warrant further investigation of the response to AR inhibitors in BRAF-mutated prostate tumors in clinical settings.