BRAF Inhibitor Vemurafenib Research Articles

Genome-wide RNAi screen for genes regulating glycolytic response to vemurafenib in BRAFV600 melanoma cells

Identification of mechanisms underlying sensitivity and response to targeted therapies, such as the BRAF inhibitor vemurafenib, is critical in order to improve efficacy of these therapies in the clinic and delay onset of resistance. Glycolysis has emerged as a key feature of the BRAF inhibitor response in melanoma cells, and importantly, the metabolic response to vemurafenib in melanoma patients can predict patient outcome. Here, we present a multiparameter genome-wide siRNA screening dataset of genes that when depleted improve the viability and glycolytic response to vemurafenib in BRAFV600 mutated melanoma cells. These datasets are suitable for analysis of genes involved in cell viability and glycolysis in steady state conditions and following treatment with vemurafenib, as well as computational approaches to identify gene regulatory networks that mediate response to BRAF inhibition in melanoma.

Design and synthesis of novel fluorescently labeled analogs of vemurafenib targeting MKK4.

The mitogen-activated protein kinase kinase 4 (MKK4) plays a key role in liver regeneration and is under investigation as a target for stimulating hepatocytes to increased proliferation. Therefore, new small molecules inhibiting MKK4 may represent a promising approach for treating acute and chronic liver diseases. Fluorescently labeled compounds are useful tools for high-throughput screenings of large compound libraries. Here we utilized the azaindole-based scaffold of FDA-approved BRAF inhibitor vemurafenib 1, which displays off-target activity on MKK4, as a starting point in our fluorescent compound design. Chemical variation of the scaffold and optimization led to a selection of fluorescent 5-TAMRA derivatives which possess high binding affinities on MKK4. Compound 45 represents a suitable tool compound for Fluorescence polarization assays to identify new small-molecule inhibitors of MKK4.

Abstract PR03: Nongenomic BAP1 aberrancy drives highly aggressive cutaneous melanoma phenotype

Abstract The purpose of this study was to determine the role of BAP1 levels in cutaneous melanoma (CM). BAP1 is a tumor suppressor in which loss of heterozygosity (LOH) from mutation and copy number alteration is well described in germline and somatic cancers. Although BAP1 genomic alterations in CM are extremely rare (2% of 665 samples from 5 datasets), marked variability in BAP1 expression is observed in CM. We show that low nuclear BAP1 levels portend a significantly worse clinical outcome in stage III CM (n=37, log rank p ≤0.01 for both overall survival and progression-free survival). Gene Set Enrichment Analysis (GSEA) revealed low BAP1 expression to be most highly ranked with an increased epithelial–mesenchymal transition (EMT) gene expression profile in CM tumors (n=379, FDR q = 1.34E-26) and cell lines (n=53, FDR q = 2.86E-116). We identify the expression of ZEB1, a master regulator of EMT, to be significantly associated with low BAP1 expression in CM tumors and cell lines (p= 1.5E-04 and 3.3E-05, respectively). Analysis of the BAP1 promoter indicates three canonical ZEB1 binding sites. Functional experiments show ZEB1 to bind to the BAP1 promoter, and luciferase activity assays indicate that ZEB1 acts as a transcriptional suppressor of BAP1 expression with differential utilization of the promoter binding sites. Targeted reduction of endogenous ZEB1 caused increased BAP1 levels, while targeted reduction of BAP1 did not modulate ZEB1 levels, consistent with ZEB1 having a suppressive effect on BAP1. Phenotypically, targeted reduction of BAP1 in CM cells resulted in a switch from a more differentiated, melanocytic state, to a less differentiated, more migratory and invasive phenotype. Extinguishing melanocyte-specific BAP1 in mice with a BRAF V600E mutant genetic background resulted in the emergence of primary melanoma tumors, with a marked EMT gene expression profile, and resultant metastases. Given the phenotypic changes associated with BAP1 levels in our mouse and human studies, we then tested the effect of modulating BAP1 on BRAF targeted therapy. Exogenous expression of BAP1 sensitized BRAF inhibitor (vemurafenib)-resistant melanoma cells, while the targeted reduction of BAP1 desensitized BRAF inhibitor-sensitive melanoma cells. BRAF mutant/BAP1 loss mice failed to exhibit a marked response to vemurafenib treatment compared to control mice. These data implicate regulation of BAP1 to be a major mechanism that characterizes a highly malignant and treatment-resistant subset of tumors. Our study indicates that nongenomic reduction in BAP1 through ZEB1 transcriptional modulation may be a key factor in aggressive CM. This abstract is also being presented as Poster A30. Citation Format: Haifeng Zhu, Junna Oba, Xiaoxing Yu, Caitlin A. Creasy, Marie-Andrée Forget, Fernando Carapeto, Cara L. Haymaker, Chang-Jiun Wu, Tatiana V. Karpinets, Wei-Lien Wang, Michael T. Tetzlaff, Alexander J. Lazar, Gordon B. Mills, Amanda R. Moore, Yu Chen, Jianhua Zhang, Jeffrey E. Gershenwald, Jennifer A. Wargo, Chantale Bernatchez, Patrick Hwu, P. Andrew Futreal, Scott E. Woodman. Nongenomic BAP1 aberrancy drives highly aggressive cutaneous melanoma phenotype [abstract]. In: Proceedings of the AACR Special Conference on Melanoma: From Biology to Target; 2019 Jan 15-18; Houston, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(19 Suppl):Abstract nr PR03.

MicroRNA-211 Modulates the DUSP6-ERK5 Signaling Axis to Promote BRAFV600E-Driven Melanoma Growth In Vivo and BRAF/MEK Inhibitor Resistance

MicroRNAs (miRs) are important posttranscriptional regulators of cell fate in both normal and disease states. miR-211 has previously been shown to be a direct regulator of metabolism in BRAFV600E-mutant melanoma cells invitro. Here, we report that miR-211 expression promotes the aggressive growth of BRAFV600E-mutant melanoma xenografts invivo. miR-211 promoted proliferation through the posttranscriptional activation of extracellular signal-regulated kinase (ERK) 5 signaling, which has recently been implicated in the resistance to BRAF and MAPK/ERK kinase inhibitors. We therefore examined whether miR-211 similarly modulated melanoma resistance to the BRAF inhibitor vemurafenib and the MAPK/ERK kinase inhibitor cobimetinib. Consistent with this model, miR-211 expression increased melanoma cell resistance to both the inhibitors, and this resistance was associated with an increased ERK5 phosphorylation. miR-211 mediates these effects by directly inhibiting the expression of DUSP6, an ERK5 pathway-specific phosphatase and now shown to be an miR-211 target gene. These results dissect the role of the miR-211-DUSP6-ERK5 axis in melanoma tumor growth and suggest a mechanism for the development of drug-resistant tumors and a target for overcoming resistance.

IBCL-386: Rituximab-Vemurafenib Combination for the Treatment of Relapsed/Refractory Hairy Cell Leukemia

Objective: The management of R/R-HCL is not standardized yet. Patients with HCL universally harbor BRAF mutations, which makes BRAF inhibitors a potential treatment approach. The efficacy and safety of the BRAF inhibitor Vemurafenib were evaluated both as a single-agent option in two phase 2 trials and also combined with Rituximab in another phase 2 trial. Patients: We have decided to present the first two consecutive patients who achieved a rapid and prolonged response, relapsing after treatment with purine analogues. The first two patients who received a combination of R-V for R/R HCL from the records of our institutional CLPD registry were reported. Interventions: Rituximab was given intravenously for a total of four injections every two weeks starting simultaneously with Vemurafenib, which was initially started with a total daily dose of 960 and decreased after 2 months up to a minimum of 240 mg/day. Main outcome measures: The efficacy of the combination treatment of R-V was assessed according to the count recovery in first 2 months and bone marrow findings at the end of 6th month. Results: The first patient was a 56-year-old male who had experienced three relapses, all treated with purine analogues. The second patient was a 33-year-old male who had a refractory disorder after administration of Cladribine. Both patients have achieved a complete count recovery in the first two months and were free of the disease regarding the bone marrow findings achieved at the end of the sixth month. Rituximab and Vemurafenib were all tolerated well with no documented infectious complications. The only dose-limiting complication reported was grade 2 maculo-papular skin rash, which could be managed with a short-term drug holiday and re-institution of Vemurafenib with a reduced dose of 240 mg per event. Conclusions: According to our experience, Rituximab and Vemurafenib combination offers a safe and possibly cost-effective therapeutic option with easily managed treatment emergent adverse events.

Abstract 4038: ABM-1310, A novel BRAF Inhibitor, combined with EGFR and MEK inhibitors, inhibits colorectal tumor growth and increases overall survival in vivo

Abstract Colorectal cancer (CRC) is a cancer that starts in the colon or the rectum, and the current treatment mainly relies on chemotherapies. For example, ERBITUX® /cetuximab is an FDA approved targetedtherapy drug to treat CRC with wild-type KRAS, the 11% low response rate limits its clinical application. BRAF inhibitors have been widely used clinically for melanoma and lung cancer, however, they have dismally low response rate at only approximately 5% of colorectal cancer patients with BRAFv600 mutation. Here, we report that ABM-1310, a novel small molecule inhibitor of BRAF (specifically inhibit BRAFv600 mutant), has shown good potency in colon cancer xenograft models, when combined with a MEK inhibitor and EGFR antibody. In the HT-29 xenograft subcutaneous model, 10 to 25mg/kg/day oral dose of ABM-1310 combined with cetuximab (0.1mg/dose, twice a week) and 3 mg/kg/day of Binimetinib (MEK inhibitor) significantly inhibited HT-29 tumor growth with TGI of 85% to 92% after 34-days treatment. As a monotherapy or combined with cetuximab alone, ABM-1310 also brought the TGI of 74% and 82% at 25mg/kg/day, which indicates ABM-1310 played a key role in tumor growth inhibition in the combinations. Beside with Binimetinib, we also tested combination of ABM-1310 with other different MEK inhibitors in this model. ABM-1310 is highly water-soluble small molecule with high cell permeability and blood brain barrier penetration. ABM-1310 shown good efficacy in melanoma A375 (luciferase labelled cells) in the subcutaneous/intracranial/intracardiac xenograft models (brain metastasis models). In the HT-29 colon intracranial model, ABM-1310 also demonstrated significant tumor inhibition effect and increased animal overall survival. Compared with vehicle or marketed BRAF inhibitor vemurafenib, the median survival time of ABM-1310 group was >90 days vs 51 days (vemurafenib) and 38 days (vehicle), respectively. In Summary, ABM-1310, as a novel small molecule BRAF inhibitor, combined with EGFR and MEK inhibitors, has shown strong anti-tumor effect in preclinical in vivo models of colon cancer with BRAFv600 mutation, especially with brain metastasis. Citation Format: Yong Hu, Chen Chen, Charles Huang, Min Xu, Youqin Chen, Xiyuan Zhao, Li Zhao. ABM-1310, A novel BRAF Inhibitor, combined with EGFR and MEK inhibitors, inhibits colorectal tumor growth and increases overall survival in vivo [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4038.

Abstract 1453: Specific detection of mutant Ras oncoproteins in cell and tissue lysates by multiplex immunoassay

Abstract Ras proteins (HRAS, KRAS, and NRAS) are small GTPases that function as molecular switches by alternating between inactive GDP-bound and active GTP-bound states. Ras-GTP activates downstream pathways, including MAPK, by binding to Raf kinase and phosphatidylinositol 3-kinase (PI3K) to promote cellular proliferation, survival, growth and differentiation. Oncogenic mutations in Ras are found in approximately 25% of human cancers. Furthermore, 90% of pancreatic cancers harbor KRAS mutations with 80% of KRAS mutations occurring at codon 12 with G12V and G12D being the most prevalent. The Ras-Raf-MEK pathway can also be activated downstream of Ras. BRAF is a well-established oncogene, with the BRAF V600E mutation being prevalent in melanoma. While targeting this BRAF oncoprotein has had therapeutic efficacy, treating cancers driven by Ras oncoproteins remains an urgent unmet clinical need. We developed a novel multiplex immunoassay capable of simultaneously detecting total Ras, RasG12V, RasG12D, phospho-MEK1 (S217/S221), phospho-BRAF (S446) and phospho-CRAF (S338) in a single well. This multiplex assay detects the H-Ras, N-Ras, and K-Ras isoforms for total Ras, RasG12D, and RasG12V. To confirm specific recognition of mutant Ras oncoproteins, this kit was able to detect the known KRAS G12V mutation found in the COR-L23 cell line and the NRAS G12D mutation found in THP-1 cell line, respectively. In addition, the response to BRAF inhibitors vemurafenib and dabrafenib was compared between MDA-MB-435S cells, which harbor the BRAF V600E mutation, and insensitive cell lines, using multiplex immunoassays. While COR-L23 and THP-1 cells were not responsive to vemurafenib and dabrafenib, MDA-MB-435S cells showed a dramatic reduction in pMEK1 and pERK, consistent with inhibition of mutant BRAF protein. We then analyzed commercially-sourced tissue lysates, using tumor and adjacent tissue from a patient with colon cancer harboring a KRAS G12D mutation. While multiplex protein analysis revealed a similar phosphorylation pattern for Raf and MEK proteins, the RasG12D oncoprotein was specifically observed in lysate from the tumor but not the adjacent tissue. Finally, exosomes were enriched from pancreatic cancer serum and tested using the Ras-Raf Oncoprotein panel. These exosomal preparations yielded detectable signal for Total Ras and phospho-BRAF. Our data demonstrate the utility of studying the effects of Ras oncoproteins by multiplex immunoassay in multiple sample types, including cell, tissue, and exosomal lysates. Citation Format: Joseph B. Hwang, Anthony Saporita, Qiang Xiao. Specific detection of mutant Ras oncoproteins in cell and tissue lysates by multiplex immunoassay [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1453.

Abstract 1935: The NEDD8 and EGFR pathways are independent therapeutic targets in colorectal cancer

Abstract Colorectal cancer (CRC) develops and progresses through an accumulation of genetic and epigenetic alterations in multiple molecular pathways. Currently, targeted therapies combined with standard chemotherapy are the first-line therapy for metastatic CRC; nevertheless, the effectiveness of these drugs is limited by primary and acquired resistance. Since pathways are highly interconnected, the development of rational combinations of targeted therapies can be exploited to circumvent resistance mechanisms. As a possible alternative pathway for CRC treatment, an attractive option is the blockade of the NEDD8-ubiquitin like protein conjugation pathway. We previously found that the NEDD8-inhibitor pevonedistat has significant in vitro and in vivo activity on a subset of CRCs. However, the in vivo response is limited to tumor stabilization rather than regression, highlighting the need for therapeutic combinations. When the optimal drug combination cannot be readily predicted, functional genetic screens represent a powerful tool for unbiased exploration. We therefore carried out a synthetic lethality screening with an shRNA library covering 200 genes associated with FDA-approved drugs. The screening was aimed at identifying shRNAs that would be depleted only in the presence of pevonedistat: such constructs were expected to target genes that could harbor synergistic effects with NEDD8 inhibition. After shRNA library transduction, CRC cell lines were grown in the absence or presence of low-dose pevonedistat; Next Generation Sequencing and bioinformatics analysis allowed comparing the transduced library repertoire with or without pevonedistat, and identifying candidate synthetic lethal genes. The screening results revealed a strong, pevonedistat-dependent depletion of constructs targeting different tyrosine kinases (i.e. EGFR, BRAF, FYN and FLT4) in specific CRC cell lines (CAR1, WIDR, LIM2099 and DIFI, respectively). Firstly, we focused on the remarkable drop-out of EGFR-targeting shRNAs in CAR1 cells, which represent a subgroup of aggressive tumors refractory to cetuximab treatment, despite the lack of currently known markers of resistance. We discovered an independent and additive effect of anti-EGFR drugs (cetuximab and lapatinib) combined with pevonedistat, which was then validated in vitro on further cell lines (HCA7 and HROC69) and in vivo on HCA7-transplanted mice. Furthermore, we considered the depletion of constructs targeting BRAF, a member of EGFR pathway, observed in WIDR BRAF-mutant cells: we found an additive effect of BRAF inhibitor vemurafenib and pevonedistat in reducing in vitro cell growth. Altogether our results suggest that the concomitant pharmacological inhibition of NEDD8 and EGFR-pathway could be a novel effective approach to treat clinically aggressive CRCs, worthy of further characterization. Citation Format: Federica Invrea, Alessandro Carugo, Consalvo Petti, Cristopher Bristow, Michael Peoples, Carlotta Cancelliere, Alessia Corrado, Alberto Bardelli, Claudio Isella, Giulio F. Draetta, Enzo Medico. The NEDD8 and EGFR pathways are independent therapeutic targets in colorectal cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1935.

Abstract 3117: Early detection of CRC Biomarker matched FFPE DNA and plasma cell-free DNA from CRC patients using a highly sensitive NGS panel

Abstract Background: Patients with later stage colorectal cancer (CRC) exhibit relatively poor prognosis, and resistance to drug treatment remains an important factor in the shorter survival rate. Particularly well known is the resistance to anti-EGFR therapy caused by the presence of mutations in the KRAS oncogene. The BRAF V600E mutation is also linked to shorter survival. Therefore, it is essential to obtain a patient's mutational profile based on a set of biomarker genes, especially in the early stages of oncogenesis. Obtaining this information is also critical for the application of companion diagnostics, where the effective use of a drug is analyzed for each patient. BioChain Institute, Inc. is currently screening formalin-fixed paraffin-embedded (FFPE) tissue along with the same donor's plasma for the ability to detect hotspot mutations in a panel of CRC-related biomarker genes. Methods: FFPE tissues from five donors exhibiting various stages of colorectal cancer were provided by BioChain. These tissues consist of primary tumor and adjacent normal for comparison purposes. For each donor, matched plasma samples were also procured. FFPE DNA was extracted from the tissues using BioChain's AnaPrep FFPE DNA Extraction kit and cell-free DNA (cfDNA) was isolated from plasma using BioChain's cfPure V2 Cell Free DNA Extraction kit. Both the FFPE DNA and cfDNA were then analyzed using Diacarta's XNA-Based OptiSeq™ Lung and Colorectal Cancer Panel. This assay provides high sensitivity for the detection of 17 hotspots in 7 genes (APC, BRAF, CTNNB1, EGFR, KRAS, NRAS, and PIK3CA) that are frequently mutated in colorectal cancer. Results: Using the aforementioned cancer panel, we detected hotspot mutations in not only the FFPE DNA isolated from cancer tissues but in the plasma-derived cfDNA as well. Among the detected hotspots are the frequently mutated G12 in the KRAS oncogene. Interestingly, the BRAF V600E mutation was also detected in the cfDNA of all five selected donors, demonstrating the utility of liquid biopsy as both diagnostic and prognostic tools in oncogenesis. Conclusions: BioChain has demonstrated the ability to detect hotspot mutations in patients of colorectal cancer not only in the tissue sample but also in the same donor's circulating cfDNA. The detection of mutants such as BRAF V600E in plasma samples highlights the application of liquid biopsy in early diagnosis of cancer and provides the basis for the application of companion diagnostics to personalize drug treatment for each unique patient profile. For example, the detection of the BRAF V600E mutation may lead to a prescription of the BRAF inhibitor vemurafenib. By providing access to a plethora of tissue types, such as colon, along with proprietary kits that deliver the highest quality cfDNA samples possible, BioChain will be able to provide researchers with powerful tools that facilitate applications of liquid biopsy along with companion diagnostics and promote biomarker discovery. Citation Format: Franklin Chin, Vidyodhaya Sundaram, Vinh Q. Lam, Dong Liu. Early detection of CRC Biomarker matched FFPE DNA and plasma cell-free DNA from CRC patients using a highly sensitive NGS panel [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3117.

Abstract 1794: Loss of Spry1 reduces growth of BRAFV600-mutant cutaneous melanoma and improves response to targeted therapy

Abstract Introduction: Targeted therapies have recently revolutionized the treatment of BRAFV600-mutant metastatic cutaneous melanoma (CM). However, most patients do not achieve tumor regression at all due to the occurrence of resistance mechanisms. Mitogen-activated protein kinase (MAPK) pathway activation is a central step in BRAFV600-mutant CM pathogenesis and a better understanding of molecular mechanisms involved MAPK modulation is necessary to develop more effective therapeutic strategies. In the last years, Spry1 has been frequently described as an upstream regulator of MAPK signaling pathway, but its specific role in BRAFV600-mutant CM is still poorly defined. Materials and methods: Autologous BRAFV600-mutant CM cell cultures were generated from CM patients resected in our institution. The expression of Spry1 was evaluated by quantitative real-time PCR (qRT-PCR) and Western blot (WB) analyses. Spry1 gene was knock out using CRISPR. RNA-seq identified mRNAs commonly differentially expressed in Spry1 knock-out (Spry1KO) clones, and their expression was further validated by qRT-PCR. WB analyses evaluated the modulation of MAPK signaling pathways in Spry1KO clones. Cell proliferation was measured using xCELLigence instrument, whereas cell cycle progression, ROS induction, and apoptosis were assessed by flow cytometry. In vivo effects of Spry1 silencing were investigated in xenograft mice treated with or without BRAF inhibitor (BRAFi). Results: The expression of Spry1 in human CM was explored using publicly available cancer gene expression profiling and transcriptome sequencing data. mRNA expression of Spry1 was significantly elevated in metastatic CM respect to primary tumors and mRNA levels of Spry1 were significantly up-regulated in metastatic CM compared with primary lesions. The function of Spry1 was evaluated by comparing three BRAFV600-mutant CM cell lines and the respective Spry1KO cells. We found that Spry1KO induced cell cycle arrest and apoptosis, repressed cell proliferation in vitro, and impaired tumor growth in vivo. Moreover Spry1KO was found to impair the expression of several markers of epithelial-mesenchimal transition. In addition, ERK1/2 was found hyperactivated together with p38 leading to an increase in basal ROS levels in Spry1KO clones. This suggests that BRAFV600-mutant CM may restrain the activity of Spry1 to avoid oncogenic stress and to enable tumor growth. Indeed, treatment with the BRAFi vemurafenib down-regulated Spry1 levels in parental CM cell lines, indicating that Spry1 expression is sustained by MAPK/ERK signaling pathway in a positive feedback loop that safeguards cells from the potentially toxic effects of ERK1/2 hyperactivation. Disruption of this feedback loop rendered Spry1KO cells more susceptible to apoptosis and markedly improved response to BRAFi both in vitro and in vivo, as a consequence of the detrimental effect of ERK1/2 hyperactivation observed upon Spry1 abrogation. Conclusions: All together, our data strongly suggest that targeting Spry1 might offer a treatment strategy for BRAFV600-mutant CM by inducing the toxic effects of ERK-mediated signaling. Citation Format: Barbara Montico, Francesca Colizzi, Giorgio Giurato, Aurora Rizzo, Annamaria Salvati, Lorena Baboci, Dania Benedetti, Eliana Pivetta, Alessia Covre, Michele Dal Bo, Alessandro Weisz, Agostino Steffan, Michele Maio, Luca Sigalotti, Elisabetta Fratta. Loss of Spry1 reduces growth of BRAFV600-mutant cutaneous melanoma and improves response to targeted therapy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1794.

BRAF Inhibitors: Molecular Targeting and Immunomodulatory Actions.

The BRAF inhibitors vemurafenib, dabrafenib and encorafenib are used in the treatment of patients with BRAF-mutant melanoma. They selectively target BRAF kinase and thus interfere with the mitogen-activated protein kinase (MAPK) signalling pathway that regulates the proliferation and survival of melanoma cells. In addition to their molecularly targeted activity, BRAF inhibitors have immunomodulatory effects. The MAPK pathway is involved in T-cell receptor signalling, and interference in the pathway by BRAF inhibitors has beneficial effects on the tumour microenvironment and anti-tumour immune response in BRAF-mutant melanoma, including increased immune-stimulatory cytokine levels, decreased immunosuppressive cytokine levels, enhanced melanoma differentiation antigen expression and presentation of tumour antigens by HLA 1, and increased intra-tumoral T-cell infiltration and activity. These effects promote recognition of the tumour by the immune system and enhance anti-tumour T-cell responses. Combining BRAF inhibitors with MEK inhibitors provides more complete blockade of the MAPK pathway. The immunomodulatory effects of BRAF inhibition alone or in combination with MEK inhibition provide a rationale for combining these targeted therapies with immune checkpoint inhibitors. Available data support the synergy between these treatment approaches, indicating such combinations provide an additional beneficial effect on the tumour microenvironment and immune response in BRAF-mutant melanoma.

Oncology Nurse Coordinators in Clinical Trials – Shaking up the Melanoma Team

In recent years, melanoma research has undergone a renaissance. The disease that was once viewed, at least in a metastatic setting, as intractable and untreatable is now revealing its molecular “weaknesses.” The year 2011 was a landmark year for melanoma therapy, with the introduction of two new agents – the anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) antibody ipilimumab and the BRAF (V-raf murine sarcoma viral oncogene homolog B1) inhibitor vemurafenib. These two agents were shown to confer a survival benefit, which was followed by the approval by the Food and Drug Administration (FDA). In 2014, other immune checkpoint inhibitors, such as pembrolizumab and nivolumab, were approved for the treatment of metastatic melanoma. By 2019, the FDA had also approved pembrolizumab as adjuvant therapy. Target therapy and immunotherapy are now the standard of care for melanoma patients. Clinical trials are currently ongoing for new neoadjuvant therapies. Rapidly evolving knowledge will perhaps downgrade melanoma to the level of a chronic, manageable disease from the intractable “black cancer,” it was in the past and a disease that struck fear into the hearts of those who were diagnosed. Changes in immunotherapy treatments were followed by a large volume of clinical trials. This situation has resulted in the need for changes in the roles of existing melanoma multidisciplinary team members, including the clinical trials nurse (CTN). The role of the CTN is not suitable for these new conditions. A new role and tasks need to be established, evolving the CTN into an oncology nurse coordinator (ONC). In this article, we have described the role and responsibilities of an ONC and the changes that have taken place within the multidisciplinary melanoma team.

Vemurafenib-related photosensitivity.

Increased photosensitivity is a common cutaneous adverse effect associated with the BRAF inhibitor vemurafenib. Clinically, it presents as an immediate sensation of heat and edematous erythema during sun exposure, as well as a sunburn reaction in terms of a late reaction. Phototesting has shown that the UVA range (320nm to 400 nm), triggers both the immediate and the late reaction. In terms of pathogenesis, photochemical studies have suggested that exposure of vemurafenib to UVA radiation produces an UVA-absorbing photoproduct. In vitro studies on various cell models have also demonstrated that the phototoxic effects of vemurafenib are exclusively caused by UVA irradiation. This latter mechanism is probably responsible for the photosensitivity clinically observed in patients receiving vemurafenib. In addition, vemurafenib is able to inhibit ferrochelatase. The resulting increase in protoporphyrinIX has also been observed in some human studies involving the drug. However, it is yet unproven whether porphyrins actually contribute to the immediate skin reactions seen in individuals on vemurafenib, even though the clinical presentation is similar to that found in erythropoietic protoporphyria with a comparable pathomechanism. Other BRAF inhibitors, such as dabrafenib and encorafenib, are associated with significantly lower photosensitivity. It is essential that patients treated with vemurafenib are informed about immediate and delayed reactions potentially caused even by low doses of UVA. This includes counseling on photoprotective measures.

Induced sarcoid-like reactions in patients with metastatic melanoma treated with dabrafenib and trametinib: a monocentric retrospective study.

Combined BRAF and MEK inhibition is one of the first-line treatment strategies for patients with advanced BRAF-mutant melanoma. Sarcoid-like reactions (SLRs) have occasionally been described with melanoma systemic treatments such as immunotherapy or the BRAF inhibitor vemurafenib, but very few cases have been reported with dabrafenib and trametinib. Our aim was to better characterize SLR induced by this combination. We conducted a monocentric retrospective observational study among patients treated with dabrafenib and trametinib for BRAF-mutant advanced melanoma from January 2015 to March 2019. Patients presenting with histologically proven SLR were included. We also searched Medline database for all reported cases of SLR induced by targeted therapy. Of 63 patients on dabrafenib/trametinib combination, seven were diagnosed with a SLR. They all had specific cutaneous involvement, and one also displayed mediastinal and salivary glands involvement. None required systemic corticosteroids or dabrafenib/trametinib discontinuation. Three of them (43%) reached melanoma complete remission and are still on targeted therapy; and four patients progressed and died. A literature review yielded 22 additional cases of SLR induced by targeted therapy: the main affected organ was the skin, 11 patients (50%) had systemic involvement, five patients (23%) required systemic corticosteroids to reach partial or complete remission of SLR, 12 (55%) reached partial or complete response of melanoma while six (27%) progressed. BRAF and MEK inhibitors are potential triggers of SLR, although pathological mechanisms remain unclear. The mainstay of treatment is systemic or topical corticotherapy; targeted therapy discontinuation is usually not necessary.

Long-term outcome of 117 patients with Erdheim-Chester disease and mixed histiocytosis receiving targeted therapies (BRAF and MEK inhibitors): A monocentric experience.

7560 Background: Erdheim–Chester disease (ECD), an inflammatory myeloid neoplasm from the L group, is an histiocytosis associated with multisystem infiltration. Around 1500 cases have been reported worldwide since 1930. In 15% of cases, ECD is associated with another histiocytosis corresponding to mixed histiocytosis. Before 2004, 60% of patients died within 3 years after diagnosis. The targetable BRAFV600Emutation is present in as much as 70% of all ECD cases. Targeted therapies (BRAF inhibitors in April 2012, followed by MEK inhibitors after 2015) have revolutionized the therapeutic options and prognosis of refractory ECD and mixed histiocytosis. Methods: This retrospective study was conducted between April 2012 and December 2019 on 117 ECD patients who received targeted therapies in the French National Referral Center for Histiocytosis at Pitié-Salpêtrière Hospital in Paris, France. 28 patients (pts) (24%) had a mixed histiocytosis. Results: 43 (36.7%) pts were female and 95/116 exploitable pts (81.9%) had a BRAF V600E mutation. 12 (10.3%) pts had a co-ocurring hemopathy (myeloproliferative neoplasm or myelodysplastic syndrom). Age at diagnosis was 57.2 yr (+/- 13.8). The main sites of involvement were: vascular (“coated aorta”) in 85 pts (73%), heart in 83 pts (71%), xanthelasma in 30 pts (26%), central nervous system in 56 pts (48%) and peri-renal (“hairy kidney”) in 84 pts (72%). 34 pts (29%) had previously received corticosteroids, and 63 pts (54%) interferon alpha regimen (mainly PEG interferon). 86 (74%) pts received the BRAF inhibitor vemurafenib, and 42 (36%) pts the MEK inhibitor cobimetinib (some patients receiving both). 25 pts died during follow-up. The median survival of patients with targeted therapies in december 2019 was undefined, whereas the patients with no targeted therapies had a median survival of 133 months (HR 0.64 (0.42-0.99); p = 0.04). Among the 117 pts, only 2 had a progression of VAF of mutations within genes frequently mutated in myeloid neoplasms. The most serious adverse events were cutaneous (squamous cell carcinoma, basocellular carcinoma, DRESS) and acute pancreatitis with BRAF inhibitors, whereas chorioretinitis and left ventricular dysfunction were seen with MEK inhibitors. None of the patients receiving targeted therapies progressed. Conclusions: Targeted therapies (BRAF and/or MEK inhibitors) were found dramatically efficacious in 117 patients with severe and refractory ECD and mixed histiocytosis, improving survival of patients.

Loss of Spry1 reduces growth of BRAFV600-mutant cutaneous melanoma and improves response to targeted therapy

Mitogen-activated protein kinase (MAPK) pathway activation is a central step in BRAFV600-mutant cutaneous melanoma (CM) pathogenesis. In the last years, Spry1 has been frequently described as an upstream regulator of MAPK signaling pathway. However, its specific role in BRAFV600-mutant CM is still poorly defined. Here, we report that Spry1 knockdown (Spry1KO) in three BRAFV600-mutant CM cell lines markedly induced cell cycle arrest and apoptosis, repressed cell proliferation in vitro, and impaired tumor growth in vivo. Furthermore, our findings indicated that Spry1KO reduced the expression of several markers of epithelial–mesenchymal transition, such as MMP-2 both in vitro and in vivo. These effects were associated with a sustained and deleterious phosphorylation of ERK1/2. In addition, p38 activation along with an increase in basal ROS levels were found in Spry1KO clones compared to parental CM cell lines, suggesting that BRAFV600-mutant CM may restrain the activity of Spry1 to avoid oncogenic stress and to enable tumor growth. Consistent with this hypothesis, treatment with the BRAF inhibitor (BRAFi) vemurafenib down-regulated Spry1 levels in parental CM cell lines, indicating that Spry1 expression is sustained by the MAPK/ERK signaling pathway in a positive feedback loop that safeguards cells from the potentially toxic effects of ERK1/2 hyperactivation. Disruption of this feedback loop rendered Spry1KO cells more susceptible to apoptosis and markedly improved response to BRAFi both in vitro and in vivo, as a consequence of the detrimental effect of ERK1/2 hyperactivation observed upon Spry1 abrogation. Therefore, targeting Spry1 might offer a treatment strategy for BRAFV600-mutant CM by inducing the toxic effects of ERK-mediated signaling.

Abstract B45: Surveillance of RAS-RAF dynamics in vivo: Tracking activity conformations and drug-induced interactions

Abstract Live-cell recordings of protein conformations and interactions yield novel mechanistic insights into physiologic and pathologic protein functions. We have developed an adaptable and genetically encoded bioluminescence-based biosensor platform to precisely measure signaling dynamics of full-length RAS GTPases and RAF kinases upon physiologic pathway activation, post-translational modifications, mutagenesis, and drug binding. We have recorded the impact of both patient mutations and bioactive small-molecule binding on kinase conformations and binary interactions of GTP-loaded H, N, KRAS with kinases such as RAF. Systematic profiling of αC-helix-OUT BRAF inhibitors (BRAFi) vemurafenib, dabrafenib, encorafenib, and PLX8394 using the BRAF reporter reporter platform (displaying 10 different patient mutations) revealed differences in drug specificities and efficacies. Unexpectedly, the αC-helix-OUT BRAFi engagement with the catalytic pocket of mutated BRAF stabilized an inactive and intermediate full-length kinase conformation, which provoked the enhancement of binary RAS:RAF interactions. We showed that the interference with RAS interactions and nanoclustering has the potential to antagonize the sequential formation of drug-induced tetrameric RAS:RAF complexes. Recently, we have bioengineered a reporter toolbox for direct in vivo recordings of RAS activity conformations. First, we demonstrated that the wild-type RAS reporter—expressed at levels far below endogenous RAS proteins—responds to physiologic pathway activation. Second, we showed that hot-spot RAS mutations display a similar effect on the intramolecular dynamics. The systematic implementation, combination, and advancement of the GTPase and kinase reporter platform have the potential to be used to identify novel means for regulating or perturbing RAS-RAF-ERK signaling in vivo. Citation Format: Ruth Röck, Johanna Mayrhofer, Omar Torres-Quesada, Florian Enzler, Jakob Troppmair, Eduard Stefan. Surveillance of RAS-RAF dynamics in vivo: Tracking activity conformations and drug-induced interactions [abstract]. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr B45.

Pan-Cancer Efficacy of Vemurafenib in BRAF V600-Mutant Non-Melanoma Cancers.

BRAF V600 mutations occur in a wide range of tumor types, and RAF inhibition has become standard in several of these cancers. Despite this progress, BRAF V600 mutations have historically been considered a clear demonstration of tumor lineage context-dependent oncogene addiction, based predominantly on the insensitivity to RAF inhibition in colorectal cancer. However, the true broader activity of RAF inhibition pan-cancer remains incompletely understood. To address this, we conducted a multicohort "basket" study of the BRAF inhibitor vemurafenib in non-melanoma BRAF V600 mutation-positive solid tumors. In total, 172 patients with 26 unique cancer types were treated, achieving an overall response rate of 33% and median duration of response of 13 months. Responses were observed in 13 unique cancer types, including historically treatment-refractory tumor types such as cholangiocarcinoma, sarcoma, glioma, neuroendocrine carcinoma, and salivary gland carcinomas. Collectively, these data demonstrate that single-agent BRAF inhibition has broader clinical activity than previously recognized. SIGNIFICANCE: These data suggest that BRAF V600 mutations lead to oncogene addiction and are clinically actionable in a broad range of non-melanoma cancers, including tumor types in which RAF inhibition is not currently considered standard of care.See related commentary by Ribas and Lo, p. 640.This article is highlighted in the In This Issue feature, p. 627.

Trying for a BRAF Slam Dunk.

The first basket clinical trial testing the BRAF inhibitor vemurafenib resulted in evidence of activity in 13 unique cancer types with BRAF V600 mutations, but the response rates were variable. Therefore, different cancer histologies with the same driver oncogene display different degrees of oncogenic pathway addiction.See related article by Subbiah et al., p. 657.

Inducing mortality by targeting mortalin

Cancer Oncogenic mutations in the kinase BRAF can enhance cell survival, even in cells exposed to targeted inhibitors. Wu et al. found that a heat shock protein family A (HSP70)–related chaperone protein called mortalin disrupted a protein-protein interaction that would ordinarily trigger cell death in BRAF mutant cells. Depleting mortalin or treating cells with either HSP70 derivatives or synthetic decoy peptides that mimic mortalin target sites increased the efficacy of the BRAF inhibitor vemurafenib in cells and in tumor-bearing mice. Sci. Signal. 13 , eaay1478 (2020).