Inhibition of BRAF and BRAF+MEK drives a metastatic switch in melanoma.

Recent analyses by our group and others showed that the majority of melanoma patients who fail BRAF inhibitor therapy do so at new disease sites. Using phosphoproteomics we showed that BRAF inhibition mediates a switch to an aggressive/metastatic melanoma phenotype that is driven by ligand-independent erythropoietin-producing hepatocellular receptor A2 (EphA2) signaling.

A rare case of leptomeningeal carcinomatosis in a patient with uveal melanoma: case report and review of literature.

Uveal melanoma is a rare subtype of melanoma, accounting for only 3-5% of all melanoma cases in the USA. Although fewer than 4% of uveal melanoma patients present with metastasis at diagnosis, approximately half will develop metastasis, more than 90% of which disseminate to the liver. Infrequently, a number of malignancies can lead to leptomeningeal metastases, a devastating and terminal complication.

Managing leptomeningeal melanoma metastases in the era of immune and targeted therapy.

Melanoma frequently metastasizes to the brain, with CNS involvement being clinically evident in ∼30% of patients (as high as 75% at autopsy). In ∼5% cases melanoma cells also metastasize to the leptomeninges, the sub-arachnoid space and cerebrospinal fluid (CSF). Patients with leptomeningeal melanoma metastases (LMM) have the worst prognosis and are characterized by rapid disease progression (mean survival 8-10 weeks) and a death from neurological causes.

BRAF Inhibition Generates a Host-Tumor Niche that Mediates Therapeutic Escape.

The current study defines a fibroblast-derived niche that facilitates the therapeutic escape of melanoma cells from BRAF inhibition. Vemurafenib treatment led to the release of transforming growth factor-β (TGF-β) from the melanoma cells that increased the differentiation state of the fibroblasts, an affect associated with fibronectin deposition, increase in α-smooth muscle actin expression, and the release of neuregulin (NRG). At the same time, vemurafenib directly activated the fibroblasts through paradoxical stimulation of the mitogen-activated protein kinase pathway, causing them to secrete hepatocyte growth factor (HGF).

Ligand-independent EPHA2 signaling drives the adoption of a targeted therapy-mediated metastatic melanoma phenotype.

Unlabelled: Many patients with BRAF inhibitor resistance can develop disease at new sites, suggesting that drug-induced selection pressure drives metastasis. Here, we used mass spectrometry-based phosphoproteomic screening to uncover ligand-independent EPHA2 signaling as an adaptation to BRAF inhibitor therapy that led to the adoption of a metastatic phenotype. The EPHA2-mediated invasion was AKT-dependent and readily reversible upon removal of the drug as well as through PI3K and AKT inhibition.

Phosphoproteomic analysis of basal and therapy-induced adaptive signaling networks in BRAF and NRAS mutant melanoma.

Basal and kinase inhibitor driven adaptive signaling has been examined in a panel of melanoma cell lines using phosphoproteomics in conjunction with pathway analysis. A considerable divergence in the spectrum of tyrosine-phosphorylated peptides was noted at the cell line level. The unification of genotype-specific cell line data revealed the enrichment for the tyrosine-phosphorylated cytoskeletal proteins to be associated with the presence of a BRAF mutation and oncogenic NRAS to be associated with increased receptor tyrosine kinase phosphorylation.

Amuvatinib has cytotoxic effects against NRAS-mutant melanoma but not BRAF-mutant melanoma.

Effective targeted therapy strategies are still lacking for the 15-20% of melanoma patients whose melanomas are driven by oncogenic NRAS. Here, we report on the NRAS-specific behavior of amuvatinib, a kinase inhibitor with activity against c-KIT, Axl, PDGFRα, and Rad51. An analysis of BRAF-mutant and NRAS-mutant melanoma cell lines showed the NRAS-mutant cohort to be enriched for targets of amuvatinib, including Axl, c-KIT, and the Axl ligand Gas6.

Evaluating melanoma drug response and therapeutic escape with quantitative proteomics.

The evolution of cancer therapy into complex regimens with multiple drugs requires novel approaches for the development and evaluation of companion biomarkers. Liquid chromatography-multiple reaction monitoring mass spectrometry (LC-MRM) is a versatile platform for biomarker measurement. In this study, we describe the development and use of the LC-MRM platform to study the adaptive signaling responses of melanoma cells to inhibitors of HSP90 (XL888) and MEK (AZD6244).

Inhibition of autophagy enhances the effects of the AKT inhibitor MK-2206 when combined with paclitaxel and carboplatin in BRAF wild-type melanoma.

This study investigates the mechanism of action behind the long-term responses (12-16 months) of two BRAF WT melanoma patients to the AKT inhibitor MK-2206 in combination with paclitaxel and carboplatin. Although single agent MK-2206 inhibited phospho-AKT signaling, it did not impact in vitro melanoma growth or survival. The combination of MK-2206 with paclitaxel and carboplatin was cytotoxic in long-term colony formation and 3D spheroid assays, and induced autophagy.

Long-term effects of BRAF inhibitors in melanoma treatment: friend or foe?

The clinical development of selective BRAF inhibitors for metastatic BRAF V600 mutant melanoma patients has been a major breakthrough in targeted therapeutics. Objective response rates of approximately 50% have been observed in the Phase III studies of the BRAF inhibitors vemurafenib and dabrafenib. The side effects can be relatively common, including proliferative skin toxicities.

Senescent fibroblasts in melanoma initiation and progression: an integrated theoretical, experimental, and clinical approach.

We present an integrated study to understand the key role of senescent fibroblasts in driving melanoma progression. Based on the hybrid cellular automata paradigm, we developed an in silico model of normal skin. The model focuses on key cellular and microenvironmental variables that regulate interactions among keratinocytes, melanocytes, and fibroblasts, key components of the skin.

Melanoma genotypes and phenotypes get personal.

Traditionally, the diagnosis of metastatic melanoma was terminal to most patients. However, the advancements towards understanding the fundamental etiology, pathophysiology, and treatment have raised melanoma to the forefront of contemporary medicine. Indeed, the evidence of durable remissions are being heard ever more frequently in clinics around the globe.

Paradoxical oncogenesis--the long-term effects of BRAF inhibition in melanoma.

The clinical benefits of BRAF inhibition in patients with advanced-stage BRAF-mutant melanoma are now well established. Although the emergence of cutaneous squamous-cell carcinomas (SCCs) and secondary melanomas in patients on BRAF-inhibitor therapy have been well described, reports are emerging of additional secondary premalignant and malignant events, including RAS-mutant leukaemia, the metastatic recurrence of RAS-mutant colorectal cancer and the development of gastric and colonic polyps. In most cases, paradoxical MAPK activation--resulting from the BRAF-inhibitor-mediated homodimerization and heterodimerization of nonmutant RAF isoforms--seems to underlie the development of these secondary tumours.

Acquired and intrinsic BRAF inhibitor resistance in BRAF V600E mutant melanoma.

The discovery of activating BRAF V600E mutations in 50% of all cutaneous melanomas has revolutionized the understanding of melanoma biology and provided new strategies for the therapeutic management of this deadly disease. Highly potent small molecule inhibitors of BRAF are now showing great promise as a novel therapeutic strategy for melanomas harboring activating BRAF V600E mutations and are associated with high levels of response. This commentary article discusses the latest data on the role of mutated BRAF in the development and progression of melanoma as the basis for understanding the mechanism of action of BRAF inhibitors in the preclinical and clinical settings.

PTEN loss confers BRAF inhibitor resistance to melanoma cells through the suppression of BIM expression.

This study addresses the role of PTEN loss in intrinsic resistance to the BRAF inhibitor PLX4720. Immunohistochemical staining of a tissue array covering all stages of melanocytic neoplasia (n = 192) revealed PTEN expression to be lost in >10% of all melanoma cases. Although PTEN expression status did not predict for sensitivity to the growth inhibitory effects of PLX4720, it was predictive for apoptosis, with only limited cell death observed in melanomas lacking PTEN expression (PTEN-).

Enhanced imaging and accelerated photothermalysis of A549 human lung cancer cells by gold nanospheres.

Background & Aims: Gold nanoparticles are excellent photon-thermal energy converters. The purpose of this work was to investigate the influence of gold nanoparticles on the photothermalysis of A549 lung tumor cells.

Materials & Methods: A549 lung tumor cells were exposed to goat antihuman immunoglobulin (Ig)G-conjugated gold nanospheres (40 nm) and were then imaged under a dark-field microscope.