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Aged melanoma patients (>65 years old) have more aggressive disease relative to young patients (5-fold levels of insulin-like growth factor binding protein 2 (IGFBP2) in the aged fibroblast secretome. IGFBP2 functionally triggers upregulation of the PI3K-dependent fatty acid biosynthesis program in melanoma cells through increases in FASN. Melanoma cells co-cultured with aged dermal fibroblasts have higher levels of lipids relative to young dermal fibroblasts, which can be lowered by silencing IGFBP2 expression in fibroblasts, prior to treating with conditioned media. Conversely, ectopically treating melanoma cells with recombinant IGFBP2 in the presence of conditioned media from young fibroblasts, promoted lipid synthesis and accumulation in the melanoma cells. Neutralizing IGFBP2in vitroreduces migration and invasion in melanoma cells, and invivostudies demonstrate that neutralizing IGFBP2 in syngeneic aged mice, ablates tumor growth as well as metastasis. Conversely, ectopic treatment of young mice with IGFBP2 in young mice increases tumor growth and metastasis. Our data reveal that aged dermal fibroblasts increase melanoma cell aggressiveness through increased secretion of IGFBP2, stressing the importance of considering age when designing studies and treatment.SignificanceThe aged microenvironment drives metastasis in melanoma cells. This study reports that IGFBP2 secretion by aged fibroblasts induces FASN in melanoma cells and drives metastasis. Neutralizing IGFBP2 decreases melanoma tumor growth and metastasis.

Resistance to combination BRAF/MEK inhibitor (BRAFi/MEKi) therapy arises in nearly every patient withBRAFV600E/Kmelanoma, despite promising initial responses. Achieving cures in this expanding BRAFi/MEKi-resistant cohort represents one of the greatest challenges to the field; few experience additional durable benefit from immunotherapy and no alternative therapies exist. To better personalize therapy in cancer patients to address therapy relapse, umbrella trials have been initiated whereby genomic sequencing of a panel of potentially actionable targets guide therapy selection for patients; however, the superior efficacy of such approaches remains to be seen. We here test the robustness of the umbrella trial rationale by analyzing relationships between genomic status of a gene and the downstream consequences at the protein level of related pathway, which find poor relationships between mutations, copy number amplification, and protein level. To profile candidate therapeutic strategies that may offer clinical benefit in the context of acquired BRAFi/MEKi resistance, we established a repository ofpatient-derivedxenograft models from heavily pretreated patients with resistance to BRAFi/MEKi and/or immunotherapy (R-PDX). With these R-PDXs, we executedin vivocompound repurposing screens using 11 FDA-approved agents from an NCI-portfolio with pan-RTK, non-RTK and/or PI3K-mTOR specificity. We identify dasatinib as capable of restoring BRAFi/MEKi antitumor efficacy in ∼70% of R-PDX tested. A systems-biology analysis indicates elevated baseline protein expression of canonical drivers of therapy resistance (e.g., AXL, YAP, HSP70, phospho-AKT) as predictive of MAPKi/dasatinib sensitivity. We therefore propose that dasatinib-based MAPKi therapy may restore antitumor efficacy in patients that have relapsed to standard-of-care therapy by broadly targeting proteins critical in melanoma therapy escape. Further, we submit that this experimental PDX paradigm could potentially improve preclinical evaluation of therapeutic modalities and augment our ability to identify biomarker-defined patient subsets that may respond to a given clinical trial.SINGLE SENTENCE SUMMARYBroad target inhibition effective as a salvage strategy in BRAF/MEK inhibitor-acquired resistance PDX

Last October, within the 2021 SMR congress, we held the inaugural Diversity in Science Session. The goal of the session was to discuss diversity, equity, and inclusion in the melanoma research community and strategies to promote the advancement of underrepresented melanoma researchers. An international survey was conducted to assess the diversity, equity, and inclusion (DEI) climate among researchers and clinicians within the Society for Melanoma Research (SMR). The findings suggest there are feelings and experiences of inequity, bias, and harassment within the melanoma community that correlate with one’s gender, ethnic/racial group, and/or geographic location. Notably, significant reports of inequity in opportunity, discrimination, and sexual harassment demonstrate there is much work remaining to ensure all scientists in our community experience an academic workplace culture built on mutual respect, fair access, inclusion, and equitable opportunity.

The loss of the intercellular adhesion molecule E-cadherin is a hallmark of the epithelial-mesenchymal transition (EMT), which promotes a transition of cancer cells to a migratory and invasive phenotype. E-cadherin is associated with a decrease in cell proliferation in normal cells. Here, using physiologically relevant 3D in vitro models, we find that E-cadherin induces hyper-proliferation in breast cancer cells through activation of the Raf/MEK/ERK signaling pathway. These results were validated and consistent across multiple in vivo models of primary tumor growth and metastatic outgrowth. E-cadherin expression dramatically increases tumor growth and, without affecting the ability of cells to extravasate and colonize the lung, significantly increases macrometastasis formation via cell proliferation at the distant site. Pharmacological inhibition of MEK1/2, blocking phosphorylation of ERK in E-cadherin-expressing cells, significantly depresses both tumor growth and macrometastasis. This work suggests a novel role of E-cadherin in tumor progression and identifies a potential new target to treat hyper-proliferative breast tumors. SUMMARY E-cadherin, an extensively studied transmembrane molecule ubiquitously expressed in normal epithelial tissues, promotes and maintains intercellular adhesion. In cancer, the loss of adhesion molecule E-cadherin is associated with onset of invasion via epithelial-to-mesenchymal transition (EMT) process.1 EMT consists of a highly orchestrated cascade of molecular events where epithelial cells switch from a non-motile phenotype to an invasive, migratory phenotype accompanied by a change in cell morphology.1,2 These processes are believed to then trigger metastasis in carcinomas (cancers of epithelial origin). Moreover, the expression of intercellular adhesion molecule E-cadherin (E-cad) is associated with a decrease in cell proliferation in normal cells. Classical experiments in fibroblasts and epithelial cells show that the expression of E-cad not only promotes cell-cell adhesion, but also reduces cell proliferation and onset of apoptosis.3,4 Altogether these results have long supported that E-cad acts as a tumor suppressor gene.1,2 However, despite its role in cell-adhesion the requirement for loss of E-cad in metastasis has recently been re-assessed.5,6,7,8 These investigations focus on E-cad’s role in EMT, even though the relationship between E-cad and proliferation is just as intriguing. While E-cad has been shown to have anit-proliferative effects in normal cells, E-cad also helps maintain a pluripotent and proliferative phenotype in stem cells, and notably is lost during differentiation, a non-proliferative step of stem cell progression.9,10 Yet, despite potentially important implications in our understanding of tumor progression, whether E-cad expression affects growth in cancer cells remains mostly unexplored. Here, utilizing a physiologically relevant 3D in vitro model and multiple in vivo models, we studied the impact of E-cad on cell proliferation at the primary tumor site and proliferation at a secondary site. Remarkably, E-cad upregulates multiple proliferation pathways, including hyper-activation of the ERK cascade within the greater MAPKinase pathway, resulting in a dramatic increase in cell proliferation in vitro and tumor growth in vivo. When the phosphorylation of ERK is blocked utilizing a MEK1/2 inhibitor, PD032590111, this effect is reversed in vitro and in vivo. Thus, E-cad plays an oncogenic role in tumorigenesis and merits evaluation as a potential new drug target.

Melanoma is a highly plastic tumor characterized by dynamic interconversion of different cell identities depending on the biological context. For example, melanoma cells with high expression of the H3K4 demethylase KDM5B (JARID1B) rest in a slow-cycling, yet reversible persister state. Over time, KDM5Bhigh cells can promote rapid tumor repopulation with equilibrated KDM5B expression heterogeneity. The cellular identity of KDM5Bhigh persister cells has not been studied so far, missing an important cell state-directed treatment opportunity in melanoma. Here, we have established a doxycycline-titratable system for genetic induction of permanent intratumor expression of KDM5B and screened for chemical agents that phenocopy this effect. Transcriptional profiling and cell functional assays confirmed that the dihydropyridine phenoxyethyl 4-(2-fluorophenyl)-2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-hexa-hydro-quinoline-3-carboxylate (termed Cpd1) supports high KDM5B expression and directs melanoma cells towards differentiation along the melanocytic lineage and to cell cycle-arrest. The high KDM5B state additionally prevents cell proliferation through negative regulation of cytokinetic abscission. Moreover, treatment with Cpd1 promoted the expression of the melanocyte-specific tyrosinase gene specifically sensitizing melanoma cells for the tyrosinase-processed antifolate prodrug 3-O-(3,4,5-trimethoxybenzoyl)-(-)-epicatechin (TMECG). In summary, our study provides proof-of-concept for a new dual hit strategy in melanoma, in which persister state-directed transitioning limits tumor growth and plasticity and primes melanoma cells towards lineage-specific elimination.

Patient-Derived Xenografts (PDXs) are tumor-in-mouse models for cancer. PDX collections, such as those supported by the NCI PDXNet program, are powerful resources for preclinical therapeutic testing. However, variations in experimental design and analysis procedures have limited interpretability. To determine the robustness of PDX studies, the PDXNet tested temozolomide drug response for three pre-validated PDX models (sensitive, resistant, and intermediate) across four blinded PDX Development and Trial Centers (PDTCs) using independently selected SOPs. Each PDTC was able to correctly identify the sensitive, resistant, and intermediate models, and statistical evaluations were concordant across all groups. We also developed and benchmarked optimized PDX informatics pipelines, and these yielded robust assessments across xenograft biological replicates. These studies show that PDX drug responses and sequence results are reproducible across diverse experimental protocols. Here we share the range of experimental procedures that maintained robustness, as well as standardized cloud-based workflows for PDX exome-seq and RNA-Seq analysis and for evaluating growth.

Background One of major issues in clinical trials in oncology is their high failure rate, despite the fact that the trials were designed based on the data from successful equivalent preclinical studies. This is in part due to the intrinsic homogeneity of preclinical model systems and the contrasting heterogeneity of actual patient responses. Methods We present a mathematical model-driven framework, phase i (virtual/imaginary) trials, that integrates the heterogeneity of actual patient responses and preclinical studies through a cohort of virtual patients. The framework includes an experimentally calibrated mathematical model, a cohort of heterogeneous virtual patients, an assessment of stratification factors, and treatment optimisation. We show the detailed process through the lens of melanoma combination therapy (chemotherapy and an AKT inhibitor), using both preclinical and clinical data. Results The mathematical model predicts melanoma treatment response and resistance to mono and combination therapies and was calibrated and then validated with in vitro experimental data. The validated model and a genetic algorithm were used to generate virtual patients whose tumour volume responses to the combination therapy matched statistically the actual heterogeneous patient responses in the clinical trial. Analyses on simulated cohorts revealed key model parameters such as a tumour volume doubling rate and a therapy-induced phenotypic switch rate that may have clinical correlates. Finally, our approach predicts optimal AKT inhibitor scheduling suggesting more effective but less toxic treatment strategies. Conclusion Our proposed computational framework to implement phase i trials in cancer can readily capture observed heterogeneous clinical outcomes and predict patient survival. Importantly, phase i trials can be used to optimise future clinical trial design.