Tumor Heterogeneity Shapes Survival Dynamics in Drug-Treated Cells, Revealing Size-Drifting Subpopulations.

The goal of this project was to demonstrate that subpopulations of cells in tumors can uniquely fluctuate in size in response to environmental conditions created during drug treatment, thereby acting as a dynamic "rheostat" to create a favorable tumor environment for growth. The cancer modeling used for these studies was subpopulations of melanoma cells existing in cultured and tumor systems that differed in aldehyde dehydrogenase (ALDH) activity. However, similar observations were found in other cancer types in addition to melanoma, making them applicable broadly across cancer.

AP-1 Mediates Cellular Adaptation and Memory Formation During Therapy Resistance.

Cellular responses to environmental stimuli are typically thought to be governed by genetically encoded programs. We demonstrate that melanoma cells can form and maintain cellular memories during the acquisition of therapy resistance that exhibit characteristics of cellular learning and are dependent on the transcription factor AP-1. We show that cells exposed to a low dose of therapy adapt to become resistant to a high dose, demonstrating that resistance was not purely selective.

ERK hyperactivation serves as a unified mechanism of escape in intrinsic and acquired CDK4/6 inhibitor resistance in acral lentiginous melanoma.

Patients with metastatic acral lentiginous melanoma (ALM) suffer worse outcomes relative to patients with other forms of cutaneous melanoma (CM), and do not benefit as well to approved melanoma therapies. Identification of cyclin-dependent kinase 4 and 6 (CDK4/6) pathway gene alterations in >60% of ALMs has led to clinical trials of the CDK4/6 inhibitor (CDK4i/6i) palbociclib for ALM; however, median progression free survival with CDK4i/6i treatment was only 2.2 months, suggesting existence of resistance mechanisms.

HRS mediates tumor immune evasion by regulating proteostasis-associated interferon pathway activation.

By sorting receptor tyrosine kinases into endolysosomes, the endosomal sorting complexes required for transport (ESCRTs) are thought to attenuate oncogenic signaling in tumor cells. Paradoxically, ESCRT members are upregulated in tumors. Here, we show that disruption of hepatocyte growth factor-regulated tyrosine kinase substrate (HRS), a pivotal ESCRT component, inhibited tumor growth by promoting CD8 T cell infiltration in melanoma and colon cancer mouse models.

Upregulation of exosome secretion from tumor-associated macrophages plays a key role in the suppression of anti-tumor immunity.

Macrophages play a pivotal role in tumor immunity. We report that reprogramming of macrophages to tumor-associated macrophages (TAMs) promotes the secretion of exosomes. Mechanistically, increased exosome secretion is driven by MADD, which is phosphorylated by Akt upon TAM induction and activates Rab27a.

Melanoma-intrinsic NR2F6 activity regulates antitumor immunity.

Nuclear receptors (NRs) are implicated in the regulation of tumors and immune cells. We identify a tumor-intrinsic function of the orphan NR, NR2F6, regulating antitumor immunity. NR2F6 was selected from 48 candidate NRs based on an expression pattern in melanoma patient specimens (i.

Tumor-Derived Small Extracellular Vesicles Inhibit the Efficacy of CAR T Cells against Solid Tumors.

Unlabelled: Chimeric antigen receptor (CAR) T-cell therapy has shown remarkable success in the treatment of hematologic malignancies. Unfortunately, it has limited efficacy against solid tumors, even when the targeted antigens are well expressed. A better understanding of the underlying mechanisms of CAR T-cell therapy resistance in solid tumors is necessary to develop strategies to improve efficacy.

A distinct pattern of growth and RAC1 signaling in melanoma brain metastasis cells.

Background: Melanoma, the deadliest of skin cancers, has a high propensity to form brain metastases that are associated with a markedly worsened prognosis. In spite of recent therapeutic advances, melanoma brain lesions remain a clinical challenge, biomarkers predicting brain dissemination are not clear and differences with other metastatic sites are poorly understood.

Methods: We examined a genetically diverse panel of human-derived melanoma brain metastasis (MBM) and extracranial cell lines using targeted sequencing, a Reverse Phase Protein Array, protein expression analyses, and functional studies in vitro and in vivo.

Targeting WEE1/AKT Restores p53-Dependent Natural Killer-Cell Activation to Induce Immune Checkpoint Blockade Responses in "Cold" Melanoma.

Immunotherapy has revolutionized cancer treatment. Unfortunately, most tumor types do not respond to immunotherapy due to a lack of immune infiltration or "cold" tumor microenvironment (TME), a contributing factor in treatment failure. Activation of the p53 pathway can increase apoptosis of cancer cells, leading to enhanced antigen presentation, and can stimulate natural killer (NK) cells through expression of stress ligands.

Targeting SOX10-deficient cells to reduce the dormant-invasive phenotype state in melanoma.

Cellular plasticity contributes to intra-tumoral heterogeneity and phenotype switching, which enable adaptation to metastatic microenvironments and resistance to therapies. Mechanisms underlying tumor cell plasticity remain poorly understood. SOX10, a neural crest lineage transcription factor, is heterogeneously expressed in melanomas.

ICAM-1-mediated adhesion is a prerequisite for exosome-induced T cell suppression.

Tumor-derived extracellular vesicles (TEVs) suppress the proliferation and cytotoxicity of CD8 T cells, thereby contributing to tumor immune evasion. Here, we report that the adhesion molecule intercellular adhesion molecule 1 (ICAM-1) co-localizes with programmed death ligand 1 (PD-L1) on the exosomes; both ICAM-1 and PD-L1 are upregulated by interferon-γ. Exosomal ICAM-1 interacts with LFA-1, which is upregulated in activated T cells.

TOP1 modulation during melanoma progression and in adaptative resistance to BRAF and MEK inhibitors.

In melanomas, therapy resistance can arise due to a combination of genetic, epigenetic and phenotypic mechanisms. Due to its crucial role in DNA supercoil relaxation, TOP1 is often considered an essential chemotherapeutic target in cancer. However, how TOP1 expression and activity might differ in therapy sensitive versus resistant cell types is unknown.

Protein Signatures of NK Cell-Mediated Melanoma Killing Predict Response to Immunotherapies.

Despite impressive advances in melanoma-directed immunotherapies, resistance is common and many patients still succumb to metastatic disease. In this context, harnessing natural killer (NK) cells, which have thus far been sidelined in the development of melanoma immunotherapy, could provide therapeutic benefits for cancer treatment. To identify molecular determinants of NK cell-mediated melanoma killing (), we quantified NK-cell cytotoxicity against a panel of genetically diverse melanoma cell lines and observed highly heterogeneous susceptibility.

TRIM15 and CYLD regulate ERK activation via lysine-63-linked polyubiquitination.

The extracellular-signal-regulated kinases ERK1 and ERK2 (hereafter ERK1/2) represent the foremost mitogenic pathway in mammalian cells, and their dysregulation drives tumorigenesis and confers therapeutic resistance. ERK1/2 are known to be activated by MAPK/ERK kinase (MEK)-mediated phosphorylation. Here, we show that ERK1/2 are also modified by lysine-63 (K63)-linked polyubiquitin chains.

Neural Crest-Like Stem Cell Transcriptome Analysis Identifies LPAR1 in Melanoma Progression and Therapy Resistance.

Metastatic melanoma is challenging to clinically address. Although standard-of-care targeted therapy has high response rates in patients with BRAF-mutant melanoma, therapy relapse occurs in most cases. Intrinsically resistant melanoma cells drive therapy resistance and display molecular and biologic properties akin to neural crest-like stem cells (NCLSC) including high invasiveness, plasticity, and self-renewal capacity.

Targeting mTOR signaling overcomes acquired resistance to combined BRAF and MEK inhibition in BRAF-mutant melanoma.

Targeting MAPK pathway using a combination of BRAF and MEK inhibitors is an efficient strategy to treat melanoma harboring BRAF-mutation. The development of acquired resistance is inevitable due to the signaling pathway rewiring. Combining western blotting, immunohistochemistry, and reverse phase protein array (RPPA), we aim to understanding the role of the mTORC1 signaling pathway, a center node of intracellular signaling network, in mediating drug resistance of BRAF-mutant melanoma to the combination of BRAF inhibitor (BRAFi) and MEK inhibitor (MEKi) therapy.

Inhibition of endothelin-B receptor signaling synergizes with MAPK pathway inhibitors in BRAF mutated melanoma.

The clinical benefit of MAPK pathway inhibition in melanoma patients carrying BRAF mutations is temporal. After the initial response to treatment, the majority of tumors will develop resistance and patients will relapse. Here we demonstrate that the endothelin-endothelin receptor B (ETBR) signaling pathway confers resistance to MAPK pathway inhibitors in BRAF mutated melanoma.

ARID2 Deficiency Correlates with the Response to Immune Checkpoint Blockade in Melanoma.

The SWI/SNF chromatin remodeler family includes the BAF and PBAF complexes. ARID2, encoding a PBAF complex subunit, is frequently mutated in melanoma independently of BRAF/RAS mutations. Emerging evidence shows that SWI/SNF complexes regulate tumor immunity; for instance, the loss of PBRM1, another PBAF complex subunit, enhances susceptibility to immune checkpoint inhibitors in melanoma.

Targeting telomerase for cancer therapy.

Telomere maintenance via telomerase reactivation is a nearly universal hallmark of cancer cells which enables replicative immortality. In contrast, telomerase activity is silenced in most adult somatic cells. Thus, telomerase represents an attractive target for highly selective cancer therapeutics.

Pre-clinical modeling of cutaneous melanoma.

Metastatic melanoma is challenging to manage. Although targeted- and immune therapies have extended survival, most patients experience therapy resistance. The adaptability of melanoma cells in nutrient- and therapeutically-challenged environments distinguishes melanoma as an ideal model for investigating therapy resistance.

Leptomeningeal disease in melanoma patients: An update to treatment, challenges, and future directions.

In February 2018, the Melanoma Research Foundation and the Moffitt Cancer Center hosted the Second Summit on Melanoma Central Nervous System Metastases in Tampa, Florida. The meeting included investigators from multiple academic centers and disciplines. A consensus summary of the progress and challenges in melanoma parenchymal brain metastases was published (Eroglu et al.

Functional Genomic Complexity Defines Intratumor Heterogeneity and Tumor Aggressiveness in Liver Cancer.

Chronic inflammation and chromosome aneuploidy are major traits of primary liver cancer (PLC), which represent the second most common cause of cancer-related death worldwide. Increased cancer fitness and aggressiveness of PLC may be achieved by enhancing tumoral genomic complexity that alters tumor biology. Here, we developed a scoring method, namely functional genomic complexity (FGC), to determine the degree of molecular heterogeneity among 580 liver tumors with diverse ethnicities and etiologies by assessing integrated genomic and transcriptomic data.

PLX3397 inhibits the accumulation of intra-tumoral macrophages and improves bromodomain and extra-terminal inhibitor efficacy in melanoma.

Bromodomain and extra-terminal inhibitors (BETi) delay tumor growth, in part, through tumor cell intrinsic alterations and initiation of anti-tumor CD8+ T-cell responses. By contrast, BETi effects on pro-tumoral immune responses remain unclear. Here, we show that the next-generation BETi, PLX51107, delayed tumor growth to differing degrees in Braf V600E melanoma syngeneic mouse models.