Epigenetic Silencing of BMP6 by the SIN3A-HDAC1/2 Repressor Complex Drives Melanoma Metastasis via FAM83G/PAWS1.

Aberrant epigenetic transcriptional regulation is linked to metastasis, a primary cause of cancer-related death. Dissecting the epigenetic mechanisms controlling metastatic progression may uncover important insights to tumor biology and potential therapeutic targets. Here, we investigated the role of the SIN3A histone deacetylase 1 and 2 (SIN3A-HDAC1/2) complex in cancer metastasis.

MITF Expression Predicts Therapeutic Vulnerability to p300 Inhibition in Human Melanoma.

Histone modifications, largely regulated by histone acetyltransferases (HAT) and histone deacetylases, have been recognized as major regulatory mechanisms governing human diseases, including cancer. Despite significant effort and recent advances, the mechanism by which the HAT and transcriptional coactivator p300 mediates tumorigenesis remains unclear. Here, we use a genetic and chemical approach to identify the microphthalmia-associated transcription factor (MITF) as a critical downstream target of p300 driving human melanoma growth.

Emerging Biomarkers in Cutaneous Melanoma.

Earlier identification of aggressive melanoma remains a goal in the field of melanoma research. With new targeted and immune therapies that have revolutionized the care of patients with melanoma, the ability to predict progression and monitor or predict response to therapy has become the new focus of research into biomarkers in melanoma. In this review, promising biomarkers are highlighted.

Targeting the CoREST complex with dual histone deacetylase and demethylase inhibitors.

Here we report corin, a synthetic hybrid agent derived from the class I HDAC inhibitor (entinostat) and an LSD1 inhibitor (tranylcypromine analog). Enzymologic analysis reveals that corin potently targets the CoREST complex and shows more sustained inhibition of CoREST complex HDAC activity compared with entinostat. Cell-based experiments demonstrate that corin exhibits a superior anti-proliferative profile against several melanoma lines and cutaneous squamous cell carcinoma lines compared to its parent monofunctional inhibitors but is less toxic to melanocytes and keratinocytes.

Quantitative assessment of neuropilin-2 as a simple and sensitive diagnostic assay for spitzoid melanocytic lesions.

There is a significant need for the development of diagnostic tools that can precisely distinguish Spitz nevi and spitzoid melanomas. Here, we report the development of a PCR-based quantitative diagnostic assay for spitzoid melanocytic lesions utilizing the expression ratio of neuropilin-2 and melan-A genes in primary tumor specimens. We find that the expression ratio of neuropilin-2/melan-A is significantly increased in spitzoid melanomas compared with Spitz nevi.

Notch3 signaling-mediated melanoma-endothelial crosstalk regulates melanoma stem-like cell homeostasis and niche morphogenesis.

Melanoma is among the most virulent cancers, owing to its propensity to metastasize and its resistance to current therapies. The treatment failure is largely attributed to tumor heterogeneity, particularly subpopulations possessing stem cell-like properties, ie, melanoma stem-like cells (MSLCs). Evidence indicates that the MSLC phenotype is malleable and may be acquired by non-MSLCs through phenotypic switching upon appropriate stimuli, the so-called 'dynamic stemness'.

A simple engineered platform reveals different modes of tumor-microenvironmental cell interaction.

How metastatic cancer lesions survive and grow in secondary locations is not fully understood. There is a growing appreciation for the importance of tumor components, i.e.

Epigenetic Silencing of SPINT2 Promotes Cancer Cell Motility via HGF-MET Pathway Activation in Melanoma.

Aberrant HGF-MET (hepatocyte growth factor-met proto-oncogene) signaling activation via interactions with surrounding stromal cells in tumor microenvironment has significant roles in malignant tumor progression. However, extracellular proteolytic regulation of HGF activation, which is influenced by the tumor microenvironment, and its consequential effects on melanoma malignancy remain uncharacterized. In this study, we identified SPINT2 (serine peptidase inhibitor Kunitz type 2), a proteolytic inhibitor of hepatocyte growth factor activator (HGFA), which has a significant role in the suppression of the HGF-MET pathway and malignant melanoma progression.

MC1R is a potent regulator of PTEN after UV exposure in melanocytes.

The individuals carrying melanocortin-1 receptor (MC1R) variants, especially those associated with red hair color, fair skin, and poor tanning ability (RHC trait), are more prone to melanoma; however, the underlying mechanism is poorly defined. Here, we report that UVB exposure triggers phosphatase and tensin homolog (PTEN) interaction with wild-type (WT), but not RHC-associated MC1R variants, which protects PTEN from WWP2-mediated degradation, leading to AKT inactivation. Strikingly, the biological consequences of the failure of MC1R variants to suppress PI3K/AKT signaling are highly context dependent.

Selective inhibition of p300 HAT blocks cell cycle progression, induces cellular senescence, and inhibits the DNA damage response in melanoma cells.

Epigenetic events, including covalent post-translational modifications of histones, have been demonstrated to have critical roles in tumor development and progression. The transcriptional coactivator p300/CBP possesses both histone acetyltransferase (HAT) activity and scaffolding properties that directly influence the transcriptional activation of targeted genes. We have used a potent and specific inhibitor of p300/CBP HAT activity, C646, in order to evaluate the functional contributions of p300/CBP HAT to tumor development and progression.

MicroRNAs as an emerging target for melanoma therapy.

Despite the growing focus on microRNAs (miRNAs) as novel diagnostic tools and therapeutic targets in cancer, global characterization of miRNA expression patterns and their specific targets in melanoma has lagged. In this issue, Reuland et al. (2012) identify miR-26a as being specifically downregulated in human melanoma cells.

Stat3-targeted therapies overcome the acquired resistance to vemurafenib in melanomas.

Vemurafenib (PLX4032), a selective inhibitor of Braf, has been approved by the US Food and Drug Administration for the treatment of unresectable or metastatic melanoma in patients with Braf(V600E) mutations. Many patients treated with vemurafenib initially display dramatic improvement, with decreases in both risk of death and tumor progression. Acquired resistance, however, rapidly arises in previously sensitive cells.

Integration of genotypic and phenotypic screening reveals molecular mediators of melanoma-stromal interaction.

Tumor-endothelium interactions are critical for tumor survival and metastasis. Melanomas can rapidly metastasize early in tumor progression, but the dependence of this aggressive behavior on tumor-stromal interaction is poorly understood. To probe the mechanisms involved, we developed a heterotypic coculture methodology, allowing simultaneous tracking of genomic and phenotypic changes in interacting tumor and endothelial cells in vitro.

Id1 delays senescence of primary human melanocytes.

The Id family of helix-loop-helix transcription factors is upregulated in a variety of human malignancies and has been implicated in promoting tumorigenesis through effects on cell growth, differentiation, and tumor angiogenesis. While expression of Id proteins has been associated with tumorigenesis, the precise mechanistic relationship between Id expression and carcinogenesis has not been clearly delineated. We have previously shown that Id1 delays cellular senescence in primary mammalian cells through inhibition of the cell cycle regulatory protein and familial melanoma gene, p16/INK4a.

Comprehensive expression profiling of tumor cell lines identifies molecular signatures of melanoma progression.

Background: Gene expression profiling has revolutionized our ability to molecularly classify primary human tumors and significantly enhanced the development of novel tumor markers and therapies; however, progress in the diagnosis and treatment of melanoma over the past 3 decades has been limited, and there is currently no approved therapy that significantly extends lifespan in patients with advanced disease. Profiling studies of melanoma to date have been inconsistent due to the heterogeneous nature of this malignancy and the limited availability of informative tissue specimens from early stages of disease.

Methodology/principle Findings: In order to gain an improved understanding of the molecular basis of melanoma progression, we have compared gene expression profiles from a series of melanoma cell lines representing discrete stages of malignant progression that recapitulate critical characteristics of the primary lesions from which they were derived.

Id1 expression is transcriptionally regulated in radial growth phase melanomas.

Id genes have been demonstrated to be upregulated in a wide variety of human malignancies and their expression has been correlated with disease prognosis; however, little is known about the mechanisms of Id gene activation in tumors. We have previously shown that the helix-loop-helix transcription factor, Id1, is highly expressed in primary human melanomas during the radial growth phase and that Id1 is a transcriptional repressor of the familial melanoma gene CDKN2A. Here we use a series of melanoma cell lines that recapitulate the phenotypic characteristics of melanomas at varying stages of malignant progression to evaluate the expression levels of Id1 in this model system and determine the mechanism of Id1 dysregulation in these tumor cells.

Malignant transformation of human cells by constitutive expression of platelet-derived growth factor-BB.

Platelet-derived growth factors (PDGFs) comprise a family of growth factors strongly implicated in human oncogenesis. A number of human tumors overexpress PDGF family members or have translocations activating PDGF receptors. Whereas the epidemiologic evidence implicating PDGF in human tumors is strong, malignant transformation of human cells by overexpression of PDGF has not been demonstrated.

Disruption of Id1 reveals major differences in angiogenesis between transplanted and autochthonous tumors.

Id genes regulate tumor angiogenesis and loss of Id1 inhibits tumor xenograft growth in mice. Here we evaluate the role of Id1 in a more clinically relevant tumor model system using a two-step chemical carcinogenesis protocol. Remarkably, we find that Id1-/- mice are more susceptible to skin tumorigenesis compared to their wild-type counterparts.

Id proteins in cell growth and tumorigenesis.

Since the gene encoding Id1 was cloned in 1990, Id proteins have been implicated in regulating a variety of cellular processes, including cellular growth, senescence, differentiation, apoptosis, angiogenesis, and neoplastic transformation. The development of knockout and transgenic animal models for many members of the Id gene family has been particularly useful in sorting out the biologic relevance of these genes and their expression during normal development, malignant transformation, and tumor progression. Here we review the current understanding of Id gene function, the biologic consequences of Id gene expression, and the implications for Id gene regulation of cell growth and tumorigenesis.

The essential similarity of TGFbeta and activin receptor transcriptional responses in cancer cells.

The binding of activin and TGFbeta to their respective receptors initiates signals that are carried by common intermediates (Smad proteins) to induce transcriptional activation of downstream genes. Mutations in tumors indicate that both receptor types convey tumorsuppressive signals, among other biologic roles, but their respective sets of transcriptional targets (transcriptomes) and the shared degree of transcriptome similarity are not well explored in these cells. Transcriptome changes were analyzed by gene expression profiling after expression of constitutively active activin type I (ALK4m) and TGFbeta type I (ALK5m) receptors and by variation of Smad4 expression in cancer cells.

Exploration of global gene expression patterns in pancreatic adenocarcinoma using cDNA microarrays.

Pancreatic cancer is the fifth leading cause of cancer death in the United States. We used cDNA microarrays to analyze global gene expression patterns in 14 pancreatic cancer cell lines, 17 resected infiltrating pancreatic cancer tissues, and 5 samples of normal pancreas to identify genes that are differentially expressed in pancreatic cancer. We found more than 400 cDNAs corresponding to genes that were differentially expressed in the pancreatic cancer tissues and cell lines as compared to normal pancreas.

Relationships and differentially expressed genes among pancreatic cancers examined by large-scale serial analysis of gene expression.

Pancreatic adenocarcinoma is among the most fatal of cancers, in part because of late diagnosis and a lack of effective therapies. Comprehensive studies are needed to better understand and address the cellular mechanisms and pathways of tumorigenesis. Serial analysis of gene expression was used to analyze gene expression profiles of pancreatic cancer cell lines, short-term cultures of normal pancreatic ductal epithelium, and primary pancreatic cancer tissue.