Microphthalmia transcription factor expression in cutaneous benign, malignant melanocytic, and nonmelanocytic tumors

Rare cases of colonic schwannomas

Schwannomas of the gastrointestinal tract are rare spindle cell tumors that account for 2-6% of mesenchymal tumors. An elderly male was found to have a left colon mass on CT scan and colonoscopy with pathology of fibrotic tissue. A laparoscopic-assisted left hemi-colectomy with primary anastomosis was performed. Pathology demonstrated spindle cell neoplasm arranged in short fascicles that were strongly and diffusely positive for S100. An elderly female was found to have a submucosal lesion on surveillance colonoscopy in the proximal transverse colon. Biopsy with jumbo forceps revealed spindle cell neoplasm positive for S100. Patient underwent an uncomplicated limited non-oncologic segmental transverse colectomy. We report only the ninth case of left and sixth in the transverse colon described in the literature. As is true for other mesenchymal tumors, mucosal biopsy is usually inconclusive and deep biopsy or submucosal resection is required, making pre-operative surgical decision difficult.

MITF Downregulation Induces Death in Human Mast Cell Leukemia Cells and Impairs IgE-Dependent Degranulation

Activating mutations in KIT (CD117) have been associated with several diseases, including gastrointestinal stromal tumors and mastocytosis. Rapidly progressing pathologies or drug resistance highlight the need for alternative treatment strategies. Previously, we reported that the adaptor molecule SH3 binding protein 2 (SH3BP2 or 3BP2) regulates KIT expression at the transcriptional level and microphthalmia-associated transcription factor (MITF) expression at the post-transcriptional level in human mast cells and gastrointestinal stromal tumor (GIST) cell lines. Lately, we have found that the SH3BP2 pathway regulates MITF through miR-1246 and miR-5100 in GIST. In this study, miR-1246 and miR-5100 were validated by qPCR in the SH3BP2-silenced human mast cell leukemia cell line (HMC-1). MiRNA overexpression reduces MITF and MITF-dependent target expression in HMC-1. The same pattern was observed after MITF silencing. In addition, MITF inhibitor ML329 treatment reduces MITF expression and affects the viability and cell cycle progression in HMC-1. We also examine whether MITF downregulation affected IgE-dependent mast cell degranulation. MiRNA overexpression, MITF silencing, and ML329 treatment reduced IgE-dependent degranulation in LAD2- and CD34⁺-derived mast cells. These findings suggest MITF may be a potential therapeutic target for allergic reactions and deregulated KIT mast-cell-mediated disorders.

Anti-Melanogenesis Effects of a Cyclic Peptide Derived from Flaxseed via Inhibition of CREB Pathway

Linosorbs (Los) are cyclic peptides from flaxseed oil composed of the LO mixture (LOMIX). The activity of LO has been reported as being anti-cancer and anti-inflammatory. However, the study of skin protection has still not proceeded. In particular, there are poorly understood mechanisms of melanogenesis to LO. Therefore, we investigated the anti-melanogenesis effects of LOMIX and LO, and its activity was examined in mouse melanoma cell lines. The treatment of LOMIX (50 and 100 μg/mL) and LO (6.25-50 μM) suppressed melanin secretion and synthesis, which were 3-fold increased, in a dose-dependent manner, up to 95%. In particular, [1-9-NαC]-linusorb B3 (LO1) and [1-9-NαC]-linusorb B2 (LO2) treatment (12.5 and 25 μM) highly suppressed the synthesis of melanin in B16F10 cell lines up to 90%, without toxicity. LOMIX and LOs decreased the 2- or 3-fold increased mRNA levels, including the microphthalmia-associated transcription factor (MITF), Tyrosinase, tyrosinase-related protein 1 (TYRP1), and tyrosinase-related protein 2 (TYRP2) at the highest concentration (25 μM). Moreover, the treatment of 25 μM LO1 and LO2 inhibited the expression of MITF and phosphorylation of upper regulatory proteins such as CREB and PKA. Taken together, these results suggested that LOMIX and its individual LO could inhibit melanin synthesis via downregulating the CREB-dependent signaling pathways, and it could be used for novel therapeutic materials in hyperpigmentation.

Anti-Melanogenesis Activity of Crocodile (Crocodylus siamensis) White Blood Cell Extract on Ultraviolet B-Irradiated Melanocytes

Ultraviolet (UV) radiation generates a range of biological effects in the skin, which includes premature skin aging, hyperpigmentation, and cancer. Therefore, the development of new effective agents for UV-related skin damage remains a challenge in the pharmaceutical industry. This study aims to test the inhibitory effect of crocodile white blood cell (cWBC) extract, a rich source of bioactive peptides, on ultraviolet B (UVB)-induced melanocyte pigmentation. The results showed that cWBC (6.25-400 μg/mL) could inhibit tyrosinase without adduct formation by 12.97 ± 4.20% on average. cWBC pretreatment (25-100 μg/mL) had no cytotoxicity and reduced intracellular melanin to 111.17 ± 5.20% compared with 124.87 ± 7.43 for UVB condition. The protective role of cWBC pretreatment against UVB was exhibited by the promotion of cell proliferation and the prevention of UVB-induced morphological change as observed from F actin staining. The decrease of microphthalmia-associated transcription factor expression levels after cWBC pretreatment might be a mechanism by which cWBC suppresses UVB-induced pigmentation. These results suggest that cWBC could be beneficial for the prevention of UVB-induced skin pigmentation.

The Spectrum of Spitz Melanocytic Lesions: From Morphologic Diagnosis to Molecular Classification

Spitz tumors represent a distinct subtype of melanocytic lesions with characteristic histopathologic features, some of which are overlapping with melanoma. More common in the pediatric and younger population, they can be clinically suspected by recognizing specific patterns on dermatoscopic examination, and several subtypes have been described. We now classify these lesions into benign Spitz nevi, intermediate lesions identified as “atypical Spitz tumors” (or Spitz melanocytoma) and malignant Spitz melanoma. More recently a large body of work has uncovered the molecular underpinning of Spitz tumors, including mutations in the HRAS gene and several gene fusions involving several protein kinases. Here we present an overarching view of our current knowledge and understanding of Spitz tumors, detailing clinical, histopathological and molecular features characteristic of these lesions.

MITF in Normal Melanocytes, Cutaneous and Uveal Melanoma: A Delicate Balance

Microphthalmia-associated transcription factor (MITF) is an important regulator of melanogenesis and melanocyte development. Although it has been studied extensively in cutaneous melanoma, the role of MITF in uveal melanoma (UM) has not been explored in much detail. We review the literature about the role of MITF in normal melanocytes, in cutaneous melanoma, and in UM. In normal melanocytes, MITF regulates melanocyte development, melanin synthesis, and melanocyte survival. The expression profile and the behaviour of MITF-expressing cells suggest that MITF promotes local proliferation and inhibits invasion, inflammation, and epithelial-to-mesenchymal (EMT) transition. Loss of MITF expression leads to increased invasion and inflammation and is more prevalent in malignant cells. Cutaneous melanoma cells switch between MITF-high and MITF-low states in different phases of tumour development. In UM, MITF loss is associated with loss of BAP1 protein expression, which is a marker of poor prognosis. These data indicate a dual role for MITF in benign and malignant melanocytic cells.

Genodermatoses associated with melanocytic nevi

Though melanocytic nevi are ubiquitous in the general population, they can also be key cutaneous manifestations of genetic syndromes. We describe genodermatoses associated with melanocytic nevi and discuss their clinical characteristics, cutaneous manifestations, underlying genetics, and, if applicable, guidelines for when genetic testing should be performed. We categorized these genodermatoses based on their association with congenital nevi, acquired nevi, or nevi whose first appearance is unknown. In many cases, the distinctive morphology or distribution of melanocytic nevi can be an important clue that an underlying genetic syndrome is present, allowing both the patient as well as family members to be screened for the more serious complications of their genetic disorder and receive education on potential preventative measures. As we continue to advance our understanding of how various genotypes give rise to the wide spectrum of phenotypes observed in these genodermatoses, we shall be able to better stratify risk and tailor our screening methods to clinically manage the heterogeneous manifestations of genodermatoses among these patients.

MITF activity is regulated by a direct interaction with RAF proteins in melanoma cells

The MITF transcription factor and the RAS/RAF/MEK/ERK pathway are two interconnected main players in melanoma. Understanding how MITF activity is regulated represents a key question since its dynamic modulation is involved in the phenotypic plasticity of melanoma cells and their resistance to therapy. By investigating the role of ARAF in NRAS-driven mouse melanoma through mass spectrometry experiments followed by a functional siRNA-based screen, we unexpectedly identified MITF as a direct ARAF partner. Interestingly, this interaction is conserved among the RAF protein kinase family since BRAF/MITF and CRAF/MITF complexes were also observed in the cytosol of NRAS-mutated mouse melanoma cells. The interaction occurs through the kinase domain of RAF proteins. Importantly, endogenous BRAF/MITF complexes were also detected in BRAF-mutated human melanoma cells. RAF/MITF complexes modulate MITF nuclear localization by inducing an accumulation of MITF in the cytoplasm, thus negatively controlling its transcriptional activity. Taken together, our study highlights a new level of regulation between two major mediators of melanoma progression, MITF and the MAPK/ERK pathway, which appears more complex than previously anticipated.

The MITF transcription factor directly binds to the kinase domain of RAF kinases, including ARAF, BRAF and CRAF in melanoma cells. RAF/MITF complex promotes cytoplasmic accumulation of MITF and thus negatively regulates its transcriptional activity.

Histone deacetylase inhibitor Vorinostat (SAHA) suppresses micropthalmia transcription factor expression and induces cell death in nevocytes from large/giant congenital melanocytic nevi

Large/giant congenital nevi (L/GCMN) are benign neoplasms of the melanocytic neural crest lineage covering extensive areas of skin presenting risk for melanoma. Surgical resection often leads to scarring and trauma. Histone deacetylase inhibitors (iHDACs) as topical therapeutic agents may prove beneficial as an alternative/adjunct to surgery in this disease. Here we describe the effect of in vitro treatment of iHDACs drugs on primary nevocytes isolated from L/GCMN patients. Micropthalmia transcription factor (MITF) expression in L/GCMN patients' lesions was detected by immunohistochemistry, in cultured nevocytes by immunofluorescence, immunoblot and quantitative polymerase chain reaction. Cellular senescence was detected by SA-ß galactosidase activity. Markers for melanocytic differentiation were evaluated by immunoblot analysis and extracted melanin content was estimated spectrophotometrically. Cell death was measured by lactate dehydrogenase (LDH) assay and necrosis confirmed by polymerase (PARP) cleavage and acridine orange staining of the nuclei. MITF was expressed ubiquitously in nevocytes and melanocytes in patients' lesions. In culture, iHDAC treatment suppressed MITF protein and mRNA expression resulting in a senescent-like phenotype with positive ß-galactosidase staining, progressing to necrotic cell death as evidenced by increased LDH activity, appearance of cleaved PARP and necrotic nuclei. This is the first report showing evidence of iHDACs-induced MITF suppression in congenital nevocytes in vitro leading to a morphologic change with positive ß-galactosidase staining, followed by necrotic cell death in nevocytes, indicating that iHDAC drugs could be valuable therapeutic agents for treatment of L/GCMN lesions.

How Neural Crest Transcription Factors Contribute to Melanoma Heterogeneity, Cellular Plasticity, and Treatment Resistance

Cutaneous melanoma represents one of the deadliest types of skin cancer. The prognosis strongly depends on the disease stage, thus early detection is crucial. New therapies, including BRAF and MEK inhibitors and immunotherapies, have significantly improved the survival of patients in the last decade. However, intrinsic and acquired resistance is still a challenge. In this review, we discuss two major aspects that contribute to the aggressiveness of melanoma, namely, the embryonic origin of melanocytes and melanoma cells and cellular plasticity. First, we summarize the physiological function of epidermal melanocytes and their development from precursor cells that originate from the neural crest (NC). Next, we discuss the concepts of intratumoral heterogeneity, cellular plasticity, and phenotype switching that enable melanoma to adapt to changes in the tumor microenvironment and promote disease progression and drug resistance. Finally, we further dissect the connection of these two aspects by focusing on the transcriptional regulators MSX1, MITF, SOX10, PAX3, and FOXD3. These factors play a key role in NC initiation, NC cell migration, and melanocyte formation, and we discuss how they contribute to cellular plasticity and drug resistance in melanoma.

The underestimated role of the microphthalmia-associated transcription factor (MiTF) in normal and pathological haematopoiesis

Haematopoiesis, the process by which a restrained population of stem cells terminally differentiates into specific types of blood cells, depends on the tightly regulated temporospatial activity of several transcription factors (TFs). The deregulation of their activity or expression is a main cause of pathological haematopoiesis, leading to bone marrow failure (BMF), anaemia and leukaemia. TFs can be induced and/or activated by different stimuli, to which they respond by regulating the expression of genes and gene networks. Most TFs are highly pleiotropic; i.e., they are capable of influencing two or more apparently unrelated phenotypic traits, and the action of a single TF in a specific setting often depends on its interaction with other TFs and signalling pathway components. The microphthalmia-associated TF (MiTF) is a prototype TF in multiple situations. MiTF has been described extensively as a key regulator of melanocyte and melanoma development because it acts mainly as an oncogene. Mitf-mutated mice show a plethora of pleiotropic phenotypes, such as microphthalmia, deafness, abnormal pigmentation, retinal degeneration, reduced mast cell numbers and osteopetrosis, revealing a greater requirement for MiTF activity in cells and tissue. A growing amount of evidence has led to the delineation of key roles for MiTF in haematopoiesis and/or in cells of haematopoietic origin, including haematopoietic stem cells, mast cells, NK cells, basophiles, B cells and osteoclasts. This review summarizes several roles of MiTF in cells of the haematopoietic system and how MiTFs can impact BM development.

Long-Term Inhibition of Notch in A-375 Melanoma Cells Enhances Tumor Growth Through the Enhancement of AXIN1, CSNK2A3, and CEBPA2 as Intermediate Genes in Wnt and Notch Pathways

Notch suppression by gamma-secretase inhibitors is a valid approach against melanoma. However, most of studies have evaluated the short-term effect of DAPT on tumor cells or even cancer stem cells. In the present study, we surveyed the short-term and long-term effects of DAPT on the stem cell properties of A375 and NA8 as melanoma cell lines. The effects of DAPT were tested both in vitro and in vivo using xenograft models. In A375 with B-raf mutation, DAPT decreased the level of NOTCH1, NOTH2, and HES1 as downstream genes of the Notch pathway. This was accompanied by enhanced apoptosis after 24 h treatment, arrest in the G₂₋M phase, and impaired ability of colony and melanosphere formation at the short term. Moreover, tumor growth also reduced during 13 days of treatment. However, long-term treatment of DAPT promoted tumor growth in the xenograft model and enhanced the number and size of colonies and spheroids in vitro. The gene expression studies confirmed the up-regulation of Wnt and Notch downstream genes as well as AXIN1, CSNK2A3, and CEBPA2 following the removal of Notch inhibitor in vitro and in the xenograft model. Moreover, the Gompertz-based mathematical model determined a new drug resistance term in the present study. Our data supported that the long-term and not short-term inhibition of Notch by DAPT may enhance tumor growth and motility through up-regulation of AXIN1, CSNK2A3, and CEBPA2 genes in B-raf mutated A375 cells.

Current Molecular Markers of Melanoma and Treatment Targets

Melanoma is a deadly skin cancer that becomes especially difficult to treat after it metastasizes. Timely identification of melanoma is critical for effective therapy, but histopathologic diagnosis can frequently pose a significant challenge to this goal. Therefore, auxiliary diagnostic tools are imperative to facilitating prompt recognition of malignant lesions. Melanoma develops as result of a number of genetic mutations, with UV radiation often acting as a mutagenic risk factor. Novel methods of genetic testing have improved detection of these molecular alterations, which subsequently revealed important information for diagnosis and prognosis. Rapid detection of genetic alterations is also significant for choosing appropriate treatment and developing targeted therapies for melanoma. This review will delve into the understanding of various mutations and the implications they may pose for clinical decision making.

Molecular phenotyping and image-guided surgical treatment of melanoma using spectrally distinct ultrasmall core-shell silica nanoparticles

Accurate detection and quantification of metastases in regional lymph nodes remain a vital prognostic predictor for cancer staging and clinical outcomes. As intratumoral heterogeneity poses a major hurdle to effective treatment planning, more reliable image-guided, cancer-targeted optical multiplexing tools are critically needed in the operative suite. For sentinel lymph node mapping indications, accurately interrogating distinct molecular signatures on cancer cells in vivo with differential levels of sensitivity and specificity remains largely unexplored. To address these challenges and demonstrate sensitivity to detecting micrometastases, we developed batches of spectrally distinct 6-nm near-infrared fluorescent core-shell silica nanoparticles, each batch surface-functionalized with different melanoma targeting ligands. Along with PET imaging, particles accurately detected and molecularly phenotyped cancerous nodes in a spontaneous melanoma miniswine model using image-guided multiplexing tools. Information afforded from these tools offers the potential to not only improve the accuracy of targeted disease removal and patient safety, but to transform surgical decision-making for oncological patients.

Cell-state dynamics and therapeutic resistance in melanoma from the perspective of MITF and IFNγ pathways

Targeted therapy and immunotherapy have greatly improved the prognosis of patients with metastatic melanoma, but resistance to these therapeutic modalities limits the percentage of patients with long-lasting responses. Accumulating evidence indicates that a persisting subpopulation of melanoma cells contributes to resistance to targeted therapy or immunotherapy, even in patients who initially have a therapeutic response; however, the root mechanism of resistance remains elusive. To address this problem, we propose a new model, in which dynamic fluctuations of protein expression at the single-cell level and longitudinal reshaping of the cellular state at the cell-population level explain the whole process of therapeutic resistance development. Conceptually, we focused on two different pivotal signalling pathways (mediated by microphthalmia-associated transcription factor (MITF) and IFNγ) to construct the evolving trajectories of melanoma and described each of the cell states. Accordingly, the development of therapeutic resistance could be divided into three main phases: early survival of cell populations, reversal of senescence, and the establishment of new homeostatic states and development of irreversible resistance. On the basis of existing data, we propose future directions in both translational research and the design of therapeutic strategies that incorporate this emerging understanding of resistance.

Microphthalmia-Associated Transcription Factor (MITF) Regulates Immune Cell Migration into Melanoma

Microphthalmia-associated transcription factor (MITF) is a key transcription factor in melanoma development and progression. MITF amplification and downregulation have been observed in a significant proportion of melanoma patients and correlate with clinical outcomes. Here, we have investigated the effect of MITF on melanoma chemokine expression and immune cell attraction. In B16F10 melanoma cells, MITF knockdown reduced expression of CXCL10, with concomitantly decreased attraction of immune cells and accelerated tumor outgrowth. Conversely, overexpression of MITF in YUMM1.1 melanoma cells also led to an increased immune cell attraction in vitro. Subcutaneous YUMM1.1 melanomas overexpressing MITF however showed a reduced immune infiltration of lymphocytes and an increased tumor growth. In human melanoma cell lines, silencing of MITF enhanced chemokine production and immune cell attraction, while overexpression of MITF led to lower immune cell attraction. In summary, our results show that MITF regulates chemokine expression in murine and in human melanoma cells, and affects in vivo immune cell attraction and tumor growth. These results reveal a functional relationship between MITF and immune cell infiltration, which may be exploited for cancer therapy.

MITF suppression improves the sensitivity of melanoma cells to a BRAF inhibitor

Microphthalmia-associated transcription factor (MITF) is expressed in melanomas and has a critical role in melanocyte development and transformation. Because inhibition of MITF inhibits cell growth in melanoma, MITF is a potential therapeutic target molecule. Here, we report the identification of CH6868398, which has a novel chemical structure and suppresses MITF expression at the protein level in melanoma cells. CH6868398 showed cell growth inhibition activity against MITF-dependent melanoma cells both with and without BRAF mutation and also exhibited anti-tumor efficacy in a melanoma xenograft model. Because selective BRAF inhibitors are standard therapeutics for BRAF-mutated melanoma, we investigated the effect of CH6868398 with a BRAF inhibitor, PLX4720, on cell growth inhibition. The addition of CH6868398 enhanced the cell growth inhibition activity of PLX4720 in melanoma cell lines. Furthermore, combination of CH6868398 and PLX4720 efficiently suppressed MITF protein and enhanced cleavage of Caspase3 and poly (ADP-ribose) polymerase (PARP) in melanoma cell lines. These data support the therapeutic potential of CH6868398 as an anti-melanoma agent that reduces MITF protein levels in combination with BRAF inhibitors.

Assessing Genetic Expression Profiles in Melanoma Diagnosis

Most melanocytic tumors can be characterized as a benign nevus or a melanoma by a trained pathologist using traditional histopathological methods. However, a minority demonstrates ambiguous features and continues to be a diagnostic challenge. Genetic expression profiling (GEP) assays have been developed in an effort to resolve this dilemma. These assays measure mRNA levels of specified genes using reverse transcription quantitative polymerase chain reaction technology. The development of GEP assays, methodology, challenges associated with GEP validation and testing, and the suitability of a currently available GEP test for clinical use are reviewed.

MITF suppression by CH5552074 inhibits cell growth in melanoma cells

PURPOSE

Although treatment of melanoma with BRAF inhibitors and immune checkpoint inhibitors achieves a high response rate, a subset of melanoma patients with intrinsic and acquired resistance are insensitive to these therapeutics, so to improve melanoma therapy other target molecules need to be found. Here, we screened our chemical library to identify an anti-melanoma agent and examined its action mechanisms to show cell growth inhibition activity.

METHODS

We screened a chemical library against multiple skin cancer cell lines and conducted ingenuity pathway analysis (IPA) to investigate the mechanisms of CH5552074 activity. Suppression of microphthalmia-associated transcription factor (MITF) expression levels was determined in melanoma cells treated with CH5552074. Cell growth inhibition activity of CH5552074 was evaluated in MITF-dependent melanoma cell lines.

RESULTS

We identified an anti-melanoma compound, CH5552074, which showed remarkable cell growth inhibition activity in melanoma cell lines. The IPA results suggested that CH5552074-sensitive cell lines had activated MITF. In further in vitro studies in the melanoma cell lines, a knockdown of MITF with siRNA resulted in cell growth inhibition, which showed that CH5552074 inhibited cell growth by reducing the expression level of MITF protein.

CONCLUSIONS

These results suggest that CH5552074 can inhibit cell growth in melanoma cells by reducing the protein level of MITF. MITF inhibition by CH5552074 would be an attractive option for melanoma treatment.

Expression of microphthalmia transcription factor, S100 protein, and HMB-45 in malignant melanoma and pigmented nevi

Malignant melanoma (MM) is a type of malignant tumor, which originates from neural crest melanocytes. MM progresses rapidly and results in a high mortality rate. The present study aims to investigate the expression of microphthalmia transcription factor (MITF), the S100 protein, and HMB-45 in MM and pigmented nevi. A total of 32 MM samples (including three skin metastasis, three lymph node metastasis and two spindle cell MM samples), two Spitz nevus samples, four pigmented nevus samples and two blue nevus samples were collected. The expression levels of S100 protein, HMB-45, and MITF were observed via immunostaining. The S100 protein exhibited high positive rates in MM and pigment disorders (96.7 and 100%, respectively), but with low specificity. The S100 protein was also expressed in fibroblasts, myoepithelial cells, histocytes and Langerhans cells in normal skin samples. HMB-45 had high specificity. Its positive expression was only confined to MM cells and junctional nevus cells. Furthermore, HMB-45 was not expressed in melanocytes in the normal tissue samples around the tumor or in the benign intradermal nevus cells. MITF exhibited high specificity and high sensitivity. It was expressed in the nuclei of melanocytes, MM cells and nevus cells. It was observed to be strongly expressed in metastatic MM and spindle cell MMs. Thus, MITF may present as a specific immunomarker for the diagnosis and differential diagnosis of MM.

Differentiation-inducing and anti-proliferative activities of isoliquiritigenin and all-trans-retinoic acid on B16F0 melanoma cells: Mechanisms profiling by RNA-seq

Melanoma is a cancer that arises from melanocytes, specialized pigmented cells that are found predominantly in the skin. The incidence of malignant melanoma has significantly increased over the last decade. With the development of therapy, the survival rate of some kind of cancer has been improved greatly. But the treatment of melanoma remains unsatisfactory. Much of melanoma's resistance to traditional chemotherapy is believed to arise intrinsically, by virtue of potent growth and cell survival-promoting genetic alteration. Therefore, significant attention has recently been focused on differentiation therapy, as well as differentiation inducer compounds. In previous study, we found isoliquiritigenin (ISL), a natural product extracted from licorice, could induce B16F0 melanoma cell differentiation. Here we investigated the transcriptional response of melanoma differentiation process induced by ISL and all-trans-retinoic acid (RA). Results showed that 390 genes involves in 201 biochemical pathways were differentially expressed in ISL treatment and 304 genes in 193 pathways in RA treatment. Differential expressed genes (DGEs, fold-change (FC)≥10) with the function of anti-proliferative and differentiation inducing indicated a loss of grade malignancy characteristic. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis indicated glutathione metabolism, glycolysis/gluconeogenesis and pentose phosphate pathway were the top three relative pathway perturbed by ISL, and mitogen-activated protein kinase (MAPK) signaling pathway was the most important pathway in RA treatment. In the analysis of hierarchical clustering of DEGs, we discovered 72 DEGs involved in the process of drug action. We thought Cited1, Tgm2, Xaf1, Cd59a, Fbxo2, Adh7 may have critical role in the differentiation of melanoma. The evidence displayed herein confirms the critical role of reactive oxygen species (ROS) in melanoma pathobiology and provides evidence for future targets in the development of next-generation biomarkers and therapeutics.

Assessment of Melanocyte Density in Anorectal Mucosa for the Evaluation of Surgical Margins in Primary Anorectal Melanoma

OBJECTIVES

Accurate histopathologic evaluation of surgical resection margins for anorectal melanoma (AM) is diagnostically challenging but essential to clinical management. We studied intraepithelial melanocyte density and growth pattern in anorectal mucosa and BRAF V600E mutation status in AM compared to controls.

METHODS

Histomorphology and melanocytic immunostains, microphthalmia transcription factor (MITF) and human melanoma black 45 (HMB45), were evaluated. Utility of VE1 immunostaining for determination of BRAF V600E mutation status was studied.

RESULTS

Immunostains aid in the distinction between "trailing" melanoma in situ (MIS) and benign melanocyte hyperplasia (BMH), by facilitating assessment of melanocyte density, and evaluation of nuclear atypia and growth pattern. While respective melanocyte densities overlapped, "trailing" MIS could be distinguished by melanocyte nuclear atypia and near confluent growth, compared to the banal cytology and scattered growth of BMH.

CONCLUSIONS

In the histopathologic assessment of AM resections, MITF and HMB45 immunostains aid in distinguishing between "trailing" MIS and BMH, by highlighting melanocyte density, nuclear atypia, and growth pattern, with the latter two being reliable features. VE1 showed nonspecific immunopositivity in anorectal glandular epithelium, a potential diagnostic pitfall when assessing BRAF mutation status.

Acute Inhibition of MEK Suppresses Congenital Melanocytic Nevus Syndrome in a Murine Model Driven by Activated NRAS and Wnt Signaling

Congenital melanocytic nevus (CMN) syndrome is the association of pigmented melanocytic nevi with extra-cutaneous features, classically melanotic cells within the central nervous system, most frequently caused by a mutation of NRAS codon 61. This condition is currently untreatable and carries a significant risk of melanoma within the skin, brain, or leptomeninges. We have previously proposed a key role for Wnt signaling in the formation of melanocytic nevi, suggesting that activated Wnt signaling may be synergistic with activated NRAS in the pathogenesis of CMN syndrome. Some familial pre-disposition suggests a germ-line contribution to CMN syndrome, as does variability of neurological phenotypes in individuals with similar cutaneous phenotypes. Accordingly, we performed exome sequencing of germ-line DNA from patients with CMN to reveal rare or undescribed Wnt-signaling alterations. A murine model harboring activated NRAS(Q61K) and Wnt signaling in melanocytes exhibited striking features of CMN syndrome, in particular neurological involvement. In the first model of treatment for this condition, these congenital, and previously assumed permanent, features were profoundly suppressed by acute post-natal treatment with a MEK inhibitor. These data suggest that activated NRAS and aberrant Wnt signaling conspire to drive CMN syndrome. Post-natal MEK inhibition is a potential candidate therapy for patients with this debilitating condition.

Microphthalmia-associated transcription factor in melanoma development and MAP-kinase pathway targeted therapy

Malignant melanoma is a neoplasm of melanocytes, and the microphthalmia-associated transcription factor (MITF) is essential for the existence of melanocytes. MITF's relevance for this cell lineage is maintained in melanoma, where it is an important regulator of survival and balances melanoma cell proliferation with terminal differentiation (pigmentation). The MITF gene is amplified in ~20% of melanomas and MITF mutation can predispose to melanoma development. Furthermore, the regulation of MITF expression and function is strongly linked to the BRAF/MEK/ERK/MAP-kinase (MAPK) pathway, which is deregulated in >90% of melanomas and central target of current therapies. MITF expression in melanoma is heterogeneous, and recent findings highlight the relevance of this heterogeneity for the response of melanoma to MAPK pathway targeting drugs, as well as for MITF's role in melanoma progression. This review aims to provide an updated overview on the regulation of MITF function and plasticity in melanoma with a focus on its link to MAPK signaling.

MITF positivity in atypical fibroxanthoma: a diagnostic pitfall

Microphthalmia transcription factor (MITF) is an established melanocytic marker originally credited with a high degree of specificity. We report a series of 11 atypical fibroxanthoma (AFX) from 2 laboratories showing positive MITF staining. Although there are multiple case reports illustrating MITF staining in a range of tumors, aberrant staining in AFX has not been previously reported. Awareness of the possibility of MITF positivity in AFX is important to avoid a misdiagnosis of melanoma. We also report positive MITF staining in 2 nonneural granular cell tumors and discuss the overlap with the granular subtype of AFX.

Molecular markers in melanoma

The last few years have witnessed the dawn of the molecular era in melanoma treatment. With the advent of successful therapy targeting mutant BRAF, melanoma is leading the field of cancer research in the molecular approach to therapy of advanced disease. Attempting to keep pace with advances in therapy are advances in the molecular assessment of melanoma progression, facilitated by the availability of genome-wide approaches to interrogate the malignant phenotype. At the DNA level, this has included approaches such as comparative genomic hybridization. At the RNA level, this has consisted of gene expression profiling using various assay methodologies. In certain instances, markers identified using these platforms have been further examined and developed using fluorescence in situ hybridization and immunohistochemical analysis. In this article, we will review recent progress in the development of novel molecular markers for melanoma that are nearing clinical application. We will review developments in the molecular classification of melanoma, in the molecular diagnosis of melanoma, and in the molecular assessment of melanoma prognosis.

Investigation of cAMP microdomains as a path to novel cancer diagnostics

Understanding of cAMP signaling has greatly improved over the past decade. The advent of live cell imaging techniques and more specific pharmacologic modulators has led to an improved understanding of the intricacies by which cAMP is able to modulate such a wide variety of cellular pathways. It is now appreciated that cAMP is able to activate multiple effector proteins at distinct areas in the cell leading to the activation of very different downstream targets. The investigation of signaling proteins in cancer is a common route to the development of diagnostic tools, prognostic tools, and/or therapeutic targets, and in this review we highlight how investigation of cAMP signaling microdomains driven by the soluble adenylyl cyclase in different cancers has led to the development of a novel cancer biomarker. Antibodies directed against the soluble adenylyl cyclase (sAC) are highly specific markers for melanoma especially for lentigo maligna melanoma and are being described as "second generation" cancer diagnostics, which are diagnostics that determine the 'state' of a cell and not just identify the cell type. Due to the wide presence of cAMP signaling pathways in cancer, we predict that further investigation of both sAC and other cAMP microdomains will lead to additional cancer biomarkers. This article is part of a Special Issue entitled: The role of soluble adenylyl cyclase in health and disease.

Value of melanocytic-associated immunohistochemical markers in the diagnosis of malignant melanoma: a review and update

Since the identification of S100 protein as an immunohistochemical marker that could be useful in the diagnosis of melanoma in the early 1980s, a large number of other melanocytic-associated markers that could potentially be used to assist in the differential diagnosis of these tumors have also been investigated. A great variation exists, however, among these markers, not only in their expression in some subtypes of melanoma, particularly desmoplastic melanoma, but also in their specificity because some of them can also be expressed in nonmelanocytic neoplasms, including various types of soft tissue tumors and carcinomas. This article reviews the information that is currently available on the practical value of some of the markers that have more often been recommended for assisting in the diagnosis of melanomas, including those that have only recently become available.

Immunohistochemical diagnostic and prognostic markers for melanoma

Recent studies in our laboratory have identified novel molecular diagnostic and prognostic markers based on analyses in large cohorts of melanoma patients. These markers were initially derived from gene expression profiling analyses of distinct stages of melanoma progression. Immunohistochemical analyses confirmed the differential expression of these markers, and immunohistochemistry-based multimarker assays were developed to assess melanoma diagnosis and prognosis at the molecular level. In this chapter we review the development of these assays and the methodologies used to assess marker expression in both nevi and primary melanomas.

Wnt signaling potentiates nevogenesis

Cellular senescence is a stable proliferation arrest associated with an altered secretory pathway (senescence-associated secretory phenotype). Cellular senescence is also a tumor suppressor mechanism, to which both proliferation arrest and senescence-associated secretory phenotype are thought to contribute. The melanocytes within benign human nevi are a paradigm for tumor-suppressive senescent cells in a premalignant neoplasm. Here a comparison of proliferating and senescent melanocytes and melanoma cell lines by RNA sequencing emphasizes the importance of senescence-associated proliferation arrest in suppression of transformation. Previous studies showed that activation of the Wnt signaling pathway can delay or bypass senescence. Consistent with this, we present evidence that repression of Wnt signaling contributes to melanocyte senescence in vitro. Surprisingly, Wnt signaling is active in many senescent human melanocytes in nevi, and this is linked to histological indicators of higher proliferative and malignant potential. In a mouse, activated Wnt signaling delays senescence-associated proliferation arrest to expand the population of senescent oncogene-expressing melanocytes. These results suggest that Wnt signaling can potentiate nevogenesis in vivo by delaying senescence. Further, we suggest that activated Wnt signaling in human nevi undermines senescence-mediated tumor suppression and enhances the probability of malignancy.

MITF accurately highlights epidermal melanocytes in atypical intraepidermal melanocytic proliferations

Atypical intraepidermal melanocytic proliferations (AIMP) have random cytologic atypia and other histologic features that are concerning for malignancy and often require immunohistochemistry to differentiate from melanoma in situ. Immunostaining with S100, Melan-A, and microphthalmia-associated transcription factor (MITF) was performed for 49 morphologically well-characterized AIMP lesions. The percentage of cells in the basal layer of the epidermis that were identified as melanocytes by immunohistochemistry was compared with the percentage observed by morphology on hematoxylin and eosin staining, which is the gold standard stain for identifying cytologic atypia within an AIMP. Melan-A estimated the highest percentage of melanocytes and S100 the fewest in 47 of the 49 lesions examined. The estimated percentage of melanocytes was 23.3% (95% confidence interval: 18.6-28.1; P < 0.001) higher for Melan-A compared with hematoxylin and eosin staining. Melanocyte estimates were similar for hematoxylin and eosin and MITF (P = 0.15) although S100 estimated 21.8% (95% confidence interval: -27.2 to -16.4; P < 0.001) fewer melanocytes than hematoxylin and eosin. Melan-A staining produces higher estimates of epidermal melanocytes than S100 and MITF, which may increase the likelihood of diagnosing melanoma in situ. In contrast, melanoma in situ may be underdiagnosed with the use of S100, which results in lower estimates of melanocytes than the other 2 immunostains. Therefore, the best immunohistochemical marker for epidermal melanocytes is MITF.

MITF mutations associated with pigment deficiency syndromes and melanoma have different effects on protein function

The basic-helix-loop-helix-leucine zipper (bHLHZip) protein MITF (microphthalmia-associated transcription factor) is a master regulator of melanocyte development. Mutations in the MITF have been found in patients with the dominantly inherited hypopigmentation and deafness syndromes Waardenburg syndrome type 2A (WS2A) and Tietz syndrome (TS). Additionally, both somatic and germline mutations have been found in MITF in melanoma patients. Here, we characterize the DNA-binding and transcription activation properties of 24 MITF mutations found in WS2A, TS and melanoma patients. We show that most of the WS2A and TS mutations fail to bind DNA and activate expression from melanocyte-specific promoters. Some of the mutations, especially R203K and S298P, exhibit normal activity and may represent neutral variants. Mutations found in melanomas showed normal DNA-binding and minor variations in transcription activation properties; some showed increased potential to form colonies. Our results provide molecular insights into how mutations in a single gene can lead to such different phenotypes.

Expression of soluble adenylyl cyclase in lentigo maligna: use of immunohistochemistry with anti-soluble adenylyl cyclase antibody (R21) in diagnosis of lentigo maligna and assessment of margins

CONTEXT

Soluble adenylyl cyclase (sAC) is an enzyme that generates cyclic adenosine monophosphate, a signaling molecule involved in regulating melanocyte functions. R21, a mouse monoclonal antibody against sAC, shows a striking pan-nuclear staining in lentigo maligna, indicating possible utility for diagnosis and margin assessment.

OBJECTIVE

To evaluate R21 in the diagnosis and evaluation of margins in lentigo maligna.

DESIGN

Thirty one re-excision specimens for lentigo maligna were evaluated for R21 expression using previously published protocol. In addition, 153 cases including 41 lentigo malignas, 30 non-lentigo maligna-type melanomas, 38 lentigos, and 44 nevi were evaluated using a modified stringent protocol to eliminate all nonmelanocyte staining.

RESULTS

The sensitivity of nuclear staining with R21 in lentigo maligna was 87.8%. Nuclear expression of sAC was observed in 40% of other melanomas and 2.3% of benign nevi. R21 did not stain nuclei of resting melanocytes but was observed in 28.9% of melanocytic hyperplasias. These cases were easily distinguished from lentigo maligna in routine sections. R21 staining facilitated extent of the lesion in resection margins. In cases examined under the less stringent conditions, interpretation was facilitated by comparing R21 and Mart1/Melan A staining. Greater than 9 pan-nuclear staining melanocytes within one high-power field along with a pan-nuclear sAC/Melan A ratio greater than 0.5 was consistent with a positive margin whereas 5 or less pan-nuclear staining melanocytes along with a sAC/Melan A ratio of less than 0.3 constituted a negative margin.

CONCLUSION

R21 is a useful diagnostic adjunct in the diagnosis and evaluation of margins in re-excision specimens in lentigo maligna.

Collagen XVII is expressed in malignant but not in benign melanocytic tumors and it can mediate antibody induced melanoma apoptosis

The 180 kDa transmembrane collagen XVII is known to anchor undifferentiated keratinocytes to the basement membrane in hemidesmosomes while constitutively shedding a 120 kDa ectodomain. Inherited mutations or auto-antibodies targeting collagen XVII cause blistering skin disease. Collagen XVII is down-regulated in mature keratinocytes but re-expressed in skin cancer. By recently detecting collagen XVII in melanocyte hyperplasia, here we tested its expression in benign and malignant melanocytic tumors using endodomain and ectodomain selective antibodies. We found the full-length collagen XVII protein in proliferating tissue melanocytes, basal keratinocytes and squamous cell carcinoma whereas resting melanocytes were negative. Furthermore, the cell-residual 60 kDa endodomain was exclusively detected in 62/79 primary and 15/18 metastatic melanomas, 8/9 melanoma cell lines, HT199 metastatic melanoma xenografts and atypical nests in 8/63 dysplastic nevi. The rest of 19 nevi including common, blue and Spitz subtypes were also negative. In line with the defective ectodomain, sequencing of COL17A1 gene revealed aberrations in the ectodomain coding region including point mutations. Collagen XVII immunoreaction-stained spindle cell melanomas, showed partly overlapping profiles with those of S100B, Melan A and HMB45. It was concentrated at vertical melanoma fronts and statistically associated with invasive phenotype. Antibody targeting the extracellular aa507-529 terminus of collagen XVII endodomain promoted apoptosis and cell adhesion, while inhibiting proliferation in HT199 cells. These results suggest that the accumulation of collagen XVII endodomain in melanocytic tumors is associated with malignant transformation to be a potential marker of malignancy and a target for antibody-induced melanoma apoptosis.

Sox10 is expressed in primary melanocytic neoplasms of various histologies but not in fibrohistiocytic proliferations and histiocytoses

BACKGROUND

Sox10 is a transcription factor associated with neural crest development. Its expression has been reported in melanocytes and peripheral nerve sheath cells and their associated tumors.

OBJECTIVE

To assess Sox10 sensitivity in benign and malignant melanocytic neoplasms of various histologic subtypes and to discern the specificity of Sox10 in distinguishing between melanocytic neoplasms and fibrohistiocytic and histiocytic mimickers.

METHODS

Sox10 expression was examined by immunohistochemistry in 145 cases of formalin-fixed paraffin-embedded tissue, including benign and malignant melanocytic lesions of various histologies and stages (n = 83), fibrohistiocytic and histiocytic lesions (n = 33), and peripheral nerve sheath tumors (n = 19), among others (n = 10).

RESULTS

Immunoreactivity with Sox10 was observed in 100% (83/83) of benign and malignant melanocytic lesions of various subtypes, as well as in 100% (19/19) of benign and malignant peripheral nerve sheath lesions. Among the fibrohistiocytic proliferations and histiocytoses examined, Sox10 was negative in all cases (0/33). Sox10 expression did not vary by histologic subtype in nevi or melanoma; however, both the percentage of tumor nuclei demonstrating Sox10 expression and the intensity of expression were inversely correlated with malignant potential (nevi, melanoma in situ, invasive and metastatic melanoma) (P < .001, P = .016, respectively). Malignant peripheral nerve sheath tumors also showed decreased mean Sox10 expression and decreased intensity of expression when compared with benign counterparts (P < .001, P = .021, respectively).

LIMITATIONS

This is a retrospective study with 145 cases included.

CONCLUSIONS

Sox10 is a highly sensitive marker for melanocytic proliferations and may be useful diagnostically when the differential diagnosis includes fibrohistiocytic and histiocytic proliferations demonstrating S100 expression.

Mohs surgery for melanoma: rationale, advances and possibilities

Mohs surgery (MS) is an effective technique for the removal of a variety of cutaneous neoplasms by virtue of its thorough assessment of margins. It has yet to become widely accepted for melanoma because recognizing melanocytes histologically in frozen section can be problematic. Recently, 'rapid' methods of immunohistochemistry have been developed that resolve this issue by staining the melanocytes in frozen section. In addition, some of the immunohistochemistry protocols that previously required up to 1 h now take 19 min or less. These technological enhancements for MS have removed some of the obstacles towards the acceptance of MS as a legitimate option for removal of melanomas, especially poorly demarcated lesions and lesions from the head and neck, the distal extremities and the genitalia. Experience thus far with MS for melanoma has shown lower recurrence rates and improved disease-specific survival compared with historical controls for standard excision, while at the same time minimizing the sacrifice of normal tissue.

Tissue microarray analysis of ezrin, KBA.62, CD166, nestin, and p-Akt in melanoma versus banal and atypical nevi, and nonmelanocytic lesions

Multiple melanocytic markers are useful for differentiating between melanoma and nonmelanocytic lesions but generally do not distinguish melanoma from nevi and atypical melanocytic lesions. We sought to determine if several immunohistochemical markers recently described in the literature, including ezrin, KBA.62, p-Akt, CD166, and nestin, may be helpful in distinguishing these lesions. One hundred ten tissue microarray samples were scored for nestin and CD166 and 220 samples for ezrin, KBA.62, and p-Akt. We found that putative stem cell markers nestin and CD166 were both expressed in most melanomas (86% and 65% of samples, respectively), including desmoplastic melanoma, but were also expressed at similar levels in nevi (79% and 74%, respectively). In addition, these markers were not specific for melanocytic lesions. Ezrin was also expressed in both nevi and melanoma (81% each), including desmoplastic melanoma (75%), and in neural tumors. KBA.62 stained more cases of nevi versus melanoma (93% and 65%, respectively) and was positive in 53% of desmoplastic melanoma. However, it was also positive in several nonmelanocytic tumors. P-Akt expression was generally weak but was increased in nevi (75%) versus melanoma (43%), and was lost in desmoplastic melanomas (5%). Overall, only KBA.62 and p-Akt expression differed between melanoma and nevi, and none of these markers were completely specific for melanocytic tumors versus nonmelanocytic lesions.

Hypoxia and MITF control metastatic behaviour in mouse and human melanoma cells

Melanomas are very aggressive neoplasms with notorious resistance to therapeutics. It was recently proposed that the remarkable phenotypic plasticity of melanoma cells allows for the rapid development of both resistance to chemotherapeutic drugs and invasive properties. Indeed, the capacity of melanoma cells to form distant metastases is the main cause of mortality in melanoma patients. Therefore, the identification of the mechanism controlling melanoma phenotype is of paramount importance. In the present report, we show that deletion of microphthalmia-associated transcription factor (MITF), the master gene in melanocyte differentiation, is sufficient to increase the metastatic potential of mouse and human melanoma cells. MITF silencing also increases fibronectin and Snail, two mesenchymal markers that might explain the increased invasiveness in vitro and in vivo. Furthermore, ablation of this population by Forskolin-induced differentiation or MITF-forced expression significantly decreases tumour and metastasis formation, suggesting that eradication of low-MITF cells might improve melanoma treatment. Moreover, we demonstrate that a hypoxic microenvironment decreases MITF expression through an indirect, hypoxia-inducible factor 1 (HIF1)α-dependant transcriptional mechanism, and increases the tumourigenic and metastatic properties of melanoma cells. We identified Bhlhb2, a new factor in melanoma biology, as the mediator of hypoxia/HIF1α inhibitory effect on MITF expression. Our results reveal a hypoxia-HIF1α-BHLHB2-MITF cascade controlling the phenotypic plasticity in melanoma cells and favouring metastasis development. Targeting this pathway might be helpful in the design of new anti-melanoma therapies.

Immunohistochemistry of melanocytic proliferations

CONTEXT

Histologic analysis allows accurate classification of most melanocytic lesions as benign or malignant. Only in a minority of lesions is it necessary to use other techniques as an aid in the diagnosis. Among them, most authors recommend immunohistochemistry.

OBJECTIVE

To describe how to apply immunohistochemistry to particular differential diagnoses and the potential pitfalls.

DATA SOURCES

Personal experience and review of literature.

CONCLUSIONS

There is no single marker, or combination thereof, that establishes an unequivocal diagnosis of melanoma or nevus. Thus it is necessary to carefully analyze the pattern of expression (patchy versus diffuse) and localization (maturation) in the context of morphologic standard features.

Quantitative comparison of MiTF, Melan-A, HMB-45 and Mel-5 in solar lentigines and melanoma in situ

BACKGROUND

It is often challenging to reliably assess the number of lesional melanocytes in intraepidermal melanocytic proliferations involving sun-damaged skin. Therefore, dermatopathologists routinely use immunostains to help differentiate melanocytes from surrounding keratinocytes.

METHODS

Forty-three cases of solar lentigo or melanoma in situ (of the lentigo maligna type) were retrospectively chosen (20 melanomas in situ and 23 solar lentigo). Microphthalmia transcription factor (MiTF), HMB-45, Melan-A and Mel-5 immunostains were performed with an Azure blue counterstain, and the mean melanocyte counts were calculated within a 1-mm segment of epidermis.

RESULTS

In solar lentigines, the mean melanocyte counts were 27 (MiTF), 23 (HMB-45 and Mel-5) and 41 (Melan-A), as compared to hematoxylin and eosin (H&E) (25). In melanoma in situ, the mean melanocyte counts were 112 (MiTF), 149 (Melan-A), 111 (HMB-45) and 80 (Mel-5), as compared to H&E (109).

CONCLUSIONS

These results show that Melan-A significantly overestimates the density of melanocytes within dermatoheliotic skin. Compared to other tested stains, nuclear staining MiTF allowed greater distinction of melanocytes from keratinocytes with melanized cytoplasm. These findings indicate that MiTF is a superior marker for quantification of melanocytes in the evaluation of subtle intraepidermal melanocytic proliferations and in the differential diagnosis of solar lentigo.