Role of epithelial–mesenchymal transition involved molecules in the progression of cutaneous melanoma

Prostate-specific antigen: An unfamiliar protein in the human salivary glands

OBJECTIVES

The presence of prostate-specific antigen (PSA) in saliva and salivary glands has been reported. Nevertheless, its release pathway in these glands remains to be elucidated. Here, we showed PSA subcellular distribution focusing on its plausible route in human salivary parenchyma.

MATERIALS AND METHODS

Sections of parotid and submandibular glands were subjected to the immunohistochemical demonstration of PSA by the streptavidin-biotin method revealed by alkaline phosphatase. Moreover, ultrathin sections were collected on nickel grids and processed for immunocytochemical analysis, to visualize the intracellular distribution pattern of PSA through the observation by transmission electron microscopy.

RESULTS

By immunohistochemistry, in both parotid and submandibular glands PSA expression was detected in serous secretory acini and striated ducts. By immunocytochemistry, immunoreactivity was retrieved in the cytoplasmic compartment of acinar and ductal cells, often associated with small cytoplasmic vesicles. PSA labeling appeared also on rough endoplasmic reticulum and in the acini's lumen. A negligible PSA labeling appeared in most of the secretory granules of both glands.

CONCLUSIONS

Our findings clearly support that human parotid and submandibular glands are involved in PSA secretion. Moreover, based on the immunoreactivity pattern, its release in oral cavity would probably occur by minor regulated secretory or constitutive-like secretory pathways.

Differentiation States of Phenotypic Transition of Melanoma Cells Are Revealed by 3D Cell Cultures

Melanoma is characterized by high metastatic potential favored by the epithelial-to-mesenchymal transition (EMT), leading melanoma cells to exhibit a spectrum of typical EMT markers. This study aimed to analyze the expression of EMT markers in A375 and BLM melanoma cell lines cultured in 2D monolayers and 3D spheroids using morphological and molecular methods. The expression of EMT markers was strongly affected by 3D arrangement and revealed a hybrid phenotype for the two cell lines. Indeed, although E-cadherin was almost undetectable in both A375 and BLM cells, cortical actin was detected in A375 2D monolayers and 3D spheroids and was strongly expressed in BLM 3D spheroids. The mesenchymal marker N-cadherin was significantly up-regulated in A375 3D spheroids while undetectable in BLM cells, but vimentin was similarly expressed in both cell lines at the gene and protein levels. This pattern suggests that A375 cells exhibit a more undifferentiated/mesenchymal phenotype, while BLM cells have more melanocytic/differentiated characteristics. Accordingly, the Zeb1 and 2, Slug, Snail and Twist gene expression analyses showed that they were differentially expressed in 2D monolayers compared to 3D spheroids, supporting this view. Furthermore, A375 cells are characterized by a greater invasive potential, strongly influenced by 3D arrangement, compared to the BLM cell line, as evaluated by SDS-zymography and TIMPs gene expression analysis. Finally, TGF-β1, a master controller of EMT, and lysyl oxidase (LOX), involved in melanoma progression, were strongly up-regulated by 3D arrangement in the metastatic BLM cells alone, likely playing a role in the metastatic phases of melanoma progression. Overall, these findings suggest that A375 and BLM cells possess a hybrid/intermediate phenotype in relation to the expression of EMT markers. The former is characterized by a more mesenchymal/undifferentiated phenotype, while the latter shows a more melanocytic/differentiated phenotype. Our results contribute to the characterization of the role of EMT in melanoma cells and confirm that a 3D cell culture model could provide deeper insight into our understanding of the biology of melanoma.

Role of PLK1/NUMB/NOTCH in epithelial-mesenchymal transition in human melanoma

Polo-like kinase 1 (PLK1), a serine/threonine kinase, is overexpressed in melanoma and its expression has been associated with poor disease prognosis. PLK1 has been shown to interact with NUMB, a NOTCH antagonist. However, the exact role of PLK1, NUMB, and NOTCH signaling in epithelial-mesenchymal transition (EMT) in melanoma progression is unclear. In this study, Affymetrix microarray analysis was performed to determine differentially expressed genes following shRNA-mediated knockdown of PLK1 in human melanoma cells that showed significant modulations in EMT and metastasis-related genes. Using multiple PLK1-modulated melanoma cell lines, we found that PLK1 is involved in the regulation of cell migration, invasion, and EMT via its kinase activity and NOTCH activation. In vitro kinase assay and mass spectrometry analysis demonstrated a previously unknown PLK1 phosphorylation site (Ser413) on NUMB. Overexpression of non-phosphorylatable (S413A) and phosphomimetic (S413D) mutants of NUMB in melanoma cells implicated the involvement of NUMB-S413 phosphorylation in cell migration and invasion, which was independent of NOTCH activation. To determine the clinical relevance of these findings, immunohistochemistry was performed using melanoma tissue microarray, which indicated a strong positive correlation between PLK1 and N-cadherin, a protein required for successful EMT. These findings were supported by TCGA analysis, where expression of high PLK1 with low NUMB or high NOTCH or N-cadherin showed a significant decrease in survival of melanoma patients. Overall, these results suggest a potential role of PLK1 in EMT, migration, and invasion of melanoma cells. Our findings support the therapeutic targeting of PLK1, NUMB, and NOTCH for melanoma management.

Sphingolipid paracrine signaling impairs keratinocyte adhesion to promote melanoma invasion

Melanoma is the deadliest form of skin cancer due to its propensity to metastasize. It arises from melanocytes, which are attached to keratinocytes within the basal epidermis. Here, we hypothesize that, in addition to melanocyte-intrinsic modifications, dysregulation of keratinocyte functions could initiate early-stage melanoma cell invasion. We identified the lysolipid sphingosine 1-phosphate (S1P) as a tumor paracrine signal from melanoma cells that modifies the keratinocyte transcriptome and reduces their adhesive properties, leading to tumor invasion. Mechanistically, tumor cell-derived S1P reduced E-cadherin expression in keratinocytes via S1P receptor dependent Snail and Slug activation. All of these effects were blocked by S1P2/3 antagonists. Importantly, we showed that epidermal E-cadherin expression was inversely correlated with the expression of the S1P-producing enzyme in neighboring tumors and the Breslow thickness in patients with early-stage melanoma. These findings support the notion that E-cadherin loss in the epidermis initiates the metastatic cascade in melanoma.

Therapeutic targeting of anoikis resistance in cutaneous melanoma metastasis

The acquisition of resistance to anoikis, the cell death induced by loss of adhesion to the extracellular matrix, is an absolute requirement for the survival of disseminating and circulating tumour cells (CTCs), and for the seeding of metastatic lesions. In melanoma, a range of intracellular signalling cascades have been identified as potential drivers of anoikis resistance, however a full understanding of the process is yet to be attained. Mechanisms of anoikis resistance pose an attractive target for the therapeutic treatment of disseminating and circulating melanoma cells. This review explores the range of small molecule, peptide and antibody inhibitors targeting molecules involved in anoikis resistance in melanoma, and may be repurposed to prevent metastatic melanoma prior to its initiation, potentially improving the prognosis for patients.

Retinoblastoma-Binding Protein 5 Regulates H3K4 Methylation Modification to Inhibit the Proliferation of Melanoma Cells by Inactivating the Wnt/β-Catenin and Epithelial-Mesenchymal Transition Pathways

Histone 3 lysine 4 methylation (H3K4me), especially histone 3 lysine 4 trimethylation (H3K4me3), is one of the most extensively studied patterns of histone modification and plays crucial roles in many biological processes. However, as a part of H3K4 methyltransferase that participates in H3K4 methylation and transcriptional regulation, retinoblastoma-binding protein 5 (RBBP5) has not been well studied in melanoma. The present study sought to explore RBBP5-mediated H3K4 histone modification and the potential mechanisms in melanoma. RBBP5 expression in melanoma and nevi specimens was detected by immunohistochemistry. Western blotting was performed for three pairs of melanoma cancer tissues and nevi tissues. In vitro and in vivo assays were used to investigate the function of RBBP5. The molecular mechanism was determined using RT-qPCR, western blotting, ChIP assays, and Co-IP assays. Our study showed that RBBP5 was significantly downregulated in melanoma tissue and cells compared with nevi tissues and normal epithelia cells (P < 0.05). Reducing RBBP5 in human melanoma cells leads to H3K4me3 downregulation and promotes cell proliferation, migration, and invasion. On the one hand, we verified that WSB2 was an upstream gene of RBBP5-mediated H3K4 modification, which could directly bind to RBBP5 and negatively regulate its expression. On the other hand, we also confirmed that p16 (a cancer suppressor gene) was a downstream target of H3K4me3, the promoter of which can directly bind to H3K4me3. Mechanistically, our data revealed that RBBP5 inactivated the Wnt/β-catenin and epithelial-mesenchymal transition (EMT) pathways (P < 0.05), leading to melanoma suppression. Histone methylation is rising as an important factor affecting tumorigenicity and tumor progression. Our findings verified the significance of RBBP5-mediated H3K4 modification in melanoma and the potential regulatory mechanisms of melanoma proliferation and growth, suggesting that RBBP5 is a potential therapeutic target for the treatment of melanoma.

The Nitric Oxide Donor [Zn(PipNONO)Cl] Exhibits Antitumor Activity through Inhibition of Epithelial and Endothelial Mesenchymal Transitions

Simple Summary

Nitric oxide (NO) plays a critical pathophysiological role in cancer by modulating several processes, such as angiogenesis, tumor growth, and metastatic potential. The aim of this study was to characterize the antitumor effects of a novel NO donor, [Zn(PipNONO)Cl], on the processes of epithelial– and endothelial–mesenchymal transitions (EMT and EndMT), known to actively participate in cancer progression. Two tumor cells lines were used in this study: human lung cancer cells (A549) and melanoma cells (A375), alone and co-cultured with human endothelial cells. Our results demonstrate that both tumor and endothelial cells were targets of NO action, which impaired EMT and EndMT functional and molecular features. Further studies are needed to finalize the therapeutic use of the novel NO donor.

Abstract

Exogenous nitric oxide appears a promising therapeutic approach to control cancer progression. Previously, a nickel-based nonoate, [Ni(SalPipNONO)], inhibited lung cancer cells, along with impairment of angiogenesis. The Zn(II) containing derivatives [Zn(PipNONO)Cl] exhibited a protective effect on vascular endothelium. Here, we have evaluated the antitumor properties of [Zn(PipNONO)Cl] in human lung cancer (A549) and melanoma (A375) cells. Metastasis initiates with the epithelial–mesenchymal transition (EMT) process, consisting of the acquisition of invasive and migratory properties by tumor cells. At not cytotoxic levels, the nonoate significantly impaired A549 and A375 EMT induced by transforming growth factor-β1 (TGF-β1). Reduction of the mesenchymal marker vimentin, upregulated by TGF-β1, and restoration of the epithelial marker E-cadherin, reduced by TGF-β1, were detected in both tumor cell lines in the presence of Zn-nonoate. Further, the endothelial–mesenchymal transition achieved in a tumor-endothelial cell co-culture was assessed. Endothelial cells co-cultured with A549 or A375 acquired a mesenchymal phenotype with increased vimentin, alpha smooth muscle actin and Smad2/3, and reduced VE-cadherin. The presence of [Zn(PipNONO)Cl] maintained a typical endothelial phenotype. In conclusion, [Zn(PipNONO)Cl] appears a promising therapeutic tool to control tumor growth and metastasis, by acting on both tumor and endothelial cells, reprogramming the cells toward their physiologic phenotypes.

Increased expression of secreted protein acidic and rich in cysteine and tissue inhibitor of metalloproteinase-3 in epidermotropic melanoma metastasis

Primary cutaneous melanoma generally arises in the epidermis, followed by invasion into the dermis. Although infrequent, invasive melanoma cells can, alternatively, migrate to the intraepidermal area and form epidermotropic melanoma metastasis (EMM). In this study, we focused on this unique manner of metastasis. To identify the key molecules which affect EMM, gene expression in EMM was compared with that in common skin metastasis (CSM). Polymerase chain reaction (PCR) analysis was performed for genes affecting the extracellular matrix, cellular adhesion, and tumor metastasis on three EMM and three CSM samples as an initial screening. For molecules showing altered expression in the EMM, expression levels were further verified using real-time quantitative PCR (qPCR) and immunohistochemistry. Five molecules showed an expression difference in the initial screening. Among these, secreted protein acidic and rich in cysteine (SPARC) was preferentially expressed in EMM (p = 0.01) by real-time qPCR. Another candidate molecule, tissue inhibitor of metalloproteinase-3 (TIMP3), was not statistically significant (p = 0.07), but showed the tendency of higher expression. These results correlated negatively to expression of N-cadherin and β-catenin. The upregulation of SPARC and TIMP3 may disrupt the continuity of the canonical Wnt pathway. This pathway regulates adhesion activity of melanoma cells to localize within the dermis, which consequently promotes EMM. Our study highlights the potential role of SPARC and TIMP3 as key molecules in EMM, and analysis of EMM may contribute for understanding melanoma invasion between the epidermis and the dermis.

Cell Adhesion Molecules in Normal Skin and Melanoma

Cell adhesion molecules (CAMs) of the cadherin, integrin, immunoglobulin, and selectin protein families are indispensable for the formation and maintenance of multicellular tissues, especially epithelia. In the epidermis, they are involved in cell–cell contacts and in cellular interactions with the extracellular matrix (ECM), thereby contributing to the structural integrity and barrier formation of the skin. Bulk and single cell RNA sequencing data show that >170 CAMs are expressed in the healthy human skin, with high expression levels in melanocytes, keratinocytes, endothelial, and smooth muscle cells. Alterations in expression levels of CAMs are involved in melanoma propagation, interaction with the microenvironment, and metastasis. Recent mechanistic analyses together with protein and gene expression data provide a better picture of the role of CAMs in the context of skin physiology and melanoma. Here, we review progress in the field and discuss molecular mechanisms in light of gene expression profiles, including recent single cell RNA expression information. We highlight key adhesion molecules in melanoma, which can guide the identification of pathways and strategies for novel anti-melanoma therapies.

Epithelial-to-mesenchymal-like transition events in melanoma

Epithelial-to-mesenchymal transition (EMT), a process through which epithelial tumor cells acquire mesenchymal phenotypic properties, contributes to both metastatic dissemination and therapy resistance in cancer. Accumulating evidence indicates that nonepithelial tumors, including melanoma, can also gain mesenchymal-like properties that increase their metastatic propensity and decrease their sensitivity to therapy. In this review, we discuss recent findings, illustrating the striking similarities-but also knowledge gaps-between the biology of mesenchymal-like state(s) in melanoma and mesenchymal state(s) from epithelial cancers. Based on this comparative analysis, we suggest hypothesis-driven experimental approaches to further deepen our understanding of the EMT-like process in melanoma and how such investigations may pave the way towards the identification of clinically relevant biomarkers for prognosis and new therapeutic strategies.

COPS8 in cutaneous melanoma: an oncogene that accelerates the malignant development of tumor cells and predicts poor prognosis

This study aimed to investigate the roles of COP9 signalosome subunit 8 (COPS8) and its underlying mechanism in cutaneous melanoma. Bioinformatics tools were utilized to analyze the expression of COPS8 in cutaneous melanoma, while Kaplan-Meier analysis was employed to assess the correlation between COPS8 and patients' overall survival. The proliferation, migration, and invasion of cells were estimated by CCK8, colony formation, and Transwell assays. Western blot was used to check the expression of epithelial-mesenchymal transition (EMT)-related proteins. Results showed that COPS8 was up-regulated and predicted a poor clinical outcome for cutaneous melanoma patients. Knockdown of COPS8 inhibited cutaneous melanoma cell proliferation, migration and invasion, whereas overexpression of COPS8 resulted in the opposite outcomes. The up-regulation of E-cadherin and down-regulation of N-cadherin, vimentin, and snail were caused by silencing COPS8 while their expression showed contrary trends in cells with overexpressed COPS8. Collectively, COPS8 is up-regulated and promotes cutaneous melanoma progression via regulating EMT.

The Role of Epithelial-to-Mesenchymal Transition in Cutaneous Squamous Cell Carcinoma : Epithelial-to-Mesenchymal Transition in Cutaneous SCC

OPINION STATEMENT

The capacity of cells to modify their phenotypes from epithelial to mesenchymal (epithelial-to-mesenchymal transition or EMT) and vice versa provides them with a dynamic plasticity essential for human life, from embryogenesis to wound healing. Current knowledge about carcinogenetic mechanisms leaves little doubts on the pivotal participation of these interchangeable processes in cancer development, and their influence has been quite clearly established in the progression of cutaneous squamous cell carcinoma. A complex and ordered interplay of signals induces the shift between both phenotypes, providing cells with the most suitable state at every moment to face the next step in tumor invasion and dissemination. Some stimulatory triggers have opposite effects according to the biological context and in many cases exert collateral functions. This scenario makes finding an ideal therapeutic target difficult but provides the opportunity to intervene simultaneously at many different levels with small actions such as targeting the tumor environment. In any case, advances in knowledge of the EMT mechanisms and their influence on carcinogenesis and drug resistance will greatly influence the therapeutic strategies for many human tumors, including cutaneous squamous cell carcinoma.

Innate and Adaptive Immunity Linked to Recognition of Antigens Shared by Neural Crest-Derived Tumors

In the adult, many embryologic processes can be co-opted by during cancer progression. The mechanisms of divisions, migration, and the ability to escape immunity recognition linked to specific embryo antigens are also expressed by malignant cells. In particular, cells derived from neural crests (NC) contribute to the development of multiple cell types including melanocytes, craniofacial cartilage, glia, neurons, peripheral and enteric nervous systems, and the adrenal medulla. This plastic performance is due to an accurate program of gene expression orchestrated with cellular/extracellular signals finalized to regulate long-distance migration, proliferation, differentiation, apoptosis, and survival. During neurulation, prior to initiating their migration, NC cells must undergo an epithelial–mesenchymal transition (EMT) in which they alter their actin cytoskeleton, lose their cell–cell junctions, apicobasal polarity, and acquire a motile phenotype. Similarly, during the development of the tumors derived from neural crests, comprising a heterogeneous group of neoplasms (Neural crest-derived tumors (NCDTs)), a group of genes responsible for the EMT pathway is activated. Here, retracing the molecular pathways performed by pluripotent cells at the boundary between neural and non-neural ectoderm in relation to the natural history of NCDT, points of contact or interposition are highlighted to better explain the intricate interplay between cancer cells and the innate and adaptive immune response.

Epithelial-Mesenchymal Transition in Skin Cancers: A Review

Epithelial-mesenchymal transition (EMT) is involved in physiologic processes such as embryogenesis and wound healing. A similar mechanism occurs in some tumors where cells leave the epithelial layer and gain mesenchymal particularities in order to easily migrate to other tissues. This process can explain the invasiveness and aggressiveness of these tumors which metastasize, by losing the epithelial phenotype (loss of E-cadherin, desmoplakin, and laminin-1) and acquiring mesenchymal markers (N-cadherin). Complex changes and interactions happen between the tumor cells and the microenvironment involving different pathways, transcription factors, altered expression of adhesion molecules, reorganization of cytoskeletal proteins, production of ECM-degrading enzymes, and changes in specific microRNAs. The purpose of this review is to determine particularities of the EMT process in the most common malignant cutaneous tumors (squamous cell carcinoma, basal cell carcinoma, and melanoma) which still have an increasingly high incidence. More studies are required on this topic in order to establish clear correlations. High costs related to skin cancer therapies in general as well as high impact on patients' quality of life demand finding new, reliable prognostic and therapeutic markers with significant public health impact.

GSTO1 regards as a meritorious regulator in cutaneous malignant melanoma cells

BACKGROUND

Glutathione S-transferase omega 1 (GSTO1), as a member of the glutathione S-transferase (GST) family genes, has been discovered to be up-regulated in several cancer cell lines which exhibited strong aggressiveness. However, the function of GSTO1 on cutaneous malignant melanoma (CMM) has not been illuminated.

METHODS

Outcome of expression level and prognosis of GSTO1 were obtained from Oncomine and TCGA database. The specific effects of GSTO1 on the characteristics and regulatory mechanism of CMM cells were demonstrated by cell counting kit-8, colony formation, flow cytometry, and transwell assays in vitro. Western blot was employed to analyze the expression of proliferating cell nuclear antigen (PCNA), p53 and epithelial-to-mesenchymal (EMT) related proteins.

RESULTS

We observed that GSTO1 was up-regulated in CMM samples when compared with the corresponding controls. Moreover, patients in CMM with high expression of GSTO1 were more likely to have a poor prognosis. Through in vitro experiments, silenced GSTO1 resulted in inhibition of CMM cells growth and aggressiveness, increased cell apoptosis, and blocked cell cycle. Finally, the expression of PCNA, p53 and EMT-related proteins were changed due to reduction of GSTO1.

CONCLUSIONS

To sum up, our outcomes exhibited that weakening GSTO1 reduced the proliferation and mobility of CMM cells, increased the apoptosis ability of CMM cells, and arrested cell cycle at G1 phase, which can be achieved by affecting the expression of PCNA, p53 and the EMT process. This discovery provided a new perspective for elucidating the mechanism of CMM, and offered theoretical support for searching clinical therapeutic targets in the future.

Tyrosinase and nestin immunohistochemical expression in melanocytic nevi as a histopathologic pattern to trace melanocyte differentiation and nevogenesis

While histological analysis represents a powerful tool for the classification of melanocytic lesions as benign or malignant, a clear-cut distinction between a nevus and a melanoma is sometimes a challenging step of the diagnostic process. The immunohistochemical detection of tyrosinase, cardinal melanogenic enzyme during melanocytic maturation, has often been helpful in formulating a differential diagnosis due to the peculiar staining pattern in nevocytes compared with melanoma cells. Tyrosinase distribution in nevi appears to overlap with the cytoarchitectural changes observable within these lesions, that result in epidermal or superficial dermal nevocytes being larger and strongly expressing melanocytic differentiation antigens, such as tyrosinase, compared with deeper dermal nevus cells. Our study aimed to evaluate the immunohistochemical expression pattern of tyrosinase in different histological types of acquired dysplastic melanocytic nevi, including junctional, compound, and intradermal nevi. Moreover, to estimate whether in nevocytes the expression of tyrosinase was associated with their differentiation state, we investigated the expression of two recognized markers of pluripotency, CD34 and nestin. In all examined nevi, our analysis revealed a remarkable immunoreactivity for tyrosinase in junctional and superficial dermal nevocytes and a decreasing gradient of staining in dermal nevocytes, up to become negative in deeper dermis. Meanwhile, junctional and dermal nevocytes were lacking in CD34 protein. Furthermore, nestin immunostaining showed an opposite distribution compared with tyrosinase, leading us to look into the tyrosinase/nestin expression pattern in melanocytic nevus as a tool to better understand the final stages of differentiation of melanocyte precursors toward their ultimate anatomical site into the epidermis.

miR-204-5p and miR-3065-5p exert antitumor effects on melanoma cells

MicroRNA (miR)-204-5p was previously identified to be downregulated in melanoma compared with melanocytic nevi. This observation prompted a functional study on miR-204-5p and the newly-identified miR-3065-5p, two miRNAs suggested to be tumor-suppressive oncomiRs. Application of miR-204-5p mimics or inhibitors resulted in a decrease or increase, respectively, in melanoma cell proliferation and colony formation. miR-204-5p mimics hindered invasion, whereas miR-204-5p inhibitors stimulated cancer cell migration. Modulation of miR-3065-5p led to a decrease in melanoma cell proliferation, altered cell cycle distribution and increased expression levels of its target genes HIPK1 and ITGA1, possibly due to functional modifications identified in these cells. miR-204-5p and miR-3065-5p demonstrated antitumor capacities that may need to be taken into account in the development of melanoma treatment approaches.