A high-throughput study in melanoma identifies epithelial-mesenchymal transition as a major determinant of metastasis

Long non-coding RNA GRASLND links melanoma differentiation and interferon-gamma response

Melanoma is a highly malignant tumor, that stands as the most lethal form of skin cancer and is characterized by notable phenotypic plasticity and intratumoral heterogeneity. Melanoma plasticity is involved in tumor growth, metastasis and therapy resistance. Long non-coding RNAs (lncRNAs) could influence plasticity due to their regulatory function. However, their role and mode of action are poorly studied. Here, we show a relevance of lncRNA GRASLND in melanoma differentiation and IFNγ signaling. GRASLND knockdown revealed switching of differentiated, melanocytic melanoma cells towards a dedifferentiated, slow-proliferating and highly-invasive cell state. Interestingly, GRASLND is overexpressed in differentiated melanomas and associated with poor prognosis. Accordingly, we found GRASLND expressed in immunological "cold" tumors and it negatively correlates with gene signatures of immune response activation. In line, silencing of GRASLND under IFNγ enhanced the expression of IFNγ-stimulated genes, including HLA-I antigen presentation, demonstrating suppressive activity of GRASLND on IFNγ signaling. Our findings demonstrate that in differentiated melanomas elevated expression of GRASLND interferes with anti-tumor effects of IFNγ, suggesting a role of GRASLND in tumor immune evasion.

Identification and characterization of TM4SF1+ tumor self-seeded cells

Tumor self-seeding is a process whereby circulating tumor cells (CTCs) recolonize the primary tumor, which promotes tumor growth, angiogenesis, and invasion. However, the detailed nature and functions of tumor self-seeded cells (TSCs) have not been well defined due to challenges in tracking and isolating TSCs. Here, we report an accurate animal model using photoconvertible tagging to recapitulate the spontaneous process of tumor self-seeding and identify TSCs as a subpopulation of primary tumor cells with enhanced invasiveness and survival. We demonstrate transmembrane-4-L-six-family-1 (TM4SF1) as a marker of TSCs, which promotes migration, invasion, and anchorage-independent survival in cancer cells. By analyzing single-cell RNA sequencing datasets, we identify a potential TSC population with a metastatic profile in patients with cancer, which is detectable in early-stage disease and expands during cancer progression. In summary, we establish a framework to study TSCs and identify emerging cell targets with diagnostic, prognostic, or therapeutic potential in cancers.

Engineering Microorganisms for Cancer Immunotherapy

Cancer immunotherapy presents a promising approach to fight against cancer by utilizing the immune system. Recently, engineered microorganisms have emerged as a potential strategy in cancer immunotherapy. These microorganisms, including bacteria and viruses, can be designed and modified using synthetic biology and genetic engineering techniques to target cancer cells and modulate the immune system. This review delves into various microorganism-based therapies for cancer immunotherapy, encompassing strategies for enhancing efficacy while ensuring safety and ethical considerations. The development of these therapies holds immense potential in offering innovative personalized treatments for cancer.

Generation of 3D melanoma models using an assembloid-based approach

While 3D tumor models have greatly evolved over the past years, there is still a strong requirement for more biosimilar models which are capable of recapitulating cellular crosstalk within the tumor microenvironment while equally displaying representative levels of tumor aggressiveness and invasion. Herein, we disclose an assembloid melanoma model based on the fusion of individual stromal multicellular spheroids (MCSs). In contrast to more traditional tumor models, we show that it is possible to develop self-organizing, heterotypic melanoma models where tumor cells present stem-cell like features like up-regulated pluripotency master regulators SOX2, POU5F1 and NANOG. Additionally, these assembloids display high levels of invasiveness while embedded in 3D matrices as evidenced by stromal cell promotion of melanoma cell invasion via metalloproteinase production. Furthermore, sensitivity to anticancer drug doxorubicin was demonstrated for the melanoma assembloid model. These findings suggest that melanoma assembloids may play a significant role in the field of 3D cancer models as they more closely mimic the tumor microenvironment when compared to more traditional MCSs, opening the doors to a better understanding of the role of tumor microenvironment in supporting tumor progression. STATEMENT OF SIGNIFICANCE: The development of complex 3D tumor models that better recapitulate the tumor microenvironment is crucial for both an improved comprehension of intercellular crosstalk and for more efficient drug screening. We have herein developed a self-organizing heterotypic assembloid-based melanoma model capable of closely mimicking the tumor microenvironment. Key features recapitulated were the preservation of cancer cell stemness, sensitivity to anti-cancer agents and tumor cell invasion promoted by stromal cells. The approach of pre-establishing distinct stromal domains for subsequent combination into more complex tumor constructs provides a route for developing superior tumor models with a higher degree of similarity to native cancer tissues.

Dormancy of cutaneous melanoma

Many cancer-related deaths including melanoma result from metastases that develop months or years after the initial cancer therapy. Even the most effective drugs and immune therapies rarely eradicate all tumor cells. Instead, they strongly reduce cancer burden, permitting dormant cancer cells to persist in niches, where they establish a cellular homeostasis with their host without causing clinical symptoms. Dormant cancers respond poorly to most drugs and therapies since they do not proliferate and hide in niches. It therefore remains a major challenge to develop novel therapies for dormant cancers. In this review we focus on the mechanisms regulating the initiation of cutaneous melanoma dormancy as well as those which are involved in reawakening of dormant cutaneous melanoma cells. In recent years the role of neutrophils and niche components in reawakening of melanoma cells came into focus and indicate possible future therapeutic applications. Sophisticated in vitro and in vivo melanoma dormancy models are needed to make progress in this field and are discussed.

The Use of Gene Expression Profiling and Biomarkers in Melanoma Diagnosis and Predicting Recurrence: Implications for Surveillance and Treatment

Cutaneous melanoma is becoming more prevalent in the United States and has the highest mortality among cutaneous malignancies. The majority of melanomas are diagnosed at an early stage and, as such, survival is generally favorable. However, there remains prognostic uncertainty among subsets of early- and intermediate-stage melanoma patients, some of whom go on to develop advanced disease while others remain disease-free. Melanoma gene expression profiling (GEP) has evolved with the notion to help bridge this gap and identify higher- or lower-risk patients to better tailor treatment and surveillance protocols. These tests seek to prognosticate melanomas independently of established AJCC 8 cancer staging and clinicopathologic features (sex, age, primary tumor location, thickness, ulceration, mitotic rate, lymphovascular invasion, microsatellites, and/or SLNB status). While there is a significant opportunity to improve the accuracy of melanoma prognostication and diagnosis, it is equally important to understand the current landscape of molecular profiling for melanoma treatment. Society guidelines currently do not recommend molecular testing outside of clinical trials for melanoma clinical decision making, citing insufficient high-quality evidence guiding indications for the testing and interpretation of results. The goal of this chapter is to review the available literature for GEP testing for melanoma diagnosis and prognostication and understand their place in current treatment paradigms.

MGRN1 depletion promotes intercellular adhesion in melanoma by upregulation of E-cadherin and inhibition of CDC42

Mahogunin Ring Finger 1 is an E3-ubiquitin ligase encoded by the color gene MGRN1. Our previous in vitro and in vivo studies demonstrated that Mgrn1 deletion in mouse melanoma cells induced cell differentiation and adhesion, and decreased cell motility and invasion on collagen I, and lung colonization in an in vivo model. Here, we investigated the role of MGRN1 on human melanoma cell morphology, adhesion and expression of genes/proteins involved in an EMT-like transition. We demonstrated that wild-type BRAF human melanoma cells adopted a clustering-like morphology on collagen I, with permanent MGRN1 abrogation resulting in bigger cell clusters. Enhanced intercellular adhesion was mostly mediated by induction of E-cadherin and higher co-localization with β-catenin. Transcriptional upregulation of E-cadherin likely occurred through downregulation of the ZEB1 repressor. Finally, pulldown assays showed reduced activation of CDC42 in the absence of MGRN1, which was reverted after E-cadherin silencing. Overall, these findings highlight a new MGRN1-dependent pathway regulating melanoma cell shape, motility, and invasion potential.

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.

Novel cellular systems unveil mucosal melanoma initiating cells and a role for PI3K/Akt/mTOR pathway in mucosal melanoma fitness

BACKGROUND

Mucosal Melanomas (MM) are highly aggressive neoplasms arising from mucosal melanocytes. Current treatments offer a limited survival benefit for patients with advanced MM; moreover, the lack of pre-clinical cellular systems has significantly limited the understanding of their immunobiology.

METHODS

Five novel cell lines were obtained from patient-derived biopsies of MM arising in the sino-nasal mucosa and designated as SN-MM1-5. The morphology, ultrastructure and melanocytic identity of SN-MM cell lines were validated by transmission electron microscopy and immunohistochemistry. Moreover, in vivo tumorigenicity of SN-MM1-5 was tested by subcutaneous injection in NOD/SCID mice. Molecular characterization of SN-MM cell lines was performed by a mass-spectrometry proteomic approach, and their sensitivity to PI3K chemical inhibitor LY294002 was validated by Akt activation, measured by pAkt(Ser473) and pAkt(Thr308) in immunoblots, and MTS assay.

RESULTS

This study reports the validation and functional characterization of five newly generated SN-MM cell lines. Compared to the normal counterpart, the proteomic profile of SN-MM is consistent with transformed melanocytes showing a heterogeneous degree of melanocytic differentiation and activation of cancer-related pathways. All SN-MM cell lines resulted tumorigenic in vivo and display recurrent structural variants according to aCGH analysis. Of relevance, the microscopic analysis of the corresponding xenotransplants allowed the identification of clusters of MITF-/CDH1-/CDH2 + /ZEB1 + /CD271 + cells, supporting the existence of melanoma-initiating cells also in MM, as confirmed in clinical samples. In vitro, SN-MM cell lines were sensitive to cisplatin, but not to temozolomide. Moreover, the proteomic analysis of SN-MM cell lines revealed that RICTOR, a subunit of mTORC2 complex, is the most significantly activated upstream regulator, suggesting a relevant role for the PI3K-Akt-mTOR pathway in these neoplasms. Consistently, phosphorylation of NDRG1 and Akt activation was observed in SN-MM, the latter being constitutive and sustained by PTEN loss in SN-MM2 and SN-MM3. The cell viability impairment induced by LY294002 confirmed a functional role for the PI3K-Akt-mTOR pathway in SN-MM cell lines.

CONCLUSIONS

Overall, these novel and unique cellular systems represent relevant experimental tools for a better understanding of the biology of these neoplasms and, as an extension, to MM from other sites.

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.

AKT2 Loss Impairs BRAF-Mutant Melanoma Metastasis

Despite recent advances in treatment, melanoma remains the deadliest form of skin cancer due to its highly metastatic nature. Melanomas harboring oncogenic BRAFV600E mutations combined with PTEN loss exhibit unrestrained PI3K/AKT signaling and increased invasiveness. However, the contribution of different AKT isoforms to melanoma initiation, progression, and metastasis has not been comprehensively explored, and questions remain about whether individual isoforms play distinct or redundant roles in each step. We investigate the contribution of individual AKT isoforms to melanoma initiation using a novel mouse model of AKT isoform-specific loss in a murine melanoma model, and we investigate tumor progression, maintenance, and metastasis among a panel of human metastatic melanoma cell lines using AKT isoform-specific knockdown studies. We elucidate that AKT2 is dispensable for primary tumor formation but promotes migration and invasion in vitro and metastatic seeding in vivo, whereas AKT1 is uniquely important for melanoma initiation and cell proliferation. We propose a mechanism whereby the inhibition of AKT2 impairs glycolysis and reduces an EMT-related gene expression signature in PTEN-null BRAF-mutant human melanoma cells to limit metastatic spread. Our data suggest that the elucidation of AKT2-specific functions in metastasis might inform therapeutic strategies to improve treatment options for melanoma patients.

AKT2 Loss Impairs BRAF-Mutant Melanoma Metastasis

Despite recent advances in treatment, melanoma remains the deadliest form of skin cancer, due to its highly metastatic nature. Melanomas harboring oncogenic BRAF V600E mutations combined with PTEN loss exhibit unrestrained PI3K/AKT signaling and increased invasiveness. However, the contribution of different AKT isoforms to melanoma initiation, progression, and metastasis has not been comprehensively explored, and questions remain whether individual isoforms play distinct or redundant roles in each step. We investigate the contribution of individual AKT isoforms to melanoma initiation using a novel mouse model of AKT isoform-specific loss in a murine melanoma model, and investigate tumor progression, maintenance, and metastasis among a panel of human metastatic melanoma cell lines using AKT-isoform specific knockdown studies. We elucidate that AKT2 is dispensable for primary tumor formation but promotes migration and invasion in vitro and metastatic seeding in vivo , while AKT1 is uniquely important for melanoma initiation and cell proliferation. We propose a mechanism whereby inhibition of AKT2 impairs glycolysis and reduces an EMT-related gene expression signature in PTEN-null BRAF-mutant human melanoma cells to limit metastatic spread. Our data suggest that elucidation of AKT2-specific functions in metastasis could inform therapeutic strategies to improve treatment options for melanoma patients.

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.

The metabolic crosstalk between PIN1 and the tumour microenvironment

Peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (PIN1) is a member of a family of peptidyl-prolyl isomerases that specifically recognizes and binds phosphoproteins, catalyzing the rapid cis-trans isomerization of phosphorylated serine/threonine-proline motifs, which leads to changes in the structures and activities of the targeted proteins. Through this complex mechanism, PIN1 regulates many hallmarks of cancer including cell autonomous metabolism and the crosstalk with the cellular microenvironment. Many studies showed that PIN1 is largely overexpressed in cancer turning on a set of oncogenes and abrogating the function of tumor suppressor genes. Among these targets, recent evidence demonstrated that PIN1 is involved in lipid and glucose metabolism and accordingly, in the Warburg effect, a characteristic of tumor cells. As an orchestra master, PIN1 finely tunes the signaling pathways allowing cancer cells to adapt and take advantage from a poorly organized tumor microenvironment. In this review, we highlight the trilogy among PIN1, the tumor microenvironment and the metabolic program rewiring.

ROR2 promotes epithelial-mesenchymal transition by hyperactivating ERK in melanoma

Receptor tyrosine kinase-like orphan receptor 2 (ROR2) is a protein with important functions during embryogenesis that is dysregulated in human cancer. An intriguing feature of this receptor is that it plays opposite roles in different tumor types either promoting or inhibiting tumor progression. Understanding the complex role of this receptor requires a more profound exploration of both the altered biological and molecular mechanisms. Here, we describe that ROR2 promotes Epithelial-Mesenchymal Transition (EMT) by inducing cadherin switch and the upregulation of the transcription factors ZEB1, Twist, Slug, Snail, and HIF1A, together with a mesenchymal phenotype and increased migration. We show that ROR2 activates both p38 and ERK mitogen-activated protein kinase pathways independently of Wnt5a. Further, we demonstrated that the upregulation of EMT-related proteins depends on the hyperactivation of the ERK pathway far above the typical high constitutive activity observed in melanoma. In addition, ROR2 also promoted ERK phosphorylation, EMT, invasion, and necrosis in xenotransplanted mice. ROR2 also associates with EMT in tumor samples from melanoma patients where analysis of large cohorts revealed that increased ROR2 levels are linked to EMT signatures. This important role of ROR2 translates into melanoma patient' s prognosis since elevated ROR2 levels reduced overall survival and distant metastasis-free survival of patients with lymph node metastasis. In sum, these results demonstrate that ROR2 contributes to melanoma progression by inducing EMT and necrosis and can be an attractive therapeutic target for melanoma.

Phenotype Switching and the Melanoma Microenvironment; Impact on Immunotherapy and Drug Resistance

Melanoma, a highly heterogeneous tumor, is comprised of a functionally diverse spectrum of cell phenotypes and subpopulations, including stromal cells in the tumor microenvironment (TME). Melanoma has been shown to dynamically shift between different transcriptional states or phenotypes. This is referred to as phenotype switching in melanoma, and it involves switching between quiescent and proliferative cell cycle states, and dramatic shifts in invasiveness, as well as changes in signaling pathways in the melanoma cells, and immune cell composition in the TME. Melanoma cell plasticity is associated with altered gene expression in immune cells and cancer-associated fibroblasts, as well as changes in extracellular matrix, which drive the metastatic cascade and therapeutic resistance. Therefore, resistance to therapy in melanoma is not only dependent on genetic evolution, but it has also been suggested to be driven by gene expression changes and adaptive phenotypic cell plasticity. This review discusses recent findings in melanoma phenotype switching, immunotherapy resistance, and the balancing of the homeostatic TME between the different melanoma cell subpopulations. We also discuss future perspectives of the biology of neural crest-like state(s) in melanoma.

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.

Extracellular Acidosis Differentially Regulates Estrogen Receptor β-Dependent EMT Reprogramming in Female and Male Melanoma Cells

Clinical outcomes of melanoma patients pointed out a gender disparity that supports a correlation between sex hormone activity on estrogen receptors (ER) and melanoma development and progression. Here, we found that the epithelial-to-mesenchymal transition (EMT) of melanoma cells induced by extracellular acidosis, which is a crucial hallmark of solid cancers, correlates with the expression of ERβ, the most representative ER on melanoma cells. Extracellular acidosis induces an enhanced expression of ERβ in female cells and EMT markers remain unchanged, while extracellular acidosis did not induce the expression of ERβ in male cells and EMT was strongly promoted. An inverse relationship between ERβ expression and EMT markers in melanoma cells of different sex exposed to extracellular acidosis was revealed by two different technical approaches: florescence-activated cell sorting of high ERβ expressing cell subpopulations and ERβ receptor silencing. Finally, we found that ERβ regulates EMT through NF-κB activation. These results demonstrate that extracellular acidosis drives a differential ERβ regulation in male and female melanoma cells and that this gender disparity might open new perspectives for personalized therapeutic approaches.

Olive leaf extract inhibits metastatic melanoma spread through suppression of epithelial to mesenchymal transition

Olive tree leaves are an abundant source of bioactive compounds with several beneficial effects for human health, including a protective role against many types of cancer. In this study, we investigated the effect of an extract, obtained from olive tree (Olea europaea L.) leaves (OLE), on proliferation, invasion, and epithelial to mesenchymal transition (EMT) on metastatic melanoma, the highly aggressive form of skin cancer and the deadliest diseases. Our results demonstrated that OLE inhibited melanoma cells proliferation through cell cycle arrest and induction of apoptotic cell death. Moreover, OLE suppressed the migration, invasion, and colonies formation of human melanoma cells. Similar to our in vitro findings, we demonstrated that the oral administration of OLE inhibited cutaneous tumor growth and lung metastasis formation in vivo by modulating the expression of EMT related factors. In addition, the anti-proliferative and anti-invasive effects of OLE against melanoma were also related to a simultaneous targeting of mitogen-activated protein kinase and PI3K pathways, both in vitro and in vivo. In conclusion, our findings suggest that OLE has the potential to inhibit the metastatic spread of melanoma cells thanks to its multifaceted mechanistic effects, and may represent a new add-on therapy for the management of metastatic melanoma.

Therapeutic Potential of Nitric Oxide‒Releasing Selective Estrogen Receptor Modulators in Malignant Melanoma

Malignant melanoma has a steadily increasing incidence, but treatment options are still limited, and the prognosis for patients, especially for men, is poor. To investigate whether targeting estrogen receptor (ER) signaling is a valid therapeutic approach, we retrospectively analyzed ER gene expression profiles in 448 patients with melanoma. High ERα gene (ESR1) expression was associated with improved overall survival (hazard ratio = 0.881; 95% confidence interval = 0.793-0.979; P = 0.018) and increased with tumor stage, whereas ERβ gene (ESR2) expression did not change with tumor progression. This seemingly protective function of ERα led us to speculate that specific targeting of ERβ has a therapeutic benefit in malignant melanoma. An ERβ-selective ER modulator with nitric oxide‒releasing moiety (nitric oxide‒releasing selective ER modulator 4d [NO-SERM 4d]) significantly reduced the prometastatic behavior of two melanoma cell lines (A2058 and MEL-JUSO). Epithelial‒mesenchymal transition in melanoma is consistent with a switch from E- to N-cadherin expression, mediating the invasive phenotype. NO-SERM 4d reduced N-cadherin expression and impaired spheroid formation in A2058 cells. In addition, the growth of A2058 spheroids was significantly reduced, confirming the antitumorigenic potential of NO-SERM 4d. Targeting ERβ signaling combined with targeted nitric oxide release represents a promising therapeutic approach in malignant melanoma that has the potential to prevent metastatic spread and reduce tumor growth.

The Role of Extracellular Matrix Remodeling in Skin Tumor Progression and Therapeutic Resistance

The extracellular matrix remodeling in the skin results from a delicate balance of synthesis and degradation of matrix components, ensuring tissue homeostasis. These processes are altered during tumor invasion and growth, generating a microenvironment that supports growth, invasion, and metastasis. Apart from the cellular component, the tumor microenvironment is rich in extracellular matrix components and bound factors that provide structure and signals to the tumor and stromal cells. The continuous remodeling in the tissue compartment sustains the developing tumor during the various phases providing matrices and proteolytic enzymes. These are produced by cancer cells and stromal fibroblasts. In addition to fostering tumor growth, the expression of specific extracellular matrix proteins and proteinases supports tumor invasion after the initial therapeutic response. Lately, the expression and structural modification of matrices were also associated with therapeutic resistance. This review will focus on the significant alterations in the extracellular matrix components and the function of metalloproteinases that influence skin cancer progression and support the acquisition of therapeutic resistance.

Multi-omics profiling shows BAP1 loss is associated with upregulated cell adhesion molecules in uveal melanoma

BRCA1-associated protein 1 (BAP1) is a tumor suppressor gene that is mutated in cancer, including uveal melanoma (UM). Loss-of-function BAP1 mutations are associated with UM metastasis and poor prognosis, but the mechanisms underlying these effects remain unclear. Upregulation of cell-cell adhesion proteins is involved with collective migration and metastatic seeding of cancer cells. Here, we show that BAP1 loss in UM patient samples is associated with upregulated gene expression of multiple cell adhesion molecules (CAMs), including E-cadherin (CDH1), cell adhesion molecule 1 (CADM1), and syndecan-2 (SDC2). Similar findings were observed in UM cell lines and scRNA seq data from UM patient samples. BAP1 re-expression in UM cells reduced E-cadherin and CADM1 levels. Functionally, knockdown of E-cadherin decreased spheroid cluster formation and knockdown of CADM1 decreased growth of BAP1 mutant UM cells. Together, our findings demonstrate that BAP1 regulates the expression of CAMs which may regulate metastatic traits. Implications: BAP1 mutations and increased metastasis may be due to upregulation of cell adhesion molecules.

CCL5/CCR5 axis in human diseases and related treatments

To defense harmful stimuli or maintain the immune homeostasis, the body produces and recruits a superfamily of cytokines such as interleukins, interferons, chemokines etc. Among them, chemokines act as crucial regulators in defense systems. CCL5/CCR5 combination is known for facilitating inflammatory responses, as well as inducing the adhesion and migration of different T cell subsets in immune responses. In addition, recent studies have shown that the interaction between CCL5 and CCR5 is involved in various pathological processes including inflammation, chronic diseases, cancers as well as the infection of COVID-19. This review focuses on how CCL5/CCR5 axis participates in the pathological processes of different diseases and their relevant signaling pathways for the regulation of the axis. Moreover, we highlighted the gene therapy and chemotherapy studies for treating CCR5-related diseases, including the ongoing clinical trials. The barriers and perspectives for future application and translational research were also summarized.

Signal pathways of melanoma and targeted therapy

Melanoma is the most lethal skin cancer that originates from the malignant transformation of melanocytes. Although melanoma has long been regarded as a cancerous malignancy with few therapeutic options, increased biological understanding and unprecedented innovations in therapies targeting mutated driver genes and immune checkpoints have substantially improved the prognosis of patients. However, the low response rate and inevitable occurrence of resistance to currently available targeted therapies have posed the obstacle in the path of melanoma management to obtain further amelioration. Therefore, it is necessary to understand the mechanisms underlying melanoma pathogenesis more comprehensively, which might lead to more substantial progress in therapeutic approaches and expand clinical options for melanoma therapy. In this review, we firstly make a brief introduction to melanoma epidemiology, clinical subtypes, risk factors, and current therapies. Then, the signal pathways orchestrating melanoma pathogenesis, including genetic mutations, key transcriptional regulators, epigenetic dysregulations, metabolic reprogramming, crucial metastasis-related signals, tumor-promoting inflammatory pathways, and pro-angiogenic factors, have been systemically reviewed and discussed. Subsequently, we outline current progresses in therapies targeting mutated driver genes and immune checkpoints, as well as the mechanisms underlying the treatment resistance. Finally, the prospects and challenges in the development of melanoma therapy, especially immunotherapy and related ongoing clinical trials, are summarized and discussed.

Glutamine-fructose-6-phosphate transaminase 2 (GFPT2) is upregulated in breast epithelial-mesenchymal transition and responds to oxidative stress

Breast cancer cells that have undergone partial epithelial–mesenchymal transition (EMT) are believed to be more invasive than cells that have completed EMT. To study metabolic reprogramming in different mesenchymal states, we analyzed protein expression following EMT in the breast epithelial cell model D492 with single-shot LFQ supported by a SILAC proteomics approach. The D492 EMT cell model contains three cell lines: the epithelial D492 cells, the mesenchymal D492M cells, and a partial mesenchymal, tumorigenic variant of D492 that overexpresses the oncogene HER2. The analysis classified the D492 and D492M cells as basal-like and D492HER2 as claudin-low. Comparative analysis of D492 and D492M to tumorigenic D492HER2 differentiated metabolic markers of migration from those of invasion. Glutamine-fructose-6-phosphate transaminase 2 (GFPT2) was one of the top dysregulated enzymes in D492HER2. Gene expression analysis of the cancer genome atlas showed that GFPT2 expression was a characteristic of claudin-low breast cancer. siRNA-mediated knockdown of GFPT2 influenced the EMT marker vimentin and both cell growth and invasion in vitro and was accompanied by lowered metabolic flux through the hexosamine biosynthesis pathway (HBP). Knockdown of GFPT2 decreased cystathionine and sulfide:quinone oxidoreductase (SQOR) in the transsulfuration pathway that regulates H₂S production and mitochondrial homeostasis. Moreover, GFPT2 was within the regulation network of insulin and EGF, and its expression was regulated by reduced glutathione (GSH) and suppressed by the oxidative stress regulator GSK3-β. Our results demonstrate that GFPT2 controls growth and invasion in the D492 EMT model, is a marker for oxidative stress, and associated with poor prognosis in claudin-low breast cancer.

•

GFPT2 is upregulated following EMT.

•

GFPT2 is a marker for claudin-low breast cancer.

•

GFPT2 affects vimentin, cell proliferation, and cell invasion.

•

GFPT2 responds to oxidative stress.

•

GFPT2 is regulated by insulin and EGF.

Knockdown of circular RNA VANGL1 inhibits TGF-β-induced epithelial-mesenchymal transition in melanoma cells by sponging miR-150-5p

Melanoma is one of the most aggressive and life-threatening skin cancers, and in this research, we aimed to explore the functional role of circular RNA VANGL1 (circVANGL1) in melanoma progression. The expression levels of circVANGL1 were observed to be significantly increased in clinical melanoma tissues and cell lines. Moreover, circVANGL1 knockdown suppressed, while circVANGL1 overexpression promoted the proliferation, migration and invasion abilities of melanoma cells. Further investigations confirmed the direct binding relation between circVANGL1 and miR-150-5p in melanoma, and restoration of miR-150-5p blocked the effects of circVANGL1 overexpression in melanoma cells. We further found that circVANGL1 was up-regulated by TGF-β treatment, and the enhanced EMT of TGF-β-treated melanoma cells was blocked by circVANGL1 knockdown. In conclusion, these results indicated that circVANGL1 might serve as a promising therapeutic target for melanoma.

A preclinical pipeline to evaluate migrastatics as therapeutic agents in metastatic melanoma

BACKGROUND

Metastasis is a hallmark of cancer and responsible for most cancer deaths. Migrastatics were defined as drugs interfering with all modes of cancer cell invasion and thus cancers' ability to metastasise. First anti-metastatic treatments have recently been approved.

METHODS

We used bioinformatic analyses of publicly available melanoma databases. Experimentally, we performed in vitro target validation (including 2.5D cell morphology analysis and mass spectrometric analysis of RhoA binding partners), developed a new traceable spontaneously metastasising murine melanoma model for in vivo validation, and employed histology (haematoxylin/eosin and phospho-myosin II staining) to confirm drug action in harvested tumour tissues.

RESULTS

Unbiased and targeted bioinformatic analyses identified the Rho kinase (ROCK)-myosin II pathway and its various components as potentially relevant targets in melanoma. In vitro validation demonstrated redundancy of several RhoGEFs upstream of RhoA and confirmed ROCK as a druggable target downstream of RhoA. The anti-metastatic effects of two ROCK inhibitors were demonstrated through in vivo melanoma metastasis tracking and inhibitor effects also confirmed ex vivo by digital pathology.

CONCLUSIONS

We proposed a migrastatic drug development pipeline. As part of the pipeline, we provide a new traceable spontaneous melanoma metastasis model for in vivo quantification of metastasis and anti-metastatic effects by non-invasive imaging.

Affinity proteomics and deglycoproteomics uncover novel EDEM2 endogenous substrates and an integrative ERAD network

Various pathologies result from disruptions to or stress of endoplasmic reticulum (ER) homeostasis, such as Parkinson's disease and most neurodegenerative illnesses, diabetes, pulmonary fibrosis, viral infections and cancers. A critical process in maintaining ER homeostasis is the selection of misfolded proteins by the ER quality-control system (ERQC) for destruction via ER-associated degradation (ERAD). One key protein proposed to act during the first steps of misfolded glycoprotein degradation is the ER degradation-enhancing α-mannosidase-like protein 2 (EDEM2). Therefore, characterization of the EDEM2 associated proteome is of great interest. We took advantage of using melanoma cells overexpressing EDEM2 as a cancer model system, to start documenting at the deglycoproteome level (N-glycosites identification) the emerging link between ER homeostasis and cancer progression. The dataset created for identifying the EDEM2 glyco-clients carrying high mannose/hybrid N-glycans provides a comprehensive N-glycosites analysis mapping over 1000 N-glycosites on more than 600 melanoma glycoproteins. To identify EDEM2-associated proteins we used affinity-proteomics and proteome-wide analysis of sucrose density fractionation in an integrative workflow. Using intensity and spectral count-based quantification, we identify seven new EDEM2 partners, all of which are involved in ERQC and ERAD. Moreover, we defined novel endogenous candidates for EDEM2-dependent ERAD by combining deglycoproteomics, SILAC-based proteomics, and biochemical methods. These included tumor antigens and several ER-transiting endogenous melanoma proteins, including ITGA1 and PCDH2, the expression of which was negatively correlated with that of EDEM2. Tumor antigens are key in the antigen presentation process, whilst ITGA1 and PCDH2 are involved in melanoma metastasis and invasion. EDEM2 could therefore have a regulatory role in melanoma through the modulation of these glycoproteins degradation and trafficking. The data presented herein suggest that EDEM2 is involved in ER homeostasis to a greater extent than previously suggested.

Salmonella Impacts Tumor-Induced Macrophage Polarization, and Inhibits SNAI1-Mediated Metastasis in Melanoma

Targeting metastasis is a vital strategy to improve the clinical outcome of cancer patients, specifically in cases with high-grade malignancies. Here, we employed a Salmonella-based treatment to address metastasis. The potential of Salmonella as an anticancer agent has been extensively studied; however, the mechanism through which it affects metastasis remains unclear. This study found that the epithelial-to-mesenchymal transition (EMT) inducer SNAI1 was markedly reduced in Salmonella-treated melanoma cells, as revealed by immunoblotting. Furthermore, wound healing and transwell assays showed a reduced in vitro cell migration following Salmonella treatment. Transfection experiments confirmed that Salmonella acted against metastasis by suppressing protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling, which in turn inhibited SNAI1 expression. Since it is known that metastasis is also influenced by inflammation, we partly characterized the immune infiltrates in melanoma as affected by Salmonella treatment. We found through tumor-macrophage co-culture that Salmonella treatment increased high mobility group box 1 (HMGB1) secretion in tumors to coax the polarization of macrophages in favor of an M1-like phenotype, as shown by increased inducible nitric oxide synthase (iNOS) expression and Interleukin 1 Beta (IL-1β) secretion. Data from our animal study corroborated the in vitro findings, wherein the Salmonella-treated group obtained the lowest lung metastases, longer survival, and increased iNOS-expressing immune infiltrates.

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.

Unraveling the role of microRNA/isomiR network in multiple primary melanoma pathogenesis

Malignant cutaneous melanoma (CM) is a potentially lethal form of skin cancer whose worldwide incidence has been constantly increasing over the past decades. During their lifetime, about 8% of CM patients will develop multiple primary melanomas (MPMs), usually at a young age and within 3 years from the first tumor/diagnosis. With the aim of improving our knowledge on MPM biology and pathogenesis, we explored the miRNome of 24 single and multiple primary melanomas, including multiple tumors from the same patient, using a small RNA-sequencing approach. From a supervised analysis, 22 miRNAs were differentially expressed in MPM compared to single CM, including key miRNAs involved in epithelial-mesenchymal transition. The first and second melanoma from the same patient presented a different miRNA profile. Ten miRNAs, including miR-25-3p, 149-5p, 92b-3p, 211-5p, 125a-5p, 125b-5p, 205-5p, 200b-3p, 21-5p, and 146a-5p, were further validated in 47 single and multiple melanoma samples. Pathway enrichment analysis of miRNA target genes revealed a more differentiated and less invasive status of MPMs compared to CMs. Bioinformatic analyses at the miRNA isoform (isomiR) level detected a panel of highly expressed isomiRs belonging to miRNA families implicated in human tumorigenesis, including miR-200, miR-30, and miR-10 family. Moreover, we identified hsa-miR-125a-5p|0|-2 isoform as tenfold over-represented in melanoma than the canonical form and differentially expressed in MPMs arising in the same patient. Target prediction analysis revealed that the miRNA shortening could change the pattern of target gene regulation, specifically in genes implicated in cell adhesion and neuronal differentiation. Overall, we provided a putative and comprehensive characterization of the miRNA/isomiR regulatory network of MPMs, highlighting mechanisms of tumor development and molecular features differentiating this subtype from single melanomas.

Melanoma Progression under Obesity: Focus on Adipokines

Simple Summary

Obesity is a rapidly growing public health problem and the reason for numerous diseases in the human body, including cancer. This article reviews the current knowledge of the effect of molecules secreted by adipose tissue-adipokines on melanoma progression. We also discuss the role of these factors as markers of incidence, metastasis, and melanoma patient survival. Understanding the functions of adipokines will lead to knowledge of whether and how obesity promotes melanoma growth.

Abstract

Obesity is a growing problem in the world and is one of the risk factors of various cancers. Among these cancers is melanoma, which accounts for the majority of skin tumor deaths. Current studies are looking for a correlation between obesity and melanoma. They suspect that a potential cause of its development is connected to the biology of adipokines, active molecules secreted by adipose tissue. Under physiological conditions, adipokines control many processes, including lipid and glucose homeostasis, insulin sensitivity, angiogenesis, and inflammations. However, when there is an increased amount of fat in the body, their secretion is dysregulated. This article reviews the current knowledge of the effect of adipokines on melanoma growth. This work focuses on the molecular pathways by which adipose tissue secreted molecules modify the angiogenesis, migration, invasion, proliferation, and death of melanoma cells. We also discuss the role of these factors as markers of incidence, metastasis, and melanoma patient survival. Understanding the functions of adipokines will lead to knowledge of whether and how obesity promotes melanoma growth. Further studies may contribute to the innovations of therapies and the use of adipokines as predictive and/or prognostic biomarkers.

Covariance thresholding to detect differentially co-expressed genes from microarray gene expression data

Gene set analysis aims to identify differentially expressed or co-expressed genes within a biological pathway between two experimental conditions, so that it can eventually reveal biological processes and pathways involved in disease development. In the last few decades, various statistical and computational methods have been proposed to improve statistical power of gene set analysis. In recent years, much attention has been paid to differentially co-expressed genes since they can be potentially disease-related genes without significant difference in average expression levels between two conditions. In this paper, we propose a new statistical method to identify differentially co-expressed genes from microarray gene expression data. The proposed method first estimates co-expression levels of paired genes using covariance regularization by thresholding, and then significance of difference in covariance estimation between two conditions is evaluated. We demonstrated that the proposed method is more powerful than the existing main-stream methods to detect co-expressed genes through extensive simulation studies. Also, we applied it to various microarray gene expression datasets related with mutant p53 transcriptional activity, and epithelium and stroma breast cancer.

FAM3C: an emerging biomarker and potential therapeutic target for cancer

FAM3C is a member of the FAM3 family. Recently, overexpression of FAM3C has been reported in numerous types of cancer, including breast and colon cancer. Increasing evidence suggests that elevated FAM3C and its altered subcellular localization are closely associated with tumor formation, invasion, metastasis and poor survival. Moreover, FAM3C has been found to be the regulator of various proteins that associate with cancer, including Ras, STAT3, TGF-β and LIFR. This review summarizes the current knowledge regarding FAM3C, including its structure, expression patterns, regulation, physiological roles and regulatory functions in various malignancies. These findings highlight the importance of FAM3C in cancer development and provide evidence that FAM3C is a novel biomarker and potential therapeutic target for various cancers.

TGFβ1 neutralization displays therapeutic efficacy through both an immunomodulatory and a non-immune tumor-intrinsic mechanism

BACKGROUND

Transforming growth factor-β (TGFβ) is emerging as a promising target for cancer therapy, given its ability to promote progression of advanced tumors and to suppress anti-tumor immune responses. However, TGFβ also plays multiple roles in normal tissues, particularly during organogenesis, raising toxicity concerns about TGFβ blockade. Dose-limiting cardiovascular toxicity was observed, possibly due to the blockade of all three TGFβ isoforms. The dominant isoform in tumors is TGFβ1, while TGFβ2 and TGFβ3 seem to be more involved in cardiovascular development. Recent data indicated that selective targeting of TGFβ1 promoted the efficacy of checkpoint inhibitor anti-PD1 in transplanted preclinical tumor models, without cardiovascular toxicity.

METHODS

To further explore the therapeutic potential of isoform-specific TGFβ blockade, we developed neutralizing mAbs targeting mature TGFβ1 or TGFβ3, and tested them, in parallel with anti-panTGFβ mAb 1D11, in two preclinical models: the transplanted colon cancer model CT26, and the autochthonous melanoma model TiRP.

RESULTS

We observed that the blockade of TGFβ1, but not that of TGFβ3, increased the efficacy of a prophylactic cellular vaccine against colon cancer CT26. This effect was similar to pan-TGFβ blockade, and was associated with increased infiltration of activated CD8 T cells in the tumor, and reduced levels of regulatory T cells and myeloid-derived suppressor cells. In contrast, in the autochthonous TiRP melanoma model, we observed therapeutic efficacy of the TGFβ1-specific mAb as a single agent, while the TGFβ3 mAb was inactive. In this model, the anti-tumor effect of TGFβ1 blockade was tumor intrinsic rather than immune mediated, as it was also observed in T-cell depleted mice. Mechanistically, TGFβ1 blockade increased mouse survival by delaying the phenotype switch, akin to epithelial-to-mesenchymal transition (EMT), which transforms initially pigmented tumors into highly aggressive unpigmented tumors.

CONCLUSIONS

Our results confirm TGFβ1 as the relevant isoform to target for cancer therapy, not only in combination with checkpoint inhibitors, but also with other immunotherapies such as cancer vaccines. Moreover, TGFβ1 blockade can also act as a monotherapy, through a tumor-intrinsic effect blocking the EMT-like transition. Because human melanomas that resist therapy often express a gene signature that links TGFβ1 with EMT-related genes, these results support the clinical development of TGFβ1-specific mAbs in melanoma.

The Carbonic Anhydrase IX inhibitor SLC-0111 as emerging agent against the mesenchymal stem cell-derived pro-survival effects on melanoma cells

Mesenchymal stem cells (MSC) take part to solid tumour-associated stroma and critically influence progression of malignancy. Our study represents a striking example of melanoma progression to a more malignant and resistant phenotype promoted by MSC and the possibility to contrast this diabolic liaison using CAIX inhibitors. In particular, we demonstrated that melanoma cells exposed to a MSC-conditioned medium switch to a more malignant phenotype, characterised by resistance to programmed cell death and endowed with an epithelial-to-mesenchymal transition and stem cell characteristics. These effects were reversed abrogating MSC CAIX activity using SLC-0111, a CAIX inhibitor. Moreover, the acquisition by melanoma cells of a Vemurafenib-resistant phenotype upon MSC-conditioned medium exposure was removed when MSC were treated with SLC-0111. Therefore, MSC may profoundly reprogramme melanoma cells towards a wide resistant phenotype through CAIX involvement, as the use of SLC-0111 is able to contrast the development of this highly risky adaptation for disease progression.

AFF4 facilitates melanoma cell progression by regulating c-Jun activity

Melanoma is characterized by high mortality and poor prognosis due to metastasis. AFF4 (AF4/FMR2 family member 4), as a scaffold protein, is a component of the super elongation complex (SEC), and is involved in the progression of tumors, e.g., leukemia, head and neck squamous cell carcinoma (HNSCC). However, few studies on AFF4 have focused on melanoma. Here, AFF4 expression levels and clinicopathological features were evaluated in melanoma tissue samples. Then, we performed cell proliferation, migration and invasion assays in A375 and A2058 cells lines in vitro to evaluate the role of AFF4 in melanoma. The effects of AFF4 knockdown in vivo were characterized via a xenograft mouse model. Finally, the correlation between c-Jun and AFF4 protein levels in melanoma was analyzed by rescue assay and immunohistochemistry (IHC). We found that AFF4 expression was upregulated in melanoma tumor tissues and that AFF4 protein expression was also closely related to the prognosis of patients with cutaneous melanoma. Moreover, AFF4 could promote the invasion and migration of melanoma cells by mediating epithelial to mesenchymal transition (EMT). AFF4 might regulate c-Jun activity to promote the invasion and migration of melanoma cells. Importantly, c-Jun was regulated by the AFF4 promoted melanoma tumorigenesis in vivo. Taken together, AFF4 may be a novel oncogene that promotes melanoma progression through regulation of c-Jun activity.

Human and mouse melanoma cells recapitulate an EMT-like program in response to mesenchymal stromal cells secretome

The mechanisms underlying the propensity of melanomas to metastasize are not completely understood. We hypothesized that melanoma cells are capable of promptly activating an epithelial-to-mesenchymal transition (EMT)-like profile in response to stroma-derived factors. Thus, we investigated the role of mesenchymal stromal cells (MSCs), a cell population considered as a precursor of tumor stroma, on the activation of an EMT-like profile and acquisition of metastatic traits in melanoma cells. After subcutaneous co-injection with mouse B16 melanoma cells, MSCs occupied perivascular sites within tumors and enhanced B16 metastasis to the lungs. In vitro, MSCs' secretome activated an EMT-like profile in B16 cells, reducing their avidity to fibronectin, and increasing their motility and invasiveness. These effects were abrogated upon blocking of MET phosphorylation in B16 cells using small molecule inhibitors. MSCs also activated an EMT-like profile in human melanoma cells from different stages of progression. Activation of EMT in human cells was associated with increased levels of p-STAT1 and p-STAT3. In conclusion, both mouse and human melanoma cells are equipped to activate an EMT-like program and acquire metastatic traits through the activation of distinct pathways by MSCs' secretome.

Growth Hormone Upregulates Mediators of Melanoma Drug Efflux and Epithelial-to-Mesenchymal Transition In Vitro and In Vivo

Simple Summary

Growth hormone (GH) action is strongly implicated in the progression and therapy resistance in several types of solid tumors which overexpress the GH receptor (GHR). The aim of our study was to characterize the effects of GH and its downstream effector insulin-like growth factor 1 (IGF-1) on melanoma using in vitro and in vivo models. We confirmed an IGF-1-independent role of elevated circulating GH in upregulating key mechanisms of therapy resistance and malignancy with analyses conducted at the molecular and cellular level. We identified that GH upregulates key mechanisms of therapy resistance and metastases in melanoma tumors in an IGF-1 dependent and independent manner by upregulating multidrug efflux pumps and EMT transcription factors. Our study reveals that GH action renders an intrinsic drug resistance phenotype to the melanoma tumors—a clinically crucial property of GH verifiable in other human cancers with GHR expression.

Abstract

Growth hormone (GH) and the GH receptor (GHR) are expressed in a wide range of malignant tumors including melanoma. However, the effect of GH/insulin-like growth factor (IGF) on melanoma in vivo has not yet been elucidated. Here we assessed the physical and molecular effects of GH on mouse melanoma B16-F10 and human melanoma SK-MEL-30 cells in vitro. We then corroborated these observations with syngeneic B16-F10 tumors in two mouse lines with different levels of GH/IGF: bovine GH transgenic mice (bGH; high GH, high IGF-1) and GHR gene-disrupted or knockout mice (GHRKO; high GH, low IGF-1). In vitro, GH treatment enhanced mouse and human melanoma cell growth, drug retention and cell invasion. While the in vivo tumor size was unaffected in both bGH and GHRKO mouse lines, multiple drug-efflux pumps were up regulated. This intrinsic capacity of therapy resistance appears to be GH dependent. Additionally, epithelial-to-mesenchymal transition (EMT) gene transcription markers were significantly upregulated in vivo supporting our current and recent in vitro observations. These syngeneic mouse melanoma models of differential GH/IGF action can be valuable tools in screening for therapeutic options where lowering GH/IGF-1 action is important.

Human Endogenous Retrovirus K Rec forms a Regulatory Loop with MITF that Opposes the Progression of Melanoma to an Invasive Stage

The HML2 subfamily of HERV-K (henceforth HERV-K) represents the most recently endogenized retrovirus in the human genome. While the products of certain HERV-K genomic copies are expressed in normal tissues, they are upregulated in several pathological conditions, including various tumors. It remains unclear whether HERV-K(HML2)-encoded products overexpressed in cancer contribute to disease progression or are merely by-products of tumorigenesis. Here, we focus on the regulatory activities of the Long Terminal Repeats (LTR5_Hs) of HERV-K and the potential role of the HERV-K-encoded Rec in melanoma. Our regulatory genomics analysis of LTR5_Hs loci indicates that Melanocyte Inducing Transcription Factor (MITF) (also known as binds to a canonical E-box motif (CA(C/T)GTG) within these elements in proliferative type of melanoma, and that depletion of MITF results in reduced HERV-K expression. In turn, experimentally depleting Rec in a proliferative melanoma cell line leads to lower mRNA levels of MITF and its predicted target genes. Furthermore, Rec knockdown leads to an upregulation of epithelial-to-mesenchymal associated genes and an enhanced invasion phenotype of proliferative melanoma cells. Together these results suggest the existence of a regulatory loop between MITF and Rec that may modulate the transition from proliferative to invasive stages of melanoma. Because HERV-K(HML2) elements are restricted to hominoid primates, these findings might explain certain species-specific features of melanoma progression and point to some limitations of animal models in melanoma studies.

Analysis of Melanoma Secretome for Factors That Directly Disrupt the Barrier Integrity of Brain Endothelial Cells

We have recently demonstrated that invasive melanoma cells are capable of disrupting the brain endothelial barrier integrity. This was shown using ECIS biosensor technology, which revealed rapid disruption via the paracellular junctions. In this paper, we demonstrate that melanoma cells secrete factors (e.g., cytokines) that weaken the endothelial barrier integrity. Through proteome profiling, we attempt to identify the barrier-disrupting cytokines. Melanoma conditioned media were collected from three New Zealand melanoma lines. ECIS technology was used to assess if the conditioned media disrupted the endothelial barrier independent of the melanoma cells. The melanoma cell secretome was assessed using cytometric bead array (CBA), Luminex immunoassay and multiplex Proteome Profilers, to detect the expression of secretory proteins, which may facilitate metastasis. Finally, ECIS technology was used to assess the direct effects of secreted proteins identified as candidates from the proteome screens. We show that melanoma-conditioned media significantly disrupted the brain endothelial barrier, however, to a much lesser extent than the cells from which they were collected. Cytokine and proteome profiling of the conditioned media showed evidence of high concentrations of approximately 15 secreted proteins (including osteopontin, IL-8, GDF-15, MIF and VEGF). These 15 secreted proteins were expressed variably across the melanoma lines. Surprisingly, the addition of these individually to the brain endothelial cells did not substantially affect the barrier integrity. ANGPTL-4 and TGFβ were also produced by the melanoma cells. Whilst TGFβ-1 had a pronounced effect on the barrier integrity, surprisingly ANGPTL-4 did not. However, its C-terminal fragment did and within a very similar period to the conditioned media, albeit not to the same extent. Herein we show that melanoma cells produce a wide-range of soluble factors at high concentrations, which most likely favour support or survival of the cancer cells. Most of these, except for TGFβ-1 and the C-terminal fragment of ANGPTL-4, did not have an impact on the integrity of the brain endothelial cells.

Loss of ADAM9 Leads to Modifications of the Extracellular Matrix Modulating Tumor Growth

ADAM9 is a metalloproteinase strongly expressed at the tumor-stroma border by both tumor and stromal cells. We previously showed that the host deletion of ADAM9 leads to enhanced growth of grafted B16F1 melanoma cells by a mechanism mediated by TIMP1 and the TNF-α/sTNFR1 pathway. This study aimed to dissect the structural modifications in the tumor microenvironment due to the stromal expression of ADAM9 during melanoma progression. We performed proteomic analysis of peritumoral areas of ADAM9 deleted mice and identified the altered expression of several matrix proteins. These include decorin, collagen type XIV, fibronectin, and collagen type I. Analysis of these matrices in the matrix producing cells of the dermis, fibroblasts, showed that ADAM9^-/- and wild type fibroblasts synthesize and secreted almost comparable amounts of decorin. Conversely, collagen type I expression was moderately, but not significantly, decreased at the transcriptional level, and the protein increased in ADAM9^-/- fibroblast mono- and co-cultures with melanoma media. We show here for the first time that ADAM9 can release a collagen fragment. Still, it is not able to degrade collagen type I. However, the deletion of ADAM9 in fibroblasts resulted in reduced MMP-13 and -14 expression that may account for the reduced processing of collagen type I. Altogether, the data show that the ablation of ADAM9 in the host leads to the altered expression of peritumoral extracellular matrix proteins that generate a more favorable environment for melanoma cell growth. These data underscore the suppressive role of stromal expression of ADAM9 in tumor growth and call for a better understanding of how protease activities function in a cellular context for improved targeting.

E-Cadherin Expression in Canine Melanocytic Tumors: Histological, Immunohistochemical, and Survival Analysis

E-cadherin, a glycoprotein involved in cell-cell adhesion, has a pivotal role in epithelial-mesenchymal transition, a process through which neoplastic epithelial cells develop an invasive phenotype. In human cutaneous melanomas, decreased E-cadherin expression is associated with shorter survival and increased Breslow thickness, whereas in the dog its role is poorly understood. Tumor thickness and modified Clark level were recently proposed as useful features to assess canine melanocytic tumors, but no studies investigated their association with E-cadherin expression. We performed immunohistochemistry on 77 formalin-fixed, paraffin-embedded primary canine melanocytic tumors. A 3-tier and a 2-tier classification system for assessing E-cadherin expression were tested, with the latter being more informative for the assessment of canine melanocytic tumors. E-cadherin expression was lower in cutaneous melanomas than melanocytomas, as well as in amelanotic tumors compared to pigmented tumors. In amelanotic melanomas, absent E-cadherin expression was associated with an unfavorable outcome, suggesting a potential use of this marker in defining the prognosis of amelanotic melanomas. E-cadherin expression was lower in tumors with greater tumor thickness and modified Clark level ≥IV, suggesting its possible utility in identifying the most invasive tumors. The expression of E-cadherin in oral melanomas was heterogeneous, but was associated with pigmentation and clinical outcome; thus, E-cadherin evaluation could be advantageous to detect the most aggressive neoplasms. However, cutaneous melanomas without E-cadherin expression frequently had a favorable clinical outcome. Hence, its importance as prognostic factor should be carefully considered depending on the tumor origin.

Membrane Transporters and Channels in Melanoma

Recent research has revealed that ion channels and transporters can be important players in tumor development, progression, and therapy resistance in melanoma. For example, members of the ABC family were shown to support cancer stemness-like features in melanoma cells, while several members of the TRP channel family were reported to act as tumor suppressors.Also, many transporter proteins support tumor cell viability and thus suppress apoptosis induction by anticancer therapy. Due to the high number of ion channels and transporters and the resulting high complexity of the field, progress in understanding is often focused on single molecules and is in total rather slow. In this review, we aim at giving an overview about a broad subset of ion transporters, also illustrating some aspects of the field, which have not been addressed in detail in melanoma. In context with the other chapters in this special issue on "Transportome Malfunctions in the Cancer Spectrum," a comparison between melanoma and these tumors will be possible.

Long non-coding RNA H19 promotes colorectal cancer metastasis via binding to hnRNPA2B1

Background

Long non-coding RNA H19 was demonstrated to be significantly correlated with tumor metastasis. However, the specific functions of H19 in colorectal cancer (CRC) metastasis and the underlying mechanism are still largely unclear.

Methods

Use public database to screen the potential lncRNA crucial for metastasis in colorectal cancer. The expression of H19 in clinical CRC specimens was detected by qRT-PCR. The effect of H19 on the metastasis of CRC cells was investigated by transwell, wound healing assays, CCK-8 assays and animal studies. The potential proteins binding to H19 were identified by LC-MS and verified by RNA immunoprecipitation (RIP). The expression of indicated RNA and proteins were measured by qRT-PCR or western blot.

Results

We found the expression of lncRNA H19 was significantly upregulated in primary tumor and metastatic tissues, correlated with poor prognosis in CRC. Ectopic H19 expression promoted the metastasis of colorectal cancer cells in vitro and in vivo, and induced epithelial-to-mesenchymal transition (EMT). Mechanistically, H19 directly bound to hnRNPA2B1. Knockdown of hnRNPA2B1 attenuated the H19-induce migration and invasion in CRC cells. Furthermore, H19 stabilized and upregulated the expression of Raf-1 by facilitated the interaction between hnRNPA2B1 and Raf-1 mRNA, resulting in activation of Raf-ERK signaling.

Conclusions

Our findings demonstrate the role of H19/hnRNPA2B1/EMT axis in regulation CRC metastasis, suggested H19 could be a potential biomarker to predict prognosis as well as a therapeutic strategy for CRC.

OSskcm: an online survival analysis webserver for skin cutaneous melanoma based on 1085 transcriptomic profiles

Background

Cutaneous melanoma is one of the most aggressive and lethal skin cancers. It is greatly important to identify prognostic biomarkers to guide the clinical management. However, it is technically challenging for untrained researchers to process high dimensional profiling data and identify potential prognostic genes in profiling datasets.

Methods

In this study, we developed a webserver to analyze the prognostic values of genes in cutaneous melanoma using data from TCGA and GEO databases. The webserver is named Online consensus Survival webserver for Skin Cutaneous Melanoma (OSskcm) which includes 1085 clinical melanoma samples. The OSskcm is hosted in a windows tomcat server. Server-side scripts were developed in Java script. The database system is managed by a SQL Server, which integrates gene expression data and clinical data. The Kaplan–Meier (KM) survival curves, Hazard ratio (HR) and 95% confidence interval (95%CI) were calculated in a univariate Cox regression analysis.

Results

In OSskcm, by inputting official gene symbol and selecting proper options, users could obtain KM survival plot with log-rank P value and HR on the output web page. In addition, clinical characters including race, stage, gender, age and type of therapy could also be included in the prognosis analysis as confounding factors to constrain the analysis in a subgroup of melanoma patients.

Conclusion

The OSskcm is highly valuable for biologists and clinicians to perform the assessment and validation of new or interested prognostic biomarkers for melanoma. OSskcm can be accessed online at: http://bioinfo.henu.edu.cn/Melanoma/MelanomaList.jsp.

Apolipoprotein A-I anti-tumor activity targets cancer cell metabolism

Previously, we reported apolipoprotein A-I (apoA-I), the major protein component of high-density lipoprotein (HDL), has potent anti-melanoma activity. We used DNA microarray and bioinformatics to interrogate gene expression profiles of tumors from apoA-I expressing (A-I Tg+/-) versus apoA-I-null (A-I KO) animals to gain insights into mechanisms of apoA-I tumor protection. Differential expression analyses of 11 distinct tumors per group with > 1.2-fold cut-off and a false discovery rate adjusted p < 0.05, identified 176 significant transcripts (71 upregulated and 105 downregulated in A-I Tg+/- versus A-I KO group). Bioinformatic analyses identified the mevalonate and de novo serine/glycine synthesis pathways as potential targets for apoA-I anti-tumor activity. Relative to A-I KO, day 7 B16F10L melanoma tumor homografts from A-I Tg+/- exhibited reduced expression of mevalonate-5-pyrophosphate decarboxylase (Mvd), a key enzyme targeted in cancer therapy, along with a number of key genes in the sterol synthesis arm of the mevalonate pathway. Phosphoglycerate dehydrogenase (Phgdh), the first enzyme branching off glycolysis into the de novo serine synthesis pathway, was the most repressed transcript in tumors from A-I Tg+/-. We validated our mouse tumor studies by comparing the significant transcripts with adverse tumor markers previously identified in human melanoma and found 45% concordance. Our findings suggest apoA-I targets the mevalonate and serine synthesis pathways in melanoma cells in vivo, thus providing anti-tumor metabolic effects by inhibiting the flux of biomolecular building blocks for macromolecule synthesis that drive rapid tumor growth.

An Unsupervised Strategy for Identifying Epithelial-Mesenchymal Transition State Metrics in Breast Cancer and Melanoma

Digital cytometry aims to identify different cell types in the tumor microenvironment, with the current focus on immune cells. Yet, identifying how changes in tumor cell phenotype, such as the epithelial-mesenchymal transition, influence the immune contexture is emerging as an important question. To extend digital cytometry, we developed an unsupervised feature extraction and selection strategy to capture functional plasticity tailored to breast cancer and melanoma separately. Specifically, principal component analysis coupled with resampling helped develop gene expression-based state metrics that characterize differentiation within an epithelial to mesenchymal-like state space and independently correlate with metastatic potential. First developed using cell lines, the orthogonal state metrics were refined to exclude the contributions of normal fibroblasts and provide tissue-level state estimates using bulk tissue RNA-seq measures. The resulting metrics for differentiation state aim to inform a more holistic view of how the malignant cell phenotype influences the immune contexture within the tumor microenvironment.

•

Unsupervised strategy to generate epithelial and mesenchymal state metrics

•

Refined metrics for use with bulk RNA-seq data by removing normal fibroblasts genes

•

Validated state predictions against independent measures of metastatic potential

•

Breast cancer and melanoma share more common genes in de-differentiated metrics

Model Combining Tumor Molecular and Clinicopathologic Risk Factors Predicts Sentinel Lymph Node Metastasis in Primary Cutaneous Melanoma

PURPOSE

More than 80% of patients who undergo sentinel lymph node (SLN) biopsy have no nodal metastasis. Here we describe a model that combines clinicopathologic and molecular variables to identify patients with thin and intermediate thickness melanomas who may forgo the SLN biopsy procedure due to their low risk of nodal metastasis.

PATIENTS AND METHODS

Genes with functional roles in melanoma metastasis were discovered by analysis of next generation sequencing data and case control studies. We then used PCR to quantify gene expression in diagnostic biopsy tissue across a prospectively designed archival cohort of 754 consecutive thin and intermediate thickness primary cutaneous melanomas. Outcome of interest was SLN biopsy metastasis within 90 days of melanoma diagnosis. A penalized maximum likelihood estimation algorithm was used to train logistic regression models in a repeated cross validation scheme to predict the presence of SLN metastasis from molecular, clinical and histologic variables.

RESULTS

Expression of genes with roles in epithelial-to-mesenchymal transition (glia derived nexin, growth differentiation factor 15, integrin β3, interleukin 8, lysyl oxidase homolog 4, TGFβ receptor type 1 and tissue-type plasminogen activator) and melanosome function (melanoma antigen recognized by T cells 1) were associated with SLN metastasis. The predictive ability of a model that only considered clinicopathologic or gene expression variables was outperformed by a model which included molecular variables in combination with the clinicopathologic predictors Breslow thickness and patient age; AUC, 0.82; 95% CI, 0.78-0.86; SLN biopsy reduction rate of 42% at a negative predictive value of 96%.

CONCLUSION

A combined model including clinicopathologic and gene expression variables improved the identification of melanoma patients who may forgo the SLN biopsy procedure due to their low risk of nodal metastasis.