Project description:A substantial part of cutaneous malignant melanomas develops from benign nevi. However, the precise molecular events driving the transformation from benign to malignant melanoma are not well understood. We used laser microdissection and mass spectrometry to analyze the proteomes of melanoma subtypes, including superficial spreading melanomas (SSM, n=17), nodular melanomas (NM, n=17), and acral melanomas (AM, n=15). Furthermore, we compared the proteomes of nevi cells and melanoma cells within the same specimens (nevus-associated melanoma (NAM, n=14)). In total, we quantified 7,935 proteins. Despite the genomic and clinical differences of the melanoma subtypes, our analysis revealed relatively similar proteomes, except for the upregulation of proteins involved in immune activation in NM vs AM. Examining NAM versus nevi, we found 1,725 differentially expressed proteins. Among these proteins were 140 that overlapped with cancer hallmarks, tumor suppressors, and regulators of metabolism and cell cycle. Pathway analysis indicated aberrant activation of the RAS/MAPK and PI3K-AKT-mTOR pathways, as well as the Hippo-YAP pathway. Using a classifier, we identified six proteins capable of distinguishing melanoma from nevi samples. Our study represents the first comprehensive comparative analysis of the proteome in melanoma subtypes and associated nevi, offering new insights into the biological behavior of these distinct entities.
Project description:Despite malignant cutaneous melanoma is relatively rare compared to other skin cancers, it is still responsible for 80% of all skin cancer-related deaths. To identify molecular signatures of melanoma progression, excisional biopsies from 18 common melanocytic nevi (CMN), 8 primary radial growth phase melanomas (RGPM), 15 primary vertical growth phase melanomas (VGPM) and 5 melanoma metastases (MTS) were profiled using whole genome oligo-microarrays. Differentially expressed genes for each progression step were identified, and validation of selected transcripts by qRT-PCR was performed on an independent cohort of fixed samples. The comparison between CMN and RGPM showed an enrichment of Gene Ontology (GO) terms related to inter and intra-cellular junctions, whereas the transition from RGPM to VGPM was characterized by the deregulation of WNT3, MAPK and AKT pathways. In this step, enrichment analysis underlined the alteration of biological processes linked to apoptosis. Upregulation of genes involved into DNA double-strand breaks repair and downregulation of cellular adhesion genes were observed in MTS respect to VGPM. Futhermore, the gene expression profiles of 11 dysplastic nevi (DN) were compared to all the others. Some genes controlling proliferation were found more expressed than in CMN. Overall, DN displayed an heterogeneous behaviour, with relevant oncogenes, such as MYC and BCL6, less expressed than in RGPM, and a modulation pattern similar to VGPM for a subset of gene families, such as mismatch repair. This suggests that DN is not an intermediate step within melanoma progression, but a separate entity with an independent risk of progression to melanoma Keywords: Melanoma progression, gene expression profiling, qPCR
Project description:The purpose of this study was to comprehensively study and compare the molecular gene expression profiles of common melanocytic nevi (GSE53223), dysplastic nevi (GSE53223), and primary melanoma.
Project description:Cutaneous melanoma is an increasingly common form of skin cancer. The molecular mechanisms regulating melanoma progression are not completely understood. We speculated that specific miRNAs may be involved in melanoma development. We compared the miRNA expression profiles of benign nevi and metastatic melanomas. Unsupervised hierarchical clustering demonstrated a distinct miRNA expression pattern in metastatic melanomas compared to nevi. We identified miRNAs that were differentially expressed in melanoma. Notably, miR-193b was significantly down-regulated in the melanoma tissue examined. Using functional studies we demonstrated that over-expression of miR-193b significantly reduced melanoma cell proliferation, and arrested cell at G1 phase. Further gene expression analysis revealed that miR-193b regulated targets involved in cell cycle. Cyclin D1 was down-regulated by miR-193b at both the mRNA and protein level. This is the first study to show that the miR-193b may reduce cell proliferation by directly repressing cyclin D1. Overall, our study suggests that miRNAs are dysregulated in metastatic melanoma, and that miR-193b may play an important role in melanoma. 8 benign nevi and 8 metastatic melanoma tissue samples were profiled by Agilent MicroRNA Microarray (V1.5).
Project description:Recent studies revealed trajectories of mutational events in early melanomagenesis, but the accompanying changes in gene expression are far less understood. Therefore, we performed a comprehensive RNA-Seq analysis of laser-microdissected melanocytic nevi (n=23) and primary melanoma samples (n=57) and characterized the molecular mechanisms of early melanoma development. Using self-organizing maps, unsupervised clustering and analysis of pseudotime (PT) dynamics to identify evolutionary trajectories, we describe here two transcriptomic types of melanocytic nevi (N1 and N2) and primary melanomas (M1 and M2). N1/M1 lesions are characterized by pigmentation-type and MITF gene signatures, and a high prevalence of NRAS mutations in M1 melanomas. N2/M2 lesions are characterized by inflammatory-type and AXL gene signatures with an equal distribution of wild type and mutated BRAF and low prevalence of NRAS mutations in M2 melanomas. Interestingly, N1 nevi and M1 melanomas and N2 nevi and M2 melanomas, respectively, cluster together, but there is no clustering in a stage-dependent manner. Transcriptional signatures of M1 melanomas harbour signatures of BRAF/MEK inhibitor resistance and M2 melanomas harbour signatures of anti-PD-1 antibody treatment resistance. Transcriptomic signatures suggest that the epigenetic regulators SMARCA2 and SMARCA4 are differentially involved in the epigenetic programming of the two melanoma types. Pseudotime dynamics of nevus and melanoma samples reflect a switch-like immune-escape mechanism in melanoma development with downregulation of immune genes paralleled by an increasing expression of a cell cycle signature in late-stage melanomas. Taken together, the transcriptome analysis identifies gene signatures and mechanisms underlying development of melanoma in early and late stages with relevance for diagnostics and therapy.
Project description:We sought to identify genes and gene signatures which correlate with progression by sampling human melanomas from nevi, primary, and metastatic tumors. The large number of samples also permits analysis within groups.
Project description:Cutaneous melanoma is an increasingly common form of skin cancer. The molecular mechanisms regulating melanoma progression are not completely understood. We speculated that specific miRNAs may be involved in melanoma development. We compared the miRNA expression profiles of benign nevi and metastatic melanomas. Unsupervised hierarchical clustering demonstrated a distinct miRNA expression pattern in metastatic melanomas compared to nevi. We identified miRNAs that were differentially expressed in melanoma. Notably, miR-193b was significantly down-regulated in the melanoma tissue examined. Using functional studies we demonstrated that over-expression of miR-193b significantly reduced melanoma cell proliferation, and arrested cell at G1 phase. Further gene expression analysis revealed that miR-193b regulated targets involved in cell cycle. Cyclin D1 was down-regulated by miR-193b at both the mRNA and protein level. This is the first study to show that the miR-193b may reduce cell proliferation by directly repressing cyclin D1. Overall, our study suggests that miRNAs are dysregulated in metastatic melanoma, and that miR-193b may play an important role in melanoma.