Melanoma-associated Genes Research Articles

Metastatic melanoma: An integrated analysis to identify critical regulators associated with prognosis, pathogenesis and targeted therapies.

Metastatic melanoma causes a high rate of mortality. We conducted an integrated analysis to identify critical regulators associated with the prognosis, pathogenesis, and targeted therapies of metastatic-melanoma. A microarray dataset, GSE15605, including 12 metastatic-melanoma and sixteen normal skin (NS) samples, were obtained from the GEO database. After exploration of DEGs of NS and metastatic-melanoma, identification of relevant transcription factors (TFs) and kinases, the Gene Ontology (GO), and pathways analyses of DEGs were performed. Protein-protein interaction (PPI) networks were evaluated by the STRING and Cytoscape. Subsequently, the hub genes were selected using GEPIA. Survival analysis was performed using the TCGA. To identify microRNA and lncRNA DEGs of the melanoma-associated genes miRwalk and FANTOM6 were employed. In metastatic-melanoma samples 285 and 1173 genes were up and down-regulated, respectively. The upregulated genes were mostly involved in granulocyte chemotaxis, positive regulation of calcium ion transmembrane transport, and melanin biosynthetic process. Five hub genes including CXCL11, ICAM1, LEF1, MITF, and STAT1 were identified, SUZ12, SOX2, TCF3, NANOG, and SMAD4 were determined as the most significant TFs in metastatic-melanoma. Furthermore, CDK2, GSK3B, CSNK2A1, and CDK1 target the highest amounts of genes associated with disease. The DGIdb analysis results show the match drugs for five hub genes. MiRNAs analysis revealed hsa-miR-181c-5p, hsa-miR-30b-3p, hsa-miR-3680-3P, hsa-miR-4659a-3p, hsa-miR-4687-3P, and hsa-miR-6808-3P could regulate the hub genes, whereas RP11-553K8.5 and SRP14-AS1 were identified as the top significant lncRNA. The items recognized in the current study can be used as potential biomarkers for diagnostic, predictive, and might helpful to develop targeted combined therapies.

Shortened progression free and overall survival to immune-checkpoint inhibitors in BRAF-, RAS- and NF1- (“Triple”) wild type melanomas

BackgroundMelanomas lacking mutations in BRAF, NRAS and NF1 are frequently referred to as “triple wild-type” (tWT) melanomas. They constitute 5–10 % of all melanomas and remain poorly characterized regarding clinical characteristics and response to therapy. This study investigates the largest multicenter collection of tWT-melanomas to date. MethodsTargeted next-generation sequencing of the TERT promoter and 29 melanoma-associated genes were performed on 3109 melanoma tissue samples of the prospective multicenter study ADOREG/TRIM of the DeCOG revealing 292 patients suffering from tWT-melanomas. Clinical characteristics and mutational patterns were analyzed. As subgroup analysis, we analyzed 141 tWT-melanoma patients receiving either anti-CTLA4 plus anti-PD1 or anti PD1 monotherapy as first line therapy in AJCC stage IV. Results184 patients with cutaneous melanomas, 56 patients with mucosal melanomas, 34 patients with acral melanomas and 18 patients with melanomas of unknown origin (MUP) were included. A TERT promoter mutation could be identified in 33.2 % of all melanomas and 70.5 % of all tWT-melanomas harbored less than three mutations per sample. For the 141 patients with stage IV disease, mPFS independent of melanoma type was 6.2 months (95 % CI: 4–9) and mOS was 24.8 months (95 % CI: 14.2–53.4) after first line anti-CTLA4 plus anti-PD1 therapy. After first-line anti-PD1 monotherapy, mPFS was 4 months (95 %CI: 2.9–8.5) and mOS was 29.18 months (95 % CI: 17.5–46.2). ConclusionsWhile known prognostic factors such as TERT promoter mutations and TMB were equally distributed among patients who received either anti-CTLA4 plus anti-PD1 combination therapy or anti-PD1 monotherapy as first line therapy, we did not find a prolonged mPFS or mOS in either of those. For both therapy concepts, mPFS and mOS were considerably shorter than reported for melanomas with known oncogene mutations.

Active natural compounds perturb the melanoma risk-gene network.

Cutaneous melanoma is an aggressive type of skin cancer with a complex genetic landscape caused by the malignant transformation of melanocytes. This study aimed at providing an in silico network model based on the systematic profiling of the melanoma-associated genes considering germline mutations, somatic mutations, and genome-wide association study signals accounting for a total of 232 unique melanoma risk genes. A protein-protein interaction network was constructed using the melanoma risk genes as seeds and evaluated to describe the functional landscape in which the melanoma genes operate within the cellular milieu. Not only were the majority of the melanoma risk genes able to interact with each other at the protein level within the core of the network, but this showed significant enrichment for genes whose expression is altered in human melanoma specimens. Functional annotation showed the melanoma risk network to be significantly associated with processes related to DNA metabolism and telomeres, DNA damage and repair, cellular ageing, and response to radiation. We further explored whether the melanoma risk network could be used as an in silico tool to predict the efficacy of anti-melanoma phytochemicals, that are considered active molecules with potentially less systemic toxicity than classical cytotoxic drugs. A significant portion of the melanoma risk network showed differential expression when SK-MEL-28 human melanoma cells were exposed to the phytochemicals harmine and berberine chloride. This reinforced our hypothesis that the network modeling approach not only provides an alternative way to identify molecular pathways relevant to disease but it may also represent an alternative screening approach to prioritize potentially active compounds.

629 Performance monitoring of a streamlined and scalable non-invasive gene expression assay for pigmented lesions

The DermTech Pigmented Lesion Assay (PLA) is a qPCR-based assay that aids in the detection of melanoma by assessing up-regulation of two melanoma-associated genes, LINC00518 and PRAME, in skin samples collected by non-invasive adhesive patches. This study is to establish assay performance characteristics of the PLA post optimization, and to investigate the prognostic potential of the assay by comparison of qPCR amplification cycle in PLA positive samples with the histopathologic diagnoses of cutaneous pigmented lesions. RNA isolated from non-invasively collected skin cells was analyzed from seventy-five pigmented lesions. The PLA was optimized to simplify the laboratory workflow and increase scalability of the assay through a series of process improvements including RNA quantification by 1-step qRT-PCR (vs. reverse transcription followed by qPCR) and assay miniaturization. PLA result was determined by evaluating qPCR amplification of LINC00518 and PRAME multiplexed with housekeeping genes β-Actin and PPIA respectively. Samples that demonstrated over-expression of LINC00518 and PRAME relative to the housekeeping genes were considered PLA positive. Blinded to the PLA results, biopsy specimens from the pigmented lesions were examined and classified by a dermatopathologist as invasive melanoma (n=22); melanoma in situ (MIS) (n=26); benign nevus (24); or other (n=3). All twenty-two lesions classified as invasive melanoma by histopathology were PLA-positive, with an average LINC00518 Ct of 32.2 and PRAME Ct of 30.9. Seventeen of the twenty-six samples classified as MIS were PLA-positive, with an average LINC00518 Ct of 33.8 and PRAME Ct of 33.2. Of the twenty-seven samples not classified as melanoma, five were PLA-positive, with an average LINC00518 Ct of 34.4 and PRAME Ct of 35.8. The results indicate that PLA Ct values are highly correlated with histopathologic diagnoses. The optimized PLA assay demonstrated a sensitivity of 100% for invasive melanoma and 65% for MIS, with an overall specificity of 81%.

Isolation of circulating tumor cells to diagnose melanoma and evaluate the efficacy of surgical resection using melanoma-specific microsystem.

Melanoma is one of the most aggressive skin cancers due to its potential to metastasize widely in the body. The risk of metastasis is increased with later detection and increased thickness of the primary lesion, thus early identification and surgical removal is critical for higher survival rates for patients. However, even with appropriate treatment, some patients will develop recurrence which may be difficult to identify until advanced or causing symptoms. Recent advances in liquid biopsy have proposed less-invasive alternatives for cancer diagnosis and monitoring using minimal/zero invasion at sample collection, and circulating tumor cells(CTCs) have been considered a promising blood-based surrogate marker of primary tumors. However, previous CTC technologies relying on epithelial-cell adhesion molecules have limited to epithelial cells, thus hampering use of CTCs for non-epithelial cancers such as melanoma. Here, we used the Melanoma-specific OncoBean platform(MelanoBean) conjugated with melanoma specific antibodies(MCAM and MCSP). The device was used in comprehensive studies for diagnosing melanoma and evaluating surgery efficacy based on change in the number and characteristics of CTCs and CTC-clusters pre- and post-surgical treatment. Our study demonstrated that melanoma patients(n=45) at all stages(I-IV) have a noticeable number of MCTCs as well as MCTC-clusters compared to healthy donors(n=9)(P=0.0011), and surgical treatment leads to a significant decrease in the number of CTCs(P<0.0001). The CTCs recovered from the device underwent molecular profiling for melanoma-associated genes expression using multiplexed qRT-PCR, demonstrating the ability to monitor molecular signature through treatment. The presented MelanoBean and the comprehensive approach will empower prognostic value of CTCs in melanoma in much larger cohort studies.

Genetic Manipulation of Sirtuin 3 Causes Alterations of Key Metabolic Regulators in Melanoma.

The mitochondrial sirtuin SIRT3 plays key roles in cellular metabolism and energy production, which makes it an obvious target for the management of cancer, including melanoma. Previously, we have demonstrated that SIRT3 was constitutively upregulated in human melanoma and its inhibition resulted in anti-proliferative effects in vitro in human melanoma cells and in vivo in human melanoma xenografts. In this study, we expanded our data employing knockdown and overexpression strategies in cell culture and mouse xenografts to further validate and establish the pro-proliferative function of SIRT3 in melanocytic cells, and its associated potential mechanisms, especially focusing on the metabolic regulation. We found that short-hairpin RNA (shRNA) mediated SIRT3 knockdown in G361 melanoma cells showed diminished tumorigenesis in immunodeficient Nu/Nu mice. Conversely, SIRT3 overexpressing Hs294T melanoma cells showed increased tumor growth. These effects were consistent with changes in markers of proliferation (PCNA), survival (Survivin) and angiogenesis (VEGF) in xenografted tissues. Further, in in vitro culture system, we determined the effect of SIRT3 knockdown on glucose metabolism in SK-MEL-2 cells, using a PCR array. SIRT3 knockdown caused alterations in a total of 37 genes involved in the regulation and enzymatic pathways of glucose (32 genes) and glycogen (5 genes) metabolism. Functions annotation of these identified genes, using the ingenuity pathway analysis (IPA), predicted cumulative actions of decreased cell viability/proliferation, tumor growth and reactive oxygen species (ROS), and increased apoptosis in response to SIRT3 knockdown. Further, IPA gene network analysis of SIRT3 modulated genes revealed the interactions among these genes in addition to several melanoma-associated genes. Sirtuin pathway was identified as one of the top canonical pathways showing the interaction of SIRT3 with metabolic regulatory genes along with other sirtuins. IPA analysis also predicted the inhibition of HIF1α, PKM, KDM8, PPARGC1A, mTOR, and activation of P53 and CLPP; the genes involved in major cancer/melanoma-associated signaling events. Collectively, these results suggest that SIRT3 inhibition affects cellular metabolism, to impart an anti-proliferative response against melanoma.

Dual-Isolation and Profiling of Circulating Tumor Cells and Cancer Exosomes from Blood Samples with Melanoma Using Immunoaffinity-Based Microfluidic Interfaces.

Melanoma is among the most aggressive cancers, and its rate of incidence continues to grow. Early detection of melanoma has been hampered due to the lack of promising markers for testing. Recent advances in liquid biopsy have proposed noninvasive alternatives for cancer diagnosis and monitoring. Circulating tumor cells (CTCs) and cancer‐exosomes are gaining influence as promising biomarkers because of their cancer‐associated molecular markers and signatures. However, technologies that offer the dual‐isolation of CTCs and exosomes using a single sample have not been thoroughly developed. The dual‐utilization OncoBean (DUO) device is conjugated with melanoma specific antibodies, MCAM and MCSP, enabling simultaneous CTC and exosome isolations. Using blood samples from patients, CTCs and exosomes are specifically isolated from a single sample and then undergo molecular profiling for comprehensive study. Melanoma patients have 0–17CTCs mL−1 and 299 µg exosomal protein mL−1 while healthy donors display fewer than 2CTCs and 75.6 µg of exosomes mL−1, respectively. It is also demonstrated that both markers express melanoma‐associated genes using multiplex qRT‐PCR to test for expression pattern of a 96 gene panel. The dual isolation and molecular characterization will allow for further research into melanoma to identify viable markers for disease progression and treatment efficacy.

Human genes differ by their UV sensitivity estimated through analysis of UV-induced silent mutations in melanoma.

We hypothesized that human genes differ by their sensitivity to ultraviolet (UV) exposure. We used somatic mutations detected by genome-wide screens in melanoma and reported in the Catalog Of Somatic Mutations In Cancer. As a measure of UV sensitivity, we used the number of silent mutations generated by C>T transitions in pyrimidine dimers of a given transcript divided by the number of potential sites for this type of mutations in the transcript. We found that human genes varied by UV sensitivity by two orders of magnitude. We noted that the melanoma-associated tumor suppressor gene CDKN2A was among the top five most UV-sensitive genes in the human genome. Melanoma driver genes have a higher UV-sensitivity compared with other genes in the human genome. The difference was more prominent for tumor suppressors compared with oncogene. The results of this study suggest that differential sensitivity of human transcripts to UV light may explain melanoma specificity of some driver genes. Practical significance of the study relates to the fact that differences in UV sensitivity among human genes need to be taken into consideration whereas predicting melanoma-associated genes by the number of somatic mutations detected in a given gene.

Intellectual Mining of Patient Data with Melanoma for Identification of Disease Markers and Critical Genes

Genotypic (DNA mutations) and phenotyping data on patients with melanoma are analyzed to identify markers of early disease diagnosis and critical involved genes. An optimal mining method was chosen from those that are traditionally used in the field. This method allows one to analyze a set of terms. Automatic and interactive approaches were performed, which both allow a considerable reduction in the computational requirements. New melanoma-associated genes and candidate relapse markers were identified. Data mining was performed with the JSM method of automated support of scientific research (JSM ASSR).

Integration of protein interaction and gene co-expression information for identification of melanoma candidate genes

Cutaneous melanoma is an aggressive form of skin cancer that causes death worldwide. Although much has been learned about the molecular basis of melanoma genesis and progression, there is also increasing appreciation for the continuing discovery of melanoma genes to improve the genetic understanding of this malignancy. In the present study, melanoma candidate genes were identified by analysis of the common network from cancer type-specific RNA-Seq co-expression data and protein-protein interaction profiles. Then, an integrated network containing the known melanoma-related genes represented as seed genes and the putative genes represented as linker genes was generated using the subnetwork extraction algorithm. According to the network topology property of the putative genes, we selected seven key genes (CREB1, XPO1, SP3, TNFRSF1B, CD40LG, UBR1, and ZNF484) as candidate genes of melanoma. Subsequent analysis showed that six of these genes are melanoma-associated genes and one (ZNF484) is a cancer-associated gene on the basis of the existing literature. A signature comprising these seven key genes was developed and an overall survival analysis of 461 cutaneous melanoma cases was carried out. This seven-gene signature can accurately determine the risk profile for cutaneous melanoma tumors (log-rank P=3.27E-05) and be validated on an independent clinical cohort (log-rank P=0.028). The presented seven genes might serve as candidates for studying the molecular mechanisms and help improve the prognostic risk assessment, which have clinical implications for melanoma patients.

‘Mind your Moles’ study: protocol of a prospective cohort study of melanocytic naevi

IntroductionHaving many melanocytic naevi or ‘moles’ on the skin is the strongest predictor of melanoma; thus, much can be learnt from investigating naevi in the general population. We aim to...

Regulatory pathway analysis of coat color genes in Mongolian horses

BackgroundStudies on the molecular genetics of horse skin pigmentation have typically focused on very few genes and proteins. In this study, we used Illumina sequencing to determine the global gene expression profiles in horses with white-colored coats and those with black-colored coats, with the goal of identifying novel genes that could regulate horse coat color.ResultsGenes encoding ribosomal-associated proteins were highly expressed in horse skin. We found a total of 231 unigenes that were differentially expressed between horses with white coats and horses with black coats; 119 were down-regulated, and 112 were up-regulated. Many of the up-regulated genes in black horses, such as genes related to tyrosine metabolism, may directly regulate dark coat color. Keratin genes, MIA family genes, fatty acid-related genes, and melanoma-associated genes were also differentially regulated, which suggests that they may play important roles in coat color formation.ConclusionsThese findings show that the transcription profiles from white and black horse skin provide useful information to understand the genetics underlying the control of skin melanin synthesis in horses, which may enhance our knowledge of human skin diseases, such as melanoma and albinism.

Mutation analysis of mucosal and cutaneous melanomas during progression.

e21047 Background: The prevalence of mutations in driver genes during progression in cutaneous and mucosal melanomas remains inconclusive. We investigated the prevalence and distribution of mutations in main candidate genes involved in melanomagenesis among different melanoma tissues using a next-generation sequencing (NGS) approach. Methods: Forty-eight tumor samples from 36 patients with mucosal melanoma (MM) and fifty-two tumor samples from 34 patients with cutaneous melanoma (CM) were collected, after obtaining patients’ written informed consent for tissue sampling. Genomic DNA was isolated from macrodissected tumor tissues containing at least 80% neoplastic cells and analyzed for mutations in 25 most common melanoma-associated oncogenes and tumor suppressor genes, using the IMI Diagnostic Melanoma Panel on the Ion Torrent platform (Life Technologies, USA). Results: A total of 100 tumor tissues from 70 melanoma patients were analyzed. BRAF mutations were detected in 21/34 (62%) CM patients and 13/36 (36%) mm patients. The second most prevalent mutations were found in K-/N-RAS (6/34; 18%) and cKIT (6/36; 17%) genes among CM and mm patients, respectively. No concomitant mutations of BRAF, RAS, and cKIT genes were detected. Among others, mutations were more frequently found in CCND1 (20%), ARID2 (16%), and NF1(12%) genes, considering the entire series of patients. Vast majority of patients who had paired samples of primary and secondary melanomas showed consistent mutation patterns between primary tumors and metastatic lesions. Similar frequencies of mutations in driver genes were seen across metastatic sites. Conclusions: In the era of targeted therapies, assessment of the spectrum and distribution of mutations in main molecular targets among patients with melanoma is needed. Our findings about the prevalence of mutations in driver genes in paired tumor lesions from patients with cutaneous and mucosal melanoma may be useful in the management of such diseases. The Italian Melanoma Intergroup (IMI) includes the following additional members who participated as investigators in this study: Mario Mandalà, Paola Queirolo, Ignazio Stanganelli, Vanna Chiarion Sileni, Pietro Quaglino, Anna Maria Di Giacomo.

Pigmented epithelioid melanocytoma (animal-type melanoma): An institutional experience

Pigmented epithelioid melanocytoma (PEM) is an uncommon, recently described entity with unknown biologic behavior. There is a high rate of regional metastases, but limited evidence of distant metastases or disease-related death. We sought to report our series of patients given a diagnosis of PEM at our institution and provide mutational analysis of genes commonly implicated in melanoma in 2 cases. The pathology database was queried for cases of PEM diagnosed at the University of Rochester. Charts were reviewed for follow-up information. Mutational analysis of melanoma-associated genes was performed on 2 cases. Nine cases of PEM were retrieved in a 10-year retrospective review. Five patients underwent sentinel lymph node biopsy with 3 of 5 having a positive sentinel lymph node. All 9 patients are alive and disease-free with average follow-up of 38.75months. Two tumors were tested for common melanoma-associated mutations, and were negative, except for a telomerase reverse transcriptase promoter deletion detected in 1 sample. The deletion has not been associated with melanoma, and therefore its biologic significance is unclear. Small sample size, retrospective nature, and single institution experience are limitations. PEM appears to have an indolent behavior. However, currently the evidence is too limited to provide insight into its true biologic potential.

DNA Methylation Levels of Melanoma Risk Genes Are Associated with Clinical Characteristics of Melanoma Patients.

In melanoma development, oncogenic process is mediated by genetic and epigenetic mutations, and few studies have so far explored the role of DNA methylation either as predisposition factor or biomarker. We tested patient samples for germline CDKN2A methylation status and found no evidence of inactivation by promoter hypermethylation. We have also investigated the association of clinical characteristics of samples with the DNA methylation pattern of twelve genes relevant for melanomagenesis. Five genes (BAP1, MGMT, MITF, PALB2, and POT1) presented statistical association between blood DNA methylation levels and either CDKN2A-mutation status, number of lesions, or Breslow thickness. In tumors, five genes (KIT, MGMT, MITF, TERT, and TNF) exhibited methylation levels significantly different between tumor groups including acral compared to nonacral melanomas and matched primary lesions and metastases. Our data pinpoint that the methylation level of eight melanoma-associated genes could potentially represent markers for this disease both in peripheral blood and in tumor samples.

The Nerve Growth Factor Receptor CD271 Is Crucial to Maintain Tumorigenicity and Stem-Like Properties of Melanoma Cells

BackgroundLarge-scale genomic analyses of patient cohorts have revealed extensive heterogeneity between individual tumors, contributing to treatment failure and drug resistance. In malignant melanoma, heterogeneity is thought to arise as a consequence of the differentiation of melanoma-initiating cells that are defined by cell-surface markers like CD271 or CD133.ResultsHere we confirmed that the nerve growth factor receptor (CD271) is a crucial determinant of tumorigenicity, stem-like properties, heterogeneity and plasticity in melanoma cells. Stable shRNA mediated knock-down of CD271 in patient-derived melanoma cells abrogated their tumor-initiating and colony-forming capacity. A genome-wide expression profiling and gene-set enrichment analysis revealed novel connections of CD271 with melanoma-associated genes like CD133 and points to a neural crest stem cell (NCSC) signature lost upon CD271 knock-down. In a meta-analysis we have determined a shared set of 271 differentially regulated genes, linking CD271 to SOX10, a marker that specifies the neural crest. To dissect the connection of CD271 and CD133 we have analyzed 10 patient-derived melanoma-cell strains for cell-surface expression of both markers compared to established cell lines MeWo and A375. We found CD271+ cells in the majority of cell strains analyzed as well as in a set of 16 different patient-derived melanoma metastases. Strikingly, only 2/12 cell strains harbored a CD133+ sub-set that in addition comprised a fraction of cells of a CD271+/CD133+ phenotype. Those cells were found in the label-retaining fraction and in vitro deduced from CD271+ but not CD271 knock-down cells.ConclusionsOur present study provides a deeper insight into the regulation of melanoma cell properties and points CD271 out as a regulator of several melanoma-associated genes. Further, our data strongly suggest that CD271 is a crucial determinant of stem-like properties of melanoma cells like colony-formation and tumorigenicity.

Melanoma-associated genes, MXI1, FN1, and NME1, are hypoxia responsive in murine and human melanoma cells

Hypoxia can influence aggressiveness of melanoma by inducing specific gene expression profiles. In our previous microarray study, we identified more than 430 hypoxia-responsive genes in the B16-F10 murine melanoma cell line in vitro. Of the genes identified, seven genes: galectin 3 (Lgals3), melanoma cell adhesion molecule (Mcam), fibronectin 1 (Fn1), signal transducer and activator of transcription 3 (Stat3), microphthalmia-associated transcription factor (Mitf), max interacting protein 1 (Max1), and non-metastatic cells 1, protein (NM23A) expressed in (Nme1) are known to be associated with melanoma, but have not yet been reported as being regulated by hypoxia in human melanoma cells. In this study, we investigated whether the expression of these genes is modulated by hypoxia in microdissected areas of experimental B16-F10 tumors in vivo, as well as in commercially available human melanoma cell lines (WM35, WM1552C, WM793B, WM278, 1205Lu, and 451Lu) exposed to hypoxic conditions in vitro. Our analysis revealed significant agreement between the in-vitro and in-vivo results showing that all genes except Mitf were hypoxia regulated in the oxygen-deprived tumor regions (P<0.05). In contrast, three genes (NME1, MXI1 and FN1) proved to be hypoxia regulated in both human and mouse melanoma cells (P<0.05). Our results link these genes, for the first time, with hypoxic microenvironment of melanoma and imply that the widely used B16-F10 melanoma experimental tumor model could be a convenient research tool for further investigation of their role in the development and course of this malignancy.

The biology of micrometastases from uveal melanoma

BackgroundThe aim of this study was to investigate the possible causes of tumour latency in uveal melanoma primarily through the analysis of micrometastases in tissue obtained from donors postmortem. Various...

Melanoblasts in culture as an in vitro system to determine molecular changes in melanoma

Many consolidated findings have revealed that cancer formation resembles events of embryonic development. In particular, the network of transcription factors and adhesion molecules is very similar when comparing neural crest-derived melanoblasts and melanoma cells. The main difference is found in the manifestation of distinct genes in melanoma, whereas in neural crest cells gene expression is tightly regulated to promote either a migratory or stationary phenotype. We established a cell culture system to generate melanoblast-related cells (MBrc) out of melanocytes as originally described by Cook et al. First, we confirmed the typical gene expression pattern of BRN-2, SOX10, PAX3 and EDNRB. Furthermore, we identified enhanced migration and proliferation similar to that of melanoma cells. Our intention of using this system was to classify the known 'melanoma-associated genes' into a subgroup of genes solely regulated by the differentiation process and a second subgroup that is unaffected by differentiation and is potentially important to the stabilization of a melanoma phenotype. The expression of melanoma-associated genes (N-cadherin, MUC-18, integrin β3, α3, α5, αv, SLUG, TBX3, HIF1-α, BMP-4 and bFGF) was enhanced in MBrc which were de-differentiated out of melanocytes. E-cadherin, H-cadherin and β-catenin, prevalently found to be downregulated in melanoma, were diminished in MBrc. Remarkably, the transcription factor SNAIL was unaffected by differentiation and could be one key molecule in early melanoma development that is of prevailing importance. In summary, we feel that the analysis of MBrc generated in a reproducible system will give new insight into the role and importance of melanoma-associated genes.

Evaluation of minimal residual disease (MRD) in peripheral blood (PB) assessed prospectively by RT-PCR for melanoma-associated genes as a prognostic factor for survival in stage III melanoma (Mel) patients (pts) enrolled onto an intergroup adjuvant trial S0008.

8513 Background: In addition to known prognostic factors, the analysis of PB for expression of mel genes by RT-PCR (MRD) may provide insight into the likelihood of relapse and/or death in pts with high-risk mel and inform decisions regarding adjuvant therapy. Prior studies have provided conflicting results on the utility of PB RT-PCR testing. Methods: In Intergroup phase III trial S0008 of adjuvant therapy in pts with stage III mel (Txb+N1a or ≥N2a or N1b) MRD was assessed by RT-PCR of mel associated genes (tyrosinase, MART-1, gp-100 or MAGE-3) at baseline, day 90, and day 365. Pts were randomized to biochemotherapy (BCT) (9 wks) or standard adjuvant interferon (HD IFN) (52 wks). MRD monitoring was instituted after trial enrollment was initiated and represented data for 219 of 420 pts. Although survival data are not yet mature, the SWOG DSMC gave permission for a preliminary analysis of the impact of MRD on clinical outcomes blinded to treatment arm. Results: Two hundred nineteen of 420 enrolled pts had pre-treatment MRD testing. The baseline characteristics of these 219 pts were similar to the entire 420 pts; 64% with macrometastases, 44% ulcerated primary, and 33% with N3 disease. In a Cox model adjusted for known baseline characteristics, baseline RT-PCR+ for ≥ 1 gene (present in 24 pts) was a significant negative prognostic factor for overall survival (OS) (p = 0.005, HR 2.26). Using landmark analysis of OS, RT-PCR+ at day 90 (216 pts, 25 RT-PCR+) was associated with poor outcome (p = 0.01) but not at day 365 (193 pts,19 RT-PCR+) (p = 0.11). The strongest association with outcome was for tyrosinase and/or MART-1 (p = 0.001) and with no impact detected for gp-100 (p = 0.43) or MAGE-3 (p = 0.59). Conclusions: This prospective analysis of pts with high-risk mel treated either with adjuvant HD IFN or BCT demonstrates that the presence of PB RT-PCR markers of 1 or more melanoma-associated genes increases the risk of death after adjusting for all other known prognostic factors. Author Disclosure Employment or Leadership Position Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Novartis, Roche, Schering-Plough Novartis, Roche, Schering-Plough