Issues affecting molecular staging in the management of patients with melanoma

Minimal residual disease in melanoma: circulating melanoma cells and predictive role of MCAM/MUC18/MelCAM/CD146

Circulating tumour cells (CTCs), identified in numerous cancers including melanoma, are unquestionably considered valuable and useful as diagnostic and prognostic markers. They can be detected at all melanoma stages and may persist long after treatment. A crucial step in metastatic processes is the intravascular invasion of neoplastic cells as circulating melanoma cells (CMCs). Only a small percentage of these released cells are efficient and capable of colonizing with a strong metastatic potential. CMCs' ability to survive in circulation express a variety of genes with continuous changes of signal pathways and proteins to escape immune surveillance. This makes it difficult to detect them; therefore, specific isolation, enrichment and characterization of CMC population could be useful to monitor disease status and patient clinical outcome. Overall and disease-free survival have been correlated with the presence of CMCs. Specific melanoma antigens, in particular MCAM (MUC18/MelCAM/CD146), could be a potentially useful tool to isolate CMCs as well as be a prognostic, predictive biomarker. These are the areas reviewed in the article.

Future of circulating tumor cells in the melanoma clinical and research laboratory settings

Circulating tumor cells (CTC) have become a field of interest for oncologists based on the premise that they constitute the underpinning for metastatic dissemination. The lethal nature of cancer is no longer attributed to solid tumor formation, but rather to the process of metastasis; shifting the focus of current studies towards the isolation and identification of metastatic progenitors, such as CTCs. CTCs originate from primary tumor masses that undergo morphologic and genetic alterations, which involve the release of mesenchymal-like cancer cells into the bloodstream, capable of invading nearby tissues for secondary tumor development. Cancerous cells contained in the primary tumor mass acquire the motile mesenchymal phenotype as a result of the Epithelial-to-Mesenchymal Transition, where substantial variations in protein expression and signaling pathways take place. CTCs that migrate from the primary tumor, intravasate into the systemic vasculature, are transported through the bloodstream, and invade tissues and organs suitable for secondary tumor development. While only a limited number of CTCs are viable in the bloodstream, their ability to elude the immune system, evade apoptosis and successfully metastasize at secondary tumor sites, makes CTCs promising candidates for unraveling the triggers that initiates the metastatic process. In this article, these subjects are explored in greater depth to elucidate the potential use of CTCs in the detection, disease staging and management of metastatic melanoma.

Multiple Molecular Pathways in Melanomagenesis: Characterization of Therapeutic Targets

Molecular mechanisms involved in pathogenesis of malignant melanoma have been widely studied and novel therapeutic treatments developed in recent past years. Molecular targets for therapy have mostly been recognized in the RAS–RAF–MEK–ERK and PI3K–AKT signaling pathways; small-molecule inhibitors were drawn to specifically target key kinases. Unfortunately, these targeted drugs may display intrinsic or acquired resistance and various evidences suggest that inhibition of a single effector of the signal transduction cascades involved in melanoma pathogenesis may be ineffective in blocking the tumor growth. In this sense, a wider comprehension of the multiple molecular alterations accounting for either response or resistance to treatments with targeted inhibitors may be helpful in assessing, which is the most effective combination of such therapies. In the present review, we summarize the known molecular mechanisms underlying either intrinsic and acquired drug resistance either alternative roads to melanoma pathogenesis, which may become targets for innovative anticancer approaches.

Circulating melanoma cells in the diagnosis and monitoring of melanoma: an appraisal of clinical potential

Circulating melanoma cells (CMCs) are thought to be the foundation for metastatic disease, which makes this cancer especially lethal. Cancer cells contained in the primary tumor undergo genotypic and phenotypic changes leading to an epithelial-to-mesenchymal transition, during which numerous changes occur in signaling pathways and proteins in the cells. CMCs are then shed off or migrate from the primary tumor and intravasate the vasculature system. A few CMCs are able to survive in the circulation through expression of a variety of genes and also by evading immune system recognition to establish metastases at distant sites after extravasating from the vessels. The presence of CMCs in the blood of a melanoma patient can be used for disease staging, predicting metastasis development, and evaluating the efficacy of therapeutic agents. Overall survival and disease-free duration can also be correlated with the presence of CMCs. Finally, analysis of CMCs for druggable therapeutic gene targets could lead to the development of personalized treatment regimens to prevent metastasis. Thus, the study of CMCs shows promise for the detection, staging, and monitoring of disease treatment, as well as for determination of prognosis and predicting overall disease-free survival. These are the areas reviewed in this article.

Comparison of molecular abnormalities in vulvar and vaginal melanomas

Malignant melanoma of the vulva and vagina is relatively uncommon and accounts for <5% of all melanomas in women. The aim of our study was to establish the biological properties and evaluate potential therapeutic targets in these tumors. We collected a series of 65 cases from three centers and re-evaluated the tumor tissue for predominant growth pattern (superficial spreading, nodular, and mucosal lentiginous) and tumor thickness. KIT (CD117) expression was detected immunohistochemically. In addition, tumors were screened for BRAF, NRAS, and KIT mutations by PCR and DNA sequencing as well as for KIT amplifications by fluorescence in situ hybridization. None of the cases contained BRAF mutations. NRAS mutations and KIT amplifications were detected in similar frequency (∼12%) in tumors of the vulva and vagina. In contrast, KIT mutations were present in 18% of primary melanomas of the vulva, but in none of the tumors arising in the vagina. Moderate or strong KIT protein expression was detected in 30 cases, including all tumors with KIT mutations and 6 of the 7 with KIT amplifications. In conclusion, BRAF mutations are virtually absent in melanomas originating from the vulva or vagina, whereas NRAS mutations and KIT amplifications occur in both locations. KIT mutations appear to be specific for melanomas of the vulva, suggesting that in spite of the anatomic proximity, the development of vulvar and vaginal melanomas involves different molecular alterations which may be targeted by novel treatment approaches.

Current concepts of metastasis in melanoma

The main cause of death in melanoma patients is widespread metastases. Staging of melanoma is based on the primary tumor thickness, ulceration, lymph node and distant metastases. Metastases develop in regional lymph nodes, as satellite or in-transit lesions, or in distant organs. Lymph flow and chemotaxis is responsible for the homing of melanoma cells to different sites. Standard pathologic evaluation of sentinel lymph nodes fails to find occult melanoma in a significant proportion of cases. Detection of small numbers of malignant melanoma cells in these and other sites, such as adjacent to the primary site, bone marrow or the systemic circulation, may be enhanced by immunohistochemistry, reverse transcription PCR, evaluation of lymphatic vessel invasion and proteomics. In the organs to which melanoma cells metastasize, extravasation of melanoma cells is regulated by adhesion molecules, matrix metalloproteases, chemokines and growth factors. Melanoma cells may travel along external vessel lattices. After settling in the metastatic sites, melanoma cells develop mechanisms that protect them against the attack of the immune system. It is thought that one of the reasons why melanoma cells are especially resistant to killing is the fact that melanocytes (cells from which melanoma cells derive) are resistant to such noxious factors as ultraviolet light and reactive oxygen species. Targeted melanoma therapies are, so far, largely unsuccessful, and new ones, such as adjuvant inhibition of melanogenesis, are under development.

Heterogeneous distribution of BRAF/NRAS mutations among Italian patients with advanced melanoma

BACKGROUND

Prevalence and distribution of pathogenetic mutations in BRAF and NRAS genes were evaluated in multiple melanoma lesions from patients with different geographical origin within the same Italian population.

METHODS

Genomic DNA from a total of 749 tumor samples (451 primary tumors and 298 metastases) in 513 consecutively-collected patients with advanced melanoma (AJCC stages III and IV) was screened for mutations in exon 15 of BRAF gene and, at lower extension (354/513; 69%), in the entire coding DNA of NRAS gene by automated direct sequencing. Among tissues, 236 paired samples of primary melanomas and synchronous or asynchronous metastases were included into the screening.

RESULTS

Overall, mutations were detected in 49% primary melanomas and 51% metastases, for BRAF gene, and 15% primary tumors and 16% secondaries, for NRAS gene. A heterogeneous distribution of mutations in both genes was observed among the 451 primary melanomas according to patients' geographical origin: 61% vs. 42% (p = 0.0372) BRAF-mutated patients and 2% vs. 21% (p < 0.0001) NRAS-mutated cases were observed in Sardinian and non-Sardinian populations, respectively. Consistency in BRAF/NRAS mutations among paired samples was high for lymph node (91%) and visceral metastases (92.5%), but significantly lower for brain (79%; p = 0.0227) and skin (71%; p = 0.0009) metastases.

CONCLUSIONS

Our findings about the two main alterations occurring in the different tumor tissues from patients with advanced melanoma may be helpful in improving the management of such a disease.

Molecular diagnostic strategies: a role in the practice of dermatology

Molecular diagnostic strategies are gaining wider acceptance and use in dermatology and dermatopathology as more practitioners in this field develop an understanding of the principles and applications of genomic technologies. Molecular testing is facilitating more accurate diagnosis, staging, and prognostication, in addition to guiding the selection of appropriate treatment, monitoring of therapy, and identification of novel therapeutic targets, for a wide variety of skin diseases.

Evaluation of a multi-marker immunomagnetic enrichment assay for the quantification of circulating melanoma cells

Background

Circulating melanoma cells (CMCs) are thought to be valuable in improving measures of prognosis in melanoma patients and may be a useful marker of residual disease to identify non-metastatic patients requiring adjuvant therapy. We investigated whether immunomagnetic enrichment targeting multiple markers allows more efficient enrichment of CMCs from patient peripheral blood than targeting a single marker. Furthermore, we aimed to determine whether the number of CMCs in patient blood was associated with disease stage.

Methods

We captured CMCs by targeting the melanoma associated markers MCSP and MCAM as well as the melanoma stem cell markers ABCB5 and CD271, both individually and in combination, by immunomagnetic enrichment. CMCs were enriched and quantified from the peripheral blood of 10 non-metastatic and 13 metastatic melanoma patients.

Results

Targeting all markers in combination resulted in the enrichment of more CMCs than when any individual marker was targeted (p < 0.001-0.028). Furthermore, when a combination of markers was targeted, a greater number of CMCs were enriched in metastatic patients compared with non-metastatic patients (p = 0.007).

Conclusions

Our results demonstrated that a combination of markers should be targeted for optimal isolation of CMCs. In addition, there are significantly more CMCs in metastatic patients compared with non-metastatic patients and therefore quantification of CMCs may prove to be a useful marker of disease progression.

BRAF/NRAS Mutation Frequencies Among Primary Tumors and Metastases in Patients With Melanoma

Purpose

The prevalence of BRAF, NRAS, and p16CDKN2A mutations during melanoma progression remains inconclusive. We investigated the prevalence and distribution of mutations in these genes in different melanoma tissues.

Patients and Methods

In all, 291 tumor tissues from 132 patients with melanoma were screened. Paired samples of primary melanomas (n = 102) and synchronous or asynchronous metastases from the same patients (n = 165) were included. Tissue samples underwent mutation analysis (automated DNA sequencing). Secondary lesions included lymph nodes (n = 84), and skin (n = 36), visceral (n = 25), and brain (n = 44) sites.

Results

BRAF/NRAS mutations were identified in 58% of primary melanomas (43% BRAF; 15% NRAS); 62% in lymph nodes, 61% subcutaneous, 56% visceral, and 70% in brain sites. Mutations were observed in 63% of metastases (48% BRAF; 15% NRAS), a nonsignificant increase in mutation frequency after progression from primary melanoma. Of the paired samples, lymph nodes (93% consistency) and visceral metastases (96% consistency) presented a highly similar distribution of BRAF/NRAS mutations versus primary melanomas, with a significantly less consistent pattern in brain (80%) and skin metastases (75%). This suggests that independent subclones are generated in some patients. p16CDKN2A mutations were identified in 7% and 14% of primary melanomas and metastases, with a low consistency (31%) between secondary and primary tumor samples.

Conclusion

In the era of targeted therapies, assessment of the spectrum and distribution of alterations in molecular targets among patients with melanoma is needed. Our findings about the prevalence of BRAF/NRAS/p16CDKN2A mutations in paired tumor lesions from patients with melanoma may be useful in the management of this disease.

Use of gene expression and pathway signatures to characterize the complexity of human melanoma

A defining characteristic of most human cancers is heterogeneity, resulting from the somatic acquisition of a complex array of genetic and genomic alterations. Dissecting this heterogeneity is critical to developing an understanding of the underlying mechanisms of disease and to paving the way toward personalized treatments of the disease. We used gene expression data sets from the analysis of primary and metastatic melanomas to develop a molecular description of the heterogeneity that characterizes this disease. Unsupervised hierarchical clustering, gene set enrichment analyses, and pathway activity analyses were used to describe the genetic heterogeneity of melanomas. Patterns of gene expression that revealed two distinct classes of primary melanoma, two distinct classes of in-transit melanoma, and at least three subgroups of metastatic melanoma were identified. Expression signatures developed to predict the status of oncogenic signaling pathways were used to explore the biological basis underlying these differential patterns of expression. This analysis of activities revealed unique pathways that distinguished the primary and metastatic subgroups of melanoma. Distinct patterns of gene expression across primary, in-transit, and metastatic melanomas underline the genetic heterogeneity of this disease. This heterogeneity can be described in terms of deregulation of signaling pathways, thus increasing the knowledge of the biological features underlying individual melanomas and potentially directing therapeutic opportunities to individual patients with melanoma.

Methods of detection of circulating melanoma cells: a comparative overview

Disease dissemination is the major cause of melanoma-related death. A crucial step in the metastatic process is the intravascular invasion and circulation of melanoma cells in the bloodstream with subsequent development of distant micrometastases that is initially clinically undetectable and will eventually progress into clinically apparent metastasis. Therefore, the use of molecular methods to detect circulating melanoma cells may be of value in risk stratification and clinical management of such patients. Herein, we review the currently applied techniques for the detection, isolation, enrichment and further characterization of circulating melanoma cells from peripheral blood samples in melanoma patients. Furthermore, we provide a brief overview of the various molecular markers currently being evaluated as prognostic indicators of melanoma progression.

Prognostic value of microphthalmia-associated transcription factor and tyrosinase as markers for circulating tumor cells detection in patients with melanoma

The aim of this study was to analyze microphthalmia-associated transcription factor (MITF) as a marker for the detection of circulating melanoma cells, determine its prognostic value in melanoma patients, and compare it with tyrosinase. Blood samples from 201 melanoma patients in all stages of the disease and 40 healthy volunteers were analyzed. RNA was isolated from mononuclear cell fraction of the blood and assayed by reverse transcription-PCR for the expression of MITF and tyrosinase. All samples from healthy volunteers were negative for both MITF and tyrosinase. Out of 201 blood samples from melanoma patients 32 were positive for MITF, 20 for tyrosinase, and four for both MITF and tyrosinase. Analysis of MITF as an additional marker to tyrosinase allowed for detection of circulating melanoma cells in a larger number of melanoma patients in comparison to tyrosinase analysis alone (48 vs. 20 positive). A positive value of MITF was associated with shorter progression-free (P=0.005) and overall survival (P=0.042). A positive value of tyrosinase was associated with shorter overall survival (P=0.012), whereas there was no significant association between the value of tyrosinase and progression-free survival. The value of MITF was selected with multivariate analysis as the independent prognostic factor for progression-free survival, whereas the only independent prognostic factor for overall survival was the stage of disease. This study has shown that MITF is a specific marker for detection of circulating melanoma cells that has a prognostic value in melanoma patients. Determination of MITF in addition to tyrosinase improved the detection of circulating melanoma cells in melanoma patients.

HCV-related hepatocellular carcinoma: From chronic inflammation to cancer

Hepatitis C virus (HCV) infection is a worldwide health problem because of its incidence and pathogenicity. It might evolve into chronic disease, cirrhosis, and/or hepatocellular carcinoma (HCC) and the outcome is mainly determined by the host immune response. For viral clearance, combined innate and adaptive immune responses are required; resolution requires a vigorous, durable, polyclonal CD4(+) and CD8(+) T-cell response, with an increase in virus-specific CD8(+) T cells or cytotoxic T lymphocytes. Failure of efficient immune response can lead to chronic inflammation, tissue remodeling through cell growth, apoptosis and/or necrosis and induction of oxidative stress. Development of fibrosis and/or cirrhosis plus a microenvironment conducive to genomic instability mutations will promote neoplastic transformation. System governance derives from cellular (regulatory cells) and humoral (cytokines and chemokines) immune networks. Therefore, HCC pathogenesis may be a model to study the disease progression from chronic inflammation to cancer allowing design of new strategies targeting the immune response, thereby modifying disease outcome.

Main roads to melanoma

The characterization of the molecular mechanisms involved in development and progression of melanoma could be helpful to identify the molecular profiles underlying aggressiveness, clinical behavior, and response to therapy as well as to better classify the subsets of melanoma patients with different prognosis and/or clinical outcome. Actually, some aspects regarding the main molecular changes responsible for the onset as well as the progression of melanoma toward a more aggressive phenotype have been described. Genes and molecules which control either cell proliferation, apoptosis, or cell senescence have been implicated. Here we provided an overview of the main molecular changes underlying the pathogenesis of melanoma. All evidence clearly indicates the existence of a complex molecular machinery that provides checks and balances in normal melanocytes. Progression from normal melanocytes to malignant metastatic cells in melanoma patients is the result of a combination of down- or up-regulation of various effectors acting on different molecular pathways.

Role of key-regulator genes in melanoma susceptibility and pathogenesis among patients from South Italy

Background

Several genetic alterations have been demonstrated to contribute to the development and progression of melanoma. In this study, we further investigated the impact of key-regulator genes in susceptibility and pathogenesis of such a disease.

Methods

A large series (N = 846) of sporadic and familial cases originating from South Italy was screened for germline mutations in p16^CDKN2A, BRCA2, and MC1R genes by DHPLC analysis and automated DNA sequencing. Paired primary melanomas and lymph node metastases from same patients (N = 35) as well as melanoma cell lines (N = 18) were analyzed for somatic mutations in NRAS, BRAF, and p16^CDKN2A genes.

Results

For melanoma susceptibility, investigations at germline level indicated that p16^CDKN2A was exclusively mutated in 16/545 (2.9%) non-Sardinian patients, whereas BRCA2 germline mutations were observed in 4/91 (4.4%) patients from North Sardinia only. Two MC1R germline variants, Arg151Cys and Asp294His, were significantly associated with melanoma in Sardinia. Regarding genetic events involved in melanoma pathogenesis at somatic level, mutually-exclusive mutations of NRAS and BRAF genes were observed at quite same rate (about two thirds) in cultured and in vivo melanomas (either primary or metastatic lesions). Conversely, p16^CDKN2A gene alterations were observed at increased rates moving from primary to metastatic melanomas and melanoma cell lines. Activation of the ERK gene product was demonstrated to be consistently induced by a combination of molecular alterations (NRAS/BRAF mutations and p16^CDKN2A silencing).

Conclusion

Our findings further clarified that: a) mutation prevalence in melanoma susceptibility genes may vary within each specific geographical area; b) multiple molecular events are accumulating during melanomagenesis.

Norepinephrine upregulates VEGF, IL-8, and IL-6 expression in human melanoma tumor cell lines: implications for stress-related enhancement of tumor progression

Studies suggest that stress can be a co-factor for the initiation and progression of cancer. The catecholamine stress hormone, norepinephrine (NE), may influence tumor progression by modulating the expression of factors implicated in angiogenesis and metastasis. The goal of this study was to examine the influence of NE on the expression of VEGF, IL-8, and IL-6 by the human melanoma cell lines, C8161, 1174MEL, and Me18105. Cells were treated with NE and levels of VEGF, IL-8, and IL-6 were measured using ELISA and real-time PCR. The expression of beta-adrenergic receptors (beta-ARs) mRNA and protein were also assessed. Finally, immunohistochemistry was utilized to examine the presence of beta1- and beta2-AR in primary and metastatic human melanoma biopsies. We show that NE treatment upregulated production of VEGF, IL-8, and IL-6 in C8161 cells and to a lesser extent 1174MEL and Me18105 cells. The upregulation was associated with induced gene expression. The effect on C8161 cells was mediated by both beta1- and beta2-ARs. Furthermore, 18 of 20 melanoma biopsies examined expressed beta2-AR while 14 of 20 melanoma biopsies expressed beta1-AR. Our data support the hypothesis that NE can stimulate the aggressive potential of melanoma tumor cells, in part, by inducing the production VEGF, IL-8, and IL-6. This line of research further suggests that interventions targeting components of the activated sympathetic-adrenal medullary (SAM) axis, or the utilization of beta-AR blocking agents, may represent new strategies for slowing down the progression of malignant disease and improving cancer patients' quality of life.

Detection of circulating tumor cells in bladder cancer patients

The methods employed for the detection of circulating bladder cancer cells (CBCs) and their use as a molecular staging tool in clinical settings are thoroughly reviewed. CBC isolation and enrichment methods are discussed according to their advantages and pitfalls along with the clinical data of PCR-based techniques used for CBC detection. In addition, we review the specificity of molecular markers that have been proposed so far for CBC identification, and we comment on the controversial clinical data, proposing laboratory approaches which may improve the clinical significance of CBC detection in bladder cancer.