Issues in the epidemiology of melanoma

c-Rel is a cell cycle modulator in human melanoma cells

Melanoma progression and resistance to therapy are associated with faulty regulation of signalling molecules including the central transcription factor NF-κB. Increased expression of the c-Rel subunit of NF-κB has been described in progressing melanoma, though mechanistic implications of this upregulation remain unclear. To elucidate the functional role of c-Rel in melanoma biology, we have assessed its expression in human melanoma as well as in melanoma cell lines. Suppression of c-Rel expression in four melanoma cell lines resulted in reduced growth and altered cell cycle regulation, namely G2/M and polyploid phase induction. Moreover, mitotic spindle morphology was profoundly altered in three of the cell lines with a predominance of monopolar structures. These findings suggest that c-Rel is involved in G2/M phase regulation, prevention of polyploidy and, consequently, chromosomal stability. Our results highlight a novel tumor-promoting function of c-Rel in human melanoma cells through governing cell cycle regulation.

Inhibitory effect of quercetin on epithelial to mesenchymal transition in SK-MEL-28 human melanoma cells defined by in vitro analysis on 3D collagen gels

Considering the emerging concept of complementary and alternative medicine under the paucity of effective treatment for melanoma, we aimed to understand the effect of quercetin (Qu) on collagen I-induced epithelial-mesenchymal transition (EMT) in melanoma cells. To investigate the effect of Qu in melanoma cells, we used multiple methods, including real-time reverse transcription polymerase chain reaction, migration assay, and wound healing assay. We found that EMT was altered by Qu in melanoma cells. Qu-treated cells exhibited decreased migration and invasion activities. Mechanistically, a high expression of epithelial markers and a decrease in the expression of mesenchymal markers were found to be associated with reversal of EMT in melanoma cells. Time-dependent apoptosis was observed in Qu-treated melanoma cells, which was further confirmed by the upregulation in the protein levels of Caspase 3, a proapoptotic marker. Thus, our findings suggest Qu as a promising dietary compound under the new complementary and alternative medicine category of therapeutic drugs in the chemoprevention of melanoma.

Differentiation-inducing and anti-proliferative activities of lupeol on canine melanoma cells

Canine melanoma is the most common oral malignant tumor reported in the field of veterinary medicine. We found that lupeol, a lupine triterpene, inhibited mouse melanoma cell growth in vitro and in vivo by inducing cell differentiation. In the present study, we examined the differentiation-inducing activities of lupeol on 4 canine melanoma cells in vitro and in vivo.

The induction of canine melanoma cell differentiation by lupeol was confirmed by evaluating some differentiation markers such as tyrosinase with real-time RT-PCR. Furthermore, we transplanted canine melanoma cells into a severe combined immunodeficiency mouse, and studied the anti-progressive effects of lupeol on tumor tissue.

The gene expression of microphthalmia-associated transcription factor, tyrosinase, and tyrosinase-related protein-2, which are markers of pigment cell differentiation, was induced in 4 canine oral malignant melanoma cells by lupeol, and the agent markedly inhibited tumor progression in canine melanoma-bearing mice.

Systemic and local injections of lupeol inhibit tumor growth in a melanoma-bearing mouse model

Melanoma is the most aggressive type of skin cancer and it is procured from activated or genetically altered epidermal melanocytes. In the present study, the tumor-suppressive effects of systemic and local injections of lupeol, a triterpene extracted from Indian lettuce (Lactuca indica), in a melanoma-bearing mouse model were evaluated. Mice were injected once with lupeol or olive oil (solvent control) subcutaneously into the skin of the back or into the tumor tissue. Seven days after the injection, the tumor growth rates were calculated and the tumor tissues were collected. Immunohistochemical staining for Ki-67 and proliferating cell nuclear antigen (PCNA) were performed. The tumor growth rates in the lupeol-injected group were significantly decreased compared to those observed in the non-treated (NT) and solvent control groups. Lupeol also significantly decreased the areas positively stained for Ki-67 and PCNA in the tumor tissues compared to those in the NT and solvent control groups. The results of the present study demonstrated that systemic and local injections of lupeol suppress tumor growth and induce cell cycle arrest in a melanoma-bearing mouse model. These data suggest that lupeol may be effective as a novel therapeutic option for melanoma patients.

NF-κB as potential target in the treatment of melanoma

The RAS/MAP kinase pathway has attracted attention because activating mutations of the BRAF serine/threonine kinase was described in over 50% of melanomas. Very recently, selective and potent BRAF inhibitors have been developed. Several other signal transduction pathways have been found to be constitutively active or mutated in other subsets of melanoma tumors that are potentially targetable with new agents. Among these, NFκB is another pathway that melanoma tumors use to achieve survival, proliferation and resistance to apoptosis. Inhibition of NF-κB activation appears to be a very promising option for anti-cancer therapies.

Agreement of dermatopathologists in the evaluation of clinically difficult melanocytic lesions: how golden is the 'gold standard'?

BACKGROUND

The 'gold standard' for the diagnosis of melanocytic lesions is dermatopathology. Although most of the diagnostic criteria are clearly defined, the interpretation of histopathology slides may be subject to interobserver variability.

OBJECTIVES

The aim of this study was to determine the variability among dermatopathologists in the interpretation of clinically difficult melanocytic lesions.

METHODS

This study used the database of MelaFind®, a computer-vision system for the diagnosis of melanoma. All lesions were surgically removed and sent for independent evaluation by four dermatopathologists. Agreement was calculated using kappa statistics.

RESULTS

A total of 1,249 pigmented melanocytic lesions were included. There was a substantial agreement among expert dermatopathologists: two-category kappa was 0.80 (melanoma vs. non-melanoma) and three-category kappa was 0.62 (malignant vs. borderline vs. benign melanocytic lesions). The agreement was significantly greater for patients ≥40 years (three-category kappa = 0.67) than for younger patients (kappa = 0.49). In addition, the agreement was significantly lower for patients with atypical mole syndrome (AMS) (kappa = 0.31) than for patients without AMS (kappa = 0.76).

LIMITATIONS

The data were limited by the inclusion/exclusion criteria of the MelaFind® study. This might represent a selection bias. The agreement was evaluated using kappa statistics. This is a standard method for evaluating agreement among pathologists, but might be considered controversial by some statisticians.

CONCLUSIONS

Expert dermatopathologists have a high level of agreement when diagnosing clinically difficult melanocytic lesions. However, even among expert dermatopathologists, the current 'gold standard' is not perfect. Our results indicate that lesions from younger patients and patients with AMS may be more problematic for the dermatopathologists, suggesting that improved diagnostic criteria are needed for such patients.

The contribution of electron paramagnetic resonance to melanoma research

The incidence of malignant melanoma, the most dangerous form of skin cancer, is rising each year. However, some aspects of the tumor initiation and development are still unclear, and the current method of diagnosis, based on the visual aspect of the tumor, shows limitations. For these reasons, developments of new techniques are ongoing to improve basic knowledge on the disease and diagnosis of tumors in individual patients. This paper shows how electron paramagnetic resonance (EPR), a method able to detect free radicals trapped in melanin pigments, has recently brought its unique value to this specific field. The general principles of the method and the convenience of melanin as an endogenous substrate for EPR measurements are explained. Then, the way by which EPR has recently helped to assess the contribution of ultraviolet rays (UVA and UVB) to the initiation of melanoma is described. Finally, we describe the improvements of EPR spectrometry and imaging in the detection and mapping of melanin pigments inside ex vivo and in vivo melanomas. We discuss how these advances might improve the diagnosis of this skin cancer and point out the present capabilities and limitations of the method.

Dermis-derived stem cells: a source of epidermal melanocytes and melanoma?

Human multipotent dermal stem cells (DSCs) have been isolated and propagated from the dermal region of neonatal foreskin. DSCs can self-renew, express the neural crest stem cell markers NGFRp75 and nestin, and are capable of differentiating into a wide variety of cell types including mesenchymal and neuronal lineages and melanocytes, indicative of their neural crest origin. When placed in the context of reconstructed skin, DSCs migrate to the basement membrane zone and differentiate into melanocytes. These findings, combined with the identification of NGFRp75-positive cells in the dermis of human foreskin, which are devoid of hair, suggest that DSCs may be a self-renewing source of extrafollicular epidermal melanocytes. In this review, we discuss the properties of DSCs, the pathways required for melanocyte differentiation, and the value of 3D reconstructed skin to assess the behavior and contribution of DSCs in the naturalized environment of human skin. Potentially, DSCs provide a link to malignant melanoma by being a target of UVA-induced transformation.

Rb-Raf-1 interaction disruptor RRD-251 induces apoptosis in metastatic melanoma cells and synergizes with dacarbazine

Metastatic melanoma is an aggressive cancer with very low response rate against conventional chemotherapeutic agents such as dacarbazine (DTIC). Inhibitor of Rb-Raf-1 interaction RRD-251 was tested against the melanoma cell lines SK-MEL-28, SK-MEL-5, and SK-MEL-2. RRD-251 was found to be a potent inhibitor of melanoma cell proliferation, irrespective of V600E B-Raf mutation status of the cell lines. In a SK-MEL-28 xenograft experiment, RRD-251 exerted a significant suppression of tumor growth compared with vehicle (P = 0.003). Similar to in vitro effects, tumors from RRD-251-treated animals showed decreased Rb-Raf-1 interaction in vivo. Growth suppressive effects of RRD-251 were associated with induction of apoptosis as well as a G(1) arrest, with an accompanying decrease in S-phase cells. RRD-251 inhibited Rb phosphorylation and downregulated E2F1 protein levels in these cells. Real-time PCR analysis showed that RRD-251 caused downregulation of cell-cycle regulatory genes thymidylate synthase (TS) and cdc6 as well as the antiapoptotic gene Mcl-1. Combinatorial treatment of RRD-251 and DTIC resulted in a significantly higher apoptosis in DTIC resistant cell lines SK-MEL-28 and SK-MEL-5, as revealed by increased caspase-3 activity and PARP cleavage. Because aberrant Rb/E2F pathway is associated with melanoma progression and resistance to apoptosis, these results suggest that the Rb-Raf-1 inhibitor could be an effective agent for melanoma treatment, either alone or in combination with DTIC.

Management of melanoma families

In this review we have aimed to focus on the clinical management of familial melanoma patients and their relatives. Along this line three major topics will be discussed: (1) management/screening of familial melanoma families: what is advised and what is the evidence thereof; (2) variability of families worldwide with regard to clinical phenotype, including cancer spectrum and likelihood of finding germline mutations and (3) background information for clinicians on the molecular biology of familial melanoma and recent developments in this field.

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.

Overcoming apoptosis deficiency of melanoma-hope for new therapeutic approaches

The increased incidence of malignant melanoma in the last decades, its high mortality and pronounced therapy resistance pose an enormous challenge. Important therapeutic targets for melanoma are the induction of apoptosis and suppression of survival pathways. Preclinical studies have demonstrated the efficacy of pro-apoptotic Bcl-2 proteins and of death receptor ligands to trigger apoptosis in melanoma cells. In the clinical setting, BH3 domain mimics and death receptor agonists are therefore considered as promising, specific novel treatments to add to the conventional pro-apoptotic strategies such as chemo- or radiotherapy. However, constitutively activated survival pathways, in particular the mitogen-activated protein kinases, protein kinase B/Akt and nuclear factor (NF)-kappaB, all may work in concert to prevent effective therapy. Thus, selective biologicals developed with the aim to inhibit pro-survival signaling are currently tested in melanoma. For highly therapy-resistant tumors such as melanoma, development of novel drug combinations will be essential, and combinations of survival inhibitors and pro-apoptotic mediators appear most promising. The challenge of the near future will be to make a rational choice of the multiple possible combinations and protocols. This review gives a critical overview of proteins involved in melanoma chemoresistance, which are targets for current drug development leading to the best choice for future trials.

Melanoma, long wavelength ultraviolet and sunscreens: Controversies and potential resolutions

Although sunlight is known to cause melanoma, there has been considerable controversy as to the importance of short (UVB) and long (UVA) ultraviolet (UV) wavelengths in causing melanoma, leading to uncertainty in how best to prevent this cancer. This uncertainty has been compounded by the difficulties in assaying the UVA protection abilities of sunscreens, as compared to widely accepted measures of UVB screening by the sun protection factor (SPF). This review discusses the controversies surrounding UVA causation of melanoma in both human and animal models and the use of sunscreens to prevent melanoma. In addition, it details the development of an electron paramagnetic resonance (EPR) technique, initially used to determine the wavelength dependence (or action spectrum) of intramelanocyte radical generation to resolve these controversies in the Xiphophorus model. It is shown how this EPR technique allows a sunscreen protection factor to be determined, that is weighted to the melanocyte, and how this also allows study of the wavelength-dependent screening ability of sunscreens.

Determination of Wavelength-Specific UV Protection Factors of Sunscreens in Intact Skin by EPR Measurement of UV-Induced Reactive Melanin Radical

There remains an unmet need for skin tissue-based assays for the measurement of the UVA protection and efficacy of sunscreens. Here we describe development of a novel electron paramagnetic resonance assay that uses the photogeneration of reactive melanin radical as a measure of UV light penetration to melanocytes in situ in skin. We have used areas of focal melanocytic hyperplasia in the skin of Monodelphis domestica to model the human nevus. We show that we are able to use this assay to determine the monochromatic protection factors (mPF) of research and commercial sunscreens at specific narrow wavebands of UVB, UVA and blue visible light. Both commercial sunscreens, a sun protection factor (SPF) 4 and an SPF 30 product, had mPFs in the UVB range that correlated well with their claimed SPF. However, their mPF in the UVA ranges were only about one-third of claimed SPF. This technique can be used to design and assay sunscreens with optimally balanced UVA and UVB protection.

Diacylglycerol kinase α suppresses tumor necrosis factor-α-induced apoptosis of human melanoma cells through NF-κB activation

We investigated the implication of diacylglycerol kinase (DGK) alpha (type I isoform) in melanoma cells because we found that this DGK isoform was expressed in several human melanoma cell lines but not in noncancerous melanocytes. Intriguingly, the overexpression of wild-type (WT) DGKalpha, but not of its kinase-dead (KD) mutant, markedly suppressed tumor necrosis factor (TNF)-alpha-induced apoptosis of AKI human melanoma cells. In the reverse experiment, siRNA-mediated knockdown of DGKalpha significantly enhanced the apoptosis. The overexpression of other type I isoforms (DGKbeta and DGKgamma) had, on the other hand, no detectable effects on the apoptosis. These results indicate that DGKalpha specifically suppresses the TNF-alpha-induced apoptosis through its catalytic action. We found that the overexpression of DGKalpha-WT, but not of DGKalpha-KD, further enhanced the TNF-alpha-stimulated transcriptional activity of an anti-apoptotic factor, NF-kappaB. Conversely, DGKalpha-knockdown considerably inhibited the NF-kappaB activity. Moreover, an NF-kappaB inhibitor blunted the anti-apoptotic effect of DGKalpha overexpression. Together, these results strongly suggest that DGKalpha is a novel positive regulator of NF-kappaB, which suppresses TNF-alpha-induced melanoma cell apoptosis.

Melanocyte transformation associated with substrate adhesion impediment

Exclude experimental models of malignant transformation employ chemical and physical carcinogens or genetic manipulations to study tumor progression. In this work, different melanoma cell lines were established after submitting a nontumorigenic melanocyte lineage (melan-a) to sequential cycles of forced anchorage impediment. The great majority of these cells underwent anoikis when maintained in suspension. After one deadhesion cycle, phenotypic alterations were noticeable in the few surviving cells, which became more numerous and showed progressive alterations after each adhesion impediment step. No significant differences in cell surface expression of integrins were detected, but a clear electrophoretic migration shift, compatible with an altered glycosylation pattern, was observed for beta1 chain in transformed cell lines. In parallel, a progressive enrichment of tri- and tetra-antennary N-glycans was apparent, suggesting increased N-acetylglucosaminyltransferase V activity. Alterations both in proteoglycan glycosylation pattern and core protein expression were detected during the transformation process. In conclusion, this model corroborates the role of adhesion state as a promoting agent in transformation process and demonstrates that cell adhesion disturbances may act as carcinogenic stimuli, at least for a nontumorigenic immortalized melanocyte lineage. These findings have intriguing implications for in vivo carcinogenesis, suggesting that anchorage independence may precede, and contribute to, neoplastic conversion.

Role of Sun Exposure in Melanoma

BACKGROUND

Malignant melanoma is the third most common skin cancer in the United States. It is commonly thought that sun exposure is causative in these tumors. Recently, however, the significance of the role of sun exposure in melanoma has come into question. Some have suggested that other factors, such as genetics, play a larger role, and that sun protection may even be harmful.

OBJECTIVE AND METHODS

To investigate the role of sun exposure in melanoma etiology. An extensive review of basic science and clinical literature on this subject was conducted.

RESULTS

Although exceptions exist, sun exposure likely plays a large role in most melanomas. The pattern of this exposure, however, is not fully known, and controversy exists, especially in the use of sunscreens. Sun exposure may interact with genetic factors to cause melanomas, and sun protective measures appear to be prudent.

CONCLUSIONS

The cause of melanoma is probably variable and multifactorial. Sun exposure may play a primary or supporting role in most melanoma tumors.

Role of nuclear factor-kappa B in melanoma

Nuclear Factor-kappa B (NF-kappa B) is an inducible transcription factor that regulates the expression of many genes involved in the immune response. Recently, NF-kappa B activity has been shown to be upregulated in many cancers, including melanoma. Data indicate that the enhanced activation of NF-kappa B may be due to deregulations in upstream signaling pathways such as Ras/Raf, PI3K/Akt, and NIK. Multiple studies have shown that NF-kappa B is involved in the regulation of apoptosis, angiogenesis, and tumor cell invasion, all of which indicate the important role of NF-kappa B in tumorigenesis. Thus, understanding the molecular mechanism of melanoma progression will aid in designing new therapeutic approaches for melanoma. In this review, the association between NF-kappa B and melanoma tumorigenesis are discussed. Additionally, the potential of emerging selective NF-kappa B inhibitors for the treatment of melanoma is reviewed.

Augmenting chemosensitivity of malignant melanoma tumors via proteasome inhibition: implication for bortezomib (VELCADE, PS-341) as a therapeutic agent for malignant melanoma

Melanoma poses a great challenge to patients, oncologists, and biologists because of its nearly universal resistance to chemotherapy. Many studies have shown that nuclear factor kappaB is constitutively activated in melanoma, thereby promoting the proliferation of melanoma cells by inhibiting the apoptotic responses to chemotherapy. Nuclear factor kappaB activity is regulated by phosphorylation and subsequent degradation of inhibitor of nuclear factor kappaB by the ubiquitin-proteasome pathway. In this study, we show that the novel proteasome inhibitor, bortezomib, inhibited the growth of melanoma cells in vitro at a concentration range of 0.1-10 nM and in combination with the chemotherapeutic agent temozolomide, the inhibitory effect on melanoma cell growth was even more prominent. Data from a murine model showed reduced tumor growth when bortezomib was administered to human melanoma tumors. Strikingly, animals receiving bortezomib in combination with temozolomide achieved complete remission of palpable tumors after only 30 days of therapy, lasting >200 days. Our data indicate strongly that bortezomib in combination with chemotherapeutic agents should be studied additionally for the treatment of melanoma.

Melanoma cell migration is upregulated by tumour necrosis factor-alpha and suppressed by alpha-melanocyte-stimulating hormone

We reported recently that the inflammatory cytokine tumour necrosis factor α (TNF-α) can upregulate integrin expression, cell attachment and invasion of cells through fibronectin in a human melanoma cell line (HBL). Furthermore, the actions of TNF-α were suppressed by the addition of an anti-inflammatory peptide α-melanocyte-stimulating hormone (α-MSH). In the current study, we extend this work investigating to what extent TNF-α might stimulate melanoma invasion by promoting cell migration and whether α-MSH is also inhibitory. Two human melanoma cell lines were examined in vitro (HBL and C8161) using a scratch migration assay. Analysis using either time-lapse video microscopy or imaging software analysis of migrating ‘fronts’ of cells revealed that C8161 cells migrated more rapidly than HBL cells. However, when cells were stimulated with TNF-α both cell types responded with a significant increase in migration distance over a 16–26 h incubation time. α-Melanocyte-stimulating hormone had an inhibitory effect on TNF-α-stimulated migration for HBL cells, completely blocking migration at 10⁻⁹ M. In contrast, C8161 cells did not respond to α-MSH (as these cells have a loss-of-function melanocortin-1 receptor). However, stable transfection of C8161 cells with the wild-type melanocortin-1 receptor produced cells whose migration was significantly inhibited by α-MSH. In addition, the use of a neutralising antibody to the β₁-integrin subunit significantly reduced migration in both cell types. This data therefore supports an inflammatory environment promoting melanoma cell migration, and in addition shows that α-MSH can inhibit inflammatory stimulated migration. The data also support a fundamental role of the β₁-integrin receptor in melanoma cell migration.

Topical Treatment with Inhibitors of the Phosphatidylinositol 3′-Kinase/Akt and Raf/Mitogen-Activated Protein Kinase Kinase/Extracellular Signal-Regulated Kinase Pathways Reduces Melanoma Development in Severe Combined Immunodeficient Mice

Topical treatment with inhibitors of the phosphatidylinositol 3'-kinase/Akt and Raf/mitogen-activated protein kinase kinase/extracellular signal-regulated kinase pathways inhibited the growth of TPras transgenic melanomas in severe combined immunodeficient mice, blocked invasive behavior, and reduced angiogenesis. The inhibitor Ly294002, which is specific for phosphatidylinositol 3'-kinase, effectively reduced melanoma cell growth both in vitro and in vivo. Both Ly294002 and U0126, a mitogen-activated protein kinase kinase 1/2 inhibitor, reduced invasion, which correlated with reduction of the metalloproteinase matrix metalloproteinase 2. Tumor angiogenesis was disrupted through inhibition of vascular endothelial growth factor production from the tumor cells and antiangiogenic effects on endothelial cells. Observations with TPras melanoma cells that express dominant negative Deltap85 or kinase-inactive Raf(301) supported the specificity of the phenomena observed with the chemical inhibitors. These studies demonstrate that topical treatment targeting Ras effectors is efficacious, without systemic toxicities, and may prove to be useful in treating and preventing the progression of cutaneous melanoma.

Biomarkers in melanoma: predisposition, screening and diagnosis

Melanoma's incidence and mortality for certain groups has appeared to level off after a steady increase over the last half century. This trend is suspected to be due to better detection and removal of thin, biological early melanomas. However, to date, no prospective evidence exists to clearly demonstrate the efficacy of prevention and early detection in decreasing melanoma mortlity. Nonetheless, many studies suggest that both self-assessment of risk factors or clinician examination can identify a proportion of patients at highest risk for melanoma who may benefit from behavior modification (primary prevention) and routine screening (secondary prevention). Compromising these goals is the fact that neither the clinical or histologic diagnosis of melanoma is 100% accurate. Clinical diagnosis of melanoma, based on evaluation of a skin lesion's color and shape, correlates best with the experience of the clinician. Ancillary technologies have been developed to improve clinical accuracy of suspicious skin lesions but a subset of melanomas exist that do not fall in the spectrum of the 'ABCDE' guidelines commonly used for melanoma identification. Similarly, at the histologic level (the 'gold standard' of diagnosis), overlap exists between benign and malignant melanocytic proliferations leading to both over and underdiagnosis of melanoma. A better understanding of melanoma's pathogenesis has identified disease-related biomarkers that may more reliably differentiate a melanocytic nevus from melanoma. In this paper, we review current and novel, potentially more accurate, biomarkers and supplementary technologies that can be used for the prevention, screening and diagnosis of melanoma.