Protein expression of melanocyte growth factors (bFGF, SCF) and their receptors (FGFR-1, c-kit) in nevi and melanoma

Fibroblast Growth Factor Receptor Inhibitors Decrease Proliferation of Melanoma Cell Lines and Their Activity Is Modulated by Vitamin D

Regardless of the unprecedented progress in malignant melanoma treatment strategies and clinical outcomes of patients during the last twelve years, this skin cancer remains the most lethal one. We have previously documented that vitamin D and its low-calcaemic analogues enhance the anticancer activity of drugs including a classic chemotherapeutic-dacarbazine-and an antiangiogenic VEGFRs inhibitor-cediranib. In this study, we explored the response of A375 and RPMI7951 melanoma lines to CPL304110 (CPL110), a novel selective inhibitor of fibroblast growth factor receptors (FGFRs), and compared its efficacy with that of AZD4547, the first-generation FGFRs selective inhibitor. We also tested whether 1,25(OH)2D3, the active form of vitamin D, modulates the response of the cells to these drugs. CPL304110 efficiently decreased the viability of melanoma cells in both A375 and RPMI7951 cell lines, with the IC50 value below 1 µM. However, the metastatic RPMI7951 melanoma cells were less sensitive to the tested drug than A375 cells, isolated from primary tumour site. Both tested FGFR inhibitors triggered G0/G1 cell cycle arrest in A375 melanoma cells and increased apoptotic/necrotic SubG1 fraction in RPMI7951 melanoma cells. 1,25(OH)2D3 modulated the efficacy of CPL304110, by decreasing the IC50 value by more than 4-fold in A375 cell line, but not in RPMI7951 cells. Further analysis revealed that both inhibitors impact vitamin D signalling to some extent, and this effect is cell line-specific. On the other hand, 1,25(OH)2D3, have an impact on the expression of FGFR receptors and phosphorylation (FGFR-Tyr653/654). Interestingly, 1,25(OH)2D3 and CPL304110 co-treatment resulted in activation of the ERK1/2 pathway in A375 cells. Our results strongly suggested possible crosstalk between vitamin D-activated pathways and activity of FGFR inhibitors, which should be considered in further clinical studies.

The markers auxiliary in differential diagnosis of early melanomas and benign nevi sharing some similar features potentially leading to misdiagnosis - a review of immunohistochemical studies

Although most melanocytic skin lesions are correctly diagnosed, numerous studies have shown interobserver disagreement. This review analyzes 20 molecules as immunohistochemical markers for distinguishing dysplastic and/or Spitz nevi from early melanomas (in situ, Clark level I or II and/or Breslow thickness at most 1 mm). The detected presence and/or level of tested molecules was significantly different in early melanomas than in dysplastic and Spitz nevi for six and seven potential markers, respectively. The most promising results were obtained for 5-hydroxymethylcytosine, cyclooxygenase-2 and PReferentially expressed Antigen in MElanoma whose levels were different in dysplastic and Spitz nevi compared to early melanomas.

Autocrine/Paracrine Loop Between SCF+/c-Kit+ Mast Cells Promotes Cutaneous Melanoma Progression

c-Kit, or mast/stem cell growth factor receptor Kit, is a tyrosine kinase receptor structurally analogous to the colony-stimulating factor-1 (CSF-1) and platelet-derived growth factor (PDGF) CSF-1/PDGF receptor Tyr-subfamily. It binds the cytokine KITLG/SCF to regulate cell survival and proliferation, hematopoiesis, stem cell maintenance, gametogenesis, mast cell development, migration and function, and it plays an essential role in melanogenesis. SCF and c-Kit are biologically active as membrane-bound and soluble forms. They can be expressed by tumor cells and cells of the microenvironment playing a crucial role in tumor development, progression, and relapses. To date, few investigations have concerned the role of SCF+/c-Kit+ mast cells in normal, premalignant, and malignant skin lesions that resemble steps of malignant melanoma progression. In this study, by immunolabeling reactions, we demonstrated that in melanoma lesions, SCF and c-Kit were expressed in mast cells and released by themselves, suggesting an autocrine/paracrine loop might be implicated in regulatory mechanisms of neoangiogenesis and tumor progression in human melanoma.

Antibody-Based Targeted Interventions for the Diagnosis and Treatment of Skin Cancers

BACKGROUND

Cutaneous malignancies most commonly arise from skin epidermal cells. These cancers may rapidly progress from benign to a metastatic phase. Surgical resection represents the gold standard therapeutic treatment of non-metastatic skin cancer while chemo- and/or radiotherapy are often used against metastatic tumors. However, these therapeutic treatments are limited by the development of resistance and toxic side effects, resulting from the passive accumulation of cytotoxic drugs within healthy cells.

OBJECTIVE

This review aims to elucidate how the use of monoclonal Antibodies (mAbs) targeting specific Tumor Associated Antigens (TAAs) is paving the way to improved treatment. These mAbs are used as therapeutic or diagnostic carriers that can specifically deliver cytotoxic molecules, fluorophores or radiolabels to cancer cells that overexpress specific target antigens.

RESULTS

mAbs raised against TAAs are widely in use for e.g. differential diagnosis, prognosis and therapy of skin cancers. Antibody-Drug Conjugates (ADCs) particularly show remarkable potential. The safest ADCs reported to date use non-toxic photo-activatable Photosensitizers (PSs), allowing targeted Photodynamic Therapy (PDT) resulting in targeted delivery of PS into cancer cells and selective killing after light activation without harming the normal cell population. The use of near-infrared-emitting PSs enables both diagnostic and therapeutic applications upon light activation at the specific wavelengths.

CONCLUSION

Antibody-based approaches are presenting an array of opportunities to complement and improve current methods employed for skin cancer diagnosis and treatment.

Cutaneous Cancer Biology

There has been a drastic increase in the incidence of nonmelanoma (NMSC), including squamous, basal cell, and melanoma skin cancers worldwide. Most cases of skin cancer can be treated effectively with surgery; fewer than 10% of cases are advanced and may require additional therapies. A better understanding of the biology of skin cancer will help contribute to better prognostic information and identification of possible new therapeutic targets. Herein, the authors review the biology and pathogenesis of both NMSC and melanoma, focusing on critical cell signaling pathways mediating the disease and current therapeutic strategies targeted to underlying genetic pathways.

Insights into Differentiation of Melanocytes from Human Stem Cells and Their Relevance for Melanoma Treatment

Simple Summary

The reactivation of embryonic developmental programs is crucial for melanoma cells to grow and to metastasize. In order to understand this process better, we first summarize the melanocytic differentiation process both in vivo and in vitro. Secondly, we compare and highlight important similarities between neural crest cell fate during differentiation and tumor cell characteristics during melanoma mestastasis. Finally, we suggest possible therapeutic targets, which could be used to inhibit phenotype switching by developmental cues and hence also suppress the metastatic melanoma spread.

Abstract

Malignant melanoma represents a highly aggressive form of skin cancer. The metastatic process itself is mostly governed by the so-called epithelial mesenchymal transition (EMT), which confers cancer cells migrative, invasive and resistance abilities. Since EMT represents a conserved developmental process, it is worthwhile further examining the nature of early developmental steps fundamental for melanocyte differentiation. This can be done either in vivo by analyzing the physiologic embryo development in different species or by in vitro studies of melanocytic differentiation originating from embryonic human stem cells. Most importantly, external cues drive progenitor cell differentiation, which can be divided in stages favoring neural crest specification or melanocytic differentiation and proliferation. In this review, we describe ectopic factors which drive human pluripotent stem cell differentiation to melanocytes in 2D, as well as in organoid models. Furthermore, we compare developmental mechanisms with processes described to occur during melanoma development. Finally, we suggest differentiation factors as potential co-treatment options for metastatic melanoma patients.

Angiomatoid Spitz nevus with surrounding pagetoid melanocytic proliferation on the sole of the foot: An unusual case report with immunohistochemical studies for angiogenic factors

Angiomatoid Spitz nevus (ASN) is a rare histological variant of Spitz nevus (SN) that is characterized by prominent blood vessel proliferation around the intradermal melanocytes of SN. In contrast, SN may have pagetoid components, which are characterized by epidermal proliferation of single melanocytes. However, cases of ASN with predominant pagetoid melanocytic proliferation in the epidermis have not been reported. Here, we report a case of ASN with surrounding pagetoid melanocytic proliferation without formation of tumor nests in the epidermis in the plantar region. A 12-year-old girl presented with a bright red nodule surrounded by a brown macule on the sole of her right foot. Histologically, the nodule showed tumor nests in the dermis, composed of spindle or epithelioid melanocytes containing abundant cytoplasm and large nuclei. Around the nests, numerous blood vessels were seen. In the overlying epidermis of the nodule, numerous eosinophilic Kamino bodies were found along the dermal-epidermal interface. In the macule, proliferation of oval melanocytes was present as single-cell units in the epidermis. Theses melanocytes had abundant cytoplasm with large nuclei, which were larger than those of the surrounding keratinocytes. From these findings, a diagnosis of ASN with surrounding pagetoid melanocytic proliferation was made. Vascular endothelial growth factor and fibroblast growth factor 2 were strongly expressed in the melanocytes as well as in the endothelial cells in our case. Therefore, angiogenic factors produced by the melanocytes of SN might have played important roles in the surrounding angiogenesis of this case.

Fibroblast Growth Factor Receptor Signaling in Skin Cancers

Fibroblast growth factor (FGF)/Fibroblast growth factor receptor (FGFR) signaling regulates various cellular processes during the embryonic development and in the adult organism. In the skin, fibroblasts and keratinocytes control proliferation and survival of melanocytes in a paracrine manner via several signaling molecules, including FGFs. FGF/FGFR signaling contributes to the skin surface expansion in childhood or during wound healing, and skin protection from UV light damage. Aberrant FGF/FGFR signaling has been implicated in many disorders, including cancer. In melanoma cells, the FGFR expression is low, probably because of the strong endogenous mutation-driven constitutive activation of the downstream mitogen-activated protein kinase-extracellular signal-regulated kinase (MAPK-ERK) signaling pathway. FGFR1 is exceptional as it is expressed in the majority of melanomas at a high level. Melanoma cells that acquired the capacity to synthesize FGFs can influence the neighboring cells in the tumor niche, such as endothelial cells, fibroblasts, or other melanoma cells. In this way, FGF/FGFR signaling contributes to intratumoral angiogenesis, melanoma cell survival, and development of resistance to therapeutics. Therefore, inhibitors of aberrant FGF/FGFR signaling are considered as drugs in combination treatment. The ongoing LOGIC-2 phase II clinical trial aims to find out whether targeting the FGF/FGFR signaling pathway with BGJ398 may be a good therapeutic strategy in melanoma patients who develop resistance to v-Raf murine sarcoma viral oncogene homolog B (BRAF)/MEK inhibitors.

CD117 (c-Kit) Is Expressed During CD8+ T Cell Priming and Stratifies Sensitivity to Apoptosis According to Strength of TCR Engagement

CD117 (cKit) is the receptor for stem cell factor (SCF) and plays an important role in early haemopoiesis. We show that CD117 is also expressed following priming of mature human CD8⁺ T cells in vitro and is detectable following primary infection in vivo. CD117 expression is mediated through an intrinsic pathway and is suppressed by IL-12. Importantly, the extent of CD117 expression is inversely related to the strength of the activating stimulus and subsequent engagement with cell-bound SCF markedly increases susceptibility to apoptosis. CD117 is therefore likely to shape the pattern of CD8⁺ T cell immunodominance during a primary immune response by rendering cells with low avidity for antigen more prone to apoptosis. Furthermore, CD117⁺ T cells are highly sensitive to apoptosis mediated by galectin-1, a molecule commonly expressed within the tumor microenvironment, and CD117 expression may therefore represent a novel and potentially targetable mechanism of tumor immune evasion.

BRAF inhibition causes resilience of melanoma cell lines by inducing the secretion of FGF1

Approximately half of all melanoma patients harbour activating mutations in the serine/threonine kinase BRAF. This is the basis for one of the main treatment strategies for this tumor type, the targeted therapy with BRAF and MEK inhibitors. While the initial responsiveness to these drugs is high, resistance develops after several months, frequently at sites of the previously responding tumor. This indicates that tumor response is incomplete and that a certain tumor fraction survives even in drug-sensitive patients, e.g., in a therapy-induced senescence-like state. Here, we show in several melanoma cell lines that BRAF inhibition induces a secretome with stimulating effect on fibroblasts and naive melanoma cells. Several senescence-associated factors were found to be transcribed and secreted in response to BRAF or MEK inhibition, among them members of the fibroblast growth factor family. We identified the growth factor FGF1 as mediator of resilience towards BRAF inhibition, which limits the pro-apoptotic effects of the drug and activates fibroblasts to secrete HGF. FGF1 regulation was mediated by the PI3K pathway and by FRA1, a direct target gene of the MAPK pathway. When FGFR inhibitors were applied in parallel to BRAF inhibitors, resilience was broken, thus providing a rationale for combined therapeutical application.

Precise role of dermal fibroblasts on melanocyte pigmentation

Dermal fibroblasts are traditionally recognized as synthesizing, remodeling and depositing collagen and extracellular matrix, the structural framework for tissues, helping to bring thickness and firmness to the skin. However, the role of fibroblasts on skin pigmentation arouses concern recently. More is known about the interactions between epidermal melanocytes and keratinocytes. This review highlights the importance of fibroblast-derived melanogenic paracrine mediators in the regulation of melanocyte activities. Fibroblasts act on melanocytes directly and indirectly through neighboring cells by secreting a large number of cytokines (SCF), proteins (DKK1, sFRP, Sema7a, CCN, FAP-α) and growth factors (KGF, HGF, bFGF, NT-3, NRG-1, TGF-β) which bind to receptors and modulate intracellular signaling cascades (MAPK/ERK, cAMP/PKA, Wnt/β-catenin, PI3K/Akt) related to melanocyte functions. These factors influence the growth, the pigmentation of melanocytes via the expression of melanin-producing enzymes and melanosome transfer, as well as their dendricity, mobility and adhesive properties. Thus, fibroblasts are implicated in both skin physiological and pathological pigmentation. In order to investigate their contribution, various in vitro models have been developed, based on cellular senescence. UV exposure, a major factor implicated in pigmentary disorders, may affect the secretory crosstalk between dermal and epithelial cells. Therefore, identification of the interactions between fibroblasts and melanocytes could provide novel insights not only for the development of melanogenic agents in the clinical and cosmetic fields, but also for a better understanding of the melanocyte biology and melanogenesis regulation.

Nanofibrous polycaprolactone scaffolds with adhered platelets stimulate proliferation of skin cells

OBJECTIVES

Faulty wound healing is a global healthcare problem. Chronic wounds are generally characterized by a reduction in availability of growth factors. New strategies are being developed to deliver growth factors more effectively.

METHODS

In this study, we introduced electrospun scaffolds composed of polycaprolactone (PCL) nanofibers functionalized with adhered platelets, as a source of numerous growth factors. Three concentrations of platelets were immobilized to nanofibrous scaffolds by simple adhesion, and their influence on adhesion, proliferation and metabolic activity of seeded cells (murine fibroblasts, keratinocytes and melanocytes) was investigated.

RESULTS

The data obtained indicated that presence of platelets significantly promoted cell spreading, proliferation and metabolic activity in all the skin-associated cell types. There were no significant differences among tested concentrations of platelets, thus even the lowest concentration sufficiently promoted proliferation of the seeded cells.

CONCLUSIONS

Such complex stimulation is needed for improved healing of chronic wounds. However, the nanofibrous system can be used not only as a skin cover, but also in broader applications in regenerative medicine.

Cutaneous malignant melanoma: update on diagnostic and prognostic biomarkers

The incidence of cutaneous malignant melanoma has rapidly increased in recent years in all parts of the world, and melanoma is a leading cause of cancer death. As even relatively small melanomas may have metastatic potential, accurate assessment of progression is critical. Although diagnosis of cutaneous malignant melanoma is usually based on histopathologic criteria, these criteria may at times be inadequate in differentiating melanoma from certain types of benign nevi. As for prognosis, tumor (Breslow) thickness, mitotic rate, and ulceration have been considered the most important prognostic indicators among histopathologic criteria. However, there are cases of thin primary melanomas that have ultimately developed metastases despite complete excision. Given this, an accurate assessment of melanoma progression is critical, and development of molecular biomarkers that identify high-risk melanoma in its early phase is urgently needed. Large-scale genomic profiling has identified considerable heterogeneity in melanoma and suggests subgrouping of tumors by patterns of gene expression and mutation will ultimately be essential to accurate staging. This subgrouping in turn may allow for more targeted therapy. In this review, we aim to provide an update on the most promising new biomarkers that may help in the identification and prognostication of melanoma.

Type II, but not type I, cGMP-dependent protein kinase reverses bFGF-induced proliferation and migration of U251 human glioma cells

Previous data have shown that the type II cGMP‑dependent protein kinase (PKG II) inhibits the EGF‑induced MAPK signaling pathway. In order to thoroughly investigate PKG, it is necessary to elucidate the function of another type of PKG, PKG I. The aim of this study was to investigate the possible inhibitory effect of PKG II and PKG I activity on the basic fibroblast growth factor (bFGF)‑induced proliferation and migration of U251 human glioma cells and the possible underlying mechanisms. U251 cells were infected with adenoviral constructs encoding cDNA of PKG I (Ad‑PKG I) or PKG II (Ad‑PKG II) to increase the expression levels of PKG I or PKG II and then treated with 8‑Br‑cGMP and 8‑pCPT‑cGMP, respectively, to activate the enzyme. An MTT assay was used to detect the proliferation of the U251 cells. The migration of the U251 cells was analyzed using a Transwell migration assay. Western blot analysis was used to detect the phosphorylation/activation of the fibroblast growth factor receptor (FGFR), MEK and ERK and the nuclear distribution of p-ERK. The results showed that bFGF treatment increased the proliferation and migration of U251 cells, accompanied by increased phosphorylation of FGFR, MEK and ERK. Furthermore, the nuclear distribution of p-ERK increased following bFGF treatment. Increasing the activity of PKG II through infection with Ad-PKG II and stimulation with 8-pCPT-cGMP significantly attenuated the aforementioned effects of the bFGF treatment, while increased PKG I activity did not inhibit the effects of bFGF treatment. These data suggest that increased PKG II activity attenuates bFGF‑induced proliferation and migration by inhibiting the MAPK/ERK signaling pathway, whereas PKG I does not.

Lack of correlation between immunohistochemical expression of CKIT and KIT mutations in atypical acral nevi

BACKGROUND

Given the correlation between KIT mutations and immunohistochemical expression of CKIT in acral melanoma, our aim was to confirm the utility of CKIT detection as a screening tool for KIT genotyping in atypical acral nevi and to ascertain the frequency of KIT mutations in the same.

DESIGN

Immunohistochemical staining for CKIT was performed and staining criteria were the following: negative = <10%, 1 = 11%-49%, and 2 = >50% of cells. Intensity grading was as follows: negative = 0, weak = 1, moderate = 2, and strong = 3. Genomic amplification was performed on KIT exons commonly mutated in acral melanomas (11, 13, and 17) from atypical acral nevi (23) ranging in severity from mild (9), moderate (10), and severe (4). The control group included acral nevi without atypia (19). For purposes of statistical analyses, cases with 11% or more staining of cells were compared with negative cases and cases with a staining intensity of 1 or higher were compared with the negatives.

RESULTS

Immunohistochemical analyses revealed the following: positive staining with an intensity 1 or more in 18 of 22 (82%) of cases with atypia (5 mild; 9 moderate and 4 severe) and in 13 of 17 (76%) nevi without atypia with no statistically significant differences between both groups. Genomic analyses of exon regions revealed no abnormalities in "hotspots" frequently associated with point mutations in acral melanomas.

CONCLUSIONS

Our findings indicate a lack of correlation between immunohistochemical expression of CKIT and KIT mutations in atypical acral nevi. Atypical acral nevi do not exhibit genetic alterations in KIT associated with acral melanomas.

Toxicarioside A inhibits SGC-7901 proliferation, migration and invasion via NF-κB/bFGF signaling

AIM: To investigate the inhibitory role of toxicarioside A on the gastric cancer cell line human gastric cancer cell line (SGC-7901) and determine the underlying molecular mechanism.

METHODS: After SGC-7901 cells were treated with toxicarioside A at various concentrations (0.5, 1.5, 4.5, 9.0 μg/mL) for 24 h or 48 h, cell viability was determined by 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assay, and the motility and invasion of tumor cells were assessed by the Transwell chamber assay. Immunofluorescence staining, reverse transcription polymerase chain reaction and Western blotting were performed to detect the expression of basic fibroblast growth factor (bFGF) and fibroblast growth factor receptor-1 (FGFR1), and nuclear factor-kappa B (NF-κB) activation was examined by electrophoretic mobility shift assay.

RESULTS: The results showed that toxicarioside A was capable of reducing cell viability, inhibiting cell growth, and suppressing cell migration and invasion activities in a time- and dose-dependent manner in SGC-7901 cells. Further analysis revealed that not only the expression of bFGF and its high-affinity receptor FGFR1 but also the NF-κB-DNA binding activity were effectively blocked by toxicarioside A in a dose-dependent manner compared with the control group (P < 0.05 or P < 0.01). Interestingly, application of the NF-κB specific inhibitor, pyrrolidinedithiocarbamate (PDTC), to SGC-7901 cells significantly potentized the toxicarioside A-induced down-regulation of bFGF compared with the control group (P < 0.05).

CONCLUSION: These findings suggest that toxicarioside A has an anti-gastric cancer activity and this effect may be achieved partly through down-regulation of NF-κB and bFGF/FGFR1 signaling.

Association between melanocytic neoplasms and seborrheic keratosis: more than a coincidental collision?

Clinical observations and an expanding knowledge of cell-to-cell communication have led us to speculate that the finding of a melanocytic nevus in conjunction with a seborrheic keratosis is more than a coincidental collision of two lesions. Here we present five cases demonstrating dermoscopic features of both melanocytic lesions and seborrheic keratoses with corresponding histology. Four cases demonstrate dermoscopic features of a melanocytic nevus and seborrheic keratosis, and the final case a melanoma arising in association with a seborrheic keratosis.

c-kit gene mutation and CD117 expression in human anorectal melanomas

c-kit and BRAF mutations play an important role during the pathogenesis of melanoma. The subtypes of melanomas arising from different parts of the body have variable c-kit or BRAF mutation frequencies. Few studies in the literature have examined c-kit and BRAF mutation status in melanomas that occur in the anus and rectum. In this study, we analyzed 40 cases of anorectal melanoma for c-kit and BRAF mutations by DNA sequencing using paraffin-embedded tissues. c-kit Mutations were detected in exons 9, 11, 13, and 17. CD117 expression in tumor cells was analyzed by immunohistochemistry. Our study showed that a c-kit mutation was found in 7 of the 40 cases of anorectal melanoma. CD117 expression was detected in 16 of the 40 cases, and 3 of these 16 cases also had c-kit mutations. Mutations in BRAF were also identified in 2 patients. These results indicate that a subset of anorectal melanomas have activating c-kit mutations, which suggests that kinase inhibitors such as imatinib may be used to treat this subset of melanoma patients. In addition, our results show that c-kit mutations do not correlate with CD117 expression.

Mutagen-specific mutation signature determines global microRNA binding

Micro-RNAs (miRNAs) are small non-coding RNAs that regulate gene products at the post-transcriptional level. It is thought that loss of cell regulation by miRNAs supports cancer development. Based on whole genome sequencing of a melanoma tumor, we predict, using three different computational algorithms, that the melanoma somatic mutations globally reduce binding of miRNAs to the mutated 3'UTRs. This phenomenon reflects the nature of the characteristic UV-induced mutation, C-to-T. Furthermore, we show that seed regions are enriched with Guanine, thus rendering miRNAs prone to reduced binding to UV-mutated 3'UTRs. Accordingly, mutation patterns in non UV-induced malignancies e.g. lung cancer and leukemia do not yield similar predictions. It is suggested that UV-induced disruption of miRNA-mediated gene regulation plays a carcinogenic role. Remarkably, dark-skinned populations have significantly higher GC content in 3'UTR SNPs than light-skinned populations, which implies on evolutionary pressure to preserve regulation by trans-acting oligonucleotides under conditions with excess UV radiation.

Receptor tyrosine kinases and their activation in melanoma

Receptor tyrosine kinases (RTKs) and their downstream signalling pathways have long been hypothesized to play key roles in melanoma development. A decade ago, evidence was derived largely from animal models, RTK expression studies and detection of activated RAS isoforms in a small fraction of melanomas. Predictions that overexpression of specific RTKs implied increased kinase activity and that some RTKs would show activating mutations in melanoma were largely untested. However, technological advances including rapid gene sequencing, siRNA methods and phospho-RTK arrays now give a more complete picture. Mutated forms of RTK genes including KIT, ERBB4, the EPH and FGFR families and others are known in melanoma. Additional over- or underexpressed RTKs and also protein tyrosine phosphatases (PTPs) have been reported, and activities measured. Complex interactions between RTKs and PTPs are implicated in the abnormal signalling driving aberrant growth and survival in malignant melanocytes, and indeed in normal melanocytic signalling including the response to ultraviolet radiation. Kinases are considered druggable targets, so characterization of global RTK activity in melanoma should assist the rational development of tyrosine kinase inhibitors for clinical use.

MicroRNA miR-196a is a central regulator of HOX-B7 and BMP4 expression in malignant melanoma

Since bone morphogenetic proteins (BMPs) play an important role in melanoma progression, we aimed to determine the molecular mechanisms leading to overexpression of BMP4 in melanoma cells compared to normal melanocytes. With our experimental approach we revealed that loss of expression of a microRNA represents the starting point for a signaling cascade finally resulting in overexpression of BMP4 in melanoma cells. In detail, strongly reduced expression of the microRNA miR-196a in melanoma cells compared to healthy melanocytes leads to enhanced HOX-B7 mRNA and protein levels, which subsequently raise Ets-1 activity by inducing basic fibroblast growth factor (bFGF). Ets-1 finally accounts for induction of BMP4 expression. We were furthermore able to demonstrate that bFGF-mediated induction of migration is achieved via activation of BMP4, thus determining BMP4 as major modulator of migration in melanoma. In summary, our study provides insights into the early steps of melanoma progression and might thereby harbor therapeutic relevance.

Biomarkers: the useful and the not so useful--an assessment of molecular prognostic markers for cutaneous melanoma

Among individuals with localized (Stage I-II) melanoma, stratifying patients by a number of phenotypic variables (e.g., depth of invasion, ulceration) yields a wide range of 10-year melanoma-specific survival rates. With the possible exception of Ki-67, no molecular assessment is routinely used. However, there have been a tremendous number of studies assessing protein expression by immunohistochemistry toward the goal of better prediction of recurrence. In a previous systematic review, which required publication of multivariable prognostic models as a strict inclusion criterion, we identified 37 manuscripts that collectively reported on 62 proteins. Data for 324 proteins extracted from 418 manuscripts did not meet our inclusion criteria for that study, but are revisited here, emphasizing trends of protein expression across either melanocytic lesion progression or gradations of tumor thickness. These identified 101 additional proteins that stratify melanoma, organized according to the Hanahan and Weinberg functional capabilities of cancer.

An extended antibody microarray for surface profiling metastatic melanoma

An antibody microarray was developed for profiling the surface proteome of melanoma cells, which may facilitate melanoma sub-classification and provide important prognostic information useful in predicting the clinical behavior of the melanoma (e.g., likely sites of metastatic spread), patient outcome and treatment response. Forty-eight antibodies were selected based on their correlation with melanoma development, progression and/or prognosis and printed on nitrocellulose slides. The immobilised antibodies capture live cells expressing corresponding antigens to produce a cell binding dot pattern representing the surface antigen profile (immunophenotype) of the melanoma. Surface antigen signatures were determined for a normal melanocyte and 6 melanoma cell lines and cell suspensions prepared from 10 surgically excised melanoma lymph node metastases. A procedure for obtaining separate surface antigen profiles for melanoma cells and leukocytes from clinical lymph node samples was also developed using anti-CD45 magnetic beads. The capture of live, bead-bound leukocytes on these antibody microarrays provides a significant enhancement of this microarray technology. The antibody microarray will be used to profile panels of surgically excised melanoma lymph node metastases (melanoma and leukocyte fractions) to determine whether the immunophenotypes correlate with clinicopathological characteristics, disease progression and clinical outcome.

Stepping up melanocytes to the challenge of UV exposure

Exposure to solar ultraviolet radiation (UV) is the main etiological factor for skin cancer, including melanoma. Cutaneous pigmentation, particularly eumelanin, afforded by melanocytes is the main photoprotective mechanism, as it prevents UV-induced DNA damage in the epidermis. Therefore, maintaining genomic stability of melanocytes is crucial for prevention of melanoma, as well as keratinocyte-derived basal and squamous cell carcinoma. A critical independent factor for preventing melanoma is DNA repair capacity. The response of melanocytes to UV is mediated mainly by a network of paracrine factors that not only activate melanogenesis, but also DNA repair, anti-oxidant, and survival pathways that are pivotal for maintenance of genomic stability and prevention of malignant transformation or apoptosis. However, little is known about the stress response of melanocytes to UV and the regulation of DNA repair pathways in melanocytes. Unraveling these mechanisms might lead to strategies to prevent melanoma, as well as non-melanoma skin cancer.

Beyond BRAF in melanoma

Recent progress in the analysis of genetic alterations in melanoma has identified recurrent mutations that result in the activation of critical signaling pathways promoting growth and survival of tumors cells. Alterations in the RAS-RAF-MAP kinase and PI3-kinase signaling pathways are commonly altered in melanoma. Mutations in BRAF, NRAS, KIT, and GNAQ occur in a mutually exclusive pattern and lead to MAP-kinase activation. Loss of PTEN function, primarily by deletion, is the most common known genetic alteration in the PI3-kinase cascade, and is commonly associated with BRAF mutations (Curtin et al., N Engl J Med 353:2135-2147, 2005; Tsao et al., Cancer Res 60:1800-1804, 2000, J Investig Dermatol 122:337-341, 2004). The growth advantage conveyed by the constitutive activation of these pathways leads to positive selection of cells that have acquired the mutations and in many instances leads to critical dependency of the cancer cells on their activation. This creates opportunities for therapeutic interventions targeted at signaling components within these pathways that are amenable for pharmacological inhibition. This concept follows the paradigm established by the landmark discovery that inhibition of the fusion kinase BCR-ABL can be used to treat chronic myelogenous leukemia (Druker et al., N Engl J Med 344:1031-037, 2001). The review will focus primarily on kinases involved in signaling that are currently being evaluated for therapeutic intervention in melanoma.

Tumor angiogenesis in melanoma

A large number of clinical studies are being conducted to assess the effects of angiogenesis inhibitors in the treatment of patients who have metastatic melanoma. It has become increasingly clear that a therapeutic approach that combines angiogenesis inhibitors with cytotoxic agents or other treatment modalities is more likely to result in a clinical benefit for patients rather than antiangiogenesis treatments alone. However, a targeted treatment approach with antiangiogenic agents needs to be based on an in-depth understanding of the complex mechanisms involved in melanoma tumor angiogenesis.

Amelanotic malignant melanoma of the esophagus: Report of two cases with immunohistochemical and molecular genetic study of KIT and PDGFRA

The author reports herein two cases of amelanotic malignant melanoma of the esophagus. Case 1 is an 87-year-old woman who was admitted to our hospital because of nausea and vomiting. Endoscopic examination revealed an ulcerated tumor of the distal esophagus, and a biopsy was taken. The biopsy showed malignant polygonal and spindle cells. No melanin pigment was recognized. Immunohistochemically, the tumor cells were positive for melanosome (HMB45), S100 protein, KIT and Platelet derived growth factor receptor-α (PDGFRA). The patient was treated by chemotherapy and radiation, but died of systemic metastasis 12 mo after the presentation. Case 2 is a 56-year-old man presenting with dysphagia. Endoscopic examination revealed a polypoid tumor in the middle esophagus, and a biopsy was obtained. The biopsy showed malignant spindle cells without melanin pigment. Immunohistochemically, the tumor cells were positively labeled for melanosome, S100 protein, KIT and PDGFRA. The patient refused operation, and was treated by palliative chemotherapy and radiation. He died of metastasis 7 mo after the admission. In both cases, molecular genetic analyses of KIT gene (exons 9, 11, 13 and 17) and PDGFRA gene (exons 12 and 18) were performed by the PCR direct sequencing method, which showed no mutations of KIT and PDGFRA genes. This is the first report of esophageal malignant melanoma with an examination of the expression of KIT and PDGFRA and the mutational status of KIT and PDGFRA genes.

Tissue biomarkers for prognosis in cutaneous melanoma: a systematic review and meta-analysis

In the clinical management of early-stage cutaneous melanoma, it is critical to determine which patients are cured by surgery alone and which should be treated with adjuvant therapy. To assist in this decision, many groups have made an effort to use molecular information. However, although there are hundreds of studies that have sought to assess the potential prognostic value of molecular markers in predicting the course of cutaneous melanoma, at this time, no molecular method to improve risk stratification is part of recommended clinical practice. To help understand this disconnect, we conducted a systematic review and meta-analysis of the published literature that reported immunohistochemistry-based protein biomarkers of melanoma outcome. Three parallel search strategies were applied to the PubMed database through January 15, 2008, to identify cohort studies that reported associations between immunohistochemical expression and survival outcomes in melanoma that conformed to the REMARK criteria. Of the 102 cohort studies, we identified only 37 manuscripts, collectively describing 87 assays on 62 distinct proteins, which met all inclusion criteria. Promising markers that emerged included melanoma cell adhesion molecule (MCAM)/MUC18 (all-cause mortality [ACM] hazard ratio [HR] = 16.34; 95% confidence interval [CI] = 3.80 to 70.28), matrix metalloproteinase-2 (melanoma-specific mortality [MSM] HR = 2.6; 95% CI = 1.32 to 5.07), Ki-67 (combined ACM HR = 2.66; 95% CI = 1.41 to 5.01), proliferating cell nuclear antigen (ACM HR = 2.27; 95% CI = 1.56 to 3.31), and p16/INK4A (ACM HR = 0.29; 95% CI = 0.10 to 0.83, MSM HR = 0.4; 95% CI = 0.24 to 0.67). We further noted incomplete adherence to the REMARK guidelines: 14 of 27 cohort studies that failed to adequately report their methods and nine studies that failed to either perform multivariable analyses or report their risk estimates were published since 2005.

Leukemic cells create bone marrow niches that disrupt the behavior of normal hematopoietic progenitor cells

The host tissue microenvironment influences malignant cell proliferation and metastasis, but little is known about how tumor-induced changes in the microenvironment affect benign cellular ecosystems. Applying dynamic in vivo imaging to a mouse model, we show that leukemic cell growth disrupts normal hematopoietic progenitor cell (HPC) bone marrow niches and creates abnormal microenvironments that sequester transplanted human CD34+ (HPC-enriched) cells. CD34+ cells in leukemic mice declined in number over time and failed to mobilize into the peripheral circulation in response to cytokine stimulation. Neutralization of stem cell factor (SCF) secreted by leukemic cells inhibited CD34+ cell migration into malignant niches, normalized CD34+ cell numbers, and restored CD34+ cell mobilization in leukemic mice. These data suggest that the tumor microenvironment causes HPC dysfunction by usurping normal HPC niches and that therapeutic inhibition of HPC interaction with tumor niches may help maintain normal progenitor cell function in the setting of malignancy.

Analysis of c-KIT expression and KIT gene mutation in human mucosal melanomas

Recent data suggested an increased frequency of KIT aberrations in mucosal melanomas, whereas c-KIT in most types of cutaneous melanomas does not appear to be of pathogenetic importance. However, studies investigating the status of the KIT gene in larger, well-characterised groups of patients with mucosal melanomas are lacking. We analysed 44 archival specimens of 39 well-characterised patients with mucosal melanomas of different locations. c-KIT protein expression was determined by immunhistochemistry, KIT gene mutations were analysed by PCR amplification and DNA sequencing of exons 9, 11, 13, 17 and 18. c-KIT protein expression could be shown in 40 out of 44 (91%) tumours in at least 10% of tumour cells. DNA sequence analysis of the KIT was successfully performed in 37 patients. In 6 out of 37 patients (16%) KIT mutations were found, five in exon 11 and one in exon 18. The presence of mutations in exon 11 correlated with a significant stronger immunohistochemical expression of c-KIT protein (P=0.015). Among the six patients with mutations, in two patients the primary tumour was located in the head/neck region, in three patients in the genitourinary tract and in one patient in the anal/rectal area. In conclusion, KIT mutations can be found in a subset of patients with mucosal melanomas irrespective of the location of the primary tumour. Our data encourage therapeutic attempts with tyrosine kinase inhibitors blocking c-KIT in these patients.

Long-lasting molecular changes in human skin after repetitive in situ UV irradiation

It is known that UV modulates the expression of paracrine factors that regulate melanocyte function in the skin. We investigated the consequences of repetitive UV exposure of human skin in biopsies of 10 subjects with phototypes 2-3.5 taken 1-4 years later. The expression of melanogenic factors (TYR, MART1, MITF), growth factors/receptors (SCF/KIT, bFGF/FGFR1, ET1/EDNRB, HGF, GM-CSF), adhesion molecules (beta-catenin, E-cadherin, N-cadherin), cell cycle proteins (PCNA, cyclins D1, E2) as well as Bcl-2, DKK1, and DKK3, were analyzed by immunohistochemistry. Most of those markers showed no detectable changes at > or = 1 year after the repetitive UV irradiation. Although increased expression of EDNRB protein was detected in 3 of 10 UV-irradiated subjects, there was no detectable change in the expression of ET1 protein or in EDNRB mRNA levels. In summary, only the expression of TYR, MART1, and/or EDNRB, and only in some subjects, was elevated at > or = 1 year after UV irradiation. Thus the long-term effects of repetitive UV irradiation on human skin did not lead to significant changes in skin morphology and there is considerable subject-to-subject variation in responses. The possibility that changes in the expression and function of EDNRB triggers downstream activation of abnormal melanocyte proliferation and differentiation deserves further investigation.

The release of fibroblast growth factor-1 from melanoma cells requires copper ions and is mediated by phosphatidylinositol 3-kinase/Akt intracellular signaling pathway

Melanoma is a highly invasive tumor with elevated mortality rates. Progression and aggressiveness appear related to the achievement of an angiogenic phenotype. Melanoma cells express several angiogenic factors, including fibroblast growth factor (FGF)-1 and FGF-2. The autocrine production and release of FGFs and the subsequent activation of FGF receptors, have a central role in melanoma tumor progression. We demonstrated that FGF-1 is secreted from a human melanoma cell line, A375, under conditions of serum deprivation. The release of FGF-1 is inhibited by the copper chelator ammonium tetrathiomolybdate, suggesting a role of copper in the secretory pathway, and is triggered by activation of phosphatidylinositol 3-kinase (PI3K)/Akt intracellular signaling. Interestingly, overexpression or activation of Akt has been correlated with poor prognosis in melanoma patients. Our data indicate a novel role for Akt in supporting the progression of human melanomas and advocate the need for new treatments targeting PI3K/Akt signaling pathway, to control tumor development and progression.

The secreted metalloprotease ADAMTS20 is required for melanoblast survival

ADAMTS20 (Adisintegrin-like and metalloprotease domain with thrombospondin type-1 motifs) is a member of a family of secreted metalloproteases that can process a variety of extracellular matrix (ECM) components and secreted molecules. Adamts20 mutations in belted (bt) mice cause white spotting of the dorsal and ventral torso, indicative of defective neural crest (NC)-derived melanoblast development. The expression pattern of Adamts20 in dermal mesenchymal cells adjacent to migrating melanoblasts led us to initially propose that Adamts20 regulated melanoblast migration. However, using a Dct-LacZ transgene to track melanoblast development, we determined that melanoblasts were distributed normally in whole mount E12.5 bt/bt embryos, but were specifically reduced in the trunk of E13.5 bt/bt embryos due to a seven-fold higher rate of apoptosis. The melanoblast defect was exacerbated in newborn skin and embryos from bt/bt animals that were also haploinsufficient for Adamts9, a close homolog of Adamts20, indicating that these metalloproteases functionally overlap in melanoblast development. We identified two potential mechanisms by which Adamts20 may regulate melanoblast survival. First, skin explant cultures demonstrated that Adamts20 was required for melanoblasts to respond to soluble Kit ligand (sKitl). In support of this requirement, bt/bt;Kit(tm1Alf)/+ and bt/bt;Kitl(Sl)/+ mice exhibited synergistically increased spotting. Second, ADAMTS20 cleaved the aggregating proteoglycan versican in vitro and was necessary for versican processing in vivo, raising the possibility that versican can participate in melanoblast development. These findings reveal previously unrecognized roles for Adamts proteases in cell survival and in mediating Kit signaling during melanoblast colonization of the skin. Our results have implications not only for understanding mechanisms of NC-derived melanoblast development but also provide insights on novel biological functions of secreted metalloproteases.

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.

Reversion of immune tolerance in advanced malignancy: modulation of myeloid-derived suppressor cell development by blockade of stem-cell factor function

Tumor growth induced a significant increase of myeloid-derived suppressor cells (MDSCs) in the tumor-bearing host. In our previous study, we showed that MDSCs induced tumor-specific T-cell tolerance and the development of T regulatory cells (Tregs). Tumor-derived factors have been implicated in the accumulation of MDSCs. We hypothesize that reduction of MDSC accumulation in tumor-bearing hosts, through the blockade of tumor factors, can prevent T-cell anergy and Treg development and thereby improve immune therapy for the treatment of advanced tumors. Several tumor-derived factors were identified by gene array analysis. Among the candidate factors, stem- cell factor (SCF) is expressed by various human and murine carcinomas and was selected for further study. Mice bearing tumor cells with SCF siRNA knockdown exhibited significantly reduced MDSC expansion and restored proliferative responses of tumor-infiltrating T cells. More importantly, blockade of SCF receptor (ckit)-SCF interaction by anti-ckit prevented tumor-specific T-cell anergy, Treg development, and tumor angiogenesis. Furthermore, the prevention of MDSC accumulation in conjunction with immune activation therapy showed synergistic therapeutic effect when treating mice bearing large tumors. This information supports the notion that modulation of MDSC development may be required to achieve effective immune-enhancing therapy for the treatment of advanced tumors.

The role of p53 in pigmentation, tanning and melanoma

p53 has a central role in skin pigmentation and may impact on melanoma at all stages, however, as it's mutation frequency in melanoma is low, it's role has been somewhat under-appreciated. During normal skin function, p53 in the keratinocyte is a transducer of the skin tanning signal and an essential component of what is effectively a keratinocyte-melanocyte signaling cycle that regulates skin pigmentation. It is clear that this cycle functions optimally in skin of dark pigmentation. When melanin biosynthesis is genetically disrupted in skin of white complexion, we propose that this cycle operates as a promoter of melanocyte proliferation. The cell autonomous function of p53 in melanocytes is not well described, however, the balance of the evidence suggests that p53 is an effective tumor suppressor and the myriad of mechanisms by which the p53 pathway may be dysregulated in tumors attests to it importance as a tumor suppressor. In this review, we outline the known mechanisms that impair p53 itself and its immediate regulators or target genes during melanomagenesis. Due to the importance of this pathway, it is clear that p53 disruptions may relate directly to a patient's prognosis. This pathway will continue to be a focus of investigation, particularly with respect to targeted experimental chemotherapeutics.

[4-t-butylphenyl]-N-(4-imidazol-1-yl phenyl)sulfonamide (ISCK03) inhibits SCF/c-kit signaling in 501mel human melanoma cells and abolishes melanin production in mice and brownish guinea pigs

It is well known that c-kit is related to pigmentation as well as to the oncology target protein. The objective of this study was to discover a skin-whitening agent that regulates c-kit activity. We have developed a high-throughput screening system using recombinant human c-kit protein. Approximately 10,000 synthetic compounds were screened for their effect on c-kit activity. Phenyl-imidazole sulfonamide derivatives showed inhibitory activity on c-kit phosphorylation in vitro. The effects of one derivative, [4-t-butylphenyl]-N-(4-imidazol-1-yl phenyl)sulfonamide (ISCK03), on stem-cell factor (SCF)/c-kit cellular signaling in 501mel human melanoma cells were examined further. Pretreatment of 501mel cells with ISCK03 inhibited SCF-induced c-kit phosphorylation dose dependently. ISCK03 also inhibited p44/42 ERK mitogen-activated protein kinase (MAPK) phosphorylation, which is known to be involved in SCF/c-kit downstream signaling. However ISCK03 did not inhibit hepatocyte growth factor (HGF)-induced phosphorylation of p44/42 ERK proteins. To determine the in vivo potency of ISCK03, it was orally administered to depilated C57BL/6 mice. Interestingly, oral administration of ISCK03 induced the dose-dependent depigmentation of newly regrown hair, and this was reversed with cessation of ISCK03 treatment. Finally, to investigate whether the inhibitory effect of ISCK03 on SCF/c-kit signaling abolished UV-induced pigmentation, ISCK03 was applied to UV-induced pigmented spots on brownish guinea pig skin. The topical application of ISCK03 promoted the depigmentation of UV-induced hyperpigmented spots. Fontana-Masson staining analysis showed epidermal melanin was diminished in spots treated with ISCK03. These results indicate that phenyl-imidazole sulfonamide derivatives are potent c-kit inhibitors and might be used as skin-whitening agents.

Mechanism of UV-related carcinogenesis and its contribution to nevi/melanoma

Melanoma consists 4-5 % of all skin cancers, but it contributes to 71-80 % of skin cancers deaths. UV light affects cell and tissue homeostasis due to its damaging effects on DNA integrity and modification of expression of a plethora of genes. DNA repair systems protect cells from UV-induced lesions. Several animal models of melanoma have been developed (Xiphophorus, Opossum Monodelphis domestica, mouse models and human skin engrafts into other animals). This review discusses possible links between UV and genes significantly related to melanoma but does not discuss melanoma genetics. These include oncogenes, tumor suppressor genes, genes related to melanocyte-keratinocyte and melanocyte-matrix interaction, growth factors and their receptors, CRH, ACTH, α-MSH, glucocorticoids, ID1, NF-kappaB and vitamin D3.