Cutaneous adverse effects of BRAF inhibitors in metastatic malignant melanoma, a prospective study in 20 patients.

BACKGROUND: BRAF inhibitors frequently cause significant cutaneous adverse reactions. OBJECTIVE: To study the timing, prevalence and response to treatment of skin lesions in patients receiving V-raf murine sarcoma viral oncogene homolog B1 (BRAF) inhibitors. METHODS: We prospectively studied the cutaneous side-effects of patients with a BRAF mutant (V600E, V600K, V600R) metastatic malignant melanoma treated with a BRAF inhibitor. We systematically registered prevalence, timing of onset and response to treatment. RESULTS: Twenty patients were treated for 2-52 weeks with a BRAF inhibitor. Eleven patients on vemurafenib (58%) developed cutaneous side-effects and 10 patients (42%) had more than one cutaneous adverse event. Verrucous papillomas were observed in eight patients (42%), after 1-12 weeks. We diagnosed four keratoacanthomas in two patients (11%) after 6-10 weeks and two squamous cell carcinomas in two patients (11%) after 10-16 weeks. Seven patients (37%) developed a hyperkeratotic, folliculocentric eruption after 2-8 weeks, resolving quickly under topical steroids. Four patients (21%) presented a facial erythema, two patients (11%) a seborrhoeic dermatitis-like eczema on the scalp. Three patients (16%) developed cystic lesions after 2-11 weeks. Three patients (16%) presented a hand-foot skin reaction after 4-6 weeks, which was successfully treated with topical steroids and keratolytics. Hyperkeratosis of the nipples was seen in one patient (5%). We observed phototoxic reactions after UV exposure in five patients (26%) and alopecia in two patients (11%) after 8-10 weeks. One patient on dabrafenib developed curly hairs (24 weeks), keratotic papules (1 and 36 weeks), a keratoacanthoma (4 weeks) and a hand-foot skin reaction (31 weeks). CONCLUSION: Multiple cutaneous toxicities were observed in patients under BRAF inhibitors, mostly well controlled with adequate treatment. We recommend a multidisciplinary approach with regular assessments of the skin by a dermatologist. This allows early identification and adequate treatment to avoid premature discontinuation of a life-prolonging therapy.

Identification of a ZEB2-MITF-ZEB1 transcriptional network that controls melanogenesis and melanoma progression.

Deregulation of signaling pathways that control differentiation, expansion and migration of neural crest-derived melanoblasts during normal development contributes also to melanoma progression and metastasis. Although several epithelial-to-mesenchymal (EMT) transcription factors, such as zinc finger E-box binding protein 1 (ZEB1) and ZEB2, have been implicated in neural crest cell biology, little is known about their role in melanocyte homeostasis and melanoma. Here we show that mice lacking Zeb2 in the melanocyte lineage exhibit a melanoblast migration defect and, unexpectedly, a severe melanocyte differentiation defect. Loss of Zeb2 in the melanocyte lineage results in a downregulation of the Microphthalmia-associated transcription factor (Mitf) and melanocyte differentiation markers concomitant with an upregulation of Zeb1. We identify a transcriptional signaling network in which the EMT transcription factor ZEB2 regulates MITF levels to control melanocyte differentiation. Moreover, our data are also relevant for human melanomagenesis as loss of ZEB2 expression is associated with reduced patient survival.

Epithelial-mesenchymal transition during invasion of cutaneous squamous cell carcinoma is paralleled by AKT activation.

BACKGROUND: Epithelial-mesenchymal transition (EMT) is required for tumour invasion and dissemination to occur. OBJECTIVES: To investigate EMT during invasion of cutaneous squamous cell carcinoma (cSCC) and the involvement of AKT. METHODS: Using a tissue microarray, we measured expression of EMT-markers and AKT activation in 140 samples from patients with skin cancer and matched samples of normal skin adjacent to cSCC in cSCC in situ (cSCCIS) and in invasive cSCC. We investigated EMT using functional assays and the expression of EMT markers in an isogenic skin cancer progression model using cell lines derived from dysplastic forehead skin (PM1), primary invasive cSCC (MET1) and its lymph node metastasis (MET4). This model was used to investigate AKT-specific inhibition of the EMT process. RESULTS: In comparison with normal skin, and normal skin plus cSCCIS, the invasive cSCCs show significantly increased vimentin expression, decreased E-cadherin expression and increased expression of the active form of AKT. In the cell culture model, the primary MET1 cells display the lowest adhesion potential, the highest migratory and invasive ability through a Matrigel-coated porous membrane, the highest expression of EMT markers vimentin and Slug and the lowest expression of the epithelial marker E-cadherin. Pharmacological AKT inhibition in this model suppressed EMT mechanisms. CONCLUSIONS: AKT may serve as a therapeutic target to avoid dissemination of cSCC cells.

Activity and mechanism of action of HDVD, a novel pyrimidine nucleoside derivative with high levels of selectivity and potency against gammaherpesviruses.

A novel nucleoside analogue, 1-[(2S,4S-2-(hydroxymethyl)-1,3-dioxolan-4-yl]5-vinylpyrimidine-2,4(1H,3H)-dione, or HDVD, was evaluated against a wide variety of herpesviruses and was found to be a highly selective inhibitor of replication of the gammaherpesviruses Kaposi's sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV). HDVD had also a pronounced inhibitory activity against murine herpesvirus 68 (MHV-68) and herpes simplex virus 1 (HSV-1). In contrast, replication of herpesvirus saimiri (HVS), HSV-2, and varicella-zoster virus (VZV) was weakly inhibited by the compound, and no antiviral activity was determined against human cytomegalovirus (HCMV) and rhesus rhadinovirus (RRV). The HDVD-resistant virus phenotype contained point mutations in the viral thymidine kinase (TK) of HSV-1, MHV-68, and HVS isolates. These mutations conferred cross-resistance to other TK-dependent drugs, with the exception of an MHV-68 mutant (E358D) that exhibited resistance only to HDVD. HSV-1 and HVS TK-mutants isolated under selective pressure with bromovinyldeoxyuridine (BVDU) also showed reduced sensitivity to HDVD. Oral treatment with HDVD and BVDU was assessed in an intranasal model of MHV-68 infection in BALB/c mice. In contrast to BVDU treatment, HDVD-treated animals showed a reduction in viral DNA loads and diminished viral gene expression during acute viral replication in the lungs in comparison to levels in untreated controls. The valyl ester prodrug of HDVD (USS-02-71-44) suppressed the latent infection in the spleen to a greater extent than HDVD. In the present study, HDVD emerged as a highly potent antiviral with a unique spectrum of activity against herpesviruses, in particular, gammaherpesviruses, and may be of interest in the treatment of virus-associated diseases.

Epithelial raft cultures for investigations of virus growth, pathogenesis and efficacy of antiviral agents.

The organotypic epithelial raft cultures, originally developed to study keratinocytes differentiation, represent a novel approach to the study of viruses able to infect epithelial cells. Organotypic epithelial raft cultures accurately reproduce the process of epithelial differentiation in vitro and can be prepared from normal keratinocytes, explanted epithelial tissue, or established cell lines. This culture system permits cells to proliferate and fully differentiate at the air-liquid interface on a dermal-equivalent support. Normal primary human keratinocytes (PHKs) stratify and fully differentiate in a manner similar to the normal squamous epithelial tissues, while transformed cell lines exhibit dysplastic morphologies similar to the (pre)neoplastic lesions seen in vivo. This three-dimensional (3D) culture system provides an essential tool for investigations of virus growth, virus-host cell interactions, for the genetic analysis of viral proteins and regulatory sequences, and for the evaluation of antiviral agents. The 3D epithelial cultures have proven a breakthrough in the research on papillomaviruses, since their life cycle is strictly linked to the differentiation of the host epithelium. In the last years, several reports have shown the usefulness of the 3D epithelial cultures for the study of other viruses that target at least during a part of their life cycles epithelial cells. The 3D epithelial cultures allow the analysis of virus-host cell interactions in stratified epithelia that more closely resemble the in vivo situation. In this review we describe the advances on research on 3D epithelial cultures for the study of virus growth and pathogenesis of different families of viruses, including papilloma-, herpes-, pox-, adeno-, and parvoviruses.

POU5F1, encoding a key regulator of stem cell pluripotency, is fused to EWSR1 in hidradenoma of the skin and mucoepidermoid carcinoma of the salivary glands.

The EWSR1 gene is known to play a crucial role in the development of a number of different bone and soft tissue tumours, notably Ewing's sarcoma. POU5F1 is expressed during early development to maintain the totipotent status of embryonic stem and germ cells. In the present study, we report the fusion of EWSR1 and POU5F1 in two types of epithelial tumours: hidradenoma of the skin and mucoepidermoid carcinoma of the salivary glands. This finding not only broadens considerably the spectrum of neoplasms associated with EWSR1 fusion genes but also strengthens the evidence for shared pathogenetic mechanisms in the development of adnexal and salivary gland tumours. Reminiscent of the previously reported fusion genes involving EWSR1, the identified transcript is predicted to encode a chimeric protein consisting of the EWSR1 amino-terminal domain and the POU5F1 carboxy-terminal domain. We assessed the transcriptional activation potential of the chimera compared to the wild-type proteins, as well as activation of transcription through the oct/sox composite element known to bind POU5F1. Among other POU5F1 target genes, this element is present in the promoter of NANOG and in the distal enhancer of POU5F1 itself. Our results show that although the chimera is capable of significant transcriptional activation, it may in fact convey a negative regulatory effect on target genes.

High expression of DNA repair pathways is associated with metastasis in melanoma patients.

We have identified a gene-profile signature for human primary malignant melanoma associated with metastasis to distant sites and poor prognosis. We analyse the differential gene expression by looking at whole biological pathways rather than individual genes. Among the most significant pathways associated with progression to metastasis, we found the DNA replication (P=10(-14)) and the DNA repair pathways (P=10(-16)). We concentrated our analysis on DNA repair and found that 48 genes of this category, among a list of 234 genes, are associated with metastatic progression. These genes belong essentially to the pathways allowing recovery of stalled replication forks due to spontaneous blockage or induced DNA lesions. Because almost all these differentially expressed repair genes were overexpressed in primary tumors with bad prognosis, we speculate that primary melanoma cells that will metastasize try to replicate in a fast and error-free mode. In contrast to the progression from melanocytes to primary melanoma, genetic stability appears to be necessary for a melanoma cell to give rise to distant metastasis. This overexpression of repair genes explains nicely the extraordinary resistance of metastatic melanoma to chemo- and radio-therapy. Our results may open a new avenue for the discovery of drugs active on human metastatic melanoma.

Photosensitizing activity of hypericin and hypericin acetate after topical application on normal mouse skin.

BACKGROUND: Hypericin, originating from Hypericum perforatum, is a potent photosensitizer known to induce skin phototoxicity when given systemically. Previously, we have examined the penetration and distribution of hypericin and its acetate ester in the skin of hairless mice after topical application. OBJECTIVES: In this study, we assessed the time course and skin histopathology of the phototoxic response after a single topical application of hypericin and hypericin acetate, and subsequent irradiation. The amount of blood-borne photosensitizer and the skin clearance, as well the remaining photosensitizing capacity as a function of time, were evaluated. Furthermore, elicited phototoxic responses were compared with those after application of methyl aminolaevulinic acid (Me-ALA). METHODS: At different time points after topical application of hypericin (0.1-1%) and hypericin acetate (0.015-1.5%) onto mouse ears, penetration and retention of hypericin were assessed by fluorescence microscopy. After definite application times, the ears were irradiated (10 J cm(-2), 20 mW cm(-2)). Ear thickness measurements were conducted daily, and frequently ear samples were taken for histological analysis. RESULTS: Application of hypericin on mouse ears resulted only in limited phototoxicity, probably due to confined penetration into the epidermal layers. Extended penetration achieved by administration of hypericin acetate did give rise to a more severe and prolonged response after irradiation, characterized by intense erythema and ear swelling. Skin damage induced by 0.15% hypericin acetate application completely healed in 14 days without scar formation. After a single application of hypericin acetate, the residual photosensitizing capacity was found to decline quickly and was hardly detectable after 7 days. Under the experimental conditions used, hypericin acetate induced equal or more severe phototoxic responses compared with Me-ALA, depending on the concentration. CONCLUSIONS: Our results indicate that hypericin is an effective photosensitizer not only after systemic administration, but also after topical application, especially when applied as its precursor acetate ester. Moreover, our data provide some insights on safety limits and the time course of skin phototoxicity following hypericin and hypericin acetate application. These data will aid in developing protocols for future photodynamic therapy in the dermatological clinic.

A rare conjunctival Spitz nevus: a case report and literature review.

A conjunctival Spitz nevus is a very rare, benign melanocytic lesion, which can be mistaken for a malignant melanoma. We present a case of a 28-year old man, who suffered from a rapidly growing, non-pigmented mass in the left caruncular area, extending to the nasal conjunctiva. The lesion was excised and pathologic examination showed nests of large, polygonal, non-pigmented epithelioid cells, located in the stroma. The overlying epithelium showed focal erosions. At the base, there was a lymphocytic infiltrate. Immunohistochemical techniques, with stainings for S-100 protein, HMB-45 and MIB-1, were used for further investigation and showed the melanocytic origin of the lesion (S-100 staining) as well as many cells in cell cycle (MIB-1 staining). However, no mitoses were seen. The clinical image, combined with pathologic and immunohistochemical findings, provided the diagnosis of a Spitz nevus localised in the conjunctiva. Although the cutaneous location of Spitz nevi is well known, conjunctival Spitz nevi are very rare and because of their mucosal origin, some of the histological features are different.

Gene expression profiling of primary cutaneous melanoma.

Cutaneous Malignant Melanoma (CMM) is the most malignant skin tumour in humans, the incidence of which is rising rapidly in most fair-skinned populations, without apparent decline in mortality. Both hereditary, constitutional and environmental factors play a role in its etiology. CMM arises from melanocytes in the epidermis, and proceeds through discrete steps of tumor-progression that consist histologically of the radial growth phase (RGP), vertical growth phase (VGP) and metastatic phase. The underlying molecular mechanisms that govern the transition between these growth phases are hardly known. The prognosis of patients with VGP melanoma depends on several clinical and histological parameters; the latter include thickness, mitotic activity, presence or absence of ulceration and regression, and pattern of lymphocytic host response. However, there is still need for new prognostic parameters. To obtain insight in the molecular mechanisms of tumor progression in CMM, and in search of new prognostic markers, we performed global gene-expression profiling using 44K oligonucleotide micro-arrays on a unique retrospective series of 83 frozen primary MM with VGP, 9 metastases and 23 benign nevi. Unsupervised analysis allowed us o identify clusters of melanoma patients with different outcome based on their gene expression profile only. Supervised analysis resulted in the identification of a genomic signature of 254 genes with prognostic significance. The large majority of the 254 enes was correlated with thickness, thereby stressing the importance of thickness in he prognosis of CMM. This signature was validated on a separate series of melanoma patients, and proved to have a predictive accuracy comparable to what can be obtained by tumour thickness and ulceration. On an immunohistochemical level, we identified 8 new markers that may help in the prognostication of melanoma patients; three of these markers, i.e. the mini-chromosome maintenance (mcm) proteins mcm3, 4 and 6, hat are involved in DNA-replication, had independent prognostic value. Additionally, upervised analysis showed similarities in gene expression profile between primary CMM and their metastases. In conclusion, our data provide new information regarding the molecules that are operative in the progression of CMM. CMM is notorious for its resistance to chemotherapy, and disseminated CMM is a uniformly fatal disease. As several of the progression-related genes, encode molecules that have been the target of established or xperimental cancer therapies, our results may hopefully contribute to the treatment of end-stage CMM-patients.

Activities of acyclic nucleoside phosphonates against Orf virus in human and ovine cell monolayers and organotypic ovine raft cultures.

Orf virus, a member of the Parapoxvirus genus, causes a contagious pustular dermatitis in sheep, goats, and humans. Previous studies have demonstrated the activity of (S)-1-[3-hydroxy-2-(phosphonomethoxy)propyl]cytosine (HPMPC; cidofovir; Vistide) against orf virus in cell culture and humans. We have evaluated a broad range of acyclic nucleoside phosphonates (ANPs) against several orf virus strains in primary lamb keratinocytes (PLKs) and human embryonic lung (HEL) monolayers. HPMPC, (S)-9-[3-hydroxy-2-(phosphonomethoxy)propyl]-2,6- diaminopurine (HPMPDAP), and (R)-9-[3-hydroxy-2-(phosphonomethoxy)propoxy]-2,4-diaminopyrimidine (HPMPO-DAPy) were three of the most active compounds that were subsequently tested in a virus yield assay with PLK and HEL cells by virus titration and DNA quantification. HPMPC, HPMPDAP, and HPMPO-DAPy were evaluated for their activities against orf virus replication in organotypic epithelial raft cultures from differentiated PLK cells. At the highest concentrations (50 and 20 microg/ml), full protection was provided by the three drugs, while at 5 microg/ml, only HPMPDAP and HPMPC offered partial protection. The activities of the three compounds in the raft culture system were confirmed by quantification of infectious virus and viral DNA. These findings provide a rationale for the use of HPMPC and other ANPs in the treatment of orf (contagious ecthyma) in humans and animals.

Chronic radiodermatitis following percutaneous coronary interventions: a report of two cases.

We describe two patients in whom chronic radiodermatitis with therapy-resistant ulceration of the right scapular region developed, following percutaneous coronary intervention with fluoroscopic imaging. Contrary to most reported cases in the literature, which involve numerous cardiac catheterization procedures, in both patients described here the total radiation dose was given during two successive procedures, involving difficult and prolonged coronary intervention with stent implantation. In both cases, local treatment of the ulcerative lesions was insufficient, necessitating excision of the radiodermatitis area and replacement with a skin graft, with good therapeutic result. The incidence of radiodermatitis after percutaneous coronary interventions is rising with the increasing number and complexity of these procedures. The main risk factor is a long duration of fluoroscopy using the same incidence. The skin lesions encompass a wide spectrum, ranging from erythema, telangiectasia, atrophy, hyperpigmentation and hypopigmentation to necrosis, chronic ulceration and squamous cell carcinoma. The lesions can appear from 15 days to 10 years after the procedure. To prevent radiation-induced injury, the radiation dose has to be limited and monitored. Also, careful inspection of the skin at the site of exposure is necessary and the radiographic beam has to be restricted to the smallest field size. A good clinical follow-up at regular intervals is important after long and complicated procedures.

Antivaccinia activities of acyclic nucleoside phosphonate derivatives in epithelial cells and organotypic cultures.

Organotypic "raft" cultures of epithelial cells allow the reconstitution of a skin equivalent that is easily infectible with different viruses with cutaneous tropism. Among these, poxvirus and particularly vaccinia virus (VV) are good candidates for use in antiviral tests, giving histological pictures comparable to those observed in humans infected with smallpox. Therefore, we decided to evaluate a series of phosphonate derivatives for their ability to inhibit VV growth in epithelial cell monolayers, and the most powerful derivatives were tested in the organotypic cultures. The most active compound was 9-(S)-[3-hydroxy-2-(phosphonomethoxy)propyl]adenine [(S)-HPMPA], followed by 9-(S)-[3-hydroxy-2-(phosphonomethoxy)propyl]-2,6-diaminopurine, cyclic (S)-HPMPA, 9-(S)-[3-hydroxy-2-(phosphonomethoxy)propyl]cytosine [(S)-HPMPC; cidofovir, Vistide], and cyclic (S)-HPMPC. Cidofovir, which is on the market for the treatment of human cytomegalovirus retinitis in immunocompromised patients, is potentially a good candidate for the treatment of a poxvirus outbreak, in the absence of any vaccination.

Microstaging in cutaneous melanoma.

Recent papers have addressed critical issues regarding the microstaging of cutaneous melanoma. They concern the new staging proposal by the American Joint Committee on Cancer (AJCC), the presentation of new prognostic models than seem applicable in daily practice, and new immunohistochemical findings than demonstrate prognostic information independently of the conventional major factors. These issues are commented on by the Pathology Committee of the EORTC Melanoma Group.

Eosinophilic rhinitis accompanies the development of lower airway inflammation and hyper-reactivity in sensitized mice exposed to aerosolized allergen.

BACKGROUND: Allergic rhinitis is a risk factor for the development of asthma. About 80% of asthmatic patients also have rhinitis. However, the pattern of induction of allergic rhinitis and asthma remains unclear. OBJECTIVE: The purpose of this study was to investigate the development of upper airway inflammation in mice during the development of an asthma-like disease and after an acute allergen provocation. METHODS: BALB-c mice were sensitized intraperitoneally (i.p) to ovalbumin (OA, days 1-13) and were challenged with aerosols of either OA or saline on 8 consecutive days (days 33-40). In a second experiment, chronic exposure for 8 days was followed by 10 days of rest and then an acute nebulized allergen provocation was performed (day 50). Inflammatory parameters were investigated at different time-points. RESULTS: Upper and lower eosinophilic airway inflammation were simultaneously induced in the course of repeated inhalations of nebulized OA, as shown by analyses of nasal and broncho-alveolar lavage fluids and histological sections of the nose and bronchi. Mice that developed bronchial hyper-responsiveness also had increased thickness of the nasal mucosa on magnetic resonance image (MRI) scans. When chronic exposure was followed by acute allergen provocation, the latter caused a systemic increase in IL-5 levels, with a concomitant rise in blood and airway eosinophils, primarily in the nose. CONCLUSIONS: Simultaneous induction of eosinophilic inflammation in the nose and lungs was found in a mouse model of respiratory allergy. These findings support the viewpoint that upper and lower airway disease represent a continuum of inflammation involving one common airway and provide evidence for the concept of global airway inflammation after inhalation of allergen.

Expression of the endothelin-B receptor in pigment cell lesions of the skin. Evidence for its role as tumor progression marker in malignant melanoma.

Endothelins (ETs) exert several functions in human melanocytes, including proliferation, dendrite formation, and melanin synthesis. Among the ET receptors, the non-selective endothelin-B (ETB) receptor is the major receptor in melanocytes and malignant melanoma (MM) cells. In spite of the important role of ETs and their receptors in the growth and differentiation of melanocytes, the distribution and expression levels of ETB receptors in tissue sections of benign and malignant pigment cell lesions is still unknown. We combined immunohistochemistry and reverse transcriptase-polymerase chain reaction (RT-PCR) to study ETB receptor expression in benign and malignant pigment cell lesions and in normal skin. Immunohistochemistry on paraffin-embedded tissue sections of 159 cases revealed a significant increase in intensity of ETB receptor expression from common nevi over dysplastic nevi and primary MM to metastatic MM. Quantitative PCR using realtime detection on 75 samples confirmed the immunohistochemical results. These data add the ETB receptor to the growing list of tumor progression markers in MM and suggest that ETs play a role in the progression of MM in the skin.

A novel N-ras mutation in malignant melanoma is associated with excellent prognosis.

Mutations in the ras gene are key events in the process of carcinogenesis; in particular, point mutations in codon 61 of exon 2 of the N-ras gene occur frequently in malignant melanoma (MM). We searched for point mutations in the N-ras gene in a large series of primary and metastatic MM from 81 different retrospectively selected patients using the very sensitive denaturing gradient gel electrophoresis technique, followed by sequencing. The classical codon 12 and codon 61 mutations were found in 21 and 17% of the cases, respectively. No codon 13 mutation was found. A novel mutation at codon 18 of exon 1, consisting of a substitution of alanine (GCA) by threonine (ACA), was found in 15% of the primary MMs but in none of the metastatic MMs. All of the other cases were free of mutations. Using microdissected cells from distinctive MM growth phases as source of DNA for mutation analysis, this particular N-ras exon 1 mutation at codon 18 was already present in the radial growth phase and preserved throughout the successive growth phases; it was also found in a dysplastic nevi in continuity with a MM, indicating a clonal relationship between both lesions. Our findings also illustrate the clonal relationship between the distinctive growth phases in MM and suggest the codon 18 mutation to occur early in MM development. The MM in patients with this mutation were significantly thinner than those without a codon 18 mutation (P = 0.0257). Statistical analysis, comparing the group of codon 18 patients with the group of patients with the classical mutations and without mutations, revealed a highly significant difference in overall outcome. The cumulative probability of developing metastasis was significantly lower for the group patients with a codon 18 mutation (P = 0.0130). We can thus conclude that this codon 18 mutation identifies a group of patients with better prognosis than patients with melanoma that harbor wild-type sequence or classical activating point mutations in codon 12 or 61. Preliminary nucleotide binding measurements could not detect a difference between wild-type Ras protein and the mutant Ras(A18T) protein. However, for a precise elucidation of the role of the N-Ras(A18T) mutant in melanoma, additional studies aimed to measure the affinity to guanine nucleotide exchange factors and GTPase-activating proteins are needed.

Expression of neurotrophins and their receptors in pigment cell lesions of the skin.

The neurotrophins (NTs) are a group of growth factors involved in the development of the nervous system and presumed to play a role in neural crest-derived tumours. The expression of three NTs (NGF, BDNF, and NT-3) and their receptors (NTRs; i.e. low-affinity pan-NT receptor p75, Trk-B, and Trk-C) was studied in frozen sections of benign and malignant cutaneous pigment cell lesions, using immunohistochemistry. In order to understand the possible role of these growth factors and their receptors in the progression of primary cutaneous malignant melanomas (PCMMs), their distribution in the radial (RGP) and vertical (VGP) growth phases was particularly studied. While most of the common acquired naevi were unreactive, Spitz and blue naevi showed scattered immunoreactive cells, especially for the p75 NTR. Dysplastic naevi, but not common naevi, expressed NT-3 in their junctional component. PCMM and melanoma metastases often showed a diffuse pattern of immunostaining. NT-3 was significantly more frequently expressed in the RGP of PCMMs than in the junctional component of benign naevi, whereas more extensive immunoreactivity for NGF was found in the VGP of PCMMs, compared with the RGP; metastases more frequently expressed NGF, BDNF, and Trk-B than PCMMs. Interestingly, neurotropic melanoma expressed all NTs/NTRs except Trk-B. These immuunohistochemical data confirm suggestions from previous in vitro studies that autocrine loops of certain NTs and their respective receptors may be involved in melanoma progression; in addition, NT-3 may be involved in the junctional growth of dysplastic naevi. The precise role of these growth factors in melanoma, however, will await further functional studies.