Transcriptome Analysis Identifies Oncogenic Tissue Remodeling during Progression from Common Nevi to Early Melanoma

Early detection and treatment of melanoma, the most aggressive skin cancer, improves the median 5-year survival rate of patients from 25% to 99%. Melanoma development involves a stepwise process during which genetic changes drive histologic alterations within nevi and surrounding tissue. Herein, a comprehensive analysis of publicly available gene expression data sets of melanoma, common or congenital nevi (CN), and dysplastic nevi (DN), assessed molecular and genetic pathways leading to early melanoma. The results demonstrate several pathways reflective of ongoing local structural tissue remodeling activity likely involved during the transition from benign to early-stage melanoma. These processes include the gene expression of cancer-associated fibroblasts, collagens, extracellular matrix, and integrins, which assist early melanoma development and the immune surveillance that plays a substantial role at this early stage. Furthermore, genes up-regulated in DN were also overexpressed in melanoma tissue, supporting the notion that DN may serve as a transitional phase toward oncogenesis. CN collected from healthy individuals exhibited different gene signatures compared with histologically benign nevi tissue located adjacent to melanoma (adjacent nevi). Finally, the expression profile of microdissected adjacent nevi tissue was more similar to melanoma compared with CN, revealing the melanoma influence on this annexed tissue.

Dysplastic nevi and melanoma: microRNAs tell a divergent story

BACKGROUND

dysplastic nevi (DN) share some clinical and histological features with melanoma and have been considered intermediate lesions toward malignant transformation. However, scientific evidence of DN representing melanoma precursors is still incomplete, and many observations pointed toward their being a distinct biological entity. The current definition of DN is also confusing and the practical consequence of this uncertainty is the excessive excision of DN with severe atypia. MicroRNAs (miRNAs) are small RNAs that regulate gene expression and whose global expression can classify normal and pathological tissues.

OBJECTIVES

given these considerations, we decided to perform a small RNA profiling study in a group of DN and invasive melanomas obtained from the same patient, to assess tumor evolution according to the global microRNA expression.

METHODS

we performed a small-RNA sequencing of 6 DN, 2 congenital nevi and 4 cutaneous melanomas obtained from 4 subjects and evaluated the global miRNA expression correlation between samples.

RESULTS AND CONCLUSIONS

the hierarchical clustering and principal component analyses of global miRNA expression, independently grouped together DN and their matching congenital nevi and showed a divergence of DN miRNA profile from melanoma. Our study suggests that DN have a peculiar and different miRNA expression profile compared to melanomas developed in the same patient, thus supporting the hypothesis that DN are distinct biological entities and not melanoma precursors.

The differential expression of micro-RNAs 21, 200c, 204, 205, and 211 in benign, dysplastic and malignant melanocytic lesions and critical evaluation of their role as diagnostic biomarkers

Overlapping histological features between benign and malignant lesions and a lack of firm diagnostic criteria for malignancy result in high rates of inter-observer variation in the diagnosis of melanocytic lesions. We aimed to investigate the differential expression of five miRNAs (21, 200c, 204, 205, and 211) in benign naevi (n = 42), dysplastic naevi (n = 41), melanoma in situ (n = 42), and melanoma (n = 42) and evaluate their potential as diagnostic biomarkers of melanocytic lesions. Real-time PCR showed differential miRNA expression profiles between benign naevi; dysplastic naevi and melanoma in situ; and invasive melanoma. We applied a random forest machine learning algorithm to classify cases based on their miRNA expression profiles, which resulted in a ROC curve analysis of 0.99 for malignant melanoma and greater than 0.9 for all other groups. This indicates an overall very high accuracy of our panel of miRNAs as a diagnostic biomarker of benign, dysplastic, and malignant melanocytic lesions. However, the impact of variable lesion percentage and spatial expression patterns of miRNAs on these real-time PCR results was also considered. In situ hybridisation confirmed the expression of miRNA 21 and 211 in melanocytes, while demonstrating expression of miRNA 205 only in keratinocytes, thus calling into question its value as a biomarker of melanocytic lesions. In conclusion, we have validated some miRNAs, including miRNA 21 and 211, as potential diagnostic biomarkers of benign, dysplastic, and malignant melanocytic lesions. However, we also highlight the crucial importance of considering tissue morphology and spatial expression patterns when using molecular techniques for the discovery and validation of new biomarkers.

Novel immune signatures associated with dysplastic naevi and primary cutaneous melanoma in human skin

Dysplastic naevi (DN) are benign lesions with atypical features intermediate between that of common melanocytic naevi (CMN) and malignant melanoma (MM). Debate remains over whether DN represent progressive lesions from CMN. Through gene expression profiling and analysis of molecular gene signatures, our study revealed progressive increases in immune activation and regulation, along with pathways implicated in melanomagenesis, from CMN to DN to MM. Using criteria of 1.5-fold change and false discovery rate ≤0.05, we found differential expression of 7186 probes (6370 unique genes) with the largest difference detected between DN and MM from the standpoint of genomic melanoma progression. Despite progressive increases in the T-helper type 1 (Th1)-inducing gene (IL-12), RT-PCR indicated impaired Th1 or cytotoxic T-cell response (decreased IFN-γ) in MM. Concordantly, our results indicated progressive increases in molecular markers associated with regulatory T cells, exhausted T cells and tolerogenic dendritic cells, including detection of increased expression of suppressor of cytokine signalling 3 (SOCS3) in dendritic cells associated with MM. All together, our findings suggest that the increased immunosuppressive microenvironment of melanoma may contribute to unhampered proliferation of neoplastic cells. In addition, the detection of increased markers associated with tolerogenic dendritic cells in MM suggests that targeting these suppressive immune cell types may represent an alternative avenue for future immunotherapy.

Altered Expression of the Dna Mismatch Repair Proteins Hmlh1 and Hmsh2 in Cutaneous Dysplastic Nevi and Malignant Melanoma

Molecular alterations in the mismatch repair system suggest that this mechanism may be important in the evolution of cutaneous melanoma. Our current study evaluated the expression of two mismatch repair proteins, hMLH1 and hMSH2, in dysplastic nevi (DN) and cutaneous melanoma (CM). Immunohistochemical staining of these proteins was performed on 55 CM and 30 DN specimens. The staining results were divided into three groups: negative, partially positive and strongly positive. Normal adjacent skin cells served as an internal control for positive immunostaining. Altered immunoreactivity of one of the proteins was found in four (13.4%) DN and seven (12.7%) CM. Lack of staining for hMLH1 was observed in two (6.7%) cases of DN and five (9.1%) cases of CM; staining for hMSH2 was absent in two (6.7%) of the DN and two (3.6%) of the CM specimens. Partially positive staining was found in 33.3% and 53.3% for hMLH1 and hMSH2, respectively, in DN, and in 54.5% and 69.1%, respectively, in CMM. Our study shows that complete or partial loss of MMR protein expression occurs in a subset of both DN and CM and may represent a distinct pathway in the development of some DN and CM.

Immunohistochemical Expression of Vascular Endothelial Growth Factor (VEGF) and C-KIT in Cutaneous Melanocytic Lesions

Vascular endothelial growth factor (VEGF) and C-KIT are involved in tumor progression in several human neoplasms. The aim of the present study has been to investigate their immunohistochemical expression in melanocytic lesions. We examined 11 compound nevi, 12 dysplastic nevi, and 18 melanomas. Immunostaining for VEGF was observed only in melanomas; c-kit expression was detected in melanomas (higher in radial than in vertical growth phase) and in nevi (predominantly in the junctional component). Our data indicate that assessment of VEGF expression might aid in the differential diagnosis between dysplastic nevi and melanomas. Moreover, VEGF might be a candidate for targeted therapy. The loss of c-kit expression might contribute to melanoma progression.

IMP-3 EXPRESSION IN BENIGN MELANOCYTIC NEVI, DYSPLASTIC NEVI AND MALIGNANT MELANOMA: PRELIMINARY FINDINGS IN BULGARIAN PATIENTS

IMP-3 is generally considered as an oncofetal protein, which plays a critical role in regulation of cell proliferation via an IGF-II-dependent pathway in K562 leukemia cells. IMP-3 expression has been detected in malignancies with various origins, while its appearance in adult tissue is generally considered abnormal, with some exceptions. IMP3 is also considered a prognostic biomarker in patients with renal cell carcinoma and clear-cell type ovarian carcinoma, hepatocellular carcinoma, pancreatic ductal adenocarcinoma and in patients with poorly differentiated thyroid carcinoma and uterine cervical carcinomas, testicular cancer and malignant melanoma. To our knowledge, no more than 4 PubMed-indexed studies have investigated the expression of IMP-3 in melanocytic lesions, namely its role in the differentiation between benign and malignant neoplasms. We investigated the expression of IMP-3 in a small series of benign melanocytic lesions, dysplastic nevi and melanomas, aiming to establish its significance as a marker for their distinction, comparing the results with those from the literature. IMP- 3 immunostaining was performed in 30 melanocytic lesions: 10 malignant melanomas, 10 dysplastic nevi and 10 benign melanocytic nevi. Our results revealed expression in 20% of dysplastic lesions and 40% of melanoma cases, while none of the benign nevi showed positive expression. These data contradict some of the results from other studies and raise some questions regarding the correlation between IMP- 3 and the degree of dysplasia of melanocytic nevi, as well as its potential relationship with prognostic parameters in melanoma, including tumor thickness and mitotic rate. Our results suggest that IMP-3 expression could be only an auxiliary marker for differentiation between dysplastic nevi and benign nevi, since although it is not expressed in all dysplastic lesions, staining correlates with the degree of dysplasia/atypia. It seems that IMP-3 expression is not a useful discriminator between dysplastic nevi and melanoma nor a good prognostic marker in melanoma.

Dysplastic Nevus Syndrome: Melanoma-prone Disease

Regardless of subsequent clinical courses of patients with dysplastic nevi (DN), substantial evidence supporting DN as one of the melanoma-prone diseases is not yet available, especially in sporadic DN, due to the lack of genetic information other than retrospective studies in clinical observation. This study aimed at the immunohistological characterization of sporadic DN distinct from common nevi (CN) and at the evaluation of the potentially of sporadic DN for malignant transformation. We considered our results together with previous immunological and epidemiological reports. We noted the following three immunohistological characteristics. 1) Proliferating cell nuclear antigen (PCNA), one of the markers for active cell division, could be detected on DN cells in junctional nests of only one among ten DN examined but not on CN cells at all. 2) The altered expression of alpha-smooth muscle actin (alpha-Sma), often observed in melanoma cells, could not be detected in DN cells. However, anti-alpha-Sma monoclonal antibody (MoAb) clearly demonstrated distinctive hypervascularity in the stroma surrounding DN when compared with CN. 3) ME491 antigen, which is known to be expressed mainly in the radial growth phase of melanoma, was detected with similar intensity on both DN and CN. These data indicate that DN has a somewhat higher potentiality than CN for cell division and secretion of some cytokines which can induce hypervascularity in the surrounding stroma, but that DN has not yet undergone the significant phenotypic changes observed in melanoma cells. Further advancements in understanding molecular events in DN cells will be of great benefit in setting DN in the multiple oncogenic spectrum from pigment cells to melanoma.

Suprabasal spread of melanocytes in dysplastic nevi and melanoma in situ: Ki-67-labeling rate of junctional melanocytes and suprabasal cells may be a helpful clue to the diagnosis

Multiple criteria on routinely stained sections allow one to make a diagnosis of a dysplastic or "Clark" nevus (CN) versus melanoma in situ (MIS), and one of these is suprabasal spread of melanocytes. The extent of suprabasal spread of melanocytes in otherwise conventional CN and the combination of a sensitive marker of melanocytes combined with Ki-67 to assess the differences between the proliferation of melanocytes at the junction and those above it have not yet been studied. Fifty classic examples of CN and 27 cases of MIS were culled from the files of a university-based dermatopathology practice. All cases were stained with a 2-color method (MART-1/tyrosinase red, Ki-67 brown) to evaluate morphologic and immunohistochemical differences in these lesions. Fifteen of 50 cases of benign CN demonstrated suprabasal spread compared with 27 of 27 cases of MIS. The majority of CNs with suprabasal spread (13 of 15) showed a 0% Ki-67-labeling rate among the suprabasal melanocytes, and the majority of MISs (23 of 27) showed a 20% or greater Ki-67-labeling rate in suprabasal cells. Suprabasal melanocytes can be seen by immunostaining in otherwise unremarkable CN, wherein they are not notable in routinely stained sections, but their proliferation rate is much less than in MIS.

HLA antigen expression in melanocytic lesions: is acquisition of HLA antigen expression a biomarker of atypical (dysplastic) melanocytes?

BACKGROUND

Although criteria are established for the histologic diagnosis of atypical nevi (AN), consensus about the criteria in the diagnosis of and in the definition of AN is limited. Moreover, intraobserver and interobserver differences in the application of these criteria for the diagnosis of AN have been observed.

OBJECTIVE

We sought to determine the usefulness of HLA antigen expression as a biomarker of AN.

METHODS

The immunoperoxidase reaction was used to mark common nevi and AN with HLA class I heavy chain-, β2microglobulin (β2m)-, and HLA class II β chain-specific monoclonal antibodies.

RESULTS

HLA class I heavy chain, β2m, and HLA class II β chain were expressed in 5 (8.6%) of the 58 common nevi and in 46 (∼72%) of the 64 atypical melanocytic lesions. Among common lesions, only halo nevi expressed HLA class I heavy chain, β2m, and HLA class II β chain. The level of HLA class I heavy chain β2m and of HLA class II β chain expression correlated with the degree of cytologic atypia and architectural disorder.

LIMITATIONS

The number of lesions tested and the subjective nature of the analysis of immunohistochemical staining of tissue sections are both limitations.

CONCLUSIONS

The data presented suggest that HLA antigen expression is an objective biomarker that correlates well with the degree of cytologic atypia in AN and may: (1) be useful to distinguish common nevi from AN, and (2) represent a more objective measure to determine which AN should be excised.

Nucleolin protein expression in cutaneous melanocytic lesions

BACKGROUND

Nucleolin is a major nucleolar argyrophilic protein involved in carcinogenesis. There are only few studies on its tissue expression in human cancer and none in melanoma. We aimed at exploring this protein and its prognostic impact in cutaneous melanocytic lesions.

METHODS

We studied 193 cases including benign, dysplastic and malignant melanocytic lesions. Nuclear positivity was evaluated by immunohistochemistry and quantified by automated image analysis.

RESULTS

Most dysplastic and malignant lesions showed high percentages of cells with abnormal patterns of nuclear positivity (Abn+N) consisting in multiple, irregular, positive dots (ID+) and a coarse, irregularly positive nucleoplasm (CNpl+) or both (ID+CNpl+). The patterns CNpl+ and/or ID+CNpl+ were never observed in benign lesions, in which ID+ were also virtually absent. Abn+N% was significantly lower in dysplastic nevi than in primary melanomas and metastases and in primary melanomas than in metastases (p < 0.05). Furthermore, Abn+N was the second powerful prognostic discriminator, after melanoma thickness, and a significantly lower survival was observed in vertical growth phase melanoma patients showing Abn+N in more than 50% of melanoma cells.

CONCLUSION

An altered nuclear nucleolin expression seems to accompany melanoma progression. Further investigation on nucleolin functionality and subcellular trafficking could add information on its altered role in melanoma.

Expression pattern of type IV collagen in sporadic dysplastic melanocytic nevi

OBJECTIVE

To investigate the expression and distribution pattern of type IV collagen in dysplastic nevi (DN) and to determine whether DN exhibits a morphologic difference from common melanocytic nevi (CMN) and cutaneous malignant melanomas (MM) and therefore can be classified as a separate entity.

STUDY DESIGN

We examined 33 DN specimens, 18 CMN specimens, and 10 MM specimens. The streptavidinbiotin immunoperoxidase method was used for immunostaining.

RESULTS

No staining was observed in most of the CMN. Twenty-one of 33 DN showed a continuous pattern of type IV collagen surrounding junctional nests in a concentric fashion while a discontinuous immunostaining pattern was observed in remaining cases. Six of 10 MM showed a continuous staining pattern; 2 exhibited discontinuous staining; and in 2 cases, no immunostaining was observed. The expression pattern of type IV collagen in DN was statistically different from CMN and MM.

CONCLUSION

Our results suggest sporadic DN is biologically different from CMN in terms of the capacity to synthesize type IV collagen, demonstrating that DN is not only morphologically but also biologically a different entity from CMN.

Myeloid leukemia-1 expression in benign and malignant melanocytic lesions

Myeloid leukemia-1 (Mcl-1) is an anti-apoptotic protein implicated in tumor progression. Its expression was found to be elevated in many types of human cancers and is correlated with tumor progression. The expression of Mcl-1 in melanoma is not fully understood. We investigated the expression of Mcl-1 in normal nevi, dysplastic nevi, primary melanoma and melanoma metastases by tissue microarray and immunohistochemistry. We found that Mcl-1 expression was significantly increased in dysplastic nevi, primary melanoma and melanoma metastases when compared to normal nevi, though the expression of Mcl-1 was decreased in metastatic melanoma when compared to dysplastic nevi. We did not find any correlation between Mcl-1 expression and melanoma patient survival. Our data suggest that Mcl-1 may play a critical role in the initiation of melanoma development.

A Subgroup of Melanocytic Nevi on the Distal Lower Extremity (Ankle) Shares Features of Acral Nevi, Dysplastic Nevi, and Melanoma In Situ

Melanocytic lesions in certain locations (eg, genital, breast, acral) may have histologic and clinical features simulating melanoma. Here we describe a group of lesions from the lower distal extremity and analyze their histologic features and possible relation to dysplastic nevi (DN) and melanomas. One hundred fifteen melanocytic lesions from the ankle were retrieved from January 1990 to August 2006 from the files of M. D. Anderson Cancer Center and were classified as benign melanocytic nevi (BN; n=17), DN (n=35), melanomas (MM; n=52), and melanocytic nevi of the ankle with atypical features (MNAAF; ie, cases that did not readily fit in any of the previous categories, n=11). Data analyzed included clinical (age and sex) and histologic features (circumscription, symmetry, cohesiveness of nests, suprabasal melanocytes, confluence, single-cell proliferation, nuclear chromasia, size, and nucleolar features). Follow-up was collected for all MNAAF. MNAAF differ from the other types of lesions in regard to sex incidence (73% in women). The median age of those patients MNAAF was 47 years (range 29 to 76 y). All MNAAF showed moderate-severe architectural disorder whereas 78% showed only mild-moderate cytologic atypia. No MNAAF cases had recurred after follow-up (4 mo to 13 y). This study highlights a group of melanocytic lesions located on the ankle that share histologic features with acral nevi, DN, and melanoma. These lesions are more predominant in females and have moderate to severe architectural atypia but only mild-moderate cytologic atypia. After complete excision, follow-up data indicate an apparently benign outcome. Pathologists should be aware of this type of lesions to avoid overdiagnosis of melanoma.

The Significance of Ki-67 Proliferative Index and Cyclin D1 Expression of Dysplastic Nevi in the Biologic Spectrum of Melanocytic Lesions

Familial acquired dysplastic nevi carry a risk for the development of melanoma. However, the results in various studies regarding the significance of sporadic dysplastic nevi as a precursor of malignant melanoma (MM), are controversial. The aim of this study is to investigate cyclin D1 expression and Ki67 proliferative index in a group of melanocytic lesions to address the biologic significance of sporadic dysplastic nevi in the progression of melanocytic lesions. Formalin-fixed paraffin-embedded material from 21 common melanocytic nevi, 42 dysplastic nevi, and 17 primary cutaneous MMs were examined. Standard streptavidin-biotin immunoperoxidase method was used for immunostaining with cyclin D1 and Ki-67 antibody. Nuclear cyclin D1 immunostaining was scored and Ki-67 proliferative index was calculated. Cyclin D1 expression was significantly higher in melanoma than those in other lesions. However, there was no significant difference between dysplastic nevi and common melanocytic nevi in terms of cyclin D1 expression. Ki-67 index was significantly higher in dysplastic nevi compared with common melanocytic nevi and to melanoma compared with dysplastic nevi. There was a significant positive correlation between cyclin D1 expression and Ki-67 proliferative index for each group. The present study indicates significant differences in cyclin D1 expressions and Ki-67 indices among melanocytic lesions. We think that dysplastic nevi are biologically separate from common melanocytic nevi in terms of proliferative activity. Additionally, our results suggest that cyclin D1 expression may be related to malignant phenotype and is associated with high proliferation rate in MM.

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

BACKGROUND

Basic fibroblast growth factor (bFGF) and stem cell factor (SCF) are essential growth factors for melanocytes which carry the receptors FGFR-1 for bFGF and c-kit for SCF. Because both factors may be involved in melanoma development, the expression of bFGF/FGFR-1 and SCF/c-kit was investigated in melanocytic tumors of different progression stages.

METHODS

Fifty primary melanomas and 44 melanocytic nevi were analyzed for the expression of SCF, c-kit, bFGF, and FGFR-1 by immunohistochemistry.

RESULTS

In melanoma, SCF and c-kit were expressed in 76 and 84%, respectively, and coexpressed in 66%. bFGF and FGFR-1 were expressed in 45 and 86%, respectively, and coexpressed in 46%. In melanocytic nevi, SCF was expressed in 23% and c-kit in 70% while coexpression was more common in dysplastic (39%) than non-dysplastic subtypes (8%). bFGF and FGFR-1 were expressed in 55 and 67%, respectively, while coexpression was found in 47% but varied considerably between different histological subtypes.

CONCLUSIONS

SCF and c-kit were frequently expressed by melanomas and dysplastic nevi suggesting an autocrine growth mechanism as described for bFGF. In both nevi and melanoma, c-kit was almost exclusively found in the epidermis while bFGF was more common in the dermis. Thus the growth factor/receptor expression seems to depend on the cutaneous localization of the melanocytic tumors.

Quantitative Analysis of Melanocytic Tissue Array Reveals Inverse Correlation between Activator Protein-2α and Protease-Activated Receptor-1 Expression during Melanoma Progression

The identification of molecular markers of melanoma progression is needed to more accurately stage and identify treatments for patients with malignant melanoma. Previously, we demonstrated that loss of the activator protein-2alpha (AP-2alpha) expression results in overexpression of the protease-activated receptor-1 (PAR-1) in human melanoma cell lines. Here, we used a tissue microarray platform that consisted of 64 melanocytic lesions, including dysplastic nevi (N=21), primary melanoma (N=20), and metastatic melanoma (N=23). We analyzed the expression of AP-2 and PAR-1 simultaneously by immunofluorescent microscopy with an automated quantification laser scanning cytometer. AP-2 was highly expressed in normal cutaneous melanocytes and dysplastic nevi but not in melanoma metastases. We observed a significantly higher number of AP-2-positive cells in the dysplastic nevi (P=0.0013) and primary melanoma (P=0.0023) compared to the metastatic melanoma. In contrast, we observed a significantly higher percentage of PAR-1-positive cells in the metastatic melanoma compared to dysplastic nevi (P=0.0072) and primary melanoma (P=0.0138). Increased expression of PAR-1 in metastatic melanomas contributes to tumor progression by modulating expression of genes, such as IL-8, matrix metalloproteinase-2, vascular endothelial growth factor, platelet-derived growth factor, and integrins. These findings support our hypothesis that loss of AP-2 is a crucial event in the progression of human melanoma and contributes to the acquisition of the metastatic phenotype via upregulation of PAR-1.

Oestrogen receptor-beta expression in melanocytic lesions

Melanomas rarely occur before puberty, have a higher death rate for males, and tend to be more invasive during pregnancy. Prior to the discovery of a second oestrogen receptor (ERbeta), studies with the initial oestrogen receptor, ERalpha, showed no obvious role for oestrogen in the pathophysiology of benign or malignant melanocytic lesions. To investigate the specific immunostaining patterns of ERalpha and ERbeta, benign nevocytic nevi, dysplastic nevi with mild, moderate and severe cytological atypia, lentigo malignas and melanomas of varying depth (Clark) and thickness (Breslow) were studied. ERbeta but not ERalpha was the predominant oestrogen receptor we found in all types of benign and malignant melanocytic lesions. The most intense ERbeta immunostaining was seen in melanocytes in dysplastic nevi with severe cytological atypia and in lentigo malignas. ERbeta expression levels also correlated with the malignant tumor microenvironment; i.e., melanocytes in proximity with keratinocytes>deeper dermal melanocytes in contact with stroma>minimally invasive melanomas>Clark Level III/IV or thick melanomas (Breslow). Discovery that ERbeta expression varies in relation to the tumor microenvironment and increasing depth of invasion suggests its possible usefulness as a surrogate marker for neoplasia and prognosis in malignant melanoma.

Aberrant DNA methylation silences the novel heat shock protein H11 in melanoma but not benign melanocytic lesions

BACKGROUND

The heat shock protein H11 is silenced in melanoma cell lines, where its forced expression by demethylation with Aza-C triggers apoptosis.

OBJECTIVE

To examine whether H11 is silenced by aberrant DNA methylation in melanoma as compared to nevi and normal skin tissues.

METHODS

Cell suspensions from benign intradermal nevi, atypical nevi and malignant melanoma tissues were used in reverse-transcriptase PCR and methylation-specific PCR. Paraffin-embedded tissues were stained with H11 antibody.

RESULTS

H11 is methylated in 60-75% of melanoma and atypical nevi, but not in normal skin or most benign nevi. Methylation is inversely correlated with H11 expression.

CONCLUSION

The heat shock protein H11 is silenced by aberrant DNA methylation in melanoma, but not benign melanocytic lesions or normal skin melanocytes. The data suggest that H11 is a promising target for the molecular therapy of melanoma.

Expression of cell cycle and apoptosis regulatory proteins and telomerase in melanocitic lesions

To gain insight into the role and association of cell cycle and apoptosis regulatory proteins and telomerase activity in the course of progression of melanocitic lesions we have examined immunohistochemicaly, expression and the distribution of p53, bcl-2, Ki-67 and telomerase in 25 samples of common and dysplastic nevi, and 45 samples of primary invasive melanomas. Protein p53 expression was significantly increased in dysplastic as compared with common nevi and melanomas (p < 0.001). Bcl-2 protein expression was significantly increased in melanomas as compared with common aquired and dysplastic nevi (p = 0.001). Nevi and melanomas exhibited clear-cut differences in terms of Ki-67 expression. Telomerase expression was significantly increased in melanomas as compared with common acquired (p = 0.014) and dysplastic nevi (p < 0.001). Enhanced telomerase activity in association with increased bcl-2 expression in the course of melanoma progression could contribute to development and progression of melanoma.

Nuclear ING2 expression is reduced in human cutaneous melanomas

Cutaneous malignant melanoma is a severe and sometimes life-threatening cancer. The molecular mechanism of melanomagenesis is incompletely understood. Deregulation of apoptosis is probably one of the key factors contributing to the progression of melanoma. The inhibitor of growth (ING) family proteins are candidate tumour suppressors which play important roles in apoptosis. Downregulated expression of ING proteins have been reported in several tumour types, including the loss of nuclear expression of p33ING1b in melanoma. As ING2 exhibits 58.9% homology with p33ING1b, we hypothesized that the aberrant expression of ING2 may be involved in melanomagenesis. Here, we used tissue microarray technology and immunohistochemistry to examine ING2 expression in human nevi and melanoma biopsies. Our data showed that nuclear ING2 expression was significantly reduced in radial growth phase (RGP), vertical growth phase (VGP), and metastatic melanomas compared with dysplastic nevi (P < 0.05). Our data also revealed that nuclear ING2 expression was not associated with patient's gender, age or tumour thickness, ulceration, American Joint Committee on Cancer (AJCC) stage, tumour subtype, location and 5-year survival (P > 0.05). Taken together, our results suggest that nuclear ING2 expression is significantly reduced in human melanomas and that reduced ING2 may be an important molecular event in the initiation of melanoma development.

Loss of claudin-1 expression in tumor-associated vessels correlates with acquisition of metastatic phenotype in melanocytic neoplasms

Claudins are a family of transmembrane proteins involved in cell-to-cell adhesion and are believed to be the main component of tight junctions. Recent studies have suggested that some metastatic solid tumors lack claudin expression. It is unknown whether claudins play a role in cutaneous melanoma. Immunohistochemical studies were performed on tissue microarrays containing 19 benign melanocytic nevi (BN), 21 dysplastic nevi (DN), 23 primary malignant melanomas (MMs), and 31 metastatic melanomas (MMMs) using a polyclonal anti-claudin-1 antibody. Immunoreactivity in tumor cells and associated vessels was graded by intensity and by percentage of reactive cells. Normal epidermis served as internal control (3+ labeling). Cases with at least 2+ labeling in more than 25% of the cells were considered positive. Claudin-1 expression was present in 37% of BN, 24% of DN, 26% of MM, and 3.2% of MMM. Tumor-associated vessels showed the following results: 11 of 19 (58%) in BN, 14 of 21 (67%) in DN, 17 of 23 (74%) in MM, and 6 of 31 (19%) in MMM. A significant loss of expression was noted between MMM and all other lesions in tumor cells and associated vessels. There was no significant difference between BN, DN, and MM. Within primary melanomas, there was a significant correlation between expression of claudin in tumor cells and Clark level/Breslow thickness. Also significant was a decreased expression of claudin in tumor vessels of lesions with higher Breslow thickness or Clark level. These data suggest that loss of claudin-1 may play a significant role in the acquisition of metastatic phenotype in cutaneous melanoma. Cohn ML, Goncharuk VN, Diwan AH, Zhang PS, Shen SS, Prieto VG. Loss of claudin-1 expression in tumor-associated vessels correlates with acquisition of metastatic phenotype in melanocytic neoplasms.

Survivin protein in UVB induced apoptosis of melanoma cells and in melanoma progression

A model system of cultivated melanoma cells and melanomas from patients were used in this study to clarify whether survivin protein was involved in UVB induced cell damage and in melanoma progression. The melanoma cells in culture were exposed to different doses of UVB and post-cultivated for various periods of time. Cell viability, apoptotic index and expression of survivin proteins were estimated. Expression of the survivin in normal tissue, nevi, primary and metastatic melanomas from the patients were also examined by immunohistochemistry. Results showed that UVB induced cell damage and apoptosis in melanoma cells. Primary and wt p53 cells were more sensitive than metastatic and mutant p53 melanoma cells. Expression of survivin protein was markedly decreased in the primary melanoma cells after exposure to UVB compared to the metastasis. The expression was markedly decreased in wt p53 melanoma cells, but not in the mutant p53 melanoma cells. Survivin protein was expressed in nevi, primary and metastatic melanomas. However, the normal tissues were not expressed in the survivin protein. Survivin plays an important role in UVB-induced apoptosis. Overexpression of survivin might be a biomarker for early diagnosis for melanoma.

Prognostic significance of activated Akt expression in melanoma: a clinicopathologic study of 292 cases

PURPOSE

Akt is a serine/threonine kinase that leads to stimulation of cell cycle progression, cell proliferation, and inhibition of apoptosis. To investigate the role of Akt in melanoma pathogenesis, we examined the expression of phospho-Akt (p-Akt; Ser-473) in melanocytic lesions at different stages and analyzed the correlations between the p-Akt expression level and clinicopathologic factors and patient survival.

PATIENTS AND METHODS

We evaluated the p-Akt expression in 12 cases of normal nevi, 58 cases of dysplastic nevi, 170 cases of primary melanomas, and 52 cases of melanoma metastases using tissue microarray and immunohistochemistry.

RESULTS

Strong p-Akt expression was observed in 17%, 43%, 49%, and 77% of the biopsies in normal nevi, dysplastic nevi, primary melanoma, and melanoma metastases, respectively. Significant differences for p-Akt staining pattern were observed between normal nevi and primary melanomas (P < .05), and between primary melanomas and melanoma metastases (P < .001). Furthermore, our Kaplan-Meier survival curves showed that strong p-Akt expression is inversely correlated with both overall and disease-specific 5-year survival of patients with primary melanoma (P < .05 for both). Strikingly, our multivariate Cox regression analysis revealed that p-Akt is an independent prognostic factor in low-risk melanomas (thickness < or = 1.5 mm; relative risk, 6.44; 95% CI, 1.28 to 32.55; P = .018).

CONCLUSION

The expression of p-Akt increases dramatically with melanoma invasion and progression and is inversely correlated with patient survival. In addition, p-Akt may serve as an independent prognostic marker and help to identify those patients with low-risk melanomas who are at increased risk of death.

Ectopic expression of tyrosinase increases melanin synthesis and cell death following UVB irradiation in fibroblasts from familial atypical multiple mole and melanoma (FAMMM) patients

Patients with familial atypical multiple mole and melanoma (FAMMM) [so-called familial dysplastic naevus syndrome (FDNS)] have a high risk for the development of malignant melanoma. The underlying gene defect has an autosomal dominant inheritance with variable expression and incomplete penetrance. Fibroblasts derived from FAMMM patients have high sensitivity to UVC and mutagens, e.g. 4-nitroquinoline-1-oxide. We were interested in identifying how the combination of inherent sensitivity to UV light and abnormal melanin synthesis interacts in the development of melanoma in FAMMM patients. Intermediates of melanin synthesis produce free radicals that are toxic to cells. Atypical moles (dysplastic naevi) are engaged in the biosynthesis of abnormal melanin pigments. This study examined whether there was any abnormal melanin pigmentation or cell damage after the ectopic expression of tyrosinase in fibroblasts from FAMMM patients when compared with fibroblasts from normal subjects. Fibroblasts from FAMMM patients (3012T and 3072T) were associated with a higher sensitivity than normal human fibroblasts to the toxicity of UVB. When cells were infected with tyrosinase-expressing adenovirus (Ad-HT) and irradiated with UVB, FAMMM fibroblasts showed higher tyrosinase activity, produced more melanin pigments and were degraded more significantly than normal human fibroblasts. Western blot analysis revealed that Ad-HT-infected 3072T produced a larger amount of tyrosinase protein than did Ad-HT-infected normal fibroblasts after UVB irradiation. Our findings suggest: (1) that FAMMM fibroblasts have an unknown machinery which enhances tyrosinase expression by UVB irradiation; and (2) that the resulting increase in melanin synthesis affects the cytotoxicity of UVB to FAMMM fibroblasts. All of these processes may be involved in the genomic instability and development of melanoma in FAMMM patients.

Expression of insulin-like growth factor-binding protein 2 in melanocytic lesions

BACKGROUND

Insulin-like growth factor-1 (IGF-1) is one of the most critical proteins required for the survival, migration, and growth of melanoma cells. IGF-binding protein 2 (IGFBP2), which binds and regulates the function of IGF-1, is upregulated in a dose-dependent manner in melanoma cells treated with IGF-1, suggesting a possible role of IGFBP2 in the pathogenesis of melanoma.

METHODS

Tissue microarrays were constructed using formalin-fixed, paraffin-embedded archival tissue blocks from 94 melanocytic lesions: 20 benign nevi, 20 dysplastic nevi, 23 primary melanomas, and 31 metastatic melanomas. IGFBP2 expression was evaluated immunohistochemically using a polyclonal antibody against the C-terminus of IGFBP2. The number of cells and labeling intensity were assessed semiquantitatively.

RESULTS

Positive IGFBP2 labeling was observed in 5.0% of benign nevi, which was significantly lower than in dysplastic nevi (35.0%), primary melanomas (52.2%), or metastatic melanomas (54.8%) (p < 0.05). Among the IGFBP2-positive cases, moderate-to-strong immunostaining was observed in 64.7% of metastatic melanomas and 33.3% of primary melanomas. But none of the dysplastic nevi had moderate-to-strong immunostaining (p < 0.05).

CONCLUSIONS

Our study shows that IGFBP2 expression increases from benign and dysplastic nevi to primary and metastatic melanomas and suggests that it may play a role in melanoma progression.

Disturbed melanin synthesis and chronic oxidative stress in dysplastic naevi

Dysplastic naevi (DN) are a known risk factor for malignant melanoma. Their occurrence is closely connected with the degree of skin pigmentation. People with a light complexion are more likely to develop DN than dark-skinned individuals. We examined the proposition that DN exhibit altered melanin formation, which may be involved in their malignant transformation. X-ray microanalysis was used to study the composition of melanosomes from DN and to compare the results with those obtained from melanomas, banal (dermal) naevi and normal cutaneous melanocytes. We analysed sulphur (an indicator of phaeomelanin) and two metals, iron and calcium, involved in oxidative stress. FACS analysis of dihydrorhodamine-123-labelled cells was employed to quantify differences in the production of radical oxygen species in DN cells and normal skin melanocytes. A significantly higher sulphur content was found in melanosomes from DN cells and melanoma cells when compared with normal melanocytes and naevus cells from banal naevi. In addition, melanosomes of DN cells and melanoma cells contained higher amounts of iron and calcium. In the case of calcium, this was associated with a significantly elevated cytoplasmic concentration. FACS analysis showed that DN cells exhibited higher concentrations of radical oxygen species than normal skin melanocytes from the same individuals. We propose that increased phaeomelanogenesis in DN cells is connected with oxidative imbalance, which is reflected by increased intracellular concentrations of reactive oxygen species and raised calcium and iron concentrations. We show that the metabolic alterations in DN cells resemble those found in melanoma cells. Our findings provide support for the idea that DN cells are true precursor lesions of melanoma.

Expression of the proteoglycans versican and mel-CSPG in dysplastic nevi

Nevi with architectural disorder and cytologic atypia of melanocytes (NAD) (also called dysplastic nevi) have been controversial with regard to their relationship with melanoma risk and to their gradation in 3 degrees of atypia. Versican and the melanoma-associated proteoglycan (mel-CSPG) are 2 major proteoglycans expressed by malignant melanoma, and they have a role in the regulation of cell adhesion, migration, and differentiation. We evaluated the differences in versican and mel-CSPG expression in nevi, NAD with several degrees of atypia, and primary malignant melanoma. Immunoreactivity for versican was negative in benign melanocytic nevi, positive in NAD (ranging from weakly to intensely positive), and intensely positive in malignant melanoma. Immunostaining for mel-CSPG was negative in benign melanocytic nevi and mild to moderately positive in NAD and melanoma. Our results suggest that versican expression may be of value for distinguishing NAD from benign melanocytic nevi and for distinguishing severe NAD from mild and moderate NAD.

Immunohistochemical expression of vascular endothelial growth factor, matrix metalloproteinase 2, and matrix metalloproteinase 9 in cutaneous melanocytic lesions

BACKGROUND

Vascular endothelial growth factor (VEGF), an endothelial cell mitogen, plays a hierarchical role in regulating physiologic and pathologic angiogenesis. Moreover, the transformation from noninvasive to invasive carcinomas is accompanied by focal disruption and discontinuity of the basement membrane. Several groups of proteases have been implicated in tumor cell invasion, including the 72-kDa gelatinase A/Type IV collagenase (matrix metalloproteinase 2 [MMP-2]) and the 92-kDa gelatinase B/Type IV collagenase (MMP-9).

METHODS

The authors assessed the immunohistochemical expression of VEGF and metalloproteinases MMP-2 and MMP-9 in paraffin embedded biopsy specimens of malignant melanomas (18 invasive melanomas and 10 in situ melanomas); dysplastic nevi with architectural disorder and cytologic atypia of melanocytes; Spitz nevi; and compound or predominantly intradermal, ordinary, benign melanocytic nevi.

RESULTS

Strong cytoplasmic staining for VEGF was observed in melanoma cells in as many as 77% of primary invasive melanomas, whereas only 25% of the in situ melanomas exhibited a detectable immunoreactivity for VEGF. It is interesting to note that no immunoreactivity was shown by any nevi; Spitz nevi, in particular, showed negative immunoreactivity to VEGF. Invasive melanomas and in situ melanomas displayed coexpression of MMP-2 and MMP-9, although to a variable extent. In particular, high MMP-2 staining was observed in 14 of 18 invasive melanomas; moreover, strong MMP-2 expression also was observed in 60% of in situ melanomas, whereas the residual 40% of those melanomas showed a moderate level of positivity.

CONCLUSIONS

On the basis of the current data showing that malignant melanocytic tumors displayed strong VEGF expression, whereas benign melanocytic proliferations showed no immunoreactivity for VEGF, VEGF also may be used as a discriminating factor to distinguish malignant melanoma from lesions of uncertain histology.

Spitz naevi may express components of the plasminogen activation system

The plasminogen activation (PA) system is involved in the process of invasion and metastasis. Its major components are urokinase (uPA) and tissue-type plasminogen activator (tPA), plasminogen activation inhibitor type 1 and 2 (PAI-1 and PAI-2) and a receptor for urokinase (uPAR). In this study, the expression of plasminogen activation components in Spitz naevi was compared with that in common and dysplastic naevi on the one hand and primary cutaneous melanomas on the other. Spitz naevi had melanocytic positivity for uPA in 0% (0/36), tPA in 30% (6/20), PAI-1 in 10% (3/35), PAI-2 in 40% (8/21) and uPAR in 60% (13/21) of cases. This far exceeded the expression found in common (n = 25) and dysplastic (n = 15) naevi, which only showed melanocytic positivity for PAI-2 (20% and 15% respectively) and in one dysplastic naevus also for uPAR. This was much (for most components significantly) less than the proportion of primary melanomas with tumour cell positivity, which was 30% (11/38) for uPA, 80% (19/24) for tPA, 75% (28/38) for PAI-1, 80% (19/24) for PAI-2 and 80% (19/24) for uPAR. The main findings of this study are that Spitz naevi, firstly, may express plasminogen activator (tPA), inhibitors and the receptor of the PA system, but in a much smaller proportion than cutaneous melanomas; and secondly, do not express urokinase, whereas some of the melanomas do. uPA positivity may therefore be suggestive of melanoma. However, overlapping staining results imply that the PA system has limited value in the differential diagnosis between Spitz naevus and primary melanoma. As serine protease components are expressed, Spitz naevi may use this proteolytic machinery to accomplish matrix degradation, although in a more restricted, possibly transient manner than melanomas.

Molecular aspects of melanocytic dysplastic nevi

Melanocytic dysplastic nevi were first described in both patients and their relatives who had one or several cutaneous malignant melanomas. Most of these dysplastic lesions are biologically stable, but some of them have severe histological atypia and can progress further to melanomas. Although several studies have suggested the etiological importance of dysplastic nevi in the development of melanomas, comprehensive reviews of the molecular changes in these dysplastic lesions are still scarce. To remedy this issue, this article analyzes the available molecular information about dysplastic nevi and provides the current state of knowledge regarding the karyotypic abnormalities of the melanoma/dysplastic nevus trait and the involvement of allelic loss, tumor suppressor genes, mismatch repair proteins, microsatellite instability, oncogenes, extracellular matrix proteins, and growth factors in the genesis of these lesions. These studies suggest that although some of these lesions represent "genetic dead-ends," others represent intermediate lesional steps in the melanoma tumorigenesis pathway.

HDM2 protein overexpression, but not gene amplification, is related to tumorigenesis of cutaneous melanoma

We investigated the role of alterations of HDM2, the human homologue of murine mdm2, in the tumorigenesis and progression of cutaneous melanoma. A well-characterized cohort of 172 cases representing different points in the spectrum of melanocyte transformation (16 dysplastic nevi, 11 melanomas in situ, 107 invasive primaries, and 38 metastatic lesions), as well as 11 human melanoma cell lines were examined by immunohistochemistry and Western blotting for HDM2 protein expression, and by either Southern blotting (SB) or fluorescence in situ hybridization for HDM2 gene amplification. HDM2 overexpression, defined as >20% tumor cells showing nuclear immunoreactivity, was observed in 1 of 16 (6%) dysplastic nevi, 3 of 11 (27%) melanomas in situ, and 81 of 145 (56%) invasive primary and metastatic melanomas. Comparable frequencies of HDM2 overexpression were observed among invasive primary cases with differing tumor thicknesses as well as among the metastatic cases: 21 of 40 (53%) at < or =1.5 mm; 31 of 50 (62%) at 1.6-3.9 mm; 10 of 17 (58%) at >4 mm; and 19 of 38 (50%) metastases. HDM2 amplification was observed in 1 of 88 (1%) primary cases using fluorescence in situ hybridization, and in 0 of 12 (0%) metastatic cases that overexpressed HDM2 using SB. Melanoma cell lines expressed HDM2 protein, but there was no evidence of amplification by SB. Our data suggest that HDM2 protein overexpression is common in invasive and metastatic melanoma. Observing HDM2 overexpression in noninvasive melanoma suggests that expression of this oncogene may play an early role in melanocyte transformation. HDM2 amplification occurs infrequently, and other mechanisms that up-regulate HDM2 expression are under investigation.

Alterations of mismatch repair protein expression in benign melanocytic nevi, melanocytic dysplastic nevi, and cutaneous malignant melanomas

Immunoperoxidase-staining methods were used to examine the expression of hMLH1, hMSH2, and hMSH6 mismatch repair (MMR) proteins in 50 melanocytic lesions. Microsatellite instability (MSI), screened previously in these lesions by polymerase chain reaction-based microsatellite assay, showed low-level microsatellite instability (MSI-L) in 11 of 22 melanocytic dysplastic nevi (MDN) and two of nine primary cutaneous malignant melanomas (CMMs) but not in the benign melanocytic nevi (BN). Mismatch repair proteins were widely expressed in the epidermis and adnexal structures. All lesions showed positive immunoreactivity with a gradual decrease in the MMR staining values during the progression from BN to MDN to CMMs. The average percentage of positively (PP) stained cells for hMLH1, hMSH2, and hMSH6 in BN was 85.50 +/- 1.95, 77.90 +/- 4.50, and 87.11 +/- 1.85, respectively. The PP cell values in CMMs were significantly reduced as compared with BN (75.22 +/- 3.57, p= 0.01; 56.11 +/- 8.73, p= 0.02; 65.22 +/- 6.47, p = 0.0002 for hMLH1, hMSH2, and hMSH6, respectively). No comparable significant difference was found between microsatellite stable and MSI-L lesions (p = 0.173, p = 0.458, and p = 0.385), suggesting a lack of correlation between MMR expression and MMR function. There was a direct correlation between PP cell values of hMSH2 and hMSH6 (R = 0.39, p = 0.008), implying that their expression could be regulated by a common mechanism. Thus, an important finding of these studies was the reduction of MMR protein levels in CMMs; whether this reflects underlying genetic or epigenetic mechanisms is still to be determined.

Cyclin D1 expression in dysplastic nevi: an immunohistochemical study

OBJECTIVE

We previously surveyed cyclin D1 expression in common acquired nevi, Spitz nevi, and malignant melanomas and reported that benign nevi maintain a zonal pattern of cyclin D1 expression, in contrast with malignant melanomas. Our aim was to extend those observations by examining cyclin D1 expression in dysplastic nevi.

METHODS

Cyclin D1 overexpression in 23 dysplastic nevi was detected by an immunohistochemical technique. The extent of atypia of the nevi was graded as mild, moderate, or severe, using previously established criteria.

RESULTS

Cyclin D1 overexpression in dysplastic nevi maintained a zonal pattern, similar to Spitz nevi. Cyclin D1 overexpression was greatest in the region of the epidermal-dermal junction and was significantly less prominent in the papillary and reticular dermis, suggesting that cyclin D1 expression is under cell control and correlates with maturation of nevus cells. Cyclin D1 overexpression also correlated with cytologic atypia, as dysplastic nevi with moderate or severe cytologic atypia contained a greater percentage of cyclin D1-positive cells than did nevi with mild atypia. Six dysplastic nevi with many cyclin D1--positive cells were assessed by fluorescence in situ hybridization studies using cyclin D1--specific and chromosome 11 centromeric probes. In all cases, there was no evidence of 11q13 translocation, amplification, or trisomy of chromosome 11.

CONCLUSIONS

Cyclin D1 may be involved in the pathogenesis of dysplastic nevi. Cyclin D1 overexpression does not appear to be explained by cyclin D1 locus amplification or translocation in most cases, and it may be a result of other cell abnormalities that up-regulate the protein level of cyclin D1.

A distinctive melanocytic lesion associated with melanoma-prone dysplastic naevus syndrome: the hybrid naevus

Clinically and histologically, the concept of dysplastic nevi remains controversial. To elaborate more precise criteria for the nevi of patients with dysplastic naevus syndrome (DNS), we examined 58 nevi from seven DNS patients who developed one or several malignant melanomas. Clinical presentation and histomorphology were evaluated, and immunohistochemistry was performed using proliferation marker Ki-S5 and antibody DO-7 to the p53 protein. Sixty nevi from individuals without history of melanoma served as controls. Of the DNS nevi, 21 (36.2%) exhibited no morphological particularities. The remaining 37 nevi presented distinctive histological features consisting of a slight epidermal acanthosis, spitzoid vertically oriented nests of dyscohesive nevus cells, and single-standing atypical melanocytes in the basal cell layer of the epidermis. Immunohistochemical analysis revealed an average proliferation index of 2.5%, which significantly surpassed the mean growth fraction of conventional dysplastic nevi (<1%). No increase in p53 expression was observed. Characteristically, active proliferation was found in junctional single-standing melanocytes with or without nuclear atypia rather than in nest-shaped compounds. In conclusion, certain moles of patients with DNS possess distinctive features. The newly characterized criteria may provide a basis for the diagnosis of DNS and might help to identify patients at increased risk for malignant melanoma by examination of a single biopsy.

Micro-anatomy related antigen expression in melanocytic lesions

The in situ expression of antigens associated with melanosomes (gp-100), pigmentation (PAA), tyrosinase (TRP-1), melanoma (MAA-1/MAA-2), and HLA-DR was investigated immunohistochemically in frozen archival specimens of common acquired melanocytic naevi, in dysplastic melanocytic naevi, and in lymph node metastases of melanoma. Expression of these antigens was also studied in established cultured normal human melanocytes, naevus-derived melanocytes and melanoma cell lines of varying metastatic potential, by immunohistochemistry and flow cytometry. Compared with normal melanocytes, melanocytic naevi exhibited increased expression of gp-100, PAA, and TRP-1 in the lesional cells at or very near the dermo-epidermal junction, but with diminishing expression towards the intra-dermal base of the lesions. In contrast, expression of MAA-1 and MAA-2 was observed in melanocytes throughout the dermal part of the naevi. Melanocytes located at the basal layer of the epidermis were positive only for gp-100, PAA, and TRP-1 antigens. Dysplastic melanocytic naevi showed staining of gp-100, PAA, TRP-1, HLA-DR, MAA-1, and MAA-2 of junctional lesional melanocytes, but less intense than that of common acquired naevi. These antigens were not detectable in the dermal part of the dysplastic naevi. Expression of these antigens in lymph node metastases of melanoma was either positive or negative. Similar results regarding antigen expression were observed in all cultured melanocytic cells, both by immunohistochemistry and by flow cytometry. The present data suggest that analysis of these antigens may contribute to the discrimination of common acquired melanocytic naevi from their dysplastic counterparts. Furthermore, variations in the levels of expression in naevi may be consistently related to the micro-anatomy of the lesions, indicating that the micro-environment may have an influence on the expression levels of these antigens in different lesional melanocytes.

Mutagen sensitivity in common cutaneous malignant melanoma and dysplastic naevus syndrome

Sunlight (ultraviolet radiation) has been identified as the major environmental risk factor for the development of cutaneous malignant melanoma and dysplastic naevi. This is, however, not sufficient to explain all melanoma cases. In recent years much emphasis has been given to genetic susceptibility to melanoma. A biomarker of susceptibility to environmentally related cancer is mutagen sensitivity. This is measured as the number of chromatid breaks in lymphocytes which are exposed to bleomycin in the G2 phase of the cell cycle. It has been described that patients with common melanoma show an increased mutagen sensitivity compared with controls. In the present study mutagen sensitivity was measured in 10 dysplastic naevus syndrome patients and compared with that in 11 patients with common melanoma. We found similar results for common melanoma patients as have been reported earlier: a relatively high mean breaks per cell value (0.93 +/- 0.31). In contrast, melanoma patients with dysplastic naevi showed a significantly (P<0.01) lower mutagen sensitivity value (0.46 +/- 0.34). This phenomenon was even more pronounced when only hereditary dysplastic naevi patients (one or more family members with dysplastic naevi) were considered (n = 5; 0.24 +/- 0.05). These results suggest a difference in the initiation of the carcinogenic process in melanoma with a dysplastic naevus as a precursor and melanoma without dysplastic naevi.

Alterations in cadherin and catenin expression during the biological progression of melanocytic tumours

AIMS

Compelling evidence from cell culture studies implicates cadherins in the neoplastic progression of melanocytic tumours but few reports describe the expression of cadherins and the related transmembrane proteins, catenins, in a full range of benign and malignant excised melanocytic tumours.

METHODS

Using immunohistochemistry and western blotting after tissue fractionation, the pattern of expression of cadherins/catenins was studied in a range of surgically excised melanocytic tumours, from dysplastic naevi to stage III cutaneous metastatic malignant melanoma.

RESULTS

Appropriate membranous expression of E-cadherins and P-cadherins is seen in dysplastic naevocytes with an epithelioid phenotype and is largely maintained with malignant transformation to radial growth phase melanoma and primary vertical growth phase malignant melanoma. Loss of membranous E-cadherin is seen in a small number of vertical growth phase melanomas only when metastasis has occurred. However, there is a concomitant dramatic loss of membranous P-cadherin expression in all melanomas at the same stage. A minority of metastatic melanomas show de novo membranous N-cadherin expression in comparison with dysplastic naevi and primary melanoma. Membranous expression of the desmosomal cadherin, desmoglein, was not seen in any tumour studied. Frequently, beta catenin is aberrantly produced in the cytoplasm of cells in dysplastic naevi and metastatic malignant melanoma, with an implied compromise to adhesive function. Furthermore, membranous gamma catenin expression was not seen in any of the 70 melanocytic tumours studied, implying obligatory transmembrane binding of cadherins to beta catenin for maintenance of adhesive function.

CONCLUSIONS

The most important alterations in membranous cadherin and catenin expression are seen late in the biological progression of melanocytic tumours at the stage of "in transit" or regional lymph node metastasis, with implications for tumour growth, invasion, and dissemination.

Benign nevus cell aggregates in the thymus: a case report

Aggregates of benign nevus cells occurring in lymph nodes are a well-described incidental finding. Nevus cell aggregates (NCAs) can mimic foci of metastatic carcinoma or other disease processes, so the surgical pathologist should be familiar with this lesion. The purpose of this report is to describe the potential diagnostic difficulties created by benign NCAs within the thymus of a 32-year-old man with dysplastic nevus syndrome and malignant melanoma involving mediastinal lymph nodes and the right lung. Morphologically, the NCAs in this case elicited the differential diagnoses of metastatic melanoma and thymoma. Immunohistochemical studies helped to establish the correct diagnosis by demonstrating reactivity for S-100 protein and negative staining for keratin and HMB-45. Unlike malignant melanomas, NCAs show no p53 protein immunoreactivity, and low proliferative activity was detected by Ki-67 antigen immunostaining. Although melanocytic cells were rarely reported in thymic neoplasms, we are not aware of any previous reports of NCAs occurring in the normal thymus.

Melanoma development in relation to non-functional p16/INK4A protein and dysplastic naevus syndrome in Swedish melanoma kindreds

The CDKN2A gene encodes the cell cycle inhibitor p16/ INK4A, which is involved in familial cutaneous melanoma. We have studied five Swedish familial melanoma kindreds characterized by germline mutations in CDKN2A and dysplastic naevus syndrome (DNS). We found significant correlations between germline CDKN2A mutations and melanoma and between DNS phenotype and melanoma, respectively. There was also a correlation between mutation status and the presence of DNS. In CDKN2A mutation carriers, all cases of early-onset melanoma occurred in DNS individuals, and the mean age at melanoma diagnosis was significantly lower in individuals with DNS than in those without a confirmed DNS phenotype. In one family where the proband had a P48L mutation in CDKN2A exon 1, the DNS phenotype was studied in detail. In vitro binding experiments established that the P48L mutant protein does not bind to cdk4 or cdk6 and thus is functionally abnormal. Furthermore, we demonstrated loss of heterozygosity at markers on chromosome 9p flanking the CDKN2A locus in a primary melanoma and a metastasis from the proband. Our results are consistent with the hypothesis that germline CDKN2A mutations and DNS both contribute to the predisposition to melanoma and may lead to the development of early-onset melanoma when present in the same individual.

CD44 and variants in melanocytic skin neoplasms

Expression of cell surface molecules that mediate cell-matrix and cell-cell interactions largely contributes to the ability of melanoma cells to migrate and spread beyond the primary site of the tumor. CD44, the principal cell-surface receptor for hyaluronate, and its numerous splice variants have been reported to play a crucial role in invasion and the metastatic process of different human neoplasms, including primary malignant melanoma (PMM). The aim of this study was to clarify which isoforms of CD44 (standard CD44 and CD44 variants) are distributed in PMM with a vertical tumor thickness of >1.4 mm. Staining of CD44 standard (CD44s) and splice variants was further examined for diagnostic and prognostic relevance in a panel of melanocytic skin lesions. Ten cases of PMM with Breslow >1.4 mm were analysed by immunohistochemistry using monoclonal antibodies specific for CD44s and the splice variants v3, v5, v6, v7, v7-8, and v10. In addition, using anti-CD44s, v5, and v6 antibodies, 55 melanocytic lesions, including dermal nevi (n=12), Clark nevi (dysplastic nevi) (CN; n=11), melanoma in situ (Mis; n=8), PMM (n=18), and cutaneous metastasis of malignant melanoma (cMMM; n=6) were assessed. Staining intensities were scored visually and evaluated by means of a staining index. In ten cases of PMM with a Breslow index >1.4 mm positive staining was ascertained for CD44s, v5 and for v6 in three cases. No staining was found for v3, v7, v7-8, and v10. Examination of CD44s, v5, and v6 in 55 melanocytic skin lesions revealed a high index for CD44s in all specimens and a weak staining of v5 in Mis; dermal nevi and CN did not stain for v5. However, in PMM and cMMM we found v5 to be strongly positive. The isoform v6 showed a variable index only in PMM, but without connection to established prognostic criteria. We conclude that CD44s and splice variants can not be regarded as indicators for tumor progression in malignant melanomas. However, v5 may potentially serve as a diagnostic marker for melanocytic skin lesions.

Impaired DNA repair capacity in skin fibroblasts from various hereditary cancer-prone syndromes

Host-cell reactivation (HCR) of UV-C-irradiated herpes simplex virus type 1 (HSV-1) has been determined in skin fibroblasts from the following hereditary cancer-prone syndromes: aniridia (AN), dysplastic nevus syndrome (DNS), Von Hippel-Lindau syndrome (VHL), Li-Fraumeni syndrome (LFS) and a family with high incidence of breast and ovarian cancer. Cells from AN, DNS or VHL patients were found to exhibit heterogeneity in HCR. Cells from individuals belonging to an LFS family show reduced HCR in all cases where the cells were derived from persons carrying one mutated p53 allele, whereas cells derived from members with two wild-type alleles show normal HCR. LFS cells with reduced HCR also reveal reduced genome overall repair, and a slower gene-specific repair of the active adenosine deaminase (ADA) gene, but little if any repair of the inactive 754 gene. In the breast/ovarian cancer family, reduced HCR is observed in skin fibroblasts derived from both afflicted and unaffected individuals. In addition, these cells display lower survival after exposure to UV-C and exhibit higher levels of SCEs than those in normal cells. These observations indicate that various hereditary cancer-prone syndromes, carrying mutations in different tumor-suppressor genes, exhibit an unexplained impairment of the capacity to repair UV-damaged DNA.

The neuropeptide/mast cell secretagogue substance P is expressed in cutaneous melanocytic lesions

Substance P (SP) is a neuropeptide found in both the central and peripheral nervous system. In the skin, SP-containing neurons stimulate the release of histamine from connective tissue mast cells (MC). SP also can potentiate neoangiogenesis and induce dermal fibrosis. MC-derived histamine has potent vasoactive effects, is angiogenic, and promotes tissue fibroplasia. In addition to histamine, MC contain many other angiogenic factors and a variety of cytokines, growth factors, and proteolytic enzymes implicated in tissue remodeling, and normal as well as tumor-associated neoangiogenesis. Many MC-derived factors, including histamine, can enhance melanoma cell growth directly. MC often concentrate around cutaneous melanomas which also frequently are associated with angiogenesis and peritumoral fibrosis. The precise mediators of these responses have not been well defined. We evaluated by immunohistochemistry cutaneous lesions representing stages of progression of malignant melanoma and its precursor lesions for the expression of SP. SP was expressed in 17/25 (68%) primary invasive malignant melanomas, 2/5 (40%) metastatic melanomas, 6/10 (60%) melanomas in situ, 7/12 (58%) atypical (dysplastic) nevi, and 4/10 (40%) spindle and epithelioid cell (Spitz) nevi, but was not detected in any (0/11, 0%) acquired benign melanocytic nevi (p<0.05). Invasive melanomas were immunolabeled in both the intraepidermal and the dermal components of the lesions. For those atypical and Spitz nevi which expressed SP, most of the immunoreactive melanocytes were located at the dermal-epidermal junction overlying areas of papillary dermal fibrosis. The results show differential expression of SP among cutaneous melanocytic lesions and suggest that the expression of this neuropeptide together with other factors may contribute to some of the host responses associated with these lesions.

The melanoma-specific XMEL antigen is expressed in dysplastic naevi

We have previously shown that a novel monoclonal antibody, XMEL, exhibited reactivity with deep primary melanomas while showing no reactivity with other tumours and normal tissue. XMEL was raised against a part of the extracellular domain of Xmrk, a growth factor receptor presumed to mediate melanoma formation in the Xiphophorus fish model. Here we investigate the range of XMEL immunohistochemical reactivity in paraffin sections from human common acquired and dysplastic naevi of both junctional and compound type. The strongest reactivity was observed with the compound dysplastic naevi. We conclude that the antigen recognized by XMEL acts early in the cascade of genetic alterations underlying progression into malignant melanoma. Our results also support the notion that the dysplastic naevus may play a role in progression of human malignant melanoma and may indeed represent the precursor stage.

Molecular analysis of melanoma precursor lesions

Atypical (dysplastic) nevi are melanocytic lesions, which are precursors of melanoma as well as markers of increased melanoma risk. Although these lesions exhibit distinct clinical and histological features, their molecular features are largely unknown. To determine whether atypical, compared to benign nevi, from patients with a clinical history of malignant melanoma reveal molecular changes, we analyzed these lesions for the expression of two growth factors (basic fibroblast growth factor and transforming growth factor alpha), their receptors (fibroblast growth factor receptor-1 and epidermal growth factor receptor), and two cell adhesion molecules (MUC18 and alpha v beta 3 integrin), all of which are expressed in primary and metastatic melanomas. The results demonstrated a statistically significant correlation (P = 0.02) between increasing degrees of histological atypia and expression of epidermal growth factor receptor in the epidermal keratinocytes of atypical melanocytic lesions. Furthermore, both atypical and benign nevi revealed considerably high levels of overall gene activity in their dermal melanocytic and epidermal keratinocytic compartments. In contrast, the epidermal-dermal junction wherein melanoma evolves showed little gene activity, suggesting that molecular events occurring adjacent to this junction may be important for melanocytic transformation.

Immunohistochemical analysis of the N-ras p21 and the p53 proteins in naevi, primary tumours and metastases of human cutaneous malignant melanoma: increased immunopositivity in hereditary melanoma

Immunohistochemical analysis of the N-ras p21 and the p53 proteins was carried out on formalin-fixed sections of naevi, primary melanomas and metastases from patients with sporadic melanoma (SCMM) and with hereditary melanoma (HCMM)/dysplastic naevus syndrome (DNS). Seven out of 11 (64%) common naevi and three out of nine (33%) dysplastic naevi showed increased cytoplasmic N-ras expression. No p53 immunopositivity could be recognized in any of the naevus samples. However, strong N-ras expression as well as immunopositivity for p53 was recognized among primary melanomas and metastases with significantly higher frequency among samples from patients with HCMM compared with samples from SCMM cases (for N-ras, 40% vs 10%, P < 0.01; and for p53 43% vs 17%, P < 0.05). We have earlier registered N-ras codon 61 mutations among metastases from 59% of patients with HCMM and from 24% of subjects with SCMM. A comparison of the genetic data with the immunohistochemical results showed occurrence of increased N-ras p21 expression in the presence and absence of detectable N-ras mutant alleles. Increased expression of wildtype N-ras p21 may contribute to tumorigenicity in the absence of mutational activation, at least in a subset of melanomas. Altogether, N-ras p21 alterations are registered at earlier stages than p53 alterations in melanoma development and may be of aetiological importance, whereas p53 alterations may be associated with tumour progression in the late stages.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of cathepsin D in primary and metastatic human melanoma and dysplastic nevi

High levels of cytosolic cathepsin D expression have been associated with poor prognosis in breast cancer node-negative patients. In this work, we provide evidence that three cell lines established from human metastatic melanomas--IIB-MEL-J, IIB-MEL-LES, and IIB-MEL-IAN--express high levels of procathepsin D mRNA. IIB-MEL-J cells secreted into the conditioned media about 30% of the newly synthesized protein, which was active at acidic pH. Melanoma tumors arising in nude mice after injection of the three different cell lines expressed high levels of procathepsin D mRNA. Moreover, 13 human metastatic melanomas expressed variable levels of procathepsin D mRNA. To study the possible association between cathepsin D expression and melanoma development, samples corresponding to 10 primary tumors, 11 metastatic melanomas, 10 dysplastic nevi, 27 nevocellular nevi, and normal melanocytes were studied by immunohistochemistry for cathepsin D-specific staining. We found that cathepsin D was expressed in all of the dysplastic nevi and primary and metastatic melanomas tested but in only 18% of nevocellular nevi (five of 27), whereas normal melanocytes showed no cathepsin D expression. The overall data indicate that cathepsin D is expressed at a high level by melanoma cells, and because of its expression in preneoplastic lesions, it may be associated with melanoma development.

Nucleolar organizer regions (AgNOR) and Ki-67 immunoreactivity in cutaneous melanocytic lesions

A stepwise schema for the developmental biology of malignant melanomas has been proposed. In this study, two properties associated with malignant transformation--AgNOR production and Ki-67 immunoreactivity--were tested on a series of lesions representative of this model. Fourteen ordinary nevi (N), seven dysplastic nevi (DN), 12 radial growth phase melanomas (RGPM), and eight vertical growth phase melanomas (VGPM) were stained for AgNORs; Ki-67 immunoreactivity was determined in paraffin sections after antigen retrieval. AgNORs averaged 2.1 in N, 3.8 in DN, 5.4 in RGPM, and 7.3 in VGPM (p < 0.001 between all groups). Ki-67 immunoreactivity averaged < 1 in nevi, 1.6 in dysplastic nevi, 23.3 in RGPM, and 20.1 in VGPM. No difference was observed between N and DN, and RGPM/VGPM had higher Ki-67 indices than N/DN (p < 0.01). Stepwise increases in cellular AgNORs parallel the melanocytic progression model and thereby corroborate the intermediate nature of the dysplastic nevus. The order of magnitude increase in Ki-67 immunoreactivity observed in RGP and VGP melanomas compared with N and DN likely reflects the onset of loss of cell cycle control in these lesions.