Malignant melanoma arising from nevi, p53, p16, and Bcl-2: expression in benign versus malignant components

The Complex Interplay between Nevi and Melanoma: Risk Factors and Precursors

One effort to combat the rising incidence of malignant melanoma is focused on early detection by the clinical and dermoscopic screening of melanocytic nevi. However, the interaction between nevi, which are congenital or acquired benign melanocytic proliferations, and melanoma is still enigmatic. On the one hand, the majority of melanomas are thought to form de novo, as only a third of primary melanomas are associated with a histologically identifiable nevus precursor. On the other hand, an increased number of melanocytic nevi is a strong risk factor for developing melanoma, including melanomas that do not derive from nevi. The formation of nevi is modulated by diverse factors, including pigmentation, genetic risk factors, and environmental sun exposure. While the molecular alterations that occur during the progression of a nevus to melanoma have been well characterized, many unanswered questions remain surrounding the process of nevus to melanoma evolution. In this review, we discuss clinical, histological, molecular, and genetic factors that influence nevus formation and progression to melanoma.

Immunohistochemical Expression of p16 in Melanocytic Lesions: An Updated Review and Meta-analysis

CONTEXT

- Making an accurate diagnosis for melanocytic lesions has always been challenging for pathologists, especially when dealing with difficult-to-diagnose cases. Misdiagnosis of melanoma and melanocytic lesions in general has tremendous medical-legal implications, often leading to unnecessary and excessive use of adjunctive tests. Although molecular testing is of much interest and there is great support for its development, currently, for most melanocytic lesions, immunohistochemical studies remain the most practical method for assistance in the routine diagnosis of melanocytic lesions for the average pathologist.

OBJECTIVES

- To review the practical use of p16 immunohistochemistry for evaluating melanocytic lesions, particularly for differentiating benign from malignant tumors, and to perform a meta-analysis of primary studies evaluating p16 immunohistochemistry in melanocytic lesions.

DATA SOURCES

- A PubMed database search for literature reporting melanocytic lesions and p16 immunohistochemistry was performed. Essential information from each study (number of samples, antibody used, collection dates, overall p16 immunohistochemistry results, and general method of interpretation) was tabulated and analyzed. Examples of representative cases showing p16 immunostaining pattern are also illustrated.

CONCLUSIONS

- Incorporation of p16 immunohistochemistry for the diagnosis of melanocytic lesions is of limited use, especially for the purpose of differentiating benign from malignant lesions. Evaluation of multiple studies reveals a wide range of results. However, there appears to be some value for the use of p16 in distinguishing nodal nevi from metastatic melanoma within nodes. The method of interpretation (nuclear versus cytoplasmic staining) also appears to give differing results, as studies considering only nuclear staining appeared to show more consistent results from study to study.

Melanocytic nevi and melanoma: unraveling a complex relationship

Approximately 33% of melanomas are derived directly from benign, melanocytic nevi. Despite this, the vast majority of melanocytic nevi, which typically form as a result of BRAF^V600E-activating mutations, will never progress to melanoma. Herein, we synthesize basic scientific insights and data from mouse models with common observations from clinical practice to comprehensively review melanocytic nevus biology. In particular, we focus on the mechanisms by which growth arrest is established after BRAF^V600E mutation. Means by which growth arrest can be overcome and how melanocytic nevi relate to melanoma are also considered. Finally, we present a new conceptual paradigm for understanding the growth arrest of melanocytic nevi in vivo termed stable clonal expansion. This review builds upon the canonical hypothesis of oncogene-induced senescence in growth arrest and tumor suppression in melanocytic nevi and melanoma.

Atypical Spitzoid neoplasms: a review of potential markers of biological behavior including sentinel node biopsy

Atypical cutaneous melanocytic lesions, including those with Spitzoid features, can be difficult to categorize as benign or malignant. This can lead to suboptimal management, with potential adverse patient outcomes. Recent studies have enhanced knowledge of the molecular and genetic biology of these lesions and, combined with clinicopathological findings, is further defining their biological spectrum, classification, and behavior. Sentinel node biopsy provides important prognostic information in patients with cutaneous melanoma, but its role in the management of melanocytic lesions of uncertain malignant potential (MELTUMP) is controversial. This paper examines the role of molecular testing and sentinel node biopsy in MELTUMPs, particularly atypical Spitzoid tumors.

Molecular pathology of skin neoplasms of the head and neck

CONTEXT

Skin neoplasms include the most common malignancies affecting humans. Many show an ultraviolet (UV)-induced pathogenesis and often affect the head and neck region.

OBJECTIVE

To review literature on cutaneous neoplasms that show a predilection for the head and neck region and that are associated with molecular alterations.

DATA SOURCES

Literature review.

CONCLUSIONS

Common nonmelanoma skin cancers, such as basal and squamous cell carcinomas, show a UV-induced pathogenesis. Basal cell carcinomas are characterized by molecular alterations of the Hedgehog pathway, affecting patched and smoothened genes. While squamous cell carcinomas show UV-induced mutations in several genes, driver mutations are only beginning to be identified. In addition, certain adnexal neoplasms also predominantly affect the head and neck region and show interesting, recently discovered molecular abnormalities, or are associated with hereditary conditions whose molecular genetic pathogenesis is well understood. Furthermore, recent advances have led to an increased understanding of the molecular pathogenesis of melanoma. Certain melanoma subtypes, such as lentigo maligna melanoma and desmoplastic melanoma, which are more often seen on the chronically sun-damaged skin of the head and neck, show differences in their molecular signature when compared to the other more common subtypes, such as superficial spreading melanoma, which are more prone to occur at sites with acute intermittent sun damage. In summary, molecular alterations in cutaneous neoplasms of the head and neck are often related to UV exposure. Their molecular footprint often reflects the histologic tumor type, and familiarity with these changes will be increasingly necessary for diagnostic and therapeutic considerations.

Ras, Raf, and MAP kinase in melanoma

A growing understanding of the biology and molecular mechanisms of melanoma has led to the identification of a number of driver mutations for this aggressive tumor. The most common mutations affect signaling of the Ras/Raf/MAPK (mitogen-activated protein kinase) pathway. This review will focus on mutations in genes encoding proteins that play a role in the MAPK pathway and that have been implicated in melanoma biology, such as BRAF, NRAS, and MEK (MAPK kinase), and detail the current understanding of their role in melanoma progression from a molecular biology perspective. Furthermore, this review will also consider some additional mutations in genes such as KIT, GNAQ, and GNA11, which can be seen in certain subtypes of melanoma and whose gene products interact with the MAPK pathway. In addition, the association of these molecular changes with clinical and classical histopathologic characteristics of melanoma will be outlined and their role in diagnosis of melanocytic lesions discussed. Finally, a basic overview of the current targeted therapy landscape, as far as relevant to the pathologist, will be provided.

The dysplastic nevus: from historical perspective to management in the modern era: part II. Molecular aspects and clinical management

The dysplastic nevus is a discreet histologic entity that exhibits some clinical and histologic features overlapping with common nevi and melanoma. These overlapping features present a therapeutic challenge, and with a lack of accepted guidelines, the management of dysplastic nevi remains a controversial subject. Although some differences between dysplastic and common nevi can be detected at the molecular level, there are currently no established markers to predict biologic behavior. In part II of this continuing medical education article, we will review the molecular aspects of dysplastic nevi and their therapeutic implications. Our goal is to provide the clinician with an up-to-date understanding of this entity to facilitate clinical management of patients with nevi that have histologic dysplasia.

Superficial spreading and nodular melanoma are distinct biological entities: a challenge to the linear progression model

The classification of melanoma subtypes into prognostically relevant and therapeutically insightful categories has been a challenge since the first description of melanoma in the 1800s. One limitation has been the assumption that the two most common histological subtypes of melanoma, superficial spreading and nodular, evolve according to a linear model of progression, as malignant melanocytes spread radially and then invade vertically. However, recent clinical, pathological, and molecular data indicate that these two histological subtypes might evolve as distinct entities. Here, we review the published data that support distinct molecular characterization of superficial spreading and nodular melanoma, the clinical significance of this distinction including prognostic relevance and the therapeutic implications.

Cell proliferation in cutaneous malignant melanoma: relationship with neoplastic progression

The establishment of the diagnosis of cutaneous malignant melanoma (CMM) always calls for histopathological confirmation. Further to the recognition of the CMM aspects, immunohistochemistry is helpful, in particular, in determining the size of the replicative compartment and the activity in each of the cell cycle phases (G(1), S, G(2), M). The involvement of cancer stem cells and transient amplifier cells in CMM genesis is beyond doubt. The proliferation activity is indicative of the neoplastic progression and is often related to the clinical growth rate of the neoplasm. It allows to distinguish high-risk CMM commonly showing a high growth rate, from those CMMs of lower malignancy associated with a more limited growth rate. The recruitment and progression of CMM cells in the cell cycle of proliferation depend on mitogen-activated protein kinase (MAPK) pathway and result from a loss of control normally involving a series of key regulatory cyclins. In addition, the apoptotic pathways potentially counteracting any excess in proliferative activity are out of the dependency of specific regulatory molecular mechanisms. Key molecular components involved in the deregulation of the growth fraction, the cell cycle phases of proliferation, and apoptosis are presently described in CMM.

Prognostic significance of regulators of cell cycle and apoptosis, p16(INK4a), p53, and bcl-2 in primary mucosal melanomas of the head and neck

Abnormalities in cell cycle regulation, tumor suppressor gene functions and apoptosis are frequent events in tumorigenesis. Their role in the pathogenesis and prognosis of primary mucosal melanomas (MM) of the upper aerodigestive tract remains unknown. Sixty-four patients (40 men, 24 women, median age 64 years) with MM were included in this study; 32 had tumors in the nasal/paranasal cavities, 28 in the oral cavity and 4 in the pharynx. Archival tissues from 47 initial mucosal tumors, 17 mucosal recurrences, and 13 nodal/distant metastases were subjected to immunohistochemistry using antibodies against p16, p53, and bcl-2. The results were correlated with histological features and survival data. Expressions of p16, p53, and bcl-2 proteins were seen in 25% (N=19/76), 21% (N=16/76), and 74% (N=56/76) of all tumors, respectively. bcl-2 expression in the initial tumors was associated with significantly longer overall and disease specific survival (3.3 vs. 1.5 years, P ≤ 0.05). Expression of p16 was increasingly lost, from 32% in initial tumors to 12% in recurrent and 15% in metastatic tumors (P=0.06). Tumors comprised of undifferentiated cells were significantly more p53 positive than epithelioid or spindle cells (80% vs. 33%, P=0.02). Expression of these markers did not correlate with necrosis, or vascular and/or deep tissue invasion. Expression of bcl-2 is associated with better survival in MM. Loss of p16 was seen with tumor progression whereas aberrant p53 expression was frequent in undifferentiated tumor cells.

The emerging role of the thrombin receptor (PAR-1) in melanoma metastasis--a possible therapeutic target

Melanoma remains as the deadliest form of skin cancer with limited and inefficient treatment options available for patients with metastatic disease. Within the last decade, the thrombin receptor, Protease Activated Receptor-1, has been described as an essential gene involved in the progression of human melanoma. PAR-1 is known to activate adhesive, invasive and angiogenic factors to promote melanoma metastasis. It is overexpressed not only in metastatic melanoma cell lines but is also highly expressed in metastatic lesions as compared to primary nevi and normal skin. Recently, PAR-1 has been described to regulate the gap junction protein Connexin 43 and the tumor suppressor gene Maspin to promote the metastatic melanoma phenotype. Herein, we review the role of PAR-1 in the progression of melanoma as well as utilizing PAR-1-regulated genes as potential therapeutic targets for melanoma treatment.

Maspin and Mutant p53 expression in malignant melanoma and carcinoma: use of tissue microarray

Maspin (mammary serine protease inhibitor), a member of the serpin family, has been shown to inhibit angiogenesis, tumor invasion, and metastasis. Previous studies suggest a p53-dependent regulatory pathway of maspin protein expression. Its loss correlates with progression of disease in both breast and prostate cancer. We studied the in vivo correlation of maspin expression with p53 mutation in malignant melanoma (MM) with and without use of tissue microarray (TMA). Seventy-seven MMs were immunostained on individual slides for maspin and p53 expression. Results were validated in 1 slide for each marker on a TMA system (TARP-2) with 498 tissue cores (0.6-mm diameter) from MM, other tumors, and normal tissue. The relationship between maspin and p53 in MM and carcinomas of other sites (breast, ovary, colon, lung, and prostate) was delineated using Pearson chi analysis. The inverse relationship between maspin and p53 expression predicted by hypothesized p53 regulation of maspin transcription, or any other correlation between these 2 markers, is not demonstrated in MM cases, using either classic individual slide (P=0.20) or TMA (P=0.85) methods when cutoffs for both markers are set at 10% or greater of cells staining. Even when cutoffs are altered with respect to either intensity or percentage of cells staining, no relationship is demonstrated between these markers, with either TMA or the conventional slide method. TMA immunostaining also showed no such relationship in carcinomas of the various other sites sampled-including breast and prostate, where previous studies have suggested a linkage. Despite published experimental evidence linking these 2 markers, this study failed to demonstrate correlation between maspin loss and p53 expression in MM using both individual slides and TMA, or in TMA of other carcinomas. Use of TMA is a quick, easy, and inexpensive method of immunohistochemical analysis of large numbers of cases, both to validate results obtained from individual slides and to assess specificity in a variety of neoplasms. However, heterogeneity and minimal tumor may lead to variable results.

Estudo genético do gene p16 pela técnica de PCR-SSCP e expressão de proteína p16 em melanomas de mucosa oral e melanomas cutâneos

FUNDAMENTOS: A deleção e mutação do gene CDKN2a que codifica um inibidor específico da ciclina dependente de quinase 4, a proteína p16, têm sido implicadas na tumorigênese do melanoma cutâneo. Entretanto, pouco se conhece sobre essas alterações genéticas em melanomas de mucosa oral. OBJETIVOS: Verificar a presença de alterações no gene p16 e sua expressão protéica em melanomas esporádicos orais e cutâneos. MATERIAL E MÉTODOS: Avaliaram-se 36 espécimes de melanoma primário (sete orais e 29 cutâneos). Analisaram-se três exons do gene p16, pela técnica da reação em cadeia da polimerase/polimorfismo conformacional de fita simples do DNA.Verificou-se a expressão tecidual de proteína p16 por técnica imuno-histoquímica. Relacionaram-se os resultados com a espessura dos melanomas cutâneos. RESULTADOS: Cinco dos sete melanomas orais e 17 dos 29 melanomas cutâneos apresentaram indício de alteração no gene p16. Alterações do exon 2 foram as mais freqüentes, sendo 19 casos nos produtos obtidos com o mesmo iniciador. Observou-se expressão tecidual de p16 em apenas um melanoma oral, em 10/13 (76,9%) casos de melanoma cutâneo de espessura até 1mm e em sete de oito (87,5%) casos de espessura superior a 1mm. CONCLUSÃO: A freqüência de indícios de alteração na análise genética de p16 nos melanomas de mucosa oral foi de 71,42% e de 58,6% nos cutâneos. É possível sugerir a participação de alterações do gene p16 na patogenia do melanoma esporádico de mucosa oral. Não houve relação da sugestão de alteração genética do gene p16 e de sua expressão tecidual com a espessura dos melanomas cutâneos de diferentes subtipos histológicos.

Molecular diagnostics in melanoma

Molecular pathology is rapidly evolving, featuring continuous technologic improvements that offer novel clinical opportunities for the recognition of disease predisposition, for identifying sub-clinical disease, for more accurate diagnosis, for selecting efficacious and non-toxic therapy, and for monitoring of disease outcome. Currently, the identification and prognosis of primary cutaneous melanoma is based on histologic factors (tumor depth and ulceration) and clinical factors (number of lymph node and/or distant metastases). However, metastasis can occur in patients with thin melanomas, and sentinel lymph node biopsy does not identify all patients at risk for distant metastasis. New markers exist that correlate with melanoma progression, which may aid in melanoma identification, prognostication, and detection of minimal residual disease/early recurrence. Moreover, not many therapeutic options exist for melanoma as no regimen prolongs survival. Emerging data with investigational therapies suggest that certain markers might play a crucial role in identifying patients who will respond to therapy or show utility in the monitoring the response to therapy. Herein, molecular diagnostics that can potentially benefit the individual melanoma patient will be discussed.

Hypervariabilité génotypique des mélanomas : Un défi thérapeutique

Cutaneous melanoma remains a management challenge. Melanoma is the leading cause of death from skin tumors worldwide. Melanoma progression is well defined in its clinical, histopathological and biological aspects, but the molecular mechanism involved and the genetic markers associated to metastatic dissemination are only beginning to be defined. The recent development of high-throughput technologies aimed at global molecular profiling of cancer is switching on the spotlight at previously unknown candidate genes involved in melanoma. Among those genes, BRAF is one of the most supposed to be of interest and targeted therapies are ongoing in clinical trials. In familial melanoma, germline mutations in two genes, CDKN2A and CDK4, that play a pivotal role in controlling cell cycle and division. It is hope that this better understanding of the biologic features of melanoma and the mechanisms underlying tumor-induced immunosuppression will lead to efficaceous targeted therapy.

Serum bcl-2 and survivin levels in melanoma

This study was conducted to investigate the serum levels of bcl-2 and survivin in patients with melanoma and the relationship with tumour progression and known prognostic parameters. Forty-four patients with cutaneous melanoma were investigated. Serum samples were obtained on first admission before adjuvant and metastatic treatment were given and at follow-up. Serum bcl-2 and survivin levels were determined using enzyme immunometric assay (EIA) and enzyme-linked immunosorbent assay (ELISA). The baseline serum bcl-2 levels were significantly higher in patients with melanoma than in the control group (P=0.01). For the serum survivin levels, no difference was found (P=0.6). No significant correlations were found between the prognostic parameters analysed and the serum survivin concentrations. The same was true of the serum bcl-2 values, except for the age of the patient (P=0.025) and nodal involvement (P=0.003). No significant relationship was found between the serum levels of bcl-2 and survivin (r=-0.13, P=0.4). In node-positive patients (n=8) both of these anti-apoptotic substances were unchanged after interferon-alpha-2b therapy. However, serum survivin concentrations were significantly increased in 10 patients with metastatic melanoma who underwent dacarbazine (DTIC)-based cytotoxic chemotherapy (P=0.047). A similar finding was not determined for the serum bcl-2 levels. In conclusion, the results of this study suggest that decreased apoptosis is associated partly with an increase in serum bcl-2. However, much research continues in this field, and exciting new knowledge will ultimately emerge.

Genetic progression of metastatic melanoma

Melanoma progression is well defined in its clinical, histopathological and biological aspects, but the molecular mechanism involved and the genetic markers associated to metastatic dissemination are only beginning to be defined. The recent development of high-throughput technologies aimed at global molecular profiling of cancer is switching on the spotlight at previously unknown candidate genes involved in melanoma, such as WNT5A and BRAF. In fact, several tumor suppressors and oncogenes have been shown to be involved in melanoma pathogenesis, including CDKN2A, PTEN, TP53, RAS and MYC, though they have not been related to melanoma subtypes or validated as prognostic markers. Here, we have reviewed the published data relative to the major genes involved in melanoma pathogenesis, which may represent important markers for the identification of genetic profiles of melanoma subtypes.

The role of Bcl-2 family members in the progression of cutaneous melanoma

The overwhelming problem of cutaneous melanoma is chemoresistance. Subversion of the biochemical changes that lead to chemoresistance intersects the apoptosis pathways. The mitochondrion has been a focal point of this intersection for the development of therapeutic strategies aimed at reducing the progression of melanoma. The Bcl-2 family of apoptotic regulators is arguably the most pivotal component to this mitochondrial response. The shear number of studies conducted on the relationship between melanoma and Bcl-2 members prompted us to evaluate the literature available and discern some rational utility of the data. We have found that there are striking inconsistencies for the expression of Bcl-2 family proteins with melanoma progression, particularly for Bcl-2. Roughly one-third of the data suggests an increase in Bcl-2 expression with advancing melanoma, while another third suggests a decrease. Furthermore, the remaining third found on the whole, a detectable level of Bcl-2 in all tissues of melanocytic origin. These discrepancies are difficult to rectify in light of the apparent success of recent clinical trials utilizing Bcl-2 antisense strategies. The general consensus in the literature is that pro-apoptotic Bax is decreased with melanoma progression while anti-apoptotic Bcl-xL and Mcl-1 appear to increase with progression. We suggest that the biochemical techniques being used for analysis present too great of a heterogeneity, which could be mitigated with more standard procedures and reagents. Finally the utility of 'multi-specific' antisense tactics could be a more effective way of targeting advanced melanoma disease.

Metastatic nevoid melanoma in a 41/2-year-old child

BACKGROUND

Childhood melanoma is a rare and controversial diagnosis.

METHODS

We present the case of a 4 1/2-year-old child found to have an expanding, elevated pigmented lesion on her back.

RESULTS

The biopsy showed a symmetrical, well circumscribed lesion. However, higher magnification revealed sheets of nevoid cells infiltrating deep into the dermis, lacking maturation, and exhibiting a high mitotic rate (average 5/10 high-power field) with deep mitoses. The possibility of nevoid melanoma was raised, and re-excision and sentinel lymph node (SLN) biopsy were recommended. Two SLNs were positive for melanoma, verified by immunohistochemical staining. In order to further characterize this melanoma, we performed immunohistochemistry for the tumor-suppressor p53, proliferation marker MIB-1, and oncogenes Bcl-2, cyclin D-1, and MDM-2. Staining for p53 was diffusely positive in the primary and the metastasis; MIB-1 showed moderate proliferative rate in the primary (approximately 10%); Bcl-2 was weakly positive in the primary and showed focal staining in the metastasis; cyclin D-1 was strongly positive in the primary and metastasis; and MDM-2 staining showed scattered positive cells in both lesions.

CONCLUSIONS

These findings are consistent with a metastatic nevoid melanoma arising in the absence of predisposing disease in a young child, a distinctly unusual occurrence.

p53-related pathways and the molecular pathogenesis of melanoma

Cutaneous malignant melanoma (CMM) is a life-threatening cancer that can have a poor prognosis with high metastatic potential. Its incidence is rapidly increasing worldwide. Its molecular alterations involve multiple pathways, including those related to p53. Since 1981, more than 380 papers containing the terms 'p53 and melanoma' as key words in the Abstract have been published in the literature. However, in spite of these extensive investigations, a review of p53 and associated genes in CMM is still lacking. To remedy this issue, this review seeks to provide a brief overview of p53 and discuss the genes targeted along its related pathways.

Apoptosis and melanoma: molecular mechanisms

Melanoma cells can undergo self-destruction via programmed cell death, i.e. apoptosis. In these tumours, the molecular components of apoptosis include positive (apoptotic) and negative (anti-apoptotic) regulators. The former include p53, Bid, Noxa, PUMA, Bax, TNF, TRAIL, Fas/FasL, PITSLRE, interferons, and c-KIT/SCF. The latter include Bcl-2, Bcl-X(L), Mcl-1, NF-(K)B, survivin, livin, and ML-IAP. Alternatively, some molecules such as TRAF-2, c-Myc, endothelins, and integrins may have either pro- or anti-apoptotic effects. Some of these molecules are of potential therapeutic use, such as: (1) p53, which influences resistance to chemotherapy; (2) Mcl-1 and Bcl-X(L), which can override apoptosis; (3) TRAIL, which has selective fatal effects on tumour cells; (4) NF-(K)B, which when downregulated sensitizes cells to TRAIL and TNF; (5) the PITSLRE kinases, whose alteration appears to result in Fas resistance; (6) interferons, which sensitize cells to other factors; and (7) survivin and other IAPs that inhibit apoptosis. This review summarizes the state of current knowledge about the key molecular components and mechanisms of apoptosis in melanoma, discusses potential therapeutic ramifications, and provides directions for future research.

Clinical significance of P16INK4A and retinoblastoma proteins in non-small-cell lung carcinoma

This study was performed to determine the frequency of expression loss of p16 and pRb; their relations with each other, tumour histology, tumour stage, nodal status, and survival in formalin fixed, paraffin embedded tumour tissues of patients with non-small-cell lung carcinoma (NSCLC). P16 and/or pRb expression loss is observed in 72 (75.8%) out of 95 patients, and 70 (73.7%) of them showed inverse correlation (P<0.05). Thirty-six (37.9%) of the p16 positive cases usually showed weak or moderate immunohistochemical staining. Loss of p16 expression was found to be significantly greater in squamous cell carcinoma than in adenocarcinoma cases, whilst no relation was observed with other clinical parameters. Immunohistochemical reactivity for pRb was generally moderate or strong. PRb expression loss was observed in 15.8% of the cases, and no relation was found between pRb loss and age, sex, tumour histology, tumour stage, or nodal status. PRb negative squamous cell carcinoma cases had significantly shorter survival independent of nodal status. These results suggest that disruption of p16/pRb pathway is frequently involved in NSCLC, and pRb expression loss in cases with squamous cell carcinoma may predict clinical outcome.

Loss of p16 expression is associated with histological features of melanoma invasion

While mutations of CDKN2A are associated with melanoma predisposition, the precise role of its gene product p16 in the development of sporadic melanoma is less clearly understood. We sought to determine the prevalence of p16 expression using immunohistochemical analysis in a population-based sample of melanoma tumours, and also to identify histological, phenotypic and environmental factors associated with the presence or absence of p16 expression. We conducted face-to-face interviews with 108 patients newly diagnosed with melanoma to ascertain their history of sun exposure, and recorded various phenotypic parameters. Paraffin sections of tumours from these patients were stained with an anti-p16 monoclonal antibody following antigen retrieval. Overall, 52 (48%) tumours expressed p16; nodular melanomas had significantly lower levels of p16 immunoreactivity than superficial spreading melanomas (P = 0.015). While no association was found between p16 expression and host phenotype, loss of p16 staining was associated with thicker lesions (p = 0.084) and a high mitotic index (P = 0.013). Taken together, these findings are consistent with loss of p16 being a late event in the progression of sporadic primary melanomas, being associated with tumours of a more aggressive nature.

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.

Bcl-2 and bcl-xL antisense oligonucleotides induce apoptosis in melanoma cells of different clinical stages

Recent clinical studies have shown the promise of bcl-2 antisense therapy in patients with melanoma. To further demonstrate the importance of bcl-2 and validate the related antiapoptotic protein bcl-xL as targets for antisense therapy in melanoma, their implication as survival factors in melanoma cells of different clinical stages as well as in normal melanocytes was investigated. Primary cell cultures derived from 17 melanomas, the cell line A375, and normal melanocytes from healthy donors were treated with antisense oligonucleotides targeting either the bcl-xL mRNA or the bcl-2 and the bcl-xL mRNAs simultaneously. Bcl-2 and bcl-xL expression in cells was analyzed by real-time polymerase chain reaction and Western blotting. Cell viability was assessed in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide and apoptosis assays. Bcl-2 expression was low in melanoma cells of stages I, II, and III, hardly detectable in A375 cells, but high in normal melanocytes. Bcl-xL expression was high in all cell types tested. As shown in A375 cells and the stage III melanoma cells 0513, both the bcl-xL monospecific oligonucleotide 4259 and the bcl-2/bcl-xL bispecific oligonucleotide 4625 effectively reduced tumor cell viability by induction of apoptosis with IC50 values ranging from 200 to 350 nM. Oligonucleotide 4625 proved to be superior to 4259, as it significantly reduced the viability of cells from all melanoma stages. Both oligonucleotides reduced also the viability of normal melanocytes. Our data suggest that bcl-2 and bcl-xL are promising targets for antisense therapy of melanoma, and that the simultaneous downregulation of their expression may provide additional clinical benefit.

Deregulation of the Rb and p53 pathways in uveal melanoma

Uveal melanoma is the most common primary eye cancer, yet its molecular pathogenesis is poorly understood. In this study, we investigated the immunohistochemical expression of proteins in the Rb and p53 tumor suppressor pathways in 33 uveal melanomas from enucleated eyes. Strong nuclear staining for Rb was present in most tumors. However, a few cases displayed weak nuclear staining and strong cytoplasmic staining (possibly indicating Rb mutation), and this aberrant staining correlated strongly with failed radiotherapy or thermotherapy before enucleation. Staining for cyclin D1 was positive in most tumors and was associated with advanced age and larger tumor size, which are both poor prognostic factors. Generally, immunostaining for p53 was weak (suggesting a lack of p53 mutations), although p53 positivity correlated strongly with staining for phosphorylated Rb, supporting the notion that inappropriate phosphorylation of Rb can induce p53. Strong immunostaining for MDM2, which can functionally block p53 activity, was observed in most tumors and correlated significantly with female sex. Strong cytoplasmic staining was observed for Bcl2, which can inhibit both p53-dependent and -independent apoptosis. We conclude that Rb and p53 are mutated infrequently in uveal melanoma, but their respective pathways may be functionally inactivated.