Cytogenetics of human malignant melanoma

Oxygen in human health from life to death--An approach to teaching redox biology and signaling to graduate and medical students

In the absence of oxygen human life is measured in minutes. In the presence of oxygen, normal metabolism generates reactive species (ROS) that have the potential to cause cell injury contributing to human aging and disease. Between these extremes, organisms have developed means for sensing oxygen and ROS and regulating their cellular processes in response. Redox signaling contributes to the control of cell proliferation and death. Aberrant redox signaling underlies many human diseases. The attributes acquired by altered redox homeostasis in cancer cells illustrate this particularly well. This teaching review and the accompanying illustrations provide an introduction to redox biology and signaling aimed at instructors of graduate and medical students.

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The ability to sense oxygen and respond to oxidative stress is ancient.

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Chemical and kinetic properties of ROS are key to understanding redox signaling.

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Redox signaling participates in normal control of cell proliferation and death.

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Aberrant redox signaling contributes to the hallmarks of cancer.

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Novel redox-based chemotherapeutics are being developed.

Functional analysis and molecular targeting of aurora kinases a and B in advanced melanoma

Over the past few years, high-throughput analyses have provided important novel insights into molecular pathways that play a crucial role in the progression from early to advanced melanoma, and at the same time, they have led to the identification of genes that as part of melanoma progression are upregulated in advanced melanoma. In the present study, we provide evidence that Aurora kinases A and B, 2 key regulators of M phase progression, are upregulated to high levels with progression from melanoma in situ to primary and metastatic melanoma and that inhibiting the expression of these 2 genes by RNA interference or blocking their function with an Aurora kinase-specific small-molecule inhibitor severely impairs melanoma cell proliferation and cell cycle progression and induces melanoma cell apoptosis. In addition, we present the results of systemic treatment of human melanoma xenografts with an Aurora kinase small-molecule inhibitor as well as Aurora kinase targeting vectors.

Fluorescence in-situ hybridization analysis for melanoma diagnosis

Melanocytic proliferation constitutes a heterogeneous group of lesions with remarkable differences in their biology and clinical outcome. Thus, accurate histological diagnosis of these cases is mandatory to establish the most appropriate surgical treatment and follow-up. Although histological examination alone is usually sufficient to identify melanomas among the greater number of nevi, the definition of the benign or malignant nature of a subset of melanocytic tumours, exhibiting atypical features, is a challenging task. Novel techniques that may assist in the histopathological diagnosis in difficult cases have been extensively researched over recent years. Fluorescence in-situ hybridization (FISH), performed with a panel of four probes, including three locus-specific identifier (RREB1, MYB, and CCND1) genes, seems to represent a sensitive and specific molecular tool for the diagnosis of non-ambiguous melanocytic lesions. Some studies have agreed that FISH may be an ancillary diagnostic instrument, but cannot replace light microscopy, to distinguish benign nevi from malignant melanomas in daily practice. However, in the context of ambiguous melanocytic tumours, results are still controversial, and additional and substantial work is needed to develop reliable probes that may identify, with high sensitivity, specific subsets of ambiguous melanocytic lesions, including spitzoid proliferation.

Malignant melanoma in the 21st century: the emerging molecular landscape

Malignant melanoma presents a substantial clinical challenge. Current diagnostic methods are limited in their ability to diagnose early disease and accurately predict individual risk of disease progression and outcome. The lack of adequate approaches to properly define disease subgroups precludes rational treatment design and selection. Better tools are urgently needed to provide more accurate and personalized melanoma patient management. Recent progress in the understanding of the molecular aberrations that underlie melanoma oncogenesis will likely advance the diagnosis, prognosis, and treatment of melanoma. The emerging pattern of molecular complexity in melanoma tumors mirrors the clinical diversity of the disease and highlights the notion that melanoma, like other cancers, is not a single disease but a heterogeneous group of disorders that arise from complex molecular changes. Understanding of molecular aberrations involving important cellular processes, such as cellular signaling networks, cell cycle regulation, and cell death, will be essential for better diagnosis, accurate assessment of prognosis, and rational design of effective therapeutics. Defining an individual patient's unique tumor characteristics may lead to personalized prediction of outcomes and selection of therapy. We review the emerging molecular landscape of melanoma and its implications for better management of patients with melanoma.

Differentiation therapy of human cancer: basic science and clinical applications

Current cancer therapies are highly toxic and often nonspecific. A potentially less toxic approach to treating this prevalent disease employs agents that modify cancer cell differentiation, termed 'differentiation therapy.' This approach is based on the tacit assumption that many neoplastic cell types exhibit reversible defects in differentiation, which upon appropriate treatment, results in tumor reprogramming and a concomitant loss in proliferative capacity and induction of terminal differentiation or apoptosis (programmed cell death). Laboratory studies that focus on elucidating mechanisms of action are demonstrating the effectiveness of 'differentiation therapy,' which is now beginning to show translational promise in the clinical setting.

Tumor progression, early diagnosis and prognosis of melanoma

Primary melanomas evolve from melanocytes or from precursor lesions through two stages: the radial and vertical growth phases. The radial growth phase may be in situ or microinvasive, but is a non-tumorigenic neoplastic process, while the vertical growth phase is tumorigenic. The prognosis in radial growth phase is excellent irrespective of thickness or other variables. Curable radial growth phase melanomas can be recognized by surveillance of patients identified by screening for risk markers which include dysplastic nevi, common nevi, freckles, and other indicators of chronic or acute sun exposure or sun sensitivity. The prognosis in vertical growth phase depends on attributes of the tumor and of the host. The tumor mitotic rate, the presence of host tumor-infiltrating lymphocytes (TIL) within the vertical growth phase, and tumor thickness are the most powerful predictors of survival. New prognostic attributes are needed not only to provide for more accurate prognosis and diagnosis, but also to test the relevance of in vitro or animal studies in a human neoplastic system. Such attributes will be developed in the future based on markers that are associated with tumor progression. Candidate markers include growth factors and cytokines and their receptors, adhesion molecules and their ligands, chemotactic and motility factors, immune response-related molecules, and tumor-associated proteases. Some of these markers that are represented in the transition from radial to vertical growth phase will be reviewed. The tumor progression model presented here has been of value in the development of more accurate prognostic models, and in the elucidation of mechanisms of the malignant phenotype in melanoma.

Involvement of chromosome losses in the progression and metastasis formation of a human malignant melanoma

To characterize the possible cytogenetic link between a primary tumor and its metastasis, interphase cytogenetic analysis was performed on tumor cells and cutaneous metastasis from a male patient with malignant melanoma by using fluorescence in situ hybridization. The numbers of distinct hybridization domains specific for ten different pericentromeric sequences were used as indicators of copy numbers of these chromosomes. In the primary tumor, the majority of cells had two copies of these chromosomes, but significant numbers of nuclei also were present with one and three copies. In addition, in almost all cells, both sex chromosomes were abnormal; nullisomy of the Y chromosome was associated with X disomy. The corresponding metastatic tumor cells were predominantly monosomic; only the distribution of chromosomes 11 and 7 was similar to the primary tumor. In the metastatic tumor, the sex chromosomes had a normal copy number; that is, one Y and one X were detected. These data indicate that both the initiation and the progression of this melanoma are associated with chromosome losses.

Comparison of genetic profiles between primary melanomas and their metastases reveals genetic alterations and clonal evolution during progression

To examine for the genetic basis of metastatic progression in cutaneous melanoma, we have compared loss of heterozygosity (LOH) of several selected chromosome regions that are implicated in the initiation and progression of melanoma, and alterations of the p16INK4a gene in 14 pairs of primary tumor and synchronous or asynchronous metastasis excised from the same patients. The most frequent genetic alteration during metastatic progression detected was the loss of p16INK4a protein expression (four of 14 cases), whereas no somatic p16INK4a gene mutations were found in any primary or metastatic tumors. LOH analyses showed that most of the chromosome losses including 6q, 8p, 9p, 9q, and 18q were shared between primary tumors and their metastases. Nevertheless, LOH of 6q and 11q and LOH of 7q not detected in primary tumors were, respectively, observed in two lymph node metastases. These results suggest that loss of p16INK4a protein expression (but not p16INK4a gene mutation) and the losses of chromosome arms 6q, 7q, and 11q play an important role in the acquisition of metastatic potential in sporadic melanoma. Furthermore, comparison of genetic profiles between the primary tumor and its metastasis revealed in several cases that heterogenous tumor cell populations might already exist at the early stage of tumorigenesis and evolve independently in the primary tumor and its metastasis, strongly suggesting that metastatic progression of sporadic melanoma is not accounted for by a linear progression model.

Development of heritable melanoma in transgenic mice

Transfer of genetic material into recipient cells by transfection has been used successfully to isolate genes responsible for particular phenotypic traits. By using this strategy, DNA fragments were isolated that when transfected into appropriate uncommitted cells will commit the recipient cells to undergo adipocyte differentiation. Transgenic mice were generated with one of the active DNA clones, Clone B. The transgenic mice were expected to display an adipocyte-related phenotype; however, the animals developed melanin containing tumors at a young age. Insertion of Clone B into the mouse DNA probably interrupted a gene(s) that is involved in the regulation of cell growth, specifically regulation of cell growth in melanin-producing cells. Histopathologic analysis of these mice showed dark spots on the ear lobes of the animals as early as 10-12 d of age. By 3 mo, in addition to the ear lobes, pigmented tumors could be observed in other organs. A significant number of these transgenic mice died within 1 y of age. The melanomas developed spontaneously in these animals in the absence of any known chemical carcinogen or ultraviolet radiation. This line of mice provides a way of identifying genes involved in regulation of cell growth control and differentiation. These mice also serve as a model system to investigate the molecular, genetic, and phenotypic characterization and development of melanomas.

Neoplastic progression and prognosis in melanoma

Most melanomas evolve through an initial stage known as radial growth phase (RGP), encompassing in situ and microinvasive malignancies in which the probability of cure approaches 100%. At the present time, despite a shift toward earlier recognition of melanoma, by the time of diagnosis roughly 70% of melanomas have evolved to a point, known as vertical growth phase (VGP) or tumorigenic melanoma, at which cure is not certain, and prognosis depends upon certain attributes of the neoplasm and the host. Attempts have been made to assemble these attributes into prognostic models to permit estimation of the probability of cure for individuals and for groups of patients. Attributes that have been identified as independent prognostic variables include thickness of the primary neoplasm, the numbers of mitotic figures, and the presence of tumor-infiltrating lymphocytes (TIL). Other biologically important prognostic variables are on the horizon, and some will likely be based on molecules (markers) expressed on neoplastic cells that show functional significance in mechanisms of metastasis.

Prognostic parameters in uveal melanoma: a review

Histologic cell type, largest tumor diameter and tumor location have traditionally been regarded as the leading predictors of survival for uveal melanoma. Morphological cell typing is, however, subjective to variations in interpretation. More objective classification parameters have emerged from extensive cytomorphometrical and DNA flow cytometrical studies. For patients with uveal melanoma there is no effective therapy if metastases have developed, and the median survival after clinical diagnosis of hepatic metastases is extremely poor. Current research focuses on the mechanisms underlying the metastatic process, including tumor vasculature, cytogenetics, oncogene activation, immunology, melanoma-associated antigens and tumor cell migration (cell-cell and cell-matrix interaction). Several new prognostic parameters have emerged from these studies, such as closed vascular patterns, loss of one chromosome 3, and different indices of cell proliferation. Furthermore, considerable genotypical and phenotypical differences have been found between uveal and cutaneous melanoma. In prospective studies on large series of melanomas a combination of histopathological and/or clinical prognostic parameters might be selected with high sensitivity and specificity, providing a way of selecting patients at high risk of developing metastatic disease, who might be eligible for adjuvant therapy.

Metastasis suppressed, but tumorigenicity and local invasiveness unaffected, in the human melanoma cell line MelJuSo after introduction of human chromosomes 1 or 6

Progression of human melanoma toward increasing malignant behavior is associated with several nonrandom chromosomal aberrations, most commonly involving chromosomes 1, 6, 7, 9, and 10. We previously showed that introduction of human chromosome 6 into the highly metastatic human malignant melanoma cell line C8161 completely suppressed metastasis without altering tumorigenicity (Welch DR, Chen P, Miele ME, et al., Oncogene 9:255-262, 1994). Alterations of chromosome 1 are the most frequent chromosome abnormality observed in melanomas, and they frequently arise late in tumor progression. The purpose of the study presented here was to compare the effects of chromosomes 1 and 6 on malignant melanoma metastasis. By using microcell-mediated chromosome transfer, single copies of neo-tagged human chromosomes 1 or 6 were introduced into the human melanoma cell line MelJuSo. The presence of the added chromosome was verified by G banding of karyotypes, fluorescence in situ hybridization, and screening for polymorphic markers on each chromosome. The incidence and number of metastases per lung after intravenous or intradermal injection of parental MelJuSo cells was significantly (P<0.01) greater than those of hybrids containing either chromosome 1 or chromosome 6, although chromosome 1 was a less potent inhibitor of metastasis than chromosome 6. Cultures established from primary tumors and metastases remained neomycin resistant, suggesting that portions of the added chromosomes were retained. These results strengthen the evidence for the presence of a melanoma metastasis suppressor gene on chromosome 6. neo6/MelJuSo hybrids expressed 2.4- to 3.4-fold more of the melanoma differentiation-associated gene mda-6 (previously shown to be identical to WAF1/CIP1/Sdi1/CAP20) than parental metastatic cells. mda-6/WAF1 is among the candidate genes on chromosome 6. These results also demonstrate, for the first time, the existence of metastasis suppressor genes on human chromosome 1, although these genes appear to be less potent than the one encoded on chromosome 6.

Conjunctival and uveal melanoma in the dysplastic nevus syndrome

The dysplastic nevus syndrome was conceptualized in the late 1970s, and the subsequent proposal of a genetic relationship with ocular melanoma has stimulated debate in the literature which remains unresolved. We present the case of a 60-year-old man with histologically proven sporadic dysplasic nevus syndrome and a prior history of nine cutaneous melanomas, who developed a large, exophytic melanoma of the cornea and limbal conjunctiva. Cytogenetic analysis of this melanoma revealed a clonal 1;14 translocation. We believe this is the first reported case to use cytogenetic techniques in the analysis of conjunctival melanoma, either associated with dysplastic nevus syndrome or in isolation. We review the clinical literature as well as the cytogenetic and molecular genetic data related to the possible association of cutaneous melanoma, conjunctival and uveal melanoma and the dysplastic nevus syndrome.