Identification of novel deletion Loci at 1p36 and 9p22-21 in melanocytic dysplastic nevi and cutaneous malignant melanomas.
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Chromosome Deletion↗
Biomedical subjects
Mahmoud R Hussein
Publications and source records attributed to Mahmoud R Hussein.
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.
Apoptosis↗
Restoration of ovarian function after autotransplantation of intact frozen-thawed sheep ovaries with microvascular anastomosis.
OBJECTIVE: To test the feasibility of transplanting an intact frozen-thawed ovary with microvascular anastomosis of the ovarian vascular pedicle to the deep inferior epigastric vessels. DESIGN: Chronic survival study. SETTING: Biological Resources Unit, The Cleveland Clinic Foundation. ANIMAL(S): Adult merino ewes. INTERVENTION(S): Bilateral laparoscopic oophorectomy was performed on 17 synchronized ewes. In one group of animals (Group I, n = 11), both ovaries were cryopreserved intact with their vascular pedicles. In another group of animals (Group II, n = 6), ovarian cortical strips were prepared from each ovary and cryopreserved. After thawing, follicular viability and apoptosis rates were assessed using one ovary. The other ovary was transplanted to the abdominal wall with microvascular anastomosis (Group I). In Group II, the ovarian cortical strips were placed in the anterior abdominal wall. Ovaries were harvested after 8-10 days in situ and subjected to histological evaluation. MAIN OUTCOME MEASURE(S): Blood flow, apoptotic signals, follicular viability, serum estradiol (E(2)), follicle-stimulating hormone (FSH), and histology. RESULT(S): No significant differences were found in the mean values of apoptosis (mostly in the atretic and some secondary follicles) and follicular viability in both groups. In Group I, immediate and long-term patency were documented in 100% and 27% (3/11) of the grafts, respectively; and postoperative FSH levels were similar to preoperative values in animals with patent vessels. In Group II, postoperative FSH levels were significantly higher than the preoperative ones (P=.03). CONCLUSION(S): Transplantation of an intact frozen-thawed ovary is technically feasible. Using this approach, immediate restoration of vascular supply and ovarian hormonal functions is possible.
Anastomosis, Surgical↗
Morphological changes and apoptosis in radial growth phase melanoma cell lines following ultraviolet-B irradiation.
BACKGROUND: Knowledge about the morphologic changes following ultraviolet irradiation in the earliest stages of melanomas is still lacking. METHODS: To investigate these changes, an in vitro system consisting of radial growth phase Wistar melanoma cell lines (WM35 and WM3211) was established. Cells were irradiated with a single erythemogenic dose of UVB (10 mJ/cm2) and evaluated for morphologic changes. RESULTS: When compared with the non-irradiated cells, inverted light microscopy revealed increased cellular branching, cytoplasmic size, and multinucleation in the irradiated cells. Transmission electron microscopy revealed the features of increased metabolic activity (hyperplasia of the mitochondria and Golgi) and those of ultrastructural atypia (pleomorphism of the nuclei and nucleoli, increased euchromatin, and nucleolar margination) in the irradiated cells. Moreover, UVB irradiation caused an increase in the apoptotic activity. These alterations were associated with up-regulation of p53, Bcl-2, and the second mismatch repair protein (hMSH2), as revealed by Western blot analysis. CONCLUSIONS: UVB irradiation can induce apoptosis, morphologic changes, and altered expression of p53, Bcl-2, and hMSH2 in radial growth phase melanoma cell lines. Up-regulation of p53, Bcl-2, and hMSH2 suggests that these factors are involved in the altered balance between survival and apoptosis induced by UVB. Further investigation will be needed to determine if apoptosis and ultrastructural atypia reflect underlying DNA damage and genomic instability induced by UVB.
Apoptosis↗
hMLH1 and hMSH2 gene mutations are present in radial growth-phase cutaneous malignant melanoma cell lines and can be induced further by ultraviolet-B irradiation.
Microsatellite instability and reduced expression of mismatch repair proteins were reported in melanomas. However, little is known about mutational changes of the mismatch repair genes in radial growth-phase melanoma especially following UVB irradiation. To investigate these changes, an in vitro system consisting of radial growth-phase Wistar melanoma cell lines (WM35, WM3211 and WM1650) was established. The cells were UVB irradiated (10 mJ/cm(2)), and evaluated for mutational changes of exon regions 13,16 and 19 (hMLH1) and 6,7 and 12 (hMLH2) of these genes before and after irradiation. The genomic DNAs were PCR amplified and the products were directly sequenced. Transition (C-->T, G-->A, T-->C) and transversion (G-->, A-->T) mutations were found in exons 6,16 and 19. Some were present in both the sham-irradiated and UV-irradiated cells but others were only detected after UVB irradiation. hMLH1 and hMLH2 gene mutations occur early in melanoma tumorigenesis. The ability of UVB irradiation to induce additional mutations in these repair genes suggests its possible role in melanoma pathogenesis. Further investigation will be needed to determine whether mutations such as these contribute to the development of microsatellite instability in melanoma.
Adaptor Proteins, Signal Transducing↗
Loss of heterozygosity, microsatellite instability, and mismatch repair protein alterations in the radial growth phase of cutaneous malignant melanomas.
Little is known about genomic alterations during development of the radial growth phase (RGP) of cutaneous malignant melanomas (CMMs). In this investigation polymerase chain reaction-based microsatellite assays were applied to analyze 13 RGP-CMMs with 18 microsatellite markers at six chromosomal regions: 1p, 3p, 4q, 6q, 9p, and 10q. Loss of heterozygosity (LOH) was found in eight cases (62%), at 9p22, 1p36, and 10q11, suggesting the presence of tumor-suppressor genes at these regions. LOH was encountered frequently at the interferon-alpha (31%) and D10S249 loci (15%). Low-level microsatellite instability (MSI) (11-16% of investigated loci unstable) was noted in three cases (23%). Two MSI banding patterns were seen: band shift and the presence of additional bands. To investigate the underlying mechanisms of the low-level MSI pattern, we analyzed the lesions for expression of mismatch repair (MMR) proteins with immunoperoxidase methods and mouse monoclonal antibodies. The average percentages of positively stained cells for human MutL homolog 1 (hMLH1), human MutS homolog 2 (hMSH2), and human MutS homolog 6 (hMSH6) in RGP-CMM (75.6 +/- 3.4%, 67.20 +/- 7.71%, and 76.6 +/- 2.1%, respectively) were reduced compared with benign nevi. No statistically significant differences in MMR protein expression were found between microsatellite-stable and low-level MSI lesions (P = 0.173, P = 0.458, and P = 0.385 for hMLH1, hMSH2, and hMSH6, respectively). There was a direct correlation between values for percentages of positively stained cells for hMSH2 and hMSH6 (r = +0.9, P = 0.03), suggesting that common mechanisms regulate their expression. In conclusion, LOH, MSI, and reduced MMR protein expression appear to be present in at least some RGP-CMMs and may play a role in their pathogenesis. Further studies are necessary to support these finding and to determine their diagnostic and prognostic significance.
Base Pair Mismatch↗
Microsatellite instability in human melanocytic skin tumors: an incidental finding or a pathogenetic mechanism?
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DNA, Neoplasm↗
Microsatellite instability and its relevance to cutaneous tumorigenesis.
Increasing evidence suggests that human tumors sequentially accumulate multiple mutations that cannot be explained by the low rates of spontaneous mutations in normal cells (2-3 mutations/cell). The mathematical models estimate that for the solid tumors to develop, as many as 6-12 mutations are required in each tumor cell. Therefore, to account for such high mutation rates, it is proposed that tumor cells are genetically unstable, i.e. they have genome-wide mutations at short repetitive DNA sequences called microsatellites. Microsatellite repeats are scattered throughout the human genome, primarily in the non-coding regions, and can give rise to variants with increased or reduced lengths, i.e. microsatellite instability (MSI). This instability has been reported in an increasing number of cutaneous tumors including: melanocytic tumors, basal cell carcinomas and primary cutaneous T-cell lymphomas. Moreover, MSI has been observed in skin tumors arising in the context of some hereditary disorders such as Muir-Torre syndrome, Von Recklinghausen's disease and disseminated superficial porokeratosis. While MSI in some of these disorders reflects underlying DNA replication errors, the mechanism of instability in others is still unknown. Thus far, MSI is considered to be a distinct tumorigenic pathway that reveals surprising versatility. The ramifications for cutaneous neoplasms warrant further investigation.
Animals↗
Building bridges in cancer: mismatch repair and microsatellite instability.
Mismatch repair (MMR) defects and microsatellite instability (MSI) are two genetic alterations that have been documented in a wide variety of human cancers, including some that involve the skin. Available evidence indicates that these two features are sometimes directly related, although their connection seems to be indirect or nonexistent in other instances. The purposes of this review are to summarize the variable relations between MMR and MSI as deduced from analysis of a diverse array of human neoplasms and to give brief insights as to the other molecular mechanisms potentially involved in the maintenance of genomic stability.
Base Pair Mismatch↗
The TP53 tumor suppressor gene and melanoma tumorigenesis: is there a relationship?
Mutations in the TP53 gene are found in about 11% of melanomas. Although nearly 600 papers have been published with varying degrees of consensus, there does not appear to be any comparable analysis that facilitates more than a glimpse into the role of p53 in melanomagenesis. This article reviews p53 alterations (at the gene and protein levels) in melanocytic skin lesions and discusses the following points: (i) p53 alterations commence as early as at the stage of benign and dysplastic nevi; (ii) these alterations are frequent in melanomas, and gradually increase with their progression; (iii) there is no concordance between the frequent p53 protein expression and the rarity of both TP53 gene mutations in melanomas, and (iv) the entire p53 pathway is a more critical determinant of the fate of the melanocytic skin lesions than the status of the p53 protein or the gene itself.
Codon↗