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- Asplund, Anna, et al.
(author)
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Genetic mosaicism in basal cell carcinoma
- 2005
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In: Experimental dermatology. - : Wiley. - 0906-6705 .- 1600-0625. ; 14:8, s. 593-600
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Journal article (peer-reviewed)abstract
- Human basal cell cancer (BCC) shows unique growth characteristics, including a virtual inability to metastasize, absence of a precursor stage and lack of tumour progression. The clonal nature of BCC has long been a subject for debate because of the tumour growth pattern. Despite a morphologically multifocal appearance, genetic analysis and three-dimensional reconstructions of tumours have favoured a unicellular origin. We have utilized the X-chromosome inactivation assay in order to examine clonality in 13 cases of BCC. Four parts of each individual tumour plus isolated samples of stroma were analysed following laser-assisted microdissection. In 12/13 tumours, the epithelial component of the tumour showed a monoclonal pattern suggesting a unicellular origin. Surprisingly, one tumour showed evidence of being composed of at least two non-related monoclonal clones. This finding was supported by the analysis of the ptch and p53 gene. Clonality analysis of tumour stroma showed both mono- and polyclonal patterns. A prerequisite for this assay is that the extent of skewing is determined and compensated for in each case. Owing to the mosaic pattern of normal human epidermis, accurate coefficients are difficult to obtain; we, therefore, performed all analyses both with and without considering skewing. This study concludes that BCC are monoclonal neoplastic growths of epithelial cells, embedded in a connective tissue stroma at least in part of polyclonal origin. The study results show that what appears to be one tumour may occasionally constitute two or more independent tumours intermingled or adjacent to each other, possibly reflecting a local predisposition to malignant transformation.
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| 2. |
- Bäckvall, Helena, 1971-
(author)
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Analysis of Sun-Damaged Skin and Epidermal p53 Clones
- 2003
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Doctoral thesis (other academic/artistic)abstract
- Sun-damaged skin is a relevant target tissue for studying the development of skin cancer. The aim of the present study was to investigate the epidermal response to ultraviolet radiation (UVR) in human skin in vivo and in vitro and to explore the mutagenic effect of UVA. The prevalence and the genetic background of epidermal p53 clones were furthermore analysed.Large inter- and intraindividual differences were observed in the epidermal response to UVR. Repair of UV-induced DNA damage appeared more efficient in chronically sun-exposed skin than in non-sun-exposed skin. Irradiation with UVA1 induced p53 mutations in keratinocytes. The pattern of mutations was indicative of oxidative damage, consistent with UVA acting as a mutagen.The prevalence of p53 clones in skin adjacent to basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and benign melanocytic nevus in patients of different age groups was analysed. An age-dependent increase in number and size of p53 clones was observed. Epidermal p53 clones were significantly larger and more frequent in skin adjancent to SCC than adjacent to BCC or melanocytic nevus. Mutation analysis of the entire coding region of the p53 gene showed that 57% of p53 clones in normal skin surrounding BCC and SCC have a mutated p53 gene. In conclusion, this study has increased our knowledge of the effects of UVR in chronically sun-exposed skin. The mutation spectra observed in epidermal p53 clones resembled that of non-melanoma skin cancer. The increased prevalence of epidermal p53 clones adjacent to SCC indicates that epidermal p53 clones may represent a step prior to actinic keratosis in the development of SCC.
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| 3. |
- Bäckvall, Helena, et al.
(author)
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Genetic tumor archeology : microdissection and genetic heterogeneity in squamous and basal cell carcinoma
- 2005
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In: Mutation research. - : Elsevier BV. - 0027-5107 .- 1873-135X. ; 571:02-jan, s. 65-79
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Research review (peer-reviewed)abstract
- Carcinogenesis is a multi-step series of somatic genetic events. The complexity of this multi-hit process makes it difficult to determine each single event and the definitive outcome of such events. To investigate the genetic alterations in cancer-related genes, sensitive and reliable detection methods are of major importance for generating relevant results. Another critical issue is the quality of starting material which largely affects the outcome of the analysis. Microdissection of cells defined under the microscope ensures a selection of representative material for subsequent genetic analysis. Skin cancer provides an advantageous model for studying the development of cancer. Detectable lesions occur early during tumor progression, facilitating molecular analysis of the cell populations from both preneoplastic and neoplastic lesions. Alterations of the p53 tumor suppressor gene are very common in non-melanoma skin cancer, and dysregulation of p53 pathways appear to be an early event in the tumor development. A high frequency of epidermal p53 clones has been detected in chronically sun-exposed skin. The abundance of clones containing p53 mutated keratinocytes adjacent to basal cell (BCC) and squamous cell carcinoma (SCC) suggests a role in human skin carcinogenesis. Studies using p53 mutations as a clonality marker have suggested a direct link between actinic keratosis, SCC in situ and invasive SCC. Microdissection-based studies have also shown that different parts of individual BCC tumors can share a common p53 mutation yet differ with respect to additional alterations within the p53 gene, consistent with subclonal development within tumors. Here, we present examples of using well-defined cell populations, including single cells, from complex tissue in combination with molecular tools to reveal features involved in skin carcinogenesis.
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| 4. |
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| 5. |
- Bäckvall, Helena, et al.
(author)
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Similar UV responses are seen in a skin organ culture as in human skin in vivo
- 2002
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In: Experimental dermatology. - : Wiley. - 0906-6705 .- 1600-0625. ; 11:4, s. 349-356
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Journal article (peer-reviewed)abstract
- Ultraviolet radiation (UVR) plays an important role in the development of non-melanoma skin cancer. Most tumors develop in chronically sun-exposed skin, most often in cosmetically sensitive locations, where in vivo experiments may be difficult to perform. In this study, we describe a skin organ culture model with preserved normal morphology and intact response to UVR. Skin explants from chronically sun-exposed and non-sun-exposed skin were irradiated with artificial UVA+UVB with and without topical sunscreen. UV-induced DNA damage, epidermal p53 response and repair kinetics were analyzed using immunohistochemistry. Four hours after UV-irradiation epidermal keratinocytes showed a strong immunoreactivity for thymine-dimers. Gradual repair during an incubation time resulted in few residual thymine-dimers after 48 h. Repair appeared to be more efficient in chronically sun-exposed skin compared with non-sun-exposed skin. There was also an accumulation of p53 protein in epidermal keratinocytes, peaking at 4-24 h after irradiation. Large interindividual differences with respect to formation and repair of thymine-dimers as well as induction and duration of the p53 response were observed. Skin explants treated with topical sunscreen prior to UV-irradiation showed a clear reduction of thymine-dimers and p53 expression. The epidermal UV-responses and repair kinetics in organ-cultured skin were similar to what was found in vivo. Our data suggest that organ-cultured skin provides a valuable tool for studies of UV-induced epidermal responses in chronically sun-exposed skin.
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| 9. |
- Persson, Asa E, et al.
(author)
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The mutagenic effect of ultraviolet-A1 on human skin demonstrated by sequencing the p53 gene in single keratinocytes.
- 2002
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In: Photodermatology, Photoimmunology & Photomedicine. - : Wiley. - 0905-4383 .- 1600-0781. ; 18:6, s. 287-293
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Journal article (peer-reviewed)abstract
- BACKGROUND: Sun exposure is accepted as the major risk factor for developing skin cancer, the most common cancer in the western world. Ultraviolet-B (UV-B) radiation is considered the causative agent, but recently several findings suggest a role also for ultraviolet-A (UV-A) radiation. Repeated suberythemal doses of ultraviolet-A1 (UV-A1) on healthy human skin induce an increase of p53 immunoreactive cells in epidermis, which may indicate cell cycle arrest and/or occurrence of p53 mutations.METHODS: We have investigated the possible mutagenic effect of UV-A1 on skin by sequencing exons 4-11 and adjacent intron sequence of the p53 gene in immunoreactive single cells from three healthy individuals. Previously unexposed buttock skin was irradiated three times a week for 2 weeks with physiological fluences (40 J/cm2) of UV-A1. Punch biopsies were taken before and at different time-points after the exposure, and from these single p53 immunoreactive cells were isolated by using laser-assisted microdissection.RESULTS: Three mutations--all being indicative of oxidative damage and most likely related to UV-A exposure--were found among the 37 single cells from exposed skin, whereas no mutations were found in the 22 single cells taken before exposure.CONCLUSIONS: The findings indicate a mutagenic effect of low-dose UV-A1 on healthy human skin, which further demonstrates the importance of considering UV-A when taking protective measures against skin cancer.
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