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  • 1
    Keywords: APOPTOSIS ; CANCER ; CELLS ; GROWTH ; IRRADIATION ; proliferation ; tumor ; TUMOR-CELLS ; MODEL ; CARCINOGENESIS ; KERATINOCYTES ; MOUSE ; EQUIVALENT ; PROGRESSION ; MUTATION ; MUTATIONS ; NEOPLASTIC PROGRESSION ; intraepithelial neoplasia ; organotypic culture ; HA-RAS ; HACAT-RAS ; HUMAN SKIN ; MALIGNANT KERATINOCYTES ; RECONSTRUCTED IN-VITRO ; SUNLIGHT ; UVB irradiation
    Abstract: Ultraviolet B irradiation is thought to enable skin cancer progression as clones of genetically damaged keratinocytes escape apoptosis and expand at the expense of adjacent normal cells. Mechanisms through which potentially malignant cells in human skin undergo clonal expansion, however, are not well understood. The goal of this study was to characterize the role of ultraviolet B irradiation on the intraepithelial expansion of early stage human tumor cells in organotypic skin cultures. To accomplish this, we have studied the effect of ultraviolet B irradiation on organotypic cultures that were fabricated by mixing normal human keratinocytes with beta-galactosidase- marked, intraepithelial tumor cells (HaCaT-ras , clone II-4), which bear mutations in both p53 alleles and harbor an activated H-ras oncogene. We found that when organotypic mixtures were exposed to an ultraviolet B dose of 50 mJ per cm(2) , intraepithelial tumor cells underwent a significant degree of proliferative expansion compared to nonirradiated cultures. To understand this response, organotypic cultures of nor-mal keratinocytes were exposed to ultraviolet B and showed a dose-dependent increase in numbers of sunburn cells and TUNEL-positive cells although their proliferation was suppressed. In contrast, neither the apoptotic nor the proliferative response of II-4 cells was altered by ultraviolet B in organotypic cultures. The differential response of these cell types suggested that II-4 cells were resistant to ultraviolet-B-induced alterations, which allowed these intraepithelial tumor cells to gain a selective growth and survival advantage relative to neighboring normal cells. These findings demonstrate that ultraviolet B exposure can induce the intraepithelial expansion of apoptosis-resistant, p53-mutant, and ras -activated keratinocytes, suggesting that this agent can act to promote the early stages of epithelial carcinogenesis
    Type of Publication: Journal article published
    PubMed ID: 12839581
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  • 2
    ISSN: 1573-5028
    Keywords: cell proliferation ; in vitro transcription and translation ; Pisum sativum ; plant promoter ; primer extension ; RACE-PCR ; transcript analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have isolated and sequenced four overlapping cDNA clones to identify the full-length cDNA for topoisomerase II (PsTopII) from pea. Using degenerate primers, based on the conserved amino acid sequences of other eukaryotic type II topoisomerases, a 680 bp fragment was PCR-amplified with pea cDNA as template. This fragment was used as a probe to screen an oligo-dT-primed pea cDNA library. A partial cDNA clone was isolated that was truncated at the 3′ end. RACE-PCR was employed to isolate the remaining portion of the gene. The total size of PsTopII is 4639 bp with an open reading frame of 4392 bp. The deduced amino acid sequence shows a strong homology to other eukaryotic topoisomerase II (topo II) at the N-terminus end. The topo II transcript was abundant in proliferative tissues. We also show that the level of topo II transcripts could be stimulated by exogenous application of growth factors that induced proliferation in vitro cultures. Light irradiation to etiolated tissue strongly stimulated the expression of topo II. These results suggest that topo II gene expression is up-regulated in response to light and hormones and correlates with cell proliferation. Besides, we have also isolated and analysed the 5′-flanking region of the pea TopII gene. This is first report on the isolation of a putative promoter for topoisomerase II from plants.
    Type of Medium: Electronic Resource
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