title: Transformation of human epidermal keratinocytes with fission neutrons.
abstract: The biological effects of exposures to high LET radiations have particular relevance to radiation protection and risk assessment. Since most cancers are of epithelial origin, it is important to obtain a better understanding of radiation-induced oncogenic transformation in this cell type. Accordingly we have initiated studies to determine whether immortalized human epidermal keratinocytes (RHEK) can be transformed with high LET radiations. Exponentially growing RHEK cells were treated with single doses (1, 10, 25, 50 and 100 cGy) of 0.85 MeV fission neutrons from the Janus reactor. Neutron exposure led to the development of morphologically altered cells and foci formation after 6 weeks at confluence. These transformed cultures grew with an increased saturation density, exhibited anchorage-independent growth and formed tumors in athymic mice. Single-strand conformational polymorphism analysis and DNA sequencing demonstrated the absence of point mutations in codons 12/13 and 61 in the Ha-ras, Ki-ras, or N-ras genes and exons 4-9 of the p53 tumor suppressor gene. These studies demonstrate that high LET radiations (fission neutrons) can transform immortalized human epithelial cells to a malignant phenotype that does not appear to involve mutations in either the cellular p53 or ras genes.
authors.affiliation: Department of Radiation Medicine, Vincent T. Lombardi Cancer Research Center, Georgetown University Medical Center, Washington, DC 20007.
authors.forename: P J
authors.initials: PJ
authors.lastname: Thraves
authors.forename: S
authors.initials: S
authors.lastname: Varghese
authors.forename: M
authors.initials: M
authors.lastname: Jung
authors.forename: D J
authors.initials: DJ
authors.lastname: Grdina
authors.forename: J S
authors.initials: JS
authors.lastname: Rhim
authors.forename: A
authors.initials: A
authors.lastname: Dritschilo
mesh_terms: D000818:Animals; D001483:Base Sequence; D002294:Carcinoma, Squamous Cell / Q000209:etiology; D002461:Cell Line, Transformed; D002471:Cell Transformation, Neoplastic / Q000528:radiation effects*; D003062:Codon / Q000235:genetics; D004273:DNA, Neoplasm / Q000235:genetics; D000078404:Epidermal Cells; D016158:Genes, p53 / Q000528:radiation effects*; D011905:Genes, ras / Q000528:radiation effects*; D006801:Humans; D015603:Keratinocytes / Q000528:radiation effects*; D018499:Linear Energy Transfer; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D008969:Molecular Sequence Data; D009381:Neoplasms, Radiation-Induced / Q000209:etiology; D009502:Neutrons; D009688:Nuclear Reactors; D018807:Polymorphism, Single-Stranded Conformational
chemical_list: D003062:Codon; D004273:DNA, Neoplasm