title: Identification of an autocrine mechanism for regulating cell-cycle progression in murine keratinocytes.
abstract: Primary murine keratinocytes possess a limited doubling potential regardless of plating density or the inclusion of competence factors insulin, epidermal growth factor, and/or fetal bovine serum within the culture medium. In contrast, a murine cell line (CH-72), derived from a 7,12-dimethylbenz[a]-anthraceneinitiated, 12-O-tetra-decanoylphorbol-13-acetate-promoted mouse skin carcinoma, was found to exhibit unlimited proliferative potential; this was demonstrated by the ability of these cells to produce the progression factor required for entry into the DNA-synthesis phase in the absence of competence-factor stimulation. Conditioned medium, collected from murine carcinoma cells, was subsequently shown to increase the level of [3H]thymidine incorporation in competence-factor-deprived CH-72 cultures by more than a factor of 4 within 16 h. Moreover, consistent with its ability of recruit cells cycling within the first gap phase directly into the DNA-synthesis phase, the autocrine progression factor present in conditioned medium decreased the G1:S ratio from the 55:29 observed with growth medium controls to 38:46. Preliminary characterization of the autocrine factor produced by cultured murine carcinoma cells using gel-filtration chromatography revealed a molecular mass of less than 2 kDa, similar in size to the factor previously shown by our laboratory to promote G1-phase progression in cultures of normal human foreskin keratinocytes.
authors.affiliation: Department of Carcinogenesis, University of Texas, M.D. Anderson Cancer Center-Science Park Research Division, Smithville 78957, USA.
authors.forename: G M
authors.initials: GM
authors.lastname: Curtin
authors.forename: S M
authors.initials: SM
authors.lastname: Fischer
authors.forename: T J
authors.initials: TJ
authors.lastname: Slaga
mesh_terms: D000818:Animals; D002277:Carcinoma / Q000473:pathology*; D002453:Cell Cycle; D002471:Cell Transformation, Neoplastic / Q000473:pathology; D002478:Cells, Cultured; D003470:Culture Media / Q000032:analysis; D004247:DNA / Q000032:analysis; D006133:Growth Substances / Q000302:isolation & purification* / Q000502:physiology; D015603:Keratinocytes / Q000166:cytology*; D051379:Mice
chemical_list: D003470:Culture Media; D006133:Growth Substances; D004247:DNA