Evaluation of a rat tracheal epithelial cell culture assay system to identify respiratory carcinogens.

To evaluate a short-term epithelial cell assay system to detect respiratory carcinogens, primary cultures of rat tracheal epithelial cells were exposed to a series of 17 compounds and scored for morphologically transformed cell colonies 28 days later. The test compounds included known carcinogens and noncarcinogens in volatile or liquids form. Tracheal epithelial cells were isolated from F344 rats, plated onto collagen-coated dishes, and exposed to the test compounds on day 1 for 24 hours. At day 30 the cultures were fixed, stained, and scored for colonies having a density greater than 1,300 cells/min2. With standardized protocols, such colonies are very infrequent in media and solvent control cultures. Concentration levels for each chemical were chosen over a range from nontoxic to toxic levels. Highly positive compounds in this assay included benzo(a)pyrene, benzo(l)acean-thyrlene, 3-methylcholanthrene, and formaldehyde. Compounds which were negative in this assay included pyrene, benzo(e)pyrene, and 4-nitroquinoline-N-oxide. Examining the concordance of in vitro results with whole animal carcinogenesis studies revealed an accuracy of 88% with one false-positive and one false-negative compound. The results of these studies indicate that the rat tracheal epithelial cell assay may be useful in identifying potential respiratory carcinogens in our environment.

Neutralizing IGF-1 monoclonal antibody with cross-species reactivity.

We report the generation of a murine IGF-1 monoclonal antibody designated 35I17, which exhibits unique cross-species reactivity. The antibody recognizes recombinant human and rat IGF-1 in ELISA, Western blots, and in an 125I-recombinant human IGF-1 Scintillation Proximity Assay. In addition, 35I17 blocks cell proliferation induced by recombinant human and rat IGF-1, and inhibits cell proliferation induced by sera from human, rat, calf, dog, goat, or mouse. The antibody inhibits rat IGF-1 binding to IGF-1 receptors, and prevents IGF-1-stimulated receptor and IRS-1 phosphorylation in LISN C4 cells, an IGF-1 receptor-transfected cell line. The cross-species and neutralizing properties of 35I17 may be useful in in vitro and in vivo animal studies for elucidating the role of IGF-1 in cancer, rheumatoid arthritis, and other diseases.