© 1994 Oxford University Press
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Granulocyte-macrophage colony stimulating factor gene expression and function during tumor promotion
1Departments of Medical Microbiology and Immunology Columbus OH 43210, USA
2Pathology The College of Medicine, The Ohio State University Columbus OH 43210, USA
1To whom correspondence should be addressed at: Department of MedicaJ Microbiology and Immunology, The Ohio State University, 2078 Graves Hall, 333 West 10th Avenue, Columbus, OH 43210, USA
Although recent evidense suggests that granulocyte-macrophage colony stimulating factor (GM-CSF) plays a role in cutaneous inflammation induced by topical exposure of phorbol ester tumor promoters to murine epidermis, there is little information available on the temporal sequence of gene expression of this cytokine over the time course of tumor promotion or about its function in this process. The goal of the present studies was to examine the potential role of GM-CSF in tumor promotion in SENCAR mice. Competitive reverse transcriptase polymerase chain reaction (RT-PCR) studies demonstrated that a single topical application of 12-O-tetradecanoylphorbol-13-acetate (TPA; 2 µg, 10 tg) to the dorsal epidermis of SENCAR mouse skin stimulated a dose and time dependent GM-CSF gene expression that was upregulated at 1 h after TPA exposure, peaked at 3 h and declined at 12 h. Although treatment with 7',12'-dbnethyl- benz[a] anthracene (DMBA) did not stimulate GM-CSF gene expression, GM-CSF gene expression was elevated in epidermal tissue isolated from SENCAR mice treated with a single application of 10 nmol DMBA followed by multiple applications of 2 µg TPA over a 1–22 week time course. Immunochemical and autoradiographic studies demonstrated that GM-CSF protein was produced by suprabasal keratino cytes, interfolilcular cells, nonproliferating papilloma cells and leukocytes within the dermis. Intraperitoneal injection of recombinant (r) GM-CSF into SENCAR mice at 2 h prior to topical application of 10 µg TPA induced a significant increase in epidermal keratinocyte proliferation, leukocyte infiltration into the dermis, hydroperoxide production by circulating neutrophils and chemotactic activity present within the plasma at 24 h compared to treatment with only 10 µg TPA. Intravenous injection of anti-GM-CSF antibodies significantly inhibited both local and systemic inflammatory events induced by topical application of TPA. The present studies suggest that GM-CSF has a broad spectrom of activity with at least two target cell populations, epidermal keratino cytes within the proliferative compartment and leukocytes.