Effect of hepatocyte örowth factor (HGF) and keratinocyte growth factor (KGF) stimulation of human cornea and mammary epithelial cells on JAK-STAT and RAS/MAP KIN äse signal transduction pathways

Purpose: We sought to determine it hepa ocyte growth (actor (HGF) and keratocyle growth factor (KGF) also activate specific Jak-Sta- and Ras-related pathways in human corneal and mammary gland epithelial celts as has been shown for EGF. Methods: Primary cultures of human coneal and mammary gland epithelial cells treated with recombinant human HGF or KGF at 100 ng/ml for 15 min. were harvested for protein preparation, immunoprecipitation was perormed with antisera to Statl, Stal3, StatS, Jak2, Tyk2, She, and MAP kinase. Immunoprscipitated protems or whole cell extracts were analyzed by western blotting with antinhosphorytyrosine antibody. Gel mobility shift experiments were carried out to detect the binding of Stats to GAS DNA element. Results: HGF receptor was phosphoryialed in response to HGF treatment in both human corneal and mammary gland epithelial cells. However, several JAK-STAT signal pathway cascade components (Stall, Stat3, StatS, Jak2, Tyk2} were not activated (phosphorylated) m response to either HGF or KGF stimulation. In gel mobility shift assay experiments, IFN-g activated Stall, and EGF activated Stall and Stat 3. However, no binding of Stats to GAS DNA sequence in response to HGF or KG!: was detected. Alternatively, the intraceltular Ras pathway-associated protein She was phosphorylated in response to HGF, but not KGF, induction in both human corneal and m;immary gland epithelial cells. MAP kinase was activated in response to either HGF or KGI, stimulation in both human epithelial cells. Conclusion: HGF and KGF do not activa e the JAK-STAT cascade components examined m this study in corneal and mammary epi helial cells. Jak1 was not evaluated in this study and, therefore, we cannot exclude its involvement in KGF or HGF signaling. Phosphorylation of MAP kinase in response to HGF or KGF treatments indicates that Ras/MAP kinase pathways are used by these growth factors in mediating their effects in corneal and mammary epithelial cells.