Growth factor regulation of the amylase promoter in a differentiating salivary acinar cell line

Salivary glands contain two major epithelial cell types: acinar cells which produce the primary salivary secretion, including amylase, and ductal cell s which reabsorb electrolytes but also secrete kallikrein. Here we investig ated salivary acinar cell differentiation in vitro using the activity of th e salivary amylase and tissue kallikrein promoters as markers of acinar cel l and ductal cell differentiation, respectively. Each of the promoter seque nces was cloned into a replication-deficient adenoviral vector containing t he luciferase reporter gene. Previous studies showed that a human submandib ular gland cell line (HSG) differentiated into acinar cells when cultured o n a reconstituted basement membrane matrix (Matrigel). The luciferase activ ity of the amylase promoter vector (AdAMY-luc) was low in HSG cells culture d on plastic, where they grow as an epithelial monolayer. The promoter acti vity increased approximately tenfold when HSG cells were cultured on Matrig el and developed an acinar phenotype. Under the same conditions, the lucife rase activity of the kallikrein promoter (AdKALL-luc) was not induced. Beca use HSG cells demonstrate acinar cell morphology, but not amylase gene expr ession, when cultured on laminin-1, certain soluble components of Matrigel were tested for their ability to induce the amylase promoter during in vitr o differentiation of acinar cells. We find that epidermal growth factor (EG F) and transforming growth factor-alpha (TGF-alpha), which are present in t he basement membrane, and hepatocyte growth factor (HGF) increase activity of the amylase promoter. Other basement membrane-derived growth factors suc h as TGF-beta, basic fibroblast growth factor (bFGF), and platelet-derived growth factor (PGDF), as well as tumor necrosis factor (TNF-alpha), keratin ocyte growth factor (KGH), nerve growth factor (NGF) and interferon gamma ( IFN-gamma) were inactive. This system will be further exploited to study th e mechanisms by which extracellular matrix molecules and growth factors reg ulate salivary acinar cell differentiation. I Cell Physiol 777.628-635, 199 8. (C) 1998 Wiley-Liss, Inc.dagger.