Regulation of extracellular matrix remodeling following transforming growth factor-β1/epidermal growth factor-stimulated epithelial-mesenchymal transition in human premalignant keratinocytes

During tumor progression, malignant cells exploit critical developmental and tissue remodeling programs, often promoting a plastic phenotype referred to as an epithelial-mesenchymal transition (EMT). Autocrine/paracrine signaling due to tumor microenvironment cytokines, such as members of the transforming growth factor-beta (TGF-beta) and epidermal growth factor (EGF) families, largely regulates the morphological and invasive phases of the EMT phenotype. Notably, epithelial cell initiation often coincides with a switch in the response of these cells to TGF-beta and is concomitant with EGF receptor amplification. Modeling these events, we have observed that premalignant human keratinocytes, HaCaTs, acquire a highly motile and scattered phenotype indicative of EMT following stimulation with TGF-beta 1 and EGF. TGF-beta 1 and EGF have been shown to upregulate a number of matrix metalloproteinases (MMP) in epithelial cells, which may in turn play a role in developing metastatic potential in these cells. We have established that an increase in MMP-10 expression occurs following treatment of HaCaT cells with a combination of TGF-beta 1 and EGF. This increase in MMP-10 expression paralleled the development of a collagenolytic phenotype that was sensitive to components of the plasminogen activation system, including the plasminogen activator inhibitor type-1 (PAI-1). Significantly high levels of MMP-10 have been detected in squamous cell carcinomas of the head and neck, esophagus, oral cavity and skin. Importantly, TGF-beta 1 in addition to upregulating MMP-10 has been shown to upregulate PAI-1 expression in HaCaT cells. Taken together, these observations suggest that TGF-beta 1 and EGF play a complex role in modulating proteolytic and transitional events such as EMT that may facilitate the progression of human premalignant epithelial cells toward a more invasive phenotype. Copyright (c) 2007 S. Karger AG, Basel.