Effects of transforming growth factor-β on human pulmonary adenocarcinoma cell adhesion, motility, and invasion in vitro

Background: Transforming growth factor-β1 (TGF-β1), a potent growth modulator produced by a variety of tumor cells, as well as by platelets, has pleiotropic effects on cell-extracellular matrix interactions and may influence tumor cell invasion and metastasis. Purpose: Our purpose was to characterize the effects of TGF-β1 on the adhesion, motility, and invasiveness of a metastatic human pulmonary carcinoma (A549 cell line) in vitro. Methods: A549 cells were seeded onto type I collagen gels, and invasion over a 9-day period was measured in the presence or absence of TGF-β1 (0.1-10 ng/mL). In addition, cell adhesion to substrata coated with type I collagen (1-100 nM) as well as haptotactic migration through filters coated with type I collagen (100 μg/mL) were measured following a 24-hour treatment with TGF-β1 (1-10 ng/mL). Results: TGF-β1 stimulated the invasion of A549 cells into type I collagen gels in a dose-dependent manner. Both the number of cells entering the gel and the depth of invasion into the gel were increased. In addition, the effects of TGF-β1 were blocked in a dose-dependent manner by a purified polyclonal IgG against TGF-β1 but not by normal rabbit IgG. A549 cell invasion was accompanied by dramatic changes in A549 cell morphology that included the appearance of numerous long pseudopodia, consistent with a change in the motile behavior of these cells. TGF-β1 stimulated by approximately fourfold the haptotactic migration of A549 cells on polycarbonate filters coated with type I collagen. The TGF-β1-mediated increase in invasion and motility was accompanied by a fourfold increase in A549 cell adhesion to type I collagen. Conclusions: The results suggest that TGF-β1 can influence cellular recognition of extracellular matrix components and can modulate cellular adhesion and migration on these components, leading to increased invasive potential. Implications: Given the wide-spread tissue distribution of TGF-β1 and its secretion by a variety of tumor cells as well as by platelets, TGF-β1 may be an important autocrine-paracrine regulator of the invasive phenotype in vivo.