Parathyroid hormone-related protein overexpression in the human colon cancer cell line HT-29 enhances adhesion of the cells to collagen type I

The present experiments examined the potential ability of parathyroid hormone-related protein (PTHrP) to influence growth of the human colon cancer cell HT-29 and the ability of the cell to adhere to several extracellular matrix (ECM) proteins found in normal tissues. Addition of PTHrP analogs, PTHrP (1–34), PTHrP (67–86), or PTHrP (107–139), to HT-29 cells in culture did not influence cell growth or the adhesion of the cells to wells coated with fibronectin, laminin, or collagen type I. Likewise, in HT-29 cells induced to overexpress PTHrP by stable transfection with PTHrP cDNA, compared to vector-transfected control HT-29 cells, no effect on cell growth occurred. However, in the transfected cells, the increased production of PTHrP significantly enhanced cell adhesion to type I collagen but not to fibronectin or laminin. The results raise the possibility that PTHrP might play a role in colon tumor invasion and metastasis by influencing cell adhesion to specific extracellular matrix proteins.