u-0126 and mannose-6-phosphate

The aspartyl-protease cathepsin D (cath-D) is overexpressed and hypersecreted by epithelial breast cancer cells and stimulates their proliferation. As tumor epithelial-fibroblast cell interactions are important events in cancer progression, we investigated whether cath-D overexpression affects also fibroblast behavior. We demonstrate a requirement of cath-D for fibroblast invasive growth using a three-dimensional (3D) coculture assay with cancer cells secreting or not pro-cath-D. Ectopic expression of cath-D in cath-D-deficient fibroblasts stimulates 3D outgrowth that is associated with a significant increase in fibroblast proliferation, survival, motility, and invasive capacity, accompanied by activation of the ras-MAPK pathway. Interestingly, all these stimulatory effects on fibroblasts are independent of cath-D proteolytic activity. Finally, we show that pro-cath-D secreted by cancer cells is captured by fibroblasts and partially mimics effects of transfected cath-D. We conclude that cath-D is crucial for fibroblast invasive outgrowth and could act as a key paracrine communicator between cancer and stromal cells, independently of its catalytic activity.

Topics: Animals; Apoptosis; Butadienes; Cathepsin D; Cell Enlargement; Cell Growth Processes; Cell Line; Cell Line, Tumor; Cell Movement; Cell Proliferation; Cell Survival; Coculture Techniques; Culture Media, Conditioned; Endocytosis; Enzyme Inhibitors; Enzyme Precursors; Fibroblasts; Humans; Mannosephosphates; Mice; Microscopy, Electron; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Neoplasm Invasiveness; Neoplasms, Glandular and Epithelial; Nitriles; Paracrine Communication; Phosphorylation; RNA, Small Interfering; Transfection; Wound Healing