Activation of fibroblast-derived matrix metalloproteinase-2 by colon-cancer cells in non-contact co-cultures

Stromal fibroblasts interact with invading cancer cells by secreting and ac tivating matrix metalloproteinases (MMPs), To elucidate the mechanisms invo lved in the expression and activation patterns of MMPs, human colon-cancer cell lines Caco-2 and LoVo and colon-fibroblast cell line CCD18-Co were co- cultivated in non-contact and contact conditions which mimic in vivo intera ction between cancer cells and fibroblasts before and after cancer invasion respectively. Gelatin zymography disclosed that MMP-2 was secreted from th e fibroblasts but not from the cancer cells. The quantity of fibroblast-der ived MMP-2 in conditioned medium was not significantly changed in either th e contact or the non-contact co-cultures when compared with that of individ ual cultures of CCD18-Co fibroblasts, Cancer cells in non-contact co-cultur es, however, enhanced the activation of fibroblast-derived MMP-2, Transcrip ts of membrane type matrix metalloproteinase-1 (MTI-MMP), which is thought to be present on the cell surface and to work as a candidate activator of M MP-2, were detected in both cancer cell lines. Plasma membrane extracts of cancer cells also activated MMP-2 in conditioned media in cell-free conditi ons. This activation of MMP-2 may be caused by MTI-MMP of the cancer cells, since it was inhibited by a series of MMP inhibitors, including ethylenedi aminetetraacetic acid (EDTA), the tissue inhibitor of metalloproteinase-2 ( TIMP-2), and the MMP inhibitor CGS 27023A, but not by TIMP-1. Our data demo nstrate that in non-contact co-cultures colon-cancer cells activate fibrobl ast-derived MMP-2 on their plasma membranes. These findings should help to elucidate the mechanism involved in the initial destruction of basement mem brane by cancer cells. Int. J. Cancer 87:165-171, 2000. (C) 2000 Wiley-Liss , Inc.