Cell Attachment and Spreading Properties of Laminin Subunits from Normal and Neoplastic Tissues

Abstract

Earlier studies from this laboratory (Ohno, M. et al., 1983) demonstrated the presence of a new laminin subunit which we termed “M” in extracts of normal placental membranes. This subunit could not be detected by immunoblot in laminin isolated from the mouse EHS tumor or in cultures of cells isolated from human neoplasms (Ohno, M. et al., 1986). In time, the presence of laminin isoforms was demonstrated in normal tissues having the molecular compositions A, B1, B2 (classical), M, B1, B2 (merosin) (Ehri& K et al., 1990) and A, S, B2 (synaptic lamimn) (Sanes, J.R. et al., 1990). Additional studies by Rao et al. (Rao, C.N. et al., 1990) demonstrated an altered ratio of B1 to B2 subunits as well as of the mRNAs for the same subunits during increased tumorigenesis of A₉ cells to A₉HT cells. In the present study we compared the cell (HT1080) attachment promoting activity of laminin molecules isolated from normal human placenta, a mouse solid tumor (EHS), a normal mouse cell line (B82) and a tumorigenic cell line (B82HT) derived from the former by serial passage in mice. Laminin at various concentrations (0.1, 0.2, 0.5 and 1.0 µg/well) was used as a substrate. HT1080 cells adhered more efficiently when laminin from B82 cells was used as a substrate (40%, 65%, 82% adhesion), compared to laminin from B82HT cells (23%, 35%, 64% and 72% adhesion, at the same substrate concentrations) and to laminin from EHS tumor (10%, 17%, 18%, 31% and 36% adhesion, at the same substrate concentrations). Spreading of HT1080 cells was maximal with the laminin from B82 cells, intermediate with that from B82HT cells and minimal with that from EHS tumor.