Laminin expression by two clones isolated from the colon carcinoma cell line lovo that differ in metastatic potential and basement-membrane organization

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Abstract
In the present report we describe the characteristics of 2 clones, E2 and C5, isolated from the human colon adenocarcinoma cell line LoVo. When grafted to immunosuppressed newborn rats, these clones formed tumors that varied with regard to differentiation rate, basement-membrane organization and lung metastatic potential. Production and distribution of laminin by E2, C5 and related tumors was studied by immunohistochemistry with an anti-laminin monoclonal antibody 4CI2 (MAb 4CI2). In lowly metastatic E2-derived tumors, strong regular stainings were observed which were strictly peri-tumoral and corresponded to the basal lamina. Since the antibody interacted with human laminin (the graft) but not with rat laminin (the host), this result indicated that basementmembrane laminin was supplied mainly by tumor-cell synthesis. In highly metastatic C5-derived tumors, the staining obtained with MAb 4CI2 was peri-cellular and unorganized. Laminin synthesis by E2 and C5 cells in sub-cultures or soon after dissociation from explanted tumors was studied by metabolic labelling with 35S-methionine under steady-state conditions followed by immunoprecipitation and SDS-PAGE. High-molecular-weight laminin comprised by disulfide-linked A and B chains, i.e., heterotrimeric laminin, was found in cell lysates and in the secretion medium of cell lines and tumor cells. In addition, BIB2 dimers and free B chains were observed in cell lysates. Quantitatively, Iaminin expression by E2 and C5 clones or tumor cells was not significantly different. These findings suggest that basementmembrane defects in invasive clone LoVo C5 were not due to laminin under-expression.
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