Production of fibronectin and adherence to fibronectin by human myeloma cell lines.

In the present study we examined the production of fibronectin (FN) in 10 human myeloma cell lines (HMCL). By Northern blot analysis we could detect the presence of FN-mRNA in most of these lines. A majority of the cell lines (LP-1, OPM1, SKMM-2, EJM, JJN3 and ARH-77) hybridized with two probes recognizing total FN while the mRNA of one cell line (LB84-1) was shown to hybridize also with a probe recognizing the EDA segment of cellular FN. In one cell line (L363) FN-mRnA could only be detected after PCR amplification. Using an enzyme-linked immunosorbent assay, we could also demonstrate that HMCL secrete FN in their culture medium. Seven myeloma cell lines that produce FN showed a significant adherence to soluble FN. By blocking experiments, this adhesion was found to be mediated by the VLA-4 (alpha 4 beta 1) receptor. The production of fibronectin and the expression of a functional receptor for this protein may represent independent features of myeloma cells but may also be functionally linked. Since fibronectin has recently been identified as a crucial co-factor of IL6 in the regulation of the terminal B cell differentiation, the endogenous FN production may be part of an autocrine-line process mediating the autonomous growth of these cell lines. Alternatively, the FN production may also reflect a mechanism that myeloma cells use to communicate with their natural environment, i.e. the bone marrow stroma.(ABSTRACT TRUNCATED AT 250 WORDS)