Interaction of B-cell hybridomas with fibroblast or hepatocyte monolayers in vitro and their metastatic behaviour in vivo.

Using an in vitro monolayer assay (MIA) we analyzed the invasive behaviour of a panel of B-cell hybridomas prepared by the fusion of non-invasive, non-metastatic NSO plasmacytoma cells and normal murine B-cells. Interaction of these hybridomas with fibroblast-like monolayers consisted mostly of adhesion on top of the monolayers, whereas only a fraction of these cells penetrated through the monolayer. This is in sharp contrast with the highly invasive properties displayed by T-cell hybridomas. Whereas T-cell hybridomas highly infiltrated monolayers of rat hepatocyte in vitro, B-cell hybridomas neither adhered to nor infiltrated hepatocyte monolayers. We found a good correlation between the degree of adhesion of B-cell hybridomas to fibroblast-like monolayers and their metastatic capabilities upon i.v. injection into syngeneic animals. Unlike T-cell hybridomas which formed diffuse metastasis in liver and spleen, B-cell hybridomas generated nodular metastatic lesions. . When normal LPS-stimulated B-lymphocytes were tested in the fibroblast-MIA, only part of the population infiltrated the monolayers. This again contrasts with T-lymphocytes where a majority of the cells penetrated through the monolayers. These results suggest that (i) B-lymphocytes express invasive properties, albeit to a lesser extent than T-lymphocytes, (ii) non-invasive B-lymphoma cells can acquire invasiveness following cell fusion with a normal B-cell, (iii) these invasive properties contribute to the malignancy of the hybridomas when tested in recipient animals.