Change in organotropism of mouse lymphoma variants associated with selective chemotactic responsiveness to organ-derived chemoattractants

Abstract

A variant of the highly metastatic mouse lymphoma ESb was isolated from ESb suspension culture by repeated selection for adhesiveness to plastic. The adhesion variant ESb-MP was shown to have greatly reduced malignant potential and a change in organotropism. ESb-MP cells metastasized into the kidney with a high frequency (80% of mice), whereas the ESb cells only rarely infiltrated the kidney (4% of mice). Two subclones of the adherent variant (ESb-M2 A8, ESb-M2 H6) showed a reduced malignant potential in vivo very similar to the ESb-MP cell line, but only the clone ESb-M2 A8 infiltrated the kidney. Cell motility and chemotaxis of the various tumor lines was tested in a modified Boyden chamber assay. ESb-MP cells always migrated about 45 microns into a nitrocellulose filter of 8 microns pore size during 4 h incubation, whereas ESb cells and the two subclones migrated only to a distance of 12-25 microns. There was no apparent correlation between in vitro motility and malignancy in vivo. The addition of several factors known to be chemoattractant for granulocytes (C5a, FMLP) or for tumor cells (FMLP, laminin, fibronectin) did not affect the migration of ESb or ESb-MP cell lines. Enhanced migration of the ESb-MP cell line was, however, observed when kidney conditioned medium (KCM) was used as attractant in the lower chamber. This was not true for ESb cells. Additionally, within the subclones of the ESb-MP cell line, there was a remarkable correlation between kidney metastasis in vivo and responsiveness to KCM in vitro. The motility stimulating effect of KCM was due to a chemotactic activity. ESb cells, which did not respond to KCM, responded to other factor(s) derived from inflammatory exudate fluid. We conclude that the stimulation of tumor cell motility by an organotropic factor was highly selective for certain tumor lines. The correlation, between responsiveness in vitro and kidney metastasis in vivo, suggests that it is not so much the random migration of tumor cells which plays a role in metastasis but the motility following selective stimulation by tissue-derived factors and chemoattractants.