THE ROLE OF THE SPLEEN IN THE ORGAN-SPECIFIC METASTASIS OF MURINE BW-5147 T-LYMPHOMAS

Organ-specific metastasis of tumour cells may result from selective in vasion and growth or from selective host cell responses. The present s tudy demonstrates how selective interactions with the host affect the metastatic pattern of two murine T cell hybridoma lines, derived from the BW 5147 thymoma. Upon intravenous inoculation into syngeneic mice BW-14 cells preferentially colonize the kidneys, whereas BW-19 cells m etastasize mainly to the spleen and the liver. The organ-specific beha viour of the two cell lines appears to be determined by a differential interaction with the spleen microenvironment. Inoculation of BW-14 ce lls into splenectomized mice results in increased liver colonization, indicating a negative effect of the spleen on BW-14 tumour development in the liver. Macrophages are likely to be involved in this inhibitio n, since inoculation of BW-14 cells into macrophage-depleted mice also leads to increased liver and spleen metastasis. In contrast, inoculat ion of BW-19 cells into splenectomized mice results in decreased liver metastasis, which indicates that the spleen exerts a stimulating effe ct or BW-19 cells. Macrophages also appear to be involved in this stim ulation, since macrophage depletion causes a similar decrease in liver and spleen colonization. Hence components of the splenic microenviron ment, probably macrophages, exert inhibiting or stimulating activities on BW-14 or BW-19 cells respectively, thereby determining the subsequ ent liver or kidney colonization.