IL-2 treatment of B16F10 melanoma cells stimulates metastatic colonization in the liver.

We had previously shown that murine B16F10 melanoma cells express the receptor for IL-2, transcribe the gene for IL-2 and respond to its factor by increasing their proliferation. In the present work we have investigated the effect of in vitro IL-2 treatment on the metastatic ability of B16F10 cells. In vivo experiments showed that the metastatic colonization of the liver was notably higher after intrasplenic inoculation of IL-2-treated cells. However, no change was observed when cells were intravenously inoculated. In vitro, cells became more resistant to NK lysis although the cytometric analysis of class 1 MHC molecules revealed a decrease in H-2Kb expression. In contrast IL-2 induced a two fold increment in the expression of la antigen. On the other hand slot-blot analysis showed that IL-2 gene expression could be upregulated, however no free IL-2 was released into the culture medium of B16F10 cells. We conclude that IL-2 increases the ability of B16F10 cells to metastase to the liver. The increase in the resistance to NK activity and in la antigen expression could be involved in the mechanisms underlying this effect.