[The roles of cytokine in organ-specific tumor metastasis]

The production of cytokines by tumor cells has been suggested as the molecular perturbation responsible for the development of malignant tumors. The behavior of tumor cells in animals is presumed to be affected by these factors, which include such hematopoietic cytokines as GM-CSF, IL-1, and IL-6. Here, we report findings demonstrating that GM-CSF is produced by many murine transplantable tumors with metastatic ability in the lungs, and IL-6 and/or IL-1 are produced by the tumors metastatic in the liver. We discuss the notion that the particular organ or organs in which tumor cells metastasize may be associated with the type of cytokines produced by the tumors. Metastatic spread requires interactions of tumor cells with components of the extracellular matrix of host tissues or with other cells, almost all of which depend on cell surface determinants such as cell adhesion molecules. We also discuss the possibility that the expression and adhesive potentials of adhesive protein (CD44) may be regulated by the cytokine (GM-CSF) excreted from the tumor cells. We then emphasize the possibility that both gene expression of cytokines and adhesive proteins play a critical role in tumor metastasis and in determining organ specificity in metastasis.