Expression of major histocompatibility class I genes in differentiating leukemic cells is temporally related to activation of c-fos proto-oncogene.

The relationship between the expression of the c-fos proto-oncogene and the expression of the class I major histocompatibility (MHC) antigens during the early stages of induced differentiation in three different leukemic cell lines was examined. In the U937 histiocytic lymphoma line TPA induced an increase in mRNA and cell surface MHC expression which followed induction of c-fos. In contrast, in the murine erythro-leukemia cell line, DMSO induced declining constitutive c-fos levels that were accompanied by declining mRNA and cell surface MHC expression. In the pluripotent HL60 promyelocytic line induction of macrophage differentiation with TPA led to c-fos induction and rising MHC levels, whereas induction of granulocyte differentiation with DMSO did not induce c-fos expression and was followed by declining MHC levels. Taken together, the results suggest that the c-fos proto-oncogene might be involved in the control of class I MHC antigen expression during differentiation.