Effect of c-Fos overexpression on the murine macrophage cell line P388DI

In order to study the role of Fos on the regulation of proliferation in the monocyte-macrophage lineage we realized a stable transfection of the murine P388D1 cell line by the murine c-fos gene under the control of the human metallothionein IIA promoter. Several clones have been selected by geneticin: they show a variable number of integrated transgene (two to ten copies). Their expression has been analyzed in the presence or absence of cadmium chloride as inducer (5 x 10(-6) M). In one clone especially, the c-fos mRNA and Fos protein levels were respectively 6- and 10-fold increased. The study of cell growth by tritiated thymidine incorporation indicates a negative effect of the overexpressed Fos protein in the absence of any other stimulus.