Correspondence

FGF2 elicits a strong mitogenic response in the mouse Y-1 adrenocor-tical tumor cell line, that includes a rapid and transient activation of the ERK-MAPK cascade and induction of the c-Fos protein. ACTH, itself a very weak mitogen, blocks the mitogenic response effect of FGF2 in the early and middle G1 phase, keeping both ERK-MAPK activation and c-Fos induction at maximal levels. Probing the mitogenic re-sponse of Y-1 cells to FGF2 with ACTH is likely to uncover reactions underlying the effects of this hormone on adrenocortical cell growth