treatment of human diploid fibroblasts at varying cell densities with 12-o-tetradecanoylphorbol-13-acetate ( tpa ) ( 10 ( -7 ) m ) resulted in a bimodal response of proliferation rate : while at low cell densities ( 3 x 10 ( 3 ) -1.5 x 10 ( 4 ) cells/cm2 ) tpa inhibited the proliferation by up to 50 % , at high cell densities ( 1-1.6 x 10 ( 5 ) cells/cm2 ) a 2-fold higher proliferation rate as in untreated cultures was observed .
C0016030
fibroblasts
C0007634
cells