Morphology of CMK cell cytospins, Wright stained, and photographed at 400×. (A) Parental CMK cells showing an immature phenotype. The majority of cells have a single noncondensed nucleus with a small amount of cytoplasm. (B) Parental CMK cells treated with PMA. The cells show signs of differentiation including increased cell size, increased amount of cytoplasm, increased vacuolation of the cytoplasm, and an increased nuclear density with areas of multinucleation. (C) Vector control transfected CMK clone showing an immature phenotype. (D) WT Mek transfected CMK clone showing an immature phenotype. (E) DE Mek transfected clone showing a differentiated phenotype. (F ) D330N Erk transfected clone showing a differentiated phenotype.