Growth morphology of control and pMT-993S transfected cells. F9-N-4 (A, D, G,J), F9-H1.6-5 (B, E, H, K), and F9-H1.6-10 (C, F, I, L) cells were grown for two (A–C) or four (D–L) days in the presence of 100 μM ZnCl2 alone (A–F), ZnCl2 + 1μM RA (G–I), or ZnCl2 + RACT (J–L), rinsed with warm PBS, and photographed with a Nikon inverted microscope equipped with Hoffman optics. Magnification is 200×.