Fig. 1. Morphological changes induced by RA in P388D1 cells. Stably transformed P388D1 cells (provided by W. Sly) overexpressing the M6P/IGF2R (C and D) and control P388D1 cells (transfected with the control vector, receptor negative; A and B) were treated with (B and D) or without (A and C) 1 µM RA for 24 h. The photographs were taken directly from a 6-well culture plate using a phase microscope.