Surface morphology of normal and neoplastic rat cells

Nontumorigenic rat cells and their tumorigenic counterparts were studied with scanning electron microscopy under controlled conditions in vitro and with transmission electron microscopy after replantation in vivo to discern if external morphology reflected the cell's neoplastic state or the etiology of transformation. Interphase cells in 6 of 7 nontumorigenic lines were flat and monolayered under confluent conditions and exhibited smooth, nonactive cell surfaces. A nontumorigenic cell line morphologically transformed with human adenovirus 2 consisted of spherical cells with blebbed surfaces. Cells from 6 tumorigenic lines transformed with avian sarcoma virus had highly active surfaces with many surface projections. Cells from 2 chemical carcinogen transformed rat embryo lines were flat with no surface projections in subconfluent culture and rounded with only a few microvilli at high densities, but cells from a sarcoma chemically induced in an adult rat were villous. When villous cells were syngeneically replanted in vivo, they lost most microvilli. The external morphology of cells was influenced by a number of factors simultaneously, with no universal pattern associated with tumorigenic capacity or transforming agent.