Flow cytometric analysis of the effect 5-bromodeoxyuridine on mouse teratocarcinoma cells

Several flow cytometric techniques were used to study the effects of 5-bromodeoxyuridine (BrdUrd) on the growth and differentiation of mouse teratocarcinoma cells. The teratocarcinoma system mimics embryogenesis, and the stem cells of this tumor, termed embryonal carcinoma (EC) cells, spontaneously differentiate in vitro to progeny that are morphologically, biochemically and biologically distinct from the EC cells. When cultures of EC cells were treated with 30 microM BrdUrd, a pleiotropic response was observed; i.e., certain parameters mimicked spontaneous differentiation but occurred 2-3 times more rapidly while others were inconsistent with, or diametric to, spontaneous differentiation. In one line of diploid EC cells in which tetraploidy accompanies spontaneous differentiation, the BrdUrd accelerated the appearance of the tetraploid population. Analysis of cell cycle distributions during the course of the BrdUrd treatment showed that virtually all of the cells had cycled 2 or more times and incorporated BrdUrd into both strands of DNA. Multiangle light-scattering and electrical impedance analyses indicated that with respect to these two parameters, cultures treated with BrdUrd for 3 days resembled spontaneously differentiating cultures of 6-8 days. However, BrdUrd treatment did not induce increases in the kinetics of esterase (EC3.1.1.) activities in teratocarcinoma cells that normally accompany spontaneous differentiation. Analysis of alkaline phosphatase (APase) EC (3.1.3.1) activities showed that unlike the decrease in APase activities which accompany spontaneous differentiation, BrdUrd treatment causes an increase in APase activities.