CHARACTERIZATION OF CYCLIN B1 EXPRESSION IN HUMAN CANCER CELL-LINES BY A NEW 3-PARAMETER BRDURD CYCLIN B1/DNA ANALYSIS/

Flow cytometric cyclin expression/DNA content analysis, now commonly u sed, provides useful information on the mechanisms regulating cell cyc le progression. However, this biparametric analysis does not make a cl ear-cut distinction between G(1) and S-early or between S-late and G(2 )M phase cells. This paper proposes a new three-parameter flow cytomet ric method with which to determine cyclin B1 levels in single cells in different cell cycle phases by coupling bromodeoxyuridine (BrdUrd) im munodetection and DNA content, DNA denaturation by HCl did not alter t he level of cyclin B1. Differences in cyclin B1 expression were observ ed in seven human cancer cell Lines of different origin, The percentag e of cyclin B1-positive cells and the cyclin B1 content per cell indic ated different patterns, In some cases cyclin B1 accumulation preceded the G(2)M checkpoint, at which its content usually started to rise. U sing available easily reproducible techniques, this flow cytometric ap proach gives details of intracellular variability in cyclin expression , (C) 1998 Wiley-Liss, Inc.