Dr. Telford raises the question as to whether it is possible to discriminate tetraploid G1 from diploid G2 cells. Cyclins E and B1 are specific markers of G1 and G2 cells, respectively and therefore bivariate analysis of DNA content vs cyclin E or cyclin B1 expression can be used to distinguish these populations, as reviewed in Cytometry, 25: 1-13, 1996. This works, however, only when expression of these cyclins is scheduled as it is in the case on normal cells or some tumor lines during their unperturbed exponential growth. Several tumor lines, on the other hand, are characterized by unscheduled expression of cyclins (i.e. G1 cyclins are expressed in G2 and vice versa). Perturbation of cell cycle progression, e.g. as induced by some synchronication techniques, also result in unscheduled expression of cyclins. In these situations, of course, bivariate analysis of cyclins E or B1 vs cellular DNA content cannot distinguish G1 tetraploid from G2 diploid cells. Zbigniew Darzynkiewicz
This archive was generated by hypermail 2b29 : Wed Apr 03 2002 - 11:49:45 EST