Measurement of c-myc protein content and cell cycle kinetics of normal and spontaneously transformed murine mastocytes by bivariate flow cytometry.
Progressive in vitro culturing of interleukin-3 (IL-3) dependent normal murine mastocytes (PB-3) resulted in a variant cell line (PB-1) able to grow without exogenous IL-3 and which was tumorogenic in syngenic mice. Bivariate flow cytometry was used to evaluate the c-myc protein and DNA content of PB-3 and PB-1 cells. The c-myc protein was detected by specific monoclonal antibodies. Kinetic characteristics of PB-3 and PB-1 cell lines, namely, the duration of the G1, S and G2 + M cell cycle phases were also evaluated using the bromodeoxyuridine (BrdU) pulse-chase method and BrdU/DNA flow cytometry. Levels of c-myc protein in PB-1 cells were about two-fold higher than those of PB-3 cells in all cell cycle phases. Mean duration of the cell cycle (Tc) was 15.3 h for PB-3 cells and 12.4 h for PB-1 cells. Shortening in Tc for the transformed cells was due to a decrease of nearly 30% in mean duration of the G1 phase (from 8 h to 5.7 h). No significant differences were found in the duration of the S and G2 + M phases. These results indicate that acquired IL-3 independency in vitro and tumorogenicity of PB-1 cells were accompanied by a doubling of c-myc protein level and by a parallel shortening, or bypass, of the regulatory events within the G1 phase of the cell cycle.
Giaretti
W
W
Biophysics Laboratory, National Institute for Cancer Research (I.S.T.), Genoa, Italy.
Di Vinci
A
A
Geido
E
E
Marsano
B
B
Minks
M
M
Bruno
S
S
D000818:Animals; D000911:Antibodies, Monoclonal; D001973:Bromodeoxyuridine / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D002461:Cell Line, Transformed; D002467:Cell Nucleus / Q000737:chemistry; D004247:DNA / Q000032:analysis / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry / Q000379:methods; D007700:Kinetics; D008407:Mast Cells / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D051379:Mice; D008811:Mice, Inbred DBA; D011419:Propidium; D016271:Proto-Oncogene Proteins c-myc / Q000032:analysis* / Q000378:metabolism
D000911:Antibodies, Monoclonal; D016271:Proto-Oncogene Proteins c-myc; D011419:Propidium; D004247:DNA; D001973:Bromodeoxyuridine