[Mouse Lewis carcinoma cell population heterogeneity and sensitivity to cyclophosphamide]

Cell kinetics in the large Lewis carcinoma growing in mice subcutaneously was characterized by the following parameters: at the tumor periphery -tc=11.3 hr, tG2=1.4 hr, tS=8.8hr, tG1=1.1 hr, LI=47%, Pc=61.8%; at the tumour center - 20.7 hr, 2.9 hr, 16.0 hr, 1.8 hr,31.2%, resp. Injection of cyclophosphamide induced degeneration of all the cells in slowly growing central part of the tumour, and only of part of cells on the fast proliferating tumour periphery. It is suggested that in the central part of the tumour there are no stem cells, and that this region regenerates when the transition of cells from the tumour periphery is arrested by cyclophosphamide.