Cell-cycle characteristics of undifferentiated and differentiating embryonal carcinoma cells

The cell-cycle parameters of undifferentiated and differentiating embryonal carcinoma cells were determined. Undifferentiated cultures of an F9 subclone, OTF9-63, had a 12-hr generation time, 10-hr S, and 2-hr G2 + M. G1 was less than 0.5 hr. In contrast, OTF9-63 cells induced to differentiate by treatment with retinoic acid had a 16.8-hr generation time, 12.5-hr S, 2-hr G2 + M, and 2.3-hr G1. Similar results were obtained with undifferentiated cultures and aggregation-induced differentiating cultures of PSA-1 cells. These data demonstrate that the undifferentiated stem cells have little or no G1, and that both G1 and S lengthen during differentiation.