title: Murine mammary tumour cells in vitro. II. Recruitment of quiescent cells.
abstract: The development of a pure quiescent (Q) tumour cell population can be induced in three mouse mammary tumour lines (66, 67 and 68H) by nutrient deprivation. When these Q cells were removed from nutrient-deprived cultures and replated in fresh medium at a lower cell concentration within 72 hr of entering quiescence virtually all of the Q cells could re-enter the proliferating (P) state. This recruitment was characterized by an increase in cell volume, an increase in total cellular RNA, and a resumption of cell division. The length of the Q to P transition varied among the three cell lines and the depth of the quiescent state depended on the amount of time the cells had been quiescent. Once re-entry into the P compartment was completed, cell-cycle times, as estimated by the culture doubling time, were the same as the cells that had not entered the Q state, however, after 72 hr in quiescence, not all of the 66 cells could reattach after trypsinization and of those that could reattach approximately equal to 50% were incapable of either increasing their RNA levels to that of proliferating G1 cells or entering S. Clonogenicity of the nutrient-deprived Q cells in these lines decreases exponentially from time the cells enter quiescence with approximate half-times of 32, 34, and 96 hr for the 66, 68H and 67 cells, respectively. Since clonogenicity was already declining at a time when all the Q cells could re-enter the P compartment, the ability of a Q cell to form a colony is not determined solely by its capacity to re-enter the proliferating compartment.
mesh_terms: D000818:Animals; D002455:Cell Division; D002460:Cell Line; D002469:Cell Separation; D002999:Clone Cells; D004247:DNA / Q000032:analysis; D005260:Female; D005434:Flow Cytometry; D007399:Interphase; D007700:Kinetics; D008325:Mammary Neoplasms, Experimental / Q000473:pathology*; D051379:Mice; D012313:RNA / Q000032:analysis
chemical_list: D012313:RNA; D004247:DNA