title: Programmed cell death by default in embryonic cells, fibroblasts, and cancer cells.
abstract: We recently proposed that most mammalian cells constitutively express all of the proteins required to undergo programmed cell death (PCD) and undergo PCD unless continuously signaled by other cells not to. Although some cells have been shown to work this way, the vast majority of cell types remain to be tested. Here we tested purified fibroblasts isolated from developing or adult rat sciatic nerve, a mixture of cell types isolated from normal or p53-null mouse embryos, an immortalized rat fibroblast cell line, and a number of cancer cell lines. We found the following: 1) All of these cells undergo PCD when cultured at low cell density in the absence of serum and exogenous signaling molecules but can be rescued by serum or specific growth factors, suggesting that they need extracellular signals to avoid PCD. (2) The mixed cell types dissociated from normal mouse embryos can only support one another's survival in culture if they are in aggregates, suggesting that cell survival in embryos may depend on short-range signals. (3) Some cancer cells secrete factors that support their own survival. (4) The survival requirements of a human leukemia cell line change when the cells differentiate. (5) All of the cells studied can undergo PCD in the presence of cycloheximide, suggesting that they constitutively express all of the protein components required to execute the death program.
authors.affiliation: Department of Physiological Chemistry, Postgraduate School, Tokyo Medical and Dental University, Tokyo.
authors.forename: Y
authors.initials: Y
authors.lastname: Ishizaki
authors.forename: L
authors.initials: L
authors.lastname: Cheng
authors.forename: A W
authors.initials: AW
authors.lastname: Mudge
authors.forename: M C
authors.initials: MC
authors.lastname: Raff
mesh_terms: D000818:Animals; D017209:Apoptosis; D002454:Cell Differentiation; D002460:Cell Line; D002470:Cell Survival; D002478:Cells, Cultured; D046508:Culture Techniques / Q000379:methods; D004253:DNA Nucleotidylexotransferase / Q000378:metabolism; D004622:Embryo, Mammalian; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D018922:HL-60 Cells; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008322:Mammals; D051379:Mice; D008807:Mice, Inbred BALB C; D051381:Rats; D017207:Rats, Sprague-Dawley; D012584:Sciatic Nerve / Q000166:cytology* / Q000502:physiology*; D015398:Signal Transduction; D013997:Time Factors; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000502:physiology
chemical_list: D004253:DNA Nucleotidylexotransferase