Apoptosis activated in fibrosarcoma growth

A protein-independent fibrosarcoma，Gc-4PF，grows exponentially in a protein-free medium。The doubling time was similar to that of the serum-dependent parental clone，Gc-4SD cultivated in the presence of fetal calf serum。The protein-free cultivation of Gc-4PF cells concomitantly activates apoptotic phenotypes(One Third Total Cell Population)，including typical morphology，high uptake of Hoechst33342dye，and cleavage of DNA to large fragments，as observed in protein-deprived Gc-4SD cell previously.Gc-4SD cells arrested in the G I D20个D 2/G个D 21个D 2 phase in response to the protein-free condition.In contrast，Gc-4PF cells did not reach G I D20个D 2/G个D 21个D 2 arrest in the protein-free condition；instead the durations of both G个D 20个D 2/G个D 21个D 2 and G个D 22个D 2 phases were markedly reduced.The estimation of one cell cycle duration revealed that the cell division cycle was accelerated to 1.7-fold。Then the growth kinetics was able to be verified quantitatively by both the cell division rate and apoptotic cell loss.Protein-free cultivation resulted in slight down-regulation of c-myc protein in both cell types，while the down-regulation of P34 I D1 cdc2 Cells，shown clearly in Gc-4SD cells，was avoided in Gc-4PF cells。Interestingly，while the expression of p53was not affected in Gc-4SD cells in response to the protein-free condition，the suppressor gene product expression was suppressed markedly in Gc-4PF cells。From these results Gc-4PF cells may have acquired an ability to accelerate cell division by shortening the cell cycle duration to maintain a proper growth rate in response to intrinsic apoptosis activation with，at least in part，a suppression of p53expression as well as an escape of down-regulation of P34 I D1 cdc2。

A protein-independent fibrosarcoma, Gc-4 PF, grows exponentially in a protein-free medium. The doubling time was similar to that of the serum-dependent parental clone, Gc-4 SD cultivated in the presence of fetal calf serum. The protein-free cultivation of Gc-4 PF cells concomitantly activates apoptotic phenotypes (one third total cell population), including typical morphology, high uptake of Hoechst 33342 dye, and cleavage of DNA to large fragments, as observed in protein-deprived Gc-4 SD cell previously. Gc-4 SD cells arrested in the GィイD20ィエD2/GィイD21ィエD2 phase in response to the protein-free condition. In contrast, Gc-4 PF cells did not reach GィイD20ィエD2/GィイD21ィエD2 arrest in the protein-free condition ; instead the durations of both GィイD20ィエD2/GィイD21ィエD2 and GィイD22ィエD2 phases were markedly reduced. The estimation of one cell cycle duration revealed that the cell division cycle was accelerated to 1.7 -fold. Then the growth kinetics was able to be verified quantitatively by both the cell division rate and apoptotic cell loss. Protein-free cultivation resulted in slight down-regulation of c-myc protein in both cell types, while the down-regulation of P34ィイD1cdc2ィエD1, shown clearly in Gc-4 SD cells, was avoided in Gc-4 PF cells. Interestingly, while the expression of p53 was not affected in Gc-4 SD cells in response to the protein-free condition, the suppressor gene product expression was suppressed markedly in Gc-4 PF cells. From these results Gc-4 PF cells may have acquired an ability to accelerate cell division by shortening the cell cycle duration to maintain a proper growth rate in response to intrinsic apoptosis activation with, at least in part, a suppression of p53 expression as well as an escape of down-regulation of P34ィイD1cdc2ィエD1.