Nerve Growth Factor Withdrawal-mediated Apoptosis in Naïve and Differentiated PC12 Cells through p53/Caspase-3-dependent and -independent Pathways

Programmed cell death is regulated in response to a variety of stimuli, including the tumor suppressor protein p53, that can mediate cell cycle arrest through p21/Waf1 and apoptosis through the Bcl-2/Bax equilibrium and caspases. Neuronal cell apoptosis has been reported to require p53, whereas other data suggest that neuronal cell death may be independent of p53. Comparison of wild type PC12 to a temperature-sensitive PC12 cell line that depresses the normal function of p53 has permitted investigation of the importance of p53 in a variety of cell functions. This study examined the role of p53 in trophic factor withdrawal-mediated apoptosis in both naïve and differentiated PC12 cells. Our data show that as PC12 cells differentiate they are more poised to undergo apoptosis than their undifferentiated counterparts. Survival assays with XTT (sodium 3′-1-(phenylaminocarbonyl)-3,4-tetrazolium-bis(4-methoxy-6-nitro)benzene sulfonic acid) and TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) demonstrated that lack of p53 is initially protective against apoptosis. The window of protection is about 20 h for naïve and 36 h for differentiated cells. Apoptosis involved caspases 3, 6, and 9. However, caspase 3 activation was absent in cells lacking p53, concomitant with the delayed apoptosis. When the expression of caspase 3 was silenced with interference RNA, wild type PC12 cells revealed a morphology and biochemistry similar to PC12[p53ts] cells, indicating that caspase 3 accounts for the observed delay in apoptosis in p53 dysfunction. These results suggest that p53 is important, but not essential, in factor withdrawal-mediated apoptosis. Parallel pathways of caspase-mediated apoptosis are activated later in the absence of functional p53. Programmed cell death is regulated in response to a variety of stimuli, including the tumor suppressor protein p53, that can mediate cell cycle arrest through p21/Waf1 and apoptosis through the Bcl-2/Bax equilibrium and caspases. Neuronal cell apoptosis has been reported to require p53, whereas other data suggest that neuronal cell death may be independent of p53. Comparison of wild type PC12 to a temperature-sensitive PC12 cell line that depresses the normal function of p53 has permitted investigation of the importance of p53 in a variety of cell functions. This study examined the role of p53 in trophic factor withdrawal-mediated apoptosis in both naïve and differentiated PC12 cells. Our data show that as PC12 cells differentiate they are more poised to undergo apoptosis than their undifferentiated counterparts. Survival assays with XTT (sodium 3′-1-(phenylaminocarbonyl)-3,4-tetrazolium-bis(4-methoxy-6-nitro)benzene sulfonic acid) and TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) demonstrated that lack of p53 is initially protective against apoptosis. The window of protection is about 20 h for naïve and 36 h for differentiated cells. Apoptosis involved caspases 3, 6, and 9. However, caspase 3 activation was absent in cells lacking p53, concomitant with the delayed apoptosis. When the expression of caspase 3 was silenced with interference RNA, wild type PC12 cells revealed a morphology and biochemistry similar to PC12[p53ts] cells, indicating that caspase 3 accounts for the observed delay in apoptosis in p53 dysfunction. These results suggest that p53 is important, but not essential, in factor withdrawal-mediated apoptosis. Parallel pathways of caspase-mediated apoptosis are activated later in the absence of functional p53. Programmed cell death, or apoptosis, is a conserved mechanism that is strictly regulated and specifically activated in response to a wide variety of stimuli such as ultraviolet radiation (1Lu X. Lane D.P. Cell. 1993; 75: 765-778Abstract Full Text PDF PubMed Scopus (775) Google Scholar), genotoxic agents (2Smith M.L. Fornace Jr., A.J. Mutat. Res. 1996; 340: 109-124Crossref PubMed Google Scholar, 3Gartenhaus R.B. Wang P. Hoffmann P. Proc. Natl. Acad. Sci. U. S. A. 1996; 93: 265-268Crossref PubMed Scopus (83) Google Scholar), and trophic factor withdrawal (4Aloyz R.S. Bamji S.X. Pozniak C.D. Toma J.G. Atwal J. Kaplan D.R. Miller F.D. J. Cell Biol. 1998; 143: 1691-1703Crossref PubMed Scopus (259) Google Scholar). Tumor suppressor protein p53 is one of the mediators of apoptosis, implicated in tumors of the central nervous system (5Eizenberg O. Faber-Elman A. Gottlieb E. Oren M. Rotter V. Schwartz M. EMBO J. 1995; 14: 1136-1144Crossref PubMed Scopus (84) Google Scholar, 6Eizenberg O. Faber-Elman A. Gottlieb E. Oren M. Rotter V. Schwartz M. Mol. Cell. Biol. 1996; 16: 5178-5185Crossref PubMed Scopus (181) Google Scholar), neurological disorders (7Kuntz C.t. Kinoshita Y. Beal M.F. Donehower L.A. Morrison R.S. Exp. Neurol. 2000; 165: 184-190Crossref PubMed Scopus (44) Google Scholar, 8Wosik K. Antel J. Kuhlmann T. Bruck W. Massie B. Nalbantoglu J. J. Neurochem. 2003; 85: 635-644Crossref PubMed Scopus (76) Google Scholar), aging (9Tyner S.D. Venkatachalam S. Choi J. Jones S. Ghebranious N. Igelmann H. Lu X. Soron G. Cooper B. Brayton C. Hee Park S. Thompson T. Karsenty G. Bradley A. Donehower L.A. Nature. 2002; 415: 45-53Crossref PubMed Scopus (1171) Google Scholar, 10Marx J. Science. 1993; 262: 1644-1645Crossref PubMed Scopus (137) Google Scholar), as well as the death of some developing neurons (11Vyas S. Biguet N.F. Michel P.P. Monaco L. Foulkes N.S. Evan G.I. Sassone-Corsi P. Agid Y. Mol. Cell Neurosci. 2002; 21: 1-14Crossref PubMed Scopus (17) Google Scholar, 12Wood K.A. Youle R.J. J. Neurosci. 1995; 15: 5851-5857Crossref PubMed Google Scholar, 13Bredesen D.E. Ann. Neurol. 1995; 38: 839-851Crossref PubMed Scopus (539) Google Scholar, 14Eves E.M. Boise L.H. Thompson C.B. Wagner A.J. Hay N. Rosner M.R. J. Neurochem. 1996; 67: 1908-1920Crossref PubMed Scopus (55) Google Scholar, 15Zaidi A.U. D'Sa-Eipper C. Brenner J. Kuida K. Zheng T.S. Flavell R.A. Rakic P. Roth K.A. J. Neurosci. 2001; 21: 169-175Crossref PubMed Google Scholar, 16Cregan S.P. MacLaurin J.G. Craig C.G. Robertson G.S. Nicholson D.W. Park D.S. Slack R.S. J. Neurosci. 1999; 19: 7860-7869Crossref PubMed Google Scholar). Transcriptional products of an activated p53 pool lead to cell cycle arrest and programmed cell death (17Ryan J.J. Danish R. Gottlieb C.A. Clarke M.F. Mol. Cell. Biol. 1993; 13: 711-719Crossref PubMed Scopus (202) Google Scholar, 18Michieli P. Chedid M. Lin Res. Google Scholar, L. E. Mol. Cell. Biol. 14: PubMed Scopus Google Scholar). such is that activation to of M. 1995; Google Scholar, G. P. A. Bradley A. Science. 1995; PubMed Scopus Google Scholar), a of cell cycle and a protein S. C. Fornace Jr., A.J. Google Scholar). of p53 mediators of apoptosis, such as caspase 3 T. G. J. Biol. Full Text PDF PubMed Google and caspase P. M. Wang X. Cell. Full Text Full Text PDF PubMed Scopus Google Scholar). The cell line PC12 is a of the and nervous system L.A. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar, L.A. J. Biol. Full Text PDF PubMed Google Scholar, L. C. L.A. J. PubMed Scopus Google that to factor p53 cell cells with temperature-sensitive cells with an deoxynucleotidyl transferase-mediated dUTP nick end 3′-1-(phenylaminocarbonyl)-3,4-tetrazolium-bis(4-methoxy-6-nitro)benzene sulfonic interference of through and R.B. Cell. Mol. Sci. 2001; PubMed Scopus Google Scholar). cell is a to study PC12 cells a more a neuronal and are in for has a PC12 cell line L. J. Biol. 2000; Full Text Full Text PDF PubMed Scopus Google a temperature-sensitive that a p53 pool that the normal function of p53 the Google Scholar). of wild type PC12 to the temperature-sensitive PC12 cell investigation of the importance of p53 in a variety of cell including PC12[p53ts] cells to to PC12 cells and differentiate the neuronal PC12[p53ts] cells to and lack cell cycle arrest L. J. Biol. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar). PC12 cells, to are and withdrawal of apoptosis J. Cell Biol. PubMed Scopus Google Scholar). about of PC12 cells differentiate a neuronal and undergo apoptosis withdrawal in the of J. Cell Biol. PubMed Scopus Google Scholar). trophic factor withdrawal a of withdrawal in naïve PC12 cells and withdrawal in PC12 cells. factor apoptosis is a programmed cell death, for in the nervous system as trophic factor is to disorders such as and J. Cell Biol. PubMed Scopus Google Scholar, A. L.A. J. Cell Biol. 1993; PubMed Scopus Google Scholar, L. J. Neurosci. Res. 1999; PubMed Scopus Google Scholar, K. N. J. Neurosci. PubMed Google Scholar, T. J. J. Exp. 2002; PubMed Scopus (259) Google Scholar, A. Mol. 2000; Google Scholar, S.P. Neurol. 2003; PubMed Scopus Google Scholar). The pathways of apoptosis been in cell factor withdrawal as a factor the Bcl-2/Bax equilibrium Jr., E.M. Exp. Neurol. 1998; PubMed Scopus Google Scholar), and the of factor C. E. L. N. N. G. 2002; PubMed Scopus Google Scholar). These that as and of apoptosis L. Park D.S. M.L. L.A. J. Biol. 1996; Full Text Full Text PDF PubMed Scopus Google Scholar). The tumor suppressor protein p53 is of a protein K. A. J. J. PubMed Google Scholar). has an an protein K. A. J. J. PubMed Google Scholar). cells the protective role of to S. 2002; PubMed Scopus Google Scholar). and S. 2002; PubMed Scopus Google a the Nature. 2000; PubMed Scopus Google Scholar). the of to an caspase that caspase 3 Nature. 2000; PubMed Scopus Google Scholar). caspase 3 and for and to programmed cell death 2002; PubMed Scopus (83) Google Scholar). programmed cell death an of of apoptosis in S. L. J. 2003; PubMed Scopus Google Scholar, H. K. Cell Res. 2002; PubMed Scopus Google Scholar). apoptosis with to a of in the that that in the can be in the D.R. J.J. J. Google Scholar). The to cells in 3 activation is as a of apoptosis of caspase activation 2002; PubMed Scopus (83) Google Scholar). in the is observed R.J. S. M.F. J. PubMed Scopus Google Scholar). of assays in The role of p53 in neuronal cell apoptosis some demonstrated that p53 in programmed cell death R.S. Kinoshita Y. W. Neurochem. Res. 2003; PubMed Scopus Google Scholar, C. E. B. J. Biol. 2002; Full Text Full Text PDF PubMed Scopus Google Scholar, Y. Mol. 2002; Google Scholar, C.B. C. Roth K.A. Cell 2002; PubMed Scopus Google Scholar, M. B. C. 2000; PubMed Scopus Google Scholar, P. R. Cooper J. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar), whereas that p53 is not in apoptosis D.W. 2001; 165: PubMed Scopus Google Scholar, W. S. 2001; PubMed Scopus Google Scholar, J. J. R. Mol. 2001; Google Scholar). This study the that p53 is involved in trophic factor withdrawal-mediated apoptosis in naïve and differentiated PC12 cells. that p53 is for apoptosis but that a delayed apoptosis in the absence of p53. differentiated PC12 cells apoptosis more and the for p53. of the p53 temperature-sensitive cells in both naïve and differentiated cells, in apoptosis. Cell and Cell PC12 cells, or PC12[p53ts] cells in as L.A. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar, Google and with and as of of PC12 cells with an of and The the of the PC12[p53ts] cells with the cells, and the results for the wild type PC12 cells not for was or PC12[p53ts] cells in a in the of and for to differentiated cells or for to differentiated cells. and of the of naïve cells, was the in and in but with and The cells in the with Apoptosis was in differentiated cells or differentiated cells the cells in and in the cells in and for the with and in The cells in the with for with with and of protein protein was a and the with caspase and caspase 3 was in in and with the in and with was the system and with similar in a to Survival in in and cells The cells that the and a well as that not the The of cells in the of cells was and XTT Survival (sodium 3′-1-(phenylaminocarbonyl)-3,4-tetrazolium-bis(4-methoxy-6-nitro)benzene sulfonic a is the in cells to an The was in an of to with a assays in with of cells in well with an and to cells with and in of the with of for cells with an of of XTT was to a of and was a to a of with assays in was as a of a to a cells to and in with of of of cells. The cells for in the with and in of of and the was in the and 20 with a a The is a that is cells, they are TUNEL TUNEL an (terminal deoxynucleotidyl to to the in the of cells. of TUNEL a and a that a TUNEL was the or differentiated PC12 or PC12[p53ts] cells in and with The cells with with with the with in and in the was in the and The was in in in in and in the was in in and TUNEL was cells well of a cells with in with with and with The was to the TUNEL to the the with 20 in of The was with of and the was a of was to the caspase the that activated caspase and was in a was to that caspase was some a was to the of the caspase and and the caspase and caspase 3 caspase and caspase and caspase and caspase 3 was and are similar to the caspase 3 cell caspase 3 was in with a caspase that to caspase 3 and a The was and the in a and of caspase 3 was in a to to other in the for the as the the was the and the end of the the of the was with a and a was for the with with a The the was against of the caspase 3 The was against of the caspase 3 The of the was cells or withdrawal to the a system of about was in naïve cells and about in differentiated cells, or was as was to When the cell line and a was When cell to the and the a was to a with examined or of a results are as S.D. or of p53 against or Apoptosis in PC12 PC12 cells with the PC12[p53ts] cells that lack a functional p53 pool to lack of functional p53 the naïve PC12 cells against apoptosis. assays in naïve cells of naïve PC12 cells and about h of PC12[p53ts] cells and of cell death was not h This that a lack of a functional p53 pool the cells to cell cell was to the of p53 in factor withdrawal-mediated cell death in PC12 cells of The results with the XTT the assays that a lack of p53 in naïve cells the cells against apoptosis. PC12 cells to the XTT h in to PC12[p53ts] cells that h of was h that was not the absence of functional p53. that not the was and results revealed similar results not PC12 cells that been differentiated a neuronal with of examined for p53 in factor withdrawal-mediated cell PC12 cells withdrawal is with a more in cell of differentiated PC12 cells h is about h than factor withdrawal-mediated apoptosis in naïve cells. to naïve cells, differentiated PC12 cells against cell death in the absence of p53, indicating the for p53 in cell death cells. both differentiated cells and differentiated of the PC12 cells in whereas of the PC12[p53ts] cells h of withdrawal However, the of both PC12 and PC12[p53ts] cells h of differentiated and naïve PC12[p53ts] cells and that cell death was delayed in cells lacking a functional p53 Apoptosis in the of a delay was observed in the death of cells that not a functional p53 an in programmed cell death, was in PC12[p53ts] cells. The in PC12 cells that was withdrawal in naïve cells h but was not observed h not PC12[p53ts] cells was was not h PC12[p53ts] to show h withdrawal not differentiated PC12 cells withdrawal h of withdrawal in of with a of than naïve PC12 cells. of p53 initially the cells against but h cells that not for that cell death was to programmed cell death and not differentiated cells a similar was observed with a delay in PC12[p53ts] cells not TUNEL that in PC12[p53ts] cells, a end in apoptosis, was TUNEL both and that lack of p53 was initially protective in PC12 cells. PC12 cells TUNEL h withdrawal 3, and naïve PC12[p53ts] cells that lack p53 h of withdrawal and differentiated PC12 cells, a delay in apoptosis was h PC12 cells TUNEL 3, and differentiated PC12[p53ts] cells TUNEL and h of withdrawal 3, and These results that lack of p53 apoptosis in differentiated or differentiated PC12 cells However, about of the cells XTT results was in PC12 cells lacking p53. The TUNEL assays 3, and with the 3, and PC12 cells TUNEL of programmed cell death h withdrawal undifferentiated PC12[p53ts] cells a delay in apoptosis with of TUNEL h of withdrawal TUNEL was delayed in differentiated and differentiated PC12 but h as the in cells These results with the TUNEL a delay in apoptosis in the absence of p53. data that both naïve PC12 and PC12[p53ts] cells factor withdrawal not as an of cells with than the normal However, PC12[p53ts] cells functional p53 demonstrated a for both naïve PC12 and PC12[p53ts] cells, or was protective not with the TUNEL data 3 in PC12 in PC12[p53ts] 3 is an of apoptosis in withdrawal-mediated apoptosis in PC12 cells T. T. J. PubMed Scopus Google Scholar, R. L. H. J. R. J. Neurosci. Res. PubMed Scopus Google Scholar). 3 withdrawal in naïve PC12 was activated h and h with of caspase 3 to a differentiated PC12 cells and differentiated PC12 cells demonstrated an caspase 3 activation 3 activation was to be with a caspase and with a caspase 3 the of the was to the in and differentiated cells with the not PC12[p53ts] cells not show caspase 3 activation to the and This that the delay in cell death in PC12[p53ts] cells is to the lack of caspase 3 activation and that the is to caspase that the caspase 3 activation was was to caspase 3 a similar of caspase 3 in PC12 cells, but not in PC12[p53ts] cells the caspase 3 activation with the the caspase 3 activated for of programmed cell The of caspase and has been to of caspase in M. S. H. D.P. D.R. G.S. Mol. Cell. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar). 3 was in the cell a cell caspase is and to the caspase a not caspase 3 was in h in and differentiated PC12 cells. However, similar to the lack of activation of caspase 3 in cell PC12[p53ts] cells not activation of caspase 3 in the results in cells well with the data a caspase in cell of p53 in PC12 reported that caspase of caspase 3, is for programmed cell death in some cells A.U. D'Sa-Eipper C. Brenner J. Kuida K. Zheng T.S. Flavell R.A. Rakic P. Roth K.A. J. Neurosci. 2001; 21: 169-175Crossref PubMed Google Scholar, S. C. K. S. M. Cell 2000; Google Scholar, L.A. M.L. J. Neurosci. 2001; 21: PubMed Google Scholar). PC12 cells that lack p53 undergo delayed apoptosis, but to caspase 3, caspase was activated factor withdrawal in PC12[p53ts] cells. in for caspase revealed that caspase activation h factor withdrawal in and differentiated PC12 cells data for naïve PC12[p53ts] cells caspase activation factor withdrawal in and differentiated cells as PC12 cells a more activation of caspase was a that caspase 3 This of caspase activation was in of differentiated PC12[p53ts] cells. The caspase activation was of the of to caspase to other caspase caspase activation factor withdrawal is independent of functional p53, in to the of caspase 3 3 and 3 Cell in PC12 to PC12 cells, PC12[p53ts] cells to caspase 3, with a delay in programmed cell of caspase 3 in PC12 cells with interference was to the delay in cell death observed in PC12[p53ts] cells be 3 was not whereas indicating the of the caspase 3 caspase 3 activation in PC12 cells, as the in not similar to the observed in PC12[p53ts] cells. factor caspase 3 to an in naïve and in differentiated PC12 cells whereas the the of in caspase 3 cells similar to the PC12[p53ts] cells, with a caspase to cell TUNEL the XTT data TUNEL in naïve and differentiated cells with or caspase 3 for was cells to for or was and was for was and the of was as cells, to cell the cells the cells the PC12 cells the and the caspase 3 was to caspase 3 and differentiated PC12 cells with the demonstrated a as the XTT or TUNEL not but cell death, similar to caspase 3 and a caspase 3 that the lack of caspase 3 activation with a delayed of programmed cell death, factor but with of apoptosis. and in PC12 and PC12[p53ts] and and for caspase activation was observed withdrawal naïve cells was to in a caspase or caspase not indicating the of the differentiated PC12 cells and differentiated cells activation of caspase in both PC12 and PC12[p53ts] cells was observed h for and h The of withdrawal-mediated caspase activation to be independent of p53 as PC12[p53ts] cells a similar of caspase was in cell a to caspase withdrawal in naïve cells and withdrawal in differentiated PC12 not activation was not in naïve differentiated cells. This study demonstrated that factor withdrawal-mediated apoptosis is delayed in PC12 cells lacking functional p53 of the apoptosis is both and through pathways such as caspase and caspase programmed cell and K. E. for This apoptosis is caspases 3, 6, and but caspase activation was not both of the about the role of p53 in apoptosis are of apoptosis, in programmed cell death, the of functional p53 to be in the of PC12 cells factor However, such a the absence of p53 to the of and death in the PC12 cells. of p53 in a in Cell the to both the and the XTT that a lack of p53 was protective against programmed cell However, the of PC12 cells as was 20 whereas the XTT to assays whereas XTT of but not programmed cell cells with and the XTT XTT is as a the of the to are central in the to be in PC12 programmed cell more assays are to apoptosis. that the cell death was programmed cell death, more assays of death an of apoptosis, that as as h withdrawal in naïve PC12 cells L. J. Biol. 2000; Full Text Full Text PDF PubMed Scopus Google and was h factor later in PC12[p53ts] cells, with the delay in apoptosis in cells. the delay in was in PC12[p53ts] cells with not for and of apoptosis Res. PubMed Scopus Google Scholar). and TUNEL that apoptosis in differentiated cells and was not observed and TUNEL assays that lack of p53 in PC12[p53ts] not apoptosis but delayed the in differentiated cells 36 was observed cell death and apoptosis in PC12 cells, as and TUNEL PC12 cells the of cell death that differentiated cells more poised to undergo apoptosis. Our results with in to be more to apoptosis as they to a in of protective and M. P. P. J. Neurosci. Res. 2002; PubMed Scopus Google Scholar). These that lack of functional p53 not of PC12 cells as factor PC12 cells functional p53 to L. J. Biol. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar), and for and in the of PC12 cells require p53 to the cell cycle L. J. Biol. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar), the lack of functional p53 not the of both naïve and differentiated PC12 cells the to undergo cell death in the absence of functional p53. Cell cycle arrest the of whereas activation to programmed cell Our results suggest that may be more than in the cell to is to is death more than or the cell are more than the for p53 has been to be for normal and p53 with a to L.A. M. Jr., C.A. Bradley A. Nature. PubMed Scopus Google Scholar, A. Neurosci. PubMed Scopus Google Scholar). and neurons the p53 as with normal can in with the of R. J. Neurosci. Res. 1996; PubMed Scopus Google Scholar). neuronal lacking functional p53 that p53 than in neurons T. Y. S. Y. S. T. T. N. Y. S. Y. S. 1993; Google Scholar). p53 is for the are regulated to be in both and central nervous system through the of in a p53 F.D. Pozniak C.D. G.S. Cell 2000; PubMed Scopus Google Scholar). the of both C.D. S. A. Kaplan D.R. Miller F.D. Science. 2000; PubMed Scopus Google and C.D. Miller F.D. J. Neurosci. 2002; PubMed Google neurons are The and p53 to be in both neuronal and aging and F.D. Pozniak C.D. G.S. Cell 2000; PubMed Scopus Google Scholar). PC12 cells, in to the has not been E.M. L. Res. Mol. Res. 2003; PubMed Scopus Google Scholar). Parallel in PC12 programmed cell death in naïve and differentiated cells of the of p53, pathways in and apoptosis factor The tumor suppressor p53 is a factor for that to for of the The is of caspase and and is in the Nature. 2000; PubMed Scopus Google Scholar). the role of caspases involved in the activation is to be involved the to of in the is to be an a H. M. X. Wang X. Cell Biol. 1999; 15: PubMed Scopus Google Scholar). caspases 3 and both h factor and that h caspase was h that caspases are activated in the of apoptosis. suggest that caspases may be activated in the M. S. H. D.P. D.R. G.S. Mol. Cell. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar, S. S. J. Biol. 1996; Full Text Full Text PDF PubMed Scopus Google Scholar, A.J. D.R. J. Exp. 1995; PubMed Scopus Google Scholar), with the data in caspase 3 and caspase in as cells This in may the XTT and the TUNEL results that that apoptosis more as PC12 cells differentiated and for cell death in the absence of is to be involved in neuronal cell death R. T. M. D.P. 2002; PubMed Scopus Google Scholar, R. Neurosci. 2002; PubMed Scopus Google and is activated in neurons trophic factor withdrawal J. Biol. 2002; Full Text Full Text PDF PubMed Scopus Google Scholar). Our data show that caspase activation was as as h independent of p53, PC12[p53ts] cells caspase activation with the and may the that both PC12 and PC12[p53ts] undergo apoptosis through a caspase the delay is not demonstrated that caspase is for the later of apoptosis. is that caspase a mechanism that is activated and poised to apoptosis in the of of of the other caspase apoptosis, TUNEL When caspase and caspase with cells apoptosis not through a programmed cell death mechanism S.P. A. MacLaurin J.G. Park D.S. G. Slack R.S. J. Cell Biol. 2002; PubMed Scopus Google Scholar, S. C. N. A.J. M. J. Biol. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar). the was more than caspase 3 not that more caspase pathways programmed cell death more than one that caspase activation to caspase 3 A.U. D'Sa-Eipper C. Brenner J. Kuida K. Zheng T.S. Flavell R.A. Rakic P. Roth K.A. J. Neurosci. 2001; 21: 169-175Crossref PubMed Google Scholar), with the in in other such as caspase and caspase P. X. Y. Science. 2002; PubMed Scopus Google Scholar), to the cell to apoptosis to some of of the pathways is in 3 and a caspase 3 to a delay in to that observed in PC12[p53ts] cells. that p53 and caspase 3 are in the of cell death factor withdrawal and the The role of p53 in programmed cell death that p53 is not in death D.W. 2001; 165: PubMed Scopus Google Scholar, W. S. 2001; PubMed Scopus Google Scholar, J. J. R. Mol. 2001; Google Scholar, P. X. Y. Science. 2002; PubMed Scopus Google Scholar), whereas that p53 is in programmed cell death R.S. Kinoshita Y. W. Neurochem. Res. 2003; PubMed Scopus Google Scholar, C. E. B. J. Biol. 2002; Full Text Full Text PDF PubMed Scopus Google Scholar, Y. Mol. 2002; Google Scholar, C.B. C. Roth K.A. Cell 2002; PubMed Scopus Google Scholar, M. B. C. 2000; PubMed Scopus Google Scholar, P. R. Cooper J. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar). demonstrated that tumor suppressor p53 is but not in programmed cell study the a programmed cell death in the absence of functional p53. p53 in the of programmed cell death in PC12 cells through caspase 3 but the absence of functional p53 results in a p53 the PC12 cell through other B. H. R.J. J. Biol. PubMed Scopus Google Scholar), including caspase that of apoptosis is p53 activation of caspase 3 of caspase or or J. Exp. 2002; PubMed Scopus Google Scholar). These suggest that both of the p53 are of apoptosis, and cell type are that death