17α-Estradiol arrests cell cycle progression at G2/M and induces apoptotic cell death in human acute leukemia Jurkat T cells

Do Youn Jun, Hae Sun Park, Jun Seok Kim, Jong Sik Kim, Wan Park, Bang Ho Song, Hee Sook Kim, Dennis Taub, Young Ho Kim

Research output: Contribution to journalArticlepeer-review

29 Scopus citations

Abstract

A pharmacological dose (2.5-10 μM) of 17α-estradiol (17α-E2) exerted a cytotoxic effect on human leukemias Jurkat T and U937 cells, which was not suppressed by the estrogen receptor (ER) antagonist ICI 182,780. Along with cytotoxicity in Jurkat T cells, several apoptotic events including mitochondrial cytochrome c release, activation of caspase-9, -3, and -8, PARP degradation, and DNA fragmentation were induced. The cytotoxicity of 17α-E2 was not blocked by the anti-Fas neutralizing antibody ZB-4. While undergoing apoptosis, there was a remarkable accumulation of G2/M cells with the upregulatoin of cdc2 kinase activity, which was reflected in the Thr56 phosphorylation of Bcl-2. Dephosphorylation at Tyr15 and phosphorylation at Thr161 of cdc2, and significant increase in the cyclin B1 level were underlying factors for the cdc2 kinase activation. Whereas the 17α-E2-induced apoptosis was completely abrogated by overexpression of Bcl-2 or by pretreatment with the pan-caspase inhibitor z-VAD-fmk, the accumulation of G2/M cells significantly increased. The caspase-8 inhibitor z-IETD-fmk failed to influence 17α-E2-mediated caspase-9 activation, but it markedly reduced caspase-3 activation and PARP degradation with the suppression of apoptosis, indicating the contribution of caspase-8; not as an upstream event of the mitochondrial cytochrome c release, but to caspase-3 activation. In the presence of hydroxyurea, which blocked the cell cycle progression at the G1/S boundary, 17α-E2 failed to induce the G2/M arrest as well as apoptosis. These results demonstrate that the cytotoxicity of 17α-E2 toward Jurkat T cells is attributable to apoptosis mainly induced in G2/M-arrested cells, in an ER-independent manner, via a mitochondria-dependent caspase pathway regulated by Bcl-2.

Original languageEnglish
Pages (from-to)401-412
Number of pages12
JournalToxicology and Applied Pharmacology
Volume231
Issue number3
DOIs
StatePublished - 15 Sep 2008

Keywords

  • 17α-Estradiol, G/M arrest
  • Apoptosis
  • Bcl-2
  • Caspase cascade
  • Leukemia cells
  • Mitochondrial cytochrome c

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