4β-Hydroxywithanolide E是秘魯苦蘵(Physalis peruviana)的活性成分，已被證實有抗腫瘤效果，但其抗腫瘤活性機制仍未被釐清。在此研究中，我們發現4β-hydroxywithanolide E能引起乳癌細胞株MCF-7產生不可逆的細胞凋亡而此凋亡與caspase-9途徑的蛋白表現有關；4β-hydroxywithanolide E 誘導MCF-7細胞週期停滯於G0/G1及S期，而且細胞週期之調控分子在4β-hydroxywithanolide E引發MCF-7細胞死亡過程中扮演重要角色。我們也探討氧化壓力於4β-hydroxywithanolide E誘發MCF-7細胞凋亡過程中所扮演的角色。本研究已證實4β-hydroxywithanolide E誘發MCF-7細胞死亡是經由活性氧物質的產生和超氧化物歧化?及過氧化氫?等抗氧化酵素的活化。Glutathione或N-acetylcysteine能顯著抑制4β-hydroxywithanolide E引起的超氧化物歧化?及過氧化氫?的活化和細胞死亡。我們也證實glutathione或N-acetylcysteine會逆轉4β-hydroxywithanolide E造成的細胞週期停滯和細胞週期調控分子之表現。4β-Hydroxywithanolide E亦造成MCF-7細胞DNA damage，本研究也證實DNA damage的感覺因子及修補酵素ATM (S1981)、??-H2AX、53BP1、BRCA1、chk2及XRCC4之表現在4β-hydroxywithanolide E引發DNA damage過程中有顯著的改變，而glutathione或N-acetylcysteine則選擇性的對4β-hydroxywithanolide E引發之感覺因子及修補酵素蛋白質改變產生影響。我們也證實MAP kinase、蛋白質降解及cAMP的途徑與4β-hydroxywithanolide E引發MCF-7細胞死亡無關。
4β-Hydroxywithanolide E, an active component from Physalis peruviana, was found to have anti-breast cancer cytotoxicity, but the mechanism still need to be further discovered. In this study, we found that 4β-hydroxywithanolide E-induced human breast cancer MCF-7 cell apoptosis is irreversible and the caspase-9 pathway is involved in the 4β-hydroxywithanolide E-induced cell death. We also investigated the role of oxidative stress in 4β-hydroxywithanolide E-induced MCF-7 cell apoptosis. Exposure of MCF-7 cells to 4β-hydroxywithanolide E caused production of reactive oxygen species and a significant increase in antioxidative enzymes activity, such as superoxide dismutase (SOD) and catalase. Glutathione or N-acetylcysteine significantly inhibited the 4β-hydroxywithanolide E-triggered activity of the radical-scavenging enzymes and cell death. The 4β-hydroxywithanolide E-induced cell cycle arrest at G0/G1- and S-phase, changes in cell cycle regulators expression and microtubule distribution were reversed by pretreatment with glutathione or N-acetylcysteine in MCF-7 cells. In addition, glutathione or N-acetylcysteine selectively inhibited the 4β-hydroxywithanolide E-induced DNA damage and changes in the protein expression of DNA damage sensors and repair enzymes such as ATM (S1981), ??-H2AX, 53BP1, BRCA1, chk2 and XRCC4 in MCF-7 cells. We also found that MAP kinase, ubiquitin-conjugated protein degradation and cAMP pathways were not important determinants of apoptotic death induced by 4β-hydroxywithanolide E in MCF-7 cells.
