Fox Chase Cancer Center, Philadelphia, PA 19111, USA.
Proc Natl Acad Sci U S A. 2011 Nov 22;108(47):18879-86. doi: 10.1073/pnas.1115188108. Epub 2011 Oct 19.
In laboratory studies, acquired resistance to long-term antihormonal therapy in breast cancer evolves through two phases over 5 y. Phase I develops within 1 y, and tumor growth occurs with either 17β-estradiol (E(2)) or tamoxifen. Phase II resistance develops after 5 y of therapy, and tamoxifen still stimulates growth; however, E(2) paradoxically induces apoptosis. This finding is the basis for the clinical use of estrogen to treat advanced antihormone-resistant breast cancer. We interrogated E(2)-induced apoptosis by analysis of gene expression across time (2-96 h) in MCF-7 cell variants that were estrogen-dependent (WS8) or resistant to estrogen deprivation and refractory (2A) or sensitive (5C) to E(2)-induced apoptosis. We developed a method termed differential area under the curve analysis that identified genes uniquely regulated by E(2) in 5C cells compared with both WS8 and 2A cells and hence, were associated with E(2)-induced apoptosis. Estrogen signaling, endoplasmic reticulum stress (ERS), and inflammatory response genes were overrepresented among the 5C-specific genes. The identified ERS genes indicated that E(2) inhibited protein folding, translation, and fatty acid synthesis. Meanwhile, the ERS-associated apoptotic genes Bcl-2 interacting mediator of cell death (BIM; BCL2L11) and caspase-4 (CASP4), among others, were induced. Evaluation of a caspase peptide inhibitor panel showed that the CASP4 inhibitor z-LEVD-fmk was the most active at blocking E(2)-induced apoptosis. Furthermore, z-LEVD-fmk completely prevented poly (ADP-ribose) polymerase (PARP) cleavage, E(2)-inhibited growth, and apoptotic morphology. The up-regulated proinflammatory genes included IL, IFN, and arachidonic acid-related genes. Functional testing showed that arachidonic acid and E(2) interacted to superadditively induce apoptosis. Therefore, these data indicate that E(2) induced apoptosis through ERS and inflammatory responses in advanced antihormone-resistant breast cancer.
在实验室研究中，乳腺癌对长期抗激素治疗的获得性耐药在 5 年内通过两个阶段演变。第 I 阶段在 1 年内发展，肿瘤生长发生在 17β-雌二醇（E（2））或他莫昔芬中。第 II 阶段耐药在治疗 5 年后发生，他莫昔芬仍能刺激生长；然而，E（2）反常地诱导细胞凋亡。这一发现是临床应用雌激素治疗晚期抗激素耐药乳腺癌的基础。我们通过分析时间（2-96 小时）跨越时间的基因表达来研究 E（2）诱导的细胞凋亡，在 MCF-7 细胞变体中，这些变体对雌激素依赖（WS8）或对雌激素剥夺和难治（2A）或对 E（2）诱导的细胞凋亡敏感（5C）。我们开发了一种称为差异曲线下面积分析的方法，该方法鉴定了与 WS8 和 2A 细胞相比，仅在 5C 细胞中受 E（2）调节的基因，因此与 E（2）诱导的细胞凋亡相关。雌激素信号、内质网应激（ERS）和炎症反应基因在 5C 特异性基因中过度表达。鉴定的 ERS 基因表明，E（2）抑制蛋白质折叠、翻译和脂肪酸合成。与此同时，ERS 相关的凋亡基因 Bcl-2 相互作用的细胞死亡介体（BIM；BCL2L11）和半胱天冬酶-4（CASP4）等被诱导。对 caspase 肽抑制剂谱的评估表明，CASP4 抑制剂 z-LEVD-fmk 是阻断 E（2）诱导的细胞凋亡最有效的抑制剂。此外，z-LEVD-fmk 完全阻止了聚（ADP-核糖）聚合酶（PARP）的切割、E（2）抑制的生长和凋亡形态。上调的促炎基因包括 IL、IFN 和花生四烯酸相关基因。功能测试表明，花生四烯酸和 E（2）相互作用，以超加性诱导细胞凋亡。因此，这些数据表明，E（2）通过 ERS 和晚期抗激素耐药乳腺癌中的炎症反应诱导细胞凋亡。
