Hyaluronan-CD44 Interaction with Protein Kinase Cε Promotes Oncogenic Signaling by the Stem Cell Marker Nanog and the Production of MicroRNA-21, Leading to Down-regulation of the Tumor Suppressor Protein PDCD4, Anti-apoptosis, and Chemotherapy Resistance in Breast Tumor Cells
Hyaluronan-CD44 Interaction with Protein Kinase Cε Promotes Oncogenic Signaling by the Stem Cell Marker Nanog and the Production of MicroRNA-21, Leading to Down-regulation of the Tumor Suppressor Protein PDCD4, Anti-apoptosis, and Chemotherapy Resistance in Breast Tumor Cells
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DOI：
10.1074/jbc.m109.027466
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发表时间：
2009-09-25
影响因子：
4.8
通讯作者：
Gilad, Eli
中科院分区：
文献类型：
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作者：
Bourguignon, Lilly Y. W.;Spevak, Christina C.;Gilad, Eli
多药耐药和疾病复发是乳腺癌治疗中的一个具有挑战性的临床问题。在这项研究中，我们研究了透明质酸（HA）诱导的CD 44（主要HA受体）和蛋白激酶C β（PKC β）之间的相互作用，它调节了许多人乳腺肿瘤细胞的功能。我们的研究结果表明，HA结合CD 44促进PKC β激活，这反过来又增加了乳腺肿瘤细胞系MCF-7中干细胞标志物Nanog的磷酸化。磷酸化的Nanog随后从胞质转移到细胞核，并与RNase III DROSHA和RNA解旋酶p68结合。这个过程导致microRNA-21（miR-21）的产生和肿瘤抑制蛋白（e. G. PDCD 4（程序性细胞死亡4））减少。所有这些事件都有助于上调凋亡抑制蛋白（IAP）和MDR 1（多药耐药蛋白），导致抗凋亡和化疗耐药性。用PKC β或Nanog特异性小干扰RNA转染MCF-7细胞可有效阻断HA介导的PKC ε-Nanog信号传导事件，消除miR-21产生，并增加PDCD 4表达/eIF 4A结合。随后，这种PKC ε-Nanog信号传导抑制导致IAP/MDR 1下调、细胞凋亡和化学敏感性。为了进一步评估miR-21在肿瘤发生和化疗耐药性中的作用，还用特异性抗miR-21抑制剂转染MCF-7细胞，以沉默miR-21表达并抑制其靶功能。我们的结果表明，抗miR-21抑制剂不仅增强PDCD 4表达/eIF 4A结合，而且阻断HA-CD 44介导的肿瘤细胞行为。因此，这一新发现的HA-CD 44信号通路将为敏化肿瘤细胞凋亡和克服乳腺癌细胞的化疗耐药性提供重要的药物靶点。
Multidrug resistance and disease relapse is a challenging clinical problem in the treatment of breast cancer. In this study, we investigated the hyaluronan (HA)-induced interaction between CD44 (a primary HA receptor) and protein kinase C epsilon (PKC epsilon), which regulates a number of human breast tumor cell functions. Our results indicate that HA binding to CD44 promotes PKC epsilon activation, which, in turn, increases the phosphorylation of the stem cell marker, Nanog, in the breast tumor cell line MCF-7. Phosphorylated Nanog is then translocated from the cytosol to the nucleus and becomes associated with RNase III DROSHA and the RNA helicase p68. This process leads to microRNA-21 (miR-21) production and a tumor suppressor protein (e. g. PDCD4 (program cell death 4)) reduction. All of these events contribute to up-regulation of inhibitors of apoptosis proteins (IAPs) and MDR1 (multidrug-resistant protein), resulting in anti-apoptosis and chemotherapy resistance. Transfection of MCF-7 cells with PKC epsilon or Nanog-specific small interfering RNAs effectively blocks HA-mediated PKC epsilon-Nanog signaling events, abrogates miR-21 production, and increases PDCD4 expression/eIF4A binding. Subsequently, this PKC epsilon-Nanog signaling inhibition causes IAP/MDR1 down-regulation, apoptosis, and chemosensitivity. To further evaluate the role of miR-21 in oncogenesis and chemoresistance, MCF-7 cells were also transfected with a specific anti-miR-21 inhibitor in order to silence miR-21 expression and inhibit its target functions. Our results indicate that anti-miR-21 inhibitor not only enhances PDCD4 expression/eIF4A binding but also blocks HA-CD44-mediated tumor cell behaviors. Thus, this newly discovered HA-CD44 signaling pathway should provide important drug targets for sensitizing tumor cell apoptosis and overcoming chemotherapy resistance in breast cancer cells.