Bambang I Fon, Lu Dan, Li Huiping, Chiu Lily-Lily, Lau Quek Choon, Koay Evelyn, Zhang Daohai
Department of Pathology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
Exp Cell Res. 2009 Jul 1;315(11):1964-74. doi: 10.1016/j.yexcr.2009.02.017. Epub 2009 Mar 2.
Cytokeratin 19 (CK19) is widely used as a biomarker for the detection of disseminated tumor cells in blood and bone marrow, and its positivity is considered as an independent prognostication indicator in cancer patients. However, its role in breast cancer progression remains unknown. We had established a stable CK19-expressing clone in the CK19-negative BT549 human breast cancer cell line and found that CK19 expression in the BT549 cells caused cell cycle arrest, reduced cell motility and increased drug resistance. Further study revealed that CK19 expression regulated endoplasmic reticulum (ER) stress signaling by up-regulating p38/RNA-dependent protein kinase-like ER kinase (PERK)/p-eIF2alpha and 78 kDa glucose-regulated protein (Bip/GRP78), and down-regulating focal adhesion kinase (FAK). The level of ER protein 29 (ERp29) was shown to be decreased in the CK19-expressing BT549 cells by proteomic analyses and verified by Western blotting and RT-PCR. Pharmacological inhibition of p38 signaling by its specific inhibitor SB203580 or knockdown of p38 and transcription factor XBP-1 by siRNA in BT549/CK19 and MDA-MB-231 cells revealed that p38/XBP-1 signaling negatively regulated ERp29 expression. Our results indicated that CK19 modulates ER stress signaling and contributes to cell survival and dormancy in breast cancer cells.
细胞角蛋白19（CK19）被广泛用作检测血液和骨髓中播散肿瘤细胞的生物标志物，其阳性被视为癌症患者的独立预后指标。然而，其在乳腺癌进展中的作用尚不清楚。我们在CK19阴性的BT549人乳腺癌细胞系中建立了一个稳定表达CK19的克隆，发现BT549细胞中CK19的表达导致细胞周期停滞、细胞运动性降低和耐药性增加。进一步研究表明，CK19表达通过上调p38/RNA依赖性蛋白激酶样内质网激酶（PERK）/磷酸化真核翻译起始因子2α（p-eIF2α）和78 kDa葡萄糖调节蛋白（结合免疫球蛋白蛋白/葡萄糖调节蛋白78，Bip/GRP78）以及下调粘着斑激酶（FAK）来调节内质网（ER）应激信号。通过蛋白质组学分析显示，在表达CK19的BT549细胞中内质网蛋白29（ERp29）水平降低，并通过蛋白质印迹和逆转录-聚合酶链反应（RT-PCR）进行了验证。在BT549/CK19和MDA-MB-231细胞中，用其特异性抑制剂SB203580对p38信号进行药理学抑制或用小干扰RNA（siRNA）敲低p38和转录因子X盒结合蛋白1（XBP-1），结果显示p38/XBP-1信号负调节ERp29表达。我们的结果表明，CK19调节内质网应激信号，有助于乳腺癌细胞的存活和休眠。
