From the Division of Nephrology, Boston Children's Hospital, Boston, Massachusetts 02115 and.
J Biol Chem. 2014 Feb 7;289(6):3126-37. doi: 10.1074/jbc.M113.508044. Epub 2013 Dec 23.
Chemokines and their receptors play diverse roles in regulating cancer growth and progression. The receptor CXCR3 can have two splice variants with opposite functions. CXCR3-A promotes cell growth, whereas CXCR3-B mediates growth-inhibitory signals. However, the negative signals through CXCR3-B in cancer cells are not well characterized. In this study, we found that CXCR3-B-mediated signaling in MCF-7 and T47D breast cancer cells induced apoptotic cell death. Signals through CXCR3-B decreased the levels of the antiapoptotic proteins Bcl-2 and Bcl-xL and increased the expression of apoptotic cleaved poly(ADP-ribose) polymerase. Along with up-regulation in apoptosis, CXCR3-B signals were associated with a decrease in cellular autophagy with reduced levels of the autophagic markers Beclin-1 and LC3B. Notably, CXCR3-B down-regulated the expression of the cytoprotective and antiapoptotic molecule heme oxygenase-1 (HO-1) at the transcriptional level. There was an increased nuclear localization of Bach-1 and nuclear export of Nrf2, which are important negative and positive transcription factors, respectively, for HO-1 expression. We also observed that CXCR3-B promoted the activation of p38 MAPK and the inhibition of ERK-1/2. CXCR3-B could not induce cancer cell apoptosis at the optimal level when we either inhibited p38 activity or knocked down Bach-1. Further, CXCR3-B-induced apoptosis was down-regulated when we overexpressed HO-1. Together, our data suggest that CXCR3-B mediates a growth-inhibitory signal in breast cancer cells through the modulations of nuclear translocation of Bach-1 and Nrf2 and down-regulation of HO-1. We suggest that the induction of CXCR3-B-mediated signaling can serve as a novel therapeutic approach where the goal is to promote tumor cell apoptosis.
趋化因子及其受体在调节癌症生长和进展方面发挥着多样化的作用。受体 CXCR3 有两种具有相反功能的剪接变体。CXCR3-A 促进细胞生长,而 CXCR3-B 介导生长抑制信号。然而,CXCR3-B 在癌细胞中的负信号尚未得到很好的描述。在这项研究中,我们发现 MCF-7 和 T47D 乳腺癌细胞中 CXCR3-B 介导的信号诱导了细胞凋亡。CXCR3-B 信号降低了抗凋亡蛋白 Bcl-2 和 Bcl-xL 的水平,并增加了凋亡性裂解多聚(ADP-核糖)聚合酶的表达。随着凋亡的上调,CXCR3-B 信号与细胞自噬减少相关,自噬标记物 Beclin-1 和 LC3B 的水平降低。值得注意的是,CXCR3-B 下调了转录水平上细胞保护和抗凋亡分子血红素加氧酶-1(HO-1)的表达。Bach-1 的核定位增加和 Nrf2 的核输出增加,Nrf2 分别是 HO-1 表达的重要负转录因子和正转录因子。我们还观察到 CXCR3-B 促进了 p38 MAPK 的激活和 ERK-1/2 的抑制。当我们抑制 p38 活性或敲低 Bach-1 时,CXCR3-B 不能诱导癌细胞凋亡达到最佳水平。此外,当我们过表达 HO-1 时,CXCR3-B 诱导的凋亡被下调。总之,我们的数据表明,CXCR3-B 通过调节 Bach-1 和 Nrf2 的核易位以及下调 HO-1,介导乳腺癌细胞中的生长抑制信号。我们建议诱导 CXCR3-B 介导的信号可以作为一种新的治疗方法,其目的是促进肿瘤细胞凋亡。
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