Labrecque Mark P, Takhar Mandeep K, Jagdeo Julienne M, Tam Kevin J, Chiu Christina, Wang Te-Yu, Prefontaine Gratien G, Cox Michael E, Beischlag Timothy V
Faculty of Health Sciences, Simon Fraser University, Burnaby, British Columbia, Canada.
Department of Urologic Sciences, The Vancouver Prostate Center, University of British Columbia, Vancouver, British Columbia, Canada.
PLoS One. 2014 Jun 11;9(6):e99214. doi: 10.1371/journal.pone.0099214. eCollection 2014.
Localized hypoxia in solid tumors activates transcriptional programs that promote the metastatic transformation of cells. Like hypoxia-inducible hyper-vascularization, loss of the retinoblastoma protein (Rb) is a trait common to advanced stages of tumor progression in many metastatic cancers. However, no link between the role of Rb and hypoxia-driven metastatic processes has been established. We demonstrated that Rb is a key mediator of the hypoxic response mediated by HIF1α/β, the master regulator of the hypoxia response, and its essential co-activator, the thyroid hormone receptor/retinoblastoma-interacting protein (TRIP230). Furthermore, loss of Rb unmasks the full co-activation potential of TRIP230. Using small inhibitory RNA approaches in vivo, we established that Rb attenuates the normal physiological response to hypoxia by HIF1α. Notably, loss of Rb results in hypoxia-dependent biochemical changes that promote acquisition of an invasive phenotype in MCF7 breast cancer cells. In addition, Rb is present in HIF1α-ARNT/HIF1β transcriptional complexes associated with TRIP230 as determined by co-immuno-precipitation, GST-pull-down and ChIP assays. These results demonstrate that Rb is a negative modulator of hypoxia-regulated transcription by virtue of its direct effects on the HIF1 complex. This work represents the first link between the functional ablation of Rb in tumor cells and HIF1α-dependent transcriptional activation and invasion.
实体瘤中的局部缺氧会激活促进细胞发生转移转化的转录程序。与缺氧诱导的血管过度生成一样，视网膜母细胞瘤蛋白（Rb）缺失是许多转移性癌症肿瘤进展晚期阶段的一个共同特征。然而，Rb的作用与缺氧驱动的转移过程之间尚未建立联系。我们证明，Rb是缺氧反应的主要调节因子HIF1α/β及其必需的共激活因子甲状腺激素受体/视网膜母细胞瘤相互作用蛋白（TRIP230）介导的缺氧反应的关键介质。此外，Rb的缺失揭示了TRIP230的完全共激活潜力。我们在体内使用小干扰RNA方法证实，Rb减弱了HIF1α对缺氧的正常生理反应。值得注意的是，Rb的缺失导致缺氧依赖性生化变化，促进MCF7乳腺癌细胞获得侵袭性表型。此外，通过免疫共沉淀、GST下拉和染色质免疫沉淀分析确定，Rb存在于与TRIP230相关的HIF1α-ARNT/HIF1β转录复合物中。这些结果表明，Rb因其对HIF1复合物的直接作用而成为缺氧调节转录的负调节因子。这项工作首次揭示了肿瘤细胞中Rb的功能缺失与HIF1α依赖性转录激活和侵袭之间的联系。
