Gupta Sounak, Hau Andrew M, Al-Ahmadie Hikmat A, Harwalkar Jyoti, Shoskes Aaron C, Elson Paul, Beach Jordan R, Hussey George S, Schiemann William P, Egelhoff Thomas T, Howe Philip H, Hansel Donna E
Department of Pathology, University of California San Diego, La Jolla, California.
Department of Pathology, Memorial Sloan Kettering Cancer Center, New York, New York.
Am J Pathol. 2016 May;186(5):1351-60. doi: 10.1016/j.ajpath.2016.01.008. Epub 2016 Mar 14.
Our prior work identified the mammalian target of rapamycin complex 2 (mTORC2) as a key regulator of bladder cancer cell migration and invasion, although upstream growth factor mediators of this pathway in bladder cancer have not been well delineated. We tested whether transforming growth factor (TGF)-β, which can function as a promotility factor in bladder cancer cells, could regulate mTORC2-dependent bladder cancer cell motility and invasion. In human bladder cancers, the highest levels of phosphorylated SMAD2, a TGF-β signaling intermediate, were present in high-grade invasive bladder cancers and associated with more frequent recurrence and decreased disease-specific survival. Increased expression of TGF-β isoforms, receptors, and signaling components was detected in invasive high-grade bladder cancer cells that expressed Vimentin and lacked E-cadherin. Application of TGF-β induced phosphorylation of the Ser473 residue of AKT, a selective target of mTORC2, in a SMAD2- and SMAD4-independent manner and increased bladder cancer cell migration in a modified scratch wound assay and invasion through Matrigel. Inhibition of TGF-β receptor I using SB431542 ablated TGF-β-induced migration and invasion. A similar effect was seen when Rictor, a key mTORC2 component, was selectively silenced. Our results suggest that TGF-β can induce bladder cancer cell invasion via mTORC2 signaling, which may be applicable in most bladder cancers.
我们之前的研究确定雷帕霉素复合物2（mTORC2）的哺乳动物靶点是膀胱癌细胞迁移和侵袭的关键调节因子，尽管该途径在膀胱癌中的上游生长因子介质尚未得到很好的描述。我们测试了可作为膀胱癌细胞促动力因子的转化生长因子（TGF）-β是否能调节mTORC2依赖的膀胱癌细胞运动和侵袭。在人类膀胱癌中，TGF-β信号中间体磷酸化SMAD2的最高水平存在于高级别浸润性膀胱癌中，并与更频繁的复发和疾病特异性生存率降低相关。在表达波形蛋白且缺乏E-钙黏蛋白的浸润性高级别膀胱癌细胞中检测到TGF-β异构体、受体和信号成分的表达增加。应用TGF-β以不依赖SMAD2和SMAD4的方式诱导mTORC2的选择性靶点AKT的Ser473残基磷酸化，并在改良的划痕试验中增加膀胱癌细胞迁移以及通过基质胶的侵袭。使用SB431542抑制TGF-β受体I可消除TGF-β诱导的迁移和侵袭。当mTORC2的关键成分Rictor被选择性沉默时，也观察到类似的效果。我们的结果表明，TGF-β可通过mTORC2信号诱导膀胱癌细胞侵袭，这可能适用于大多数膀胱癌。
