Department of Pharmaceutical Sciences and Center for Cancer Research, University of Tennessee Health Science Center, Memphis, TN 38163, USA.
Department of Pathology, University of Tennessee Health Science Center, Memphis, TN 38163, USA.
Br J Cancer. 2018 Feb 20;118(4):587-599. doi: 10.1038/bjc.2017.431.
Cancer progression and metastasis is profoundly influenced by protein kinase D1 (PKD1) and metastasis-associated protein 1 (MTA1) in addition to other pathways. However, the nature of regulatory relationship between the PKD1 and MTA1, and its resulting impact on cancer metastasis remains unknown. Here we present evidence to establish that PKD1 is an upstream regulatory kinase of MTA1.
Protein and mRNA expression of MTA1 in PKD1-overexpressing cells were determined using western blotting and reverse-transcription quantitative real-time PCR. Immunoprecipitation and proximity ligation assay (PLA) were used to determine the interaction between PKD1 and MTA1. PKD1-mediated nucleo-cytoplasmic export and polyubiquitin-dependent proteosomal degradation was determined using immunostaining. The correlation between PKD1 and MTA1 was determined using intra-tibial, subcutaneous xenograft, PTEN-knockout (PTEN-KO) and transgenic adenocarcinoma of mouse prostate (TRAMP) mouse models, as well as human cancer tissues.
We found that MTA1 is a PKD1-interacting substrate, and that PKD1 phosphorylates MTA1, supports its nucleus-to-cytoplasmic redistribution and utilises its N-terminal and kinase domains to effectively inhibit the levels of MTA1 via polyubiquitin-dependent proteosomal degradation. PKD1-mediated downregulation of MTA1 was accompanied by a significant suppression of prostate cancer progression and metastasis in physiologically relevant spontaneous tumour models. Accordingly, progression of human prostate tumours to increased invasiveness was also accompanied by decreased and increased levels of PKD1 and MTA1, respectively.
Overall, this study, for the first time, establishes that PKD1 is an upstream regulatory kinase of MTA1 status and its associated metastatic activity, and that the PKD1-MTA1 axis could be targeted for anti-cancer strategies.
除了其他途径外，蛋白激酶 D1（PKD1）和转移相关蛋白 1（MTA1）也深刻影响着癌症的进展和转移。然而，PKD1 和 MTA1 之间调节关系的本质及其对癌症转移的影响尚不清楚。在这里，我们提供的证据表明 PKD1 是 MTA1 的上游调节激酶。
通过 Western blot 和反转录定量实时 PCR 测定 PKD1 过表达细胞中 MTA1 的蛋白和 mRNA 表达。免疫沉淀和邻近连接分析（PLA）用于确定 PKD1 和 MTA1 之间的相互作用。使用免疫染色法测定 PKD1 介导的核质输出和多聚泛素依赖性蛋白酶体降解。通过胫骨内、皮下异种移植、PTEN 敲除（PTEN-KO）和转基因腺癌小鼠前列腺（TRAMP）小鼠模型以及人类癌症组织来确定 PKD1 和 MTA1 之间的相关性。
我们发现 MTA1 是 PKD1 的相互作用底物，PKD1 磷酸化 MTA1，支持其核质分布，并利用其 N 端和激酶结构域通过多聚泛素依赖性蛋白酶体降解有效抑制 MTA1 的水平。PKD1 介导的 MTA1 下调伴随着前列腺癌进展和转移的显著抑制，在生理相关的自发肿瘤模型中也是如此。相应地，人前列腺肿瘤进展为侵袭性增加也伴随着 PKD1 和 MTA1 水平的降低和升高。
总的来说，这项研究首次确立了 PKD1 是 MTA1 状态及其相关转移活性的上游调节激酶，PKD1-MTA1 轴可作为抗癌策略的靶点。
