与TGF-β通路交互作用的PML剪接异构体的确定及其对乳腺癌细胞EMT和转移调控作用研究

Metastasis is the leading cause of breast cancer-associated deaths. Epithelial–mesenchymal transition (EMT) induced by TGF-β/Smads pathway results in an increased migration and invasive ability in cancer cells，which is a key event involved in the metastasis of cancer cells. Others and we have confirmed the cross talking between promyelocytic leukemia protein (PML) and TGF-β/Smads pathway. However, the type of PML splice variant that plays a leading role in TGF-β1 induced EMT is not clear. This project has found that TGF-β1 can promote the SUMOylation modification of PML, promote the assembly of PML-NBs, and establish a positive regulatory mechanism that PML nuclear bodies contribute to the increasing expression of TGF-β1 by recruiting Pin1. On the other hand we screened PML splice variant types in PML-NBs and Smad2/3 coupling, established a molecular mechanism of PML-NBs and Smad2/3 co-coupling in regulation of breast cancer EMT. Based on previous studies, this project explored the cross talking between PML and TGF-β/Smads pathway, and elucidated the effect of this interaction on EMT and metastasis of breast cancer. It will provide new ideas for inhibiting metastasis treatment of breast cancer.

肿瘤转移是乳腺癌患者死亡的最主要原因。TGF-β/Smads通路诱导的上皮细胞-间质细胞转化（EMT）使肿瘤细胞获得迁移及侵袭的能力，是肿瘤转移的关键。我们和已有研究证实早幼粒细胞白血病蛋白(PML)与TGF-β/Smads通路存在交互作用，然而在TGF-β1诱导的EMT过程中起主导调控作用的PML剪接异构体类型尚不清楚。本项目发现TGF-β1能促进PML发生SUMO化，促进PML-NBs组装，建立PML-NBs通过募集Pin1促TGF-β1表达的正调控机制；另一方面我们筛选在PML-NBs中与Smad2/3共偶联的PML剪接异构体类型，建立核体内PML与Smad2/3共偶联调控乳腺癌EMT的分子机制。本项目在原有研究基础上深入探讨PML与TGF-β/Smads通路的交互作用，阐明这种交互作用对乳腺癌EMT发生及转移的影响，将对抑制乳腺癌转移治疗提供新思路。

乳腺癌是女性最常见的恶性肿瘤之一，肿瘤转移是乳腺癌患者死亡的最主要原因。TGF-β/Smads通路诱导的上皮细胞-间质细胞转化（EMT）使肿瘤细胞获得侵袭及迁移的能力，是肿瘤转移的关键。本项目证实早幼粒细胞白血病蛋白(PML)与TGF-β/Smads通路存在交互作用。本项目研究了TGF-β1通过PML促进自身表达的正调控机制: TGF-β1诱导PML SUMO化，促进PML-NBs结构组装，通过募集Pin1，Pin1蛋白可直接作用于AUF1，通过异构高度磷酸化的AUF1，抑制AUF1与TGF-β1mRNA的结合，使TGF-β1mRNA不易被降解，增加TGF-β1mRNA的稳定性，从而TGF-β1蛋白表达增加，进一步调控乳腺癌的EMT。另一方面我们筛选出了在PML-NBs中与Smad2/3共偶联的PML剪接异构体类型，我们研究证实七种PML剪接异构体中只有PMLI 和PMLIV型剪接异构体与Smad2 /3有相互作用，并且过表达PMLI和PMLIV的细胞中有更高磷酸化水平的Smad2/3，还发现一些磷酸化Smad2/3定位在PMLIV核小体结构中，过表达PMLIV能够在乳腺癌MCF-7细胞中促进TGF-β1诱导的EMT，间接地证实了PMLIV型异构体可能通过与Smad2/3共偶联，并且为TGF-β信号通路的传递所必需，对乳腺癌EMT起重要调控作用。本项目在原有研究基础上深入探讨了PML与TGF-β/Smads通路的交互作用，阐明这种交互作用对乳腺癌发生EMT及转移的影响，将对抑制乳腺癌转移治疗提供新思路。