FOXO4抑制前列腺癌侵袭、转移的分子机制研究

Metastasis remains the primary cause of prostate cancer (CaP)-related death. Androgen receptor (AR) and PI3K/AKT signaling pathway play a critical role in the progression of CaP. Therefore, further understanding of the molecular mechanisms underlying CaP metastasis is critical to improving patients' survival. Employing Decode lentiviruses encoding the entire human genomic shRNA library and subsequent in vitro and in vivo studies, we identified FOXO4 as a potential metastasis suppressor. FOXO4, an important downstream target of PI3K/AKT pathway, can induce growth arrest and apoptosis by inhibiting AKT activation. FOXO1 was found to directly associate with AR, and thereby inhibit its transcriptional activity and reduce prostate cancer cells proliferation. Given the importance of the crosstalk between PI3K/AKT and AR signaling pathways in CaP progression, and the correlations between FOXO, PI3K/AKT and AR, we hypothesize that FOXO4 acts through interacting with and inhibiting PI3K/AKT and AR signal pathways. We will further dissect the mechanisms for FOXO4 modulation of CaP cell metastasis by combined CHIP-seq assay and Digital Gene Expression-Tag Profiling approach to identify novel target genes of FOXO4, and studying its interaction with AR and PI3K/AKT pathways using co-IP, pulldown and mutation assays. Together, this project will further our understanding of the molecular mechanisms underlying the progression of CaP to the metastatic phase, and lead to the identification of potential therapeutic targets.

转移仍是前列腺癌死亡的首要原因。PI3K/AKT与雄激素受体（AR）通路的相互作用在前列腺癌进展、转移中起关键作用。因此，加深理解这些信号通路的分子机制对提高病人生存率至关重要。我们利用针对人类全基因组的shRNA库和体外、内转移分析，发现FOXO4是一个新的前列腺癌转移抑制基因。FOXO4是PI3K/AKT信号通路中一个重要的下游分子，可拮抗PI3K/AKT的活性，并已知FOXO1与AR结合来抑制其活性。因此，我们认为FOXO4可能通过抑制PI3K/AKT和AR信号途径来发挥作用。本项目拟在前期研究基础上，进一步探讨FOXO4在AR与PI3K/AKT信号通路起的作用，明确FOXO4是否通过与AR相互作用来发挥其抑制前列腺癌转移的作用，并通过数字化基因表达谱分析和CHIP-seq分析FOXO4转录调控的基因。本项目旨在揭示FOXO4在前列腺癌进展、转移中的作用机制，并发现新的肿瘤治疗途径。

目前，转移仍是前列腺癌死亡的首要原因。因此，迫切需要阐明前列腺癌的转移机制，以发展新的有效的诊断和治疗途径。我们应用慢病毒包装的针对人基因组的shRNA文库(~10,000 shRNAs)，通过体外基质胶侵袭试验筛选鉴定了叉头蛋白O4 （Forkhead box protein O4，FOXO4) 是一个新的前列腺癌侵袭抑制基因。利用原始和淋巴结转移的LNCaP/FOXO4 shRNA 和对照细胞，抽提RNA进行数字化基因表达谱分析，发现4个基因（PIP, CAMK2N1, PLA2G16 and PGC）的表达受FOXO4调控。进一步，发现FOXO4通过调控RUNX2基因的功能来抑制这些基因，从而发挥其转移抑制功能。为了进一步探讨前列腺癌侵袭、转移的分子机制，shRNA慢病毒文库前列腺癌原位移植裸鼠模型体内筛选前列腺转移相关基因。体内筛选初步发现γ氨基丁酸A受体相关类蛋白1 （gamma-aminobutyric acid (GABA) A receptor-associated protein-like 1，Gabarapl1）抑制前列腺癌淋巴结转移，且其是FOXOs的下游基因。有趣地，我们体外和体内筛选的基因都能拮抗Akt促进前列腺癌侵袭的作用。PI3K/Akt信号通路在前列腺癌转移中起至关重要的作用。因此，我们假设PI3K/Akt和FOXOs及其调控基因之间的相互作用在前列腺癌转移中起主要作用。总之，通过这些研究我们将揭示前列腺癌转移的机制并研发新的前列腺癌精准治疗途径。