Bidirectional role of KLF5 in prostatic epithelial homeostasis and tumorigenesis

描述（由申请人提供）：概述：KLF 5是一种在上皮细胞中大量表达的基本转录因子。它在细胞增殖控制中具有双向作用，促进和抑制细胞增殖，即使在相同的细胞中也依赖于生长因子。这种双向作用是否以及如何在体内发生尚不清楚。KLF 5在肿瘤发生中也具有相反的功能，具有肿瘤抑制和肿瘤促进活性。KLF 5如何在肿瘤发生中执行相反的功能是另一个需要解决的重要问题。在探索KLF 5如何以一种不寻常的相反方式发挥作用时，我们发现，在上皮内稳态的体外模型中，KLF 5在没有TGF-β的情况下是未乙酰化的和促增殖的，但当TGF-β存在时，KLF 5变得乙酰化以抑制细胞增殖。这种功能转换的机制是未乙酰化的促增殖KLF 5转录复合物在TGF-β诱导的KLF 5乙酰化后重新组装，以改变基因调控和细胞增殖控制。在人类肿瘤中，Ac-KLF 5下调，unAc-KLF 5上调。因此，我们假设，在成人前列腺上皮稳态，KLF 5具有双重作用，这是由其乙酰化状态。在没有分化信号的情况下，KLF 5是未乙酰化的，并且是祖细胞增殖所必需的。当分化信号 当KLF 5被激活时，KLF 5被乙酰化以改变基因转录并启动细胞分化，KLF 5乙酰化的不足和缺乏破坏细胞分化和上皮稳态，导致前列腺癌。我们计划在三个具体目标中检验这一假设。(1)Klf 5在前列腺不同类型细胞中的表达及其在上皮细胞稳态中的双向作用组织学和分子方法将应用于正常和遗传修饰的小鼠，以检查Klf 5在不同类型的前列腺上皮细胞中的表达，并解决Klf 5乙酰化不足（敲除）和缺陷（敲入）是否会破坏增殖和分化。(2)Klf 5在前列腺肿瘤发生中的相反功能 和进步。Klf 5将在前列腺上皮细胞中被敲除。它也将被乙酰化缺陷Klf 5 K358 R突变体（敲入）取代。然后，我们将测试Klf 5乙酰化不足（敲除）和缺陷（敲入）是否分别损害和消除Klf 5的肿瘤抑制功能。还将在人前列腺癌异种移植模型中检测乙酰化缺陷。(3)KLF 5如何在上皮稳态和肿瘤发生中执行相反的功能。将结合ChIP-Seq进行表达谱分析，以鉴定与KLF 5双向功能以及乙酰化和非乙酰化KLF 5相关的基因和基因特征。这些基因特征将与文献中的TGF-β和Pten进行比较，以评估它们与KLF 5的相互作用。我们还将测试当KLF 5未缺失时，过量的生长信号是否以及如何干扰KLF 5的乙酰化，这可能导致KLF 5的脱乙酰化，从而使KLF 5致癌。介导KLF 5致癌功能的基因有可能成为生物标志物和治疗靶点。

DESCRIPTION (provided by applicant): Summary: KLF5 is a basic transcription factor abundantly expressed in epithelial cells. It has a bidirectional role in cell proliferation control both promoting and inhibiting cell proliferation even in the same cells depending on growth factors. Whether and how such a bidirectional role occurs in vivo is unknown. KLF5 also has opposing functions in tumorigenesis, possessing both tumor suppressive and tumor promoter activities. How KLF5 executes opposing functions in tumorigenesis is another important question to address. In exploring how KLF5 functions in an unusual opposite manner, we found that in an in-vitro model of epithelial homeostasis, KLF5 is unacetylated and pro-proliferative without TGF-¿, but becomes acetylated to inhibit cell proliferation when TGF-¿ is present. The mechanism for this functional switch is that the unacetylated pro-proliferative KLF5 transcriptional complex is reassembled upon TGF-¿-induced KLF5 acetylation to alter gene regulation and cell proliferation control. In human tumors, Ac-KLF5 is downregulated and unAc-KLF5 is upregulated. We thus hypothesize that during epithelial homeostasis in adult prostates, KLF5 has a dual role that is determined by its acetylation status. Without differentiation signal, KLF5 is unacetylated and essential for progenitor cells to proliferate. When differentiation signal is activated, KLF5 becomes acetylated to alter gene transcription and initiate cell differentiation Insufficiency and deficiency of KLF5 acetylation disrupt cell differentiation and epithelial homeostasis, causing prostate cancer. We plan to test this hypothesis in three specific aims. (1) Expression of Klf5 in different types of cells and its bidirectional role in epithelial homeostasisin the prostate. Histological and molecular approaches will be applied to normal and genetically modified mice to examine Klf5 expression in different types of prostatic epithelial cells and address whether insufficiency (knockout) and deficiency (knockin) in Klf5 acetylation disrupt both proliferation and differentiation. (2) Opposite functions of Klf5 in prostate tumor initiation and progression. Klf5 will be knocked out in prostate epithelial cells. It will also be replaced wih acetylation-deficient Klf5K358R mutant (knockin). We will then test whether insufficiency (knockout) and deficiency (knockin) in Klf5 acetylation impair and abolish respectively Klf5's tumor suppressor function. Acetylation deficiency will be also tested in xenograft models of human prostate cancer. (3) How KLF5 executes opposing functions in epithelial homeostasis and tumorigenesis. Expression profiling combined with ChIP-Seq will be conducted to identify genes and gene signatures that are associated with KLF5's bidirectional function and acetylated and unacetylated KLF5. Such gene signatures will be compared with those of TGF-¿ and Pten from literature to evaluate their interactions with KLF5. We will also test whether and how excess growth signaling interferes with the acetylation of KLF5 when KLF5 is not deleted, which could lead to deacetylation of KLF5 and thus make KLF5 oncogenic. Genes mediating KLF5's oncogenic function have the potential to become biomarkers and therapeutic targets.