Bidirectional role of KLF5 in prostatic epithelial homeostasis and tumorigenesis

描述(申请人提供)：摘要：KLF5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，可促进细胞增殖，也可抑制细胞增殖，甚至在同一细胞中也依赖生长因子。这种双向作用是否以及如何在体内发生尚不清楚。KLF5在肿瘤发生中也具有相反的作用，既具有肿瘤抑制活性，又具有肿瘤促进活性。KLF5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KLF5如何以一种不寻常的相反方式发挥作用时，我们发现，在一个上皮细胞动态平衡的体外模型中，KLF5是非乙酰化的，在没有转化生长因子β的情况下促进增殖，但当转化生长因子β存在时，KLF5变为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KLF5转录复合体在转化生长因子β诱导的KLF5乙酰化后重新组装，从而改变基因调控和细胞增殖控制。在人类肿瘤中，Ac-KLF5表达下调，Unac-KLF5表达上调。因此，我们假设，在成人前列腺上皮细胞动态平衡期间，KLF5具有双重作用，这是由其乙酰化状态决定的。在没有分化信号的情况下，KLF5是非乙酰化的，是祖细胞增殖所必需的。当区分信号出现时 当KLF5被激活时，KLF5被乙酰化，从而改变基因转录，启动细胞分化。KLF5乙酰化不足和缺失扰乱了细胞分化和上皮细胞的动态平衡，导致前列腺癌。我们计划在三个具体目标上检验这一假设。(1)KLF5在不同类型细胞中的表达及其在前列腺上皮内稳态中的双向作用。组织学和分子生物学方法将应用于正常和转基因小鼠，以检测KLF5在不同类型的前列腺上皮细胞中的表达，并解决KLF5乙酰化不足(敲除)和缺乏(敲打)是否扰乱增殖和分化。(2)KLF5在前列腺癌发生中的相反作用 和进步。KLF5将在前列腺上皮细胞中被敲除。它也将被乙酰化缺陷的Klf5K358R突变体(敲门)所取代。然后，我们将测试KLF5乙酰化不足(基因敲除)和缺失(敲打)是否分别损害和取消KLF5‘S的肿瘤抑制功能。乙酰化缺陷也将在人类前列腺癌的异种移植模型中进行测试。(3)KLF5在上皮动态平衡和肿瘤发生中如何执行相反的功能。表达谱结合CHIP-SEQ将用于识别与KLF5的S双向功能以及乙酰化和非乙酰化KLF5相关的基因和基因签名。这些基因签名将与文献中的转化生长因子β和Pten的基因签名进行比较，以评估它们与KLF5的相互作用。我们还将测试当KLF5没有缺失时，过量的生长信号是否以及如何干扰KLF5的乙酰化，这可能导致KLF5的去乙酰化，从而使KLF5致癌。介导KLF5 S癌基因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.