P53 AND ESTROGEN IN PCNA EXPRESSION OSTEOSARCOMA CELLS

本研究的目的是分析人骨肉瘤细胞中抑癌蛋白p53和雌激素信号通路之间的相互作用。 p53基因是各种人类癌症中最常改变的基因。 p53的失活被认为是骨肉瘤发展的重要步骤。 雌激素在成骨细胞谱系的发育和功能中是重要的，并且雌激素刺激骨肉瘤细胞的增殖。 然而，雌激素作用在存在和不存在功能性野生型p53的情况下的后果尚不清楚。 虽然已知p300/CBP是p53介导和雌激素受体介导的基因调控的共激活剂，但p53与雌激素功能之间的关系仍不清楚。 我们建议研究p53介导的和雌激素介导的基因调控的途径之间的功能相互关系，其相关性的细胞增殖和扰动的细胞周期，使用PCNA基因表达在骨肉瘤细胞作为一个模型。PCNA是细胞DNA复制和DNA修复机制的重要组成部分。 骨肉瘤细胞PCNA表达受p53调控 我们的研究结果表明，PCNA基因是雌激素诱导的。 此外，初步实验已经揭示了p300/CBP在介导p53调节PCNA表达中的重要作用。基于早期的研究和初步的数据，我们假设有显着的p53和雌激素信号通路之间的串扰调节PCNA的表达。 为了验证这一假设，我们将分析p53和雌激素受体的共激活因子p300/CBP调节p53介导的PCNA基因表达的机制。 我们建议确定p53-CBP途径在雌激素诱导的PCNA表达和骨肉瘤细胞增殖中的作用。 由于PCNA的相对量是重要的，在指定其与其他蛋白质的相互作用的细胞周期的重要性，它也被假设，PCNA的表达是差异调节的协调作用的p53和雌激素在细胞周期的不同阶段。为了验证这一假设，我们将分析p53和雌激素在细胞周期中对PCNA转录的调控。 这项研究将提供重要的信息，雌激素在增殖和细胞周期检查点功能的存在和不存在的功能p53的作用。 它也将提供一个范例，用于分析类固醇激素和p53之间的串扰，在正常和异常的细胞过程，如肿瘤发生的基因表达的调节。

The objective of the proposed study is to analyze the cross-talk between the tumor suppressor protein p53 and estrogen signaling pathways in human osteosarcoma cells. The p53 gene is the most frequently altered gene in various human cancers. Inactivation of p53 is considered to be an important step in the development of osteosarcomas. Estrogens are important in the development and functioning of the osteoblast lineage and estrogens stimulate proliferation of osteosarcoma cells. However, consequence of estrogen action in the presence and in the absence of functional wild type p53 is not clear. Although it is known that p300/CBP is a coactivator for both p53-mediated and estrogen receptor-mediated gene regulation, the relationship between p53 and estrogen functions remains unknown. We propose to investigate the functional interrelationship between pathways of p53-mediated and estrogen-mediated gene regulation and its relevance to cell proliferation and perturbation of cell cycle, using PCNA gene expression in osteosarcoma cells as a model. PCNA is a critical component of the cellular DNA replication and DNA repair machineries. PCNA expression in osteosarcoma cells is regulated by p53. Our results show that the PCNA gene is estrogen-inducible. Furthermore, preliminary experiments have revealed a major role for p300/CBP in mediating regulation of PCNA expression by p53. Based on earlier studies and preliminary data, we hypothesize that there is significant cross-talk between p53 and estrogen signaling pathways in regulating PCNA expression. To test this hypothesis, we will analyze the mechanisms by which p300/CBP, a coactivator for both p53 and estrogen receptor, regulates p53-mediated PCNA gene expression. We propose to determine the role of p53-CBP pathway in estrogen-induced PCNA expression and proliferation of osteosarcoma cells. Since the relative amount of PCNA is important in specifying its interaction with other proteins important for the cell cycle, it is also hypothesized that PCNA expression is differentially regulated by coordinated action of p53 and estrogen in different stages of the cell cycle. To test this hypothesis, PCNA transcriptional regulation by p53 and estrogen during the cell cycle will be analyzed. The proposed study will provide important information on the role of estrogen in proliferation and cell cycle checkpoint function in the presence and in the absence of functional p53. It will also provide a paradigm for analyzing cross-talk between steroid hormones and p53 in regulating gene expression in both normal and abnormal cellular processes such as oncogenesis.