Cyclin D1 function in tumorigenesis and differentiation

描述(由申请人提供)：在不同组织类型的上皮性肿瘤中观察到细胞周期蛋白D1基因的遗传改变以及由此导致的编码蛋白的过度表达。同样，三种C/EBP2亚型的异常表达是几种上皮性癌的特征。然而，对细胞周期蛋白D1和C/EBP2影响肿瘤发生的途径知之甚少。对人类癌症基因表达模式的生物信息学分析和直接实验相结合表明，细胞周期蛋白D1可以激活C/EBP2的转录功能。此外，在几种类型的人类上皮性肿瘤中都可以看到Cyclin D1和C/EBP2带来的转录程序-然而，这种转录程序与肿瘤发生之间的因果关系尚未建立。将要进行的研究将包括结构-功能分析，以从机制上了解细胞周期蛋白D1如何激活C/EBP2在细胞周期蛋白D1靶基因启动子上的转录功能。这些研究的目的也是为了提供试剂，例如C/EBP2和Cyclin D1突变体，以探索Cyclin D1和C/EBP2之间功能相互作用的生物学意义。为了研究细胞周期蛋白D_1‘S转录功能的生物学效应，利用黑素细胞和乳腺上皮细胞建立了细胞周期蛋白D_1依赖性转化试验。利用这些系统，将从遗传角度评估细胞周期蛋白D1‘S C/EBP2依赖的转录功能对转化的贡献。第三条研究路线的灵感来自于观察到怀孕期间乳腺发育需要细胞周期蛋白D1和C/EBP2。这一观察结合上述对人类肿瘤的分析表明，由于Cyclin D1过表达对C/EBP2转录活性的影响而导致的分化受阻可能参与了肿瘤的发生。这项研究将测试细胞周期蛋白D1和C/EBP2之间的功能相互作用是否有助于乳腺上皮细胞的分化。这将需要使用Cyclin D1和C/EBP2缺陷的乳腺上皮细胞以及野生型细胞进行遗传分析。与公共卫生相关：细胞周期蛋白D1，由于其在人类上皮性肿瘤--包括黑色素瘤和乳腺癌--中的基因改变，被认为是导致癌症的重要因素。为了以细胞周期蛋白D1为靶点进行治疗，有必要了解它的作用途径。为了回应这一需求，这项拟议的研究将试图阐明细胞周期蛋白D1如何影响肿瘤发生。

DESCRIPTION (provided by applicant): Genetic alterations in the cyclin D1 gene with consequent overexpression of the encoded protein are observed in epithelial tumors of diverse histological types. Similarly, aberrant expression of the three C/EBP2 isoforms characterizes several epithelial cancers. However, the pathways through which cyclin D1 and C/EBP2 operate to effect tumorigenesis are poorly understood. A combination of bioinformatic analyses of the patterns of gene expression in human cancer and direct experimentation suggests that cyclin D1 can activate the transcriptional function of C/EBP2. Further, the transcriptional program brought about by cyclin D1 and C/EBP2 can be seen in several types of human epithelial tumors-however, the causal relationship between this transcriptional program and tumorigenesis has not been established. Research to be conducted will involve structure-function analyses to understand mechanistically how cyclin D1 activates the transcriptional function of C/EBP2 at cyclin D1 target gene promoters. The intent of these studies is also to provide reagents, e.g., C/EBP2 and cyclin D1 mutants, to probe the biological significance of the functional interaction between cyclin D1 and C/EBP2. To address the biological consequences of cyclin D1's transcriptional function, cyclin D1-dependent transformation assays have been developed, using melanocytes and mammary epithelial cells. With these systems, the contribution of cyclin D1's C/EBP2-dependent transcriptional function to transformation will be assessed genetically. A third line of investigation is inspired by the observation that cyclin D1 and C/EBP2 are required for mammary gland development during pregnancy. This observation, together with the analysis of human tumors noted above, suggests that blocked differentiation resulting from the effect of overexpressed cyclin D1 on the transcriptional activity of C/EBP2 may contribute to tumorigenesis. The research will test the possibility that the functional interaction between cyclin D1 and C/EBP2 contributes to mammary epithelial cell differentiation. This will entail a genetic analysis employing cyclin D1- and C/EBP2 -deficient mammary epithelial cells, as well as wild-type cells. PUBLIC HEALTH RELEVANCE: Cyclin D1, by virtue of its genetic alterations in human epithelial tumors-including melanoma and breast cancer-is thought to contribute materially to cancer. In order to target cyclin D1 therapeutically, it is necessary to understand the pathways through which it operates. Responding to this need, the proposed research will attempt to elucidate how cyclin D1 effects tumorigenesis.