Breast Cancer Biology of Translational De-repression

描述(申请人提供)：蛋白质合成机制是乳腺癌和其他上皮性癌症致癌转化的主要靶点，也是新疗法(如雷帕霉素类似物)的靶点。然而，这一主题仍未得到研究，具有5个抑制翻译的UTR结构特征的mRNAs，如血管内皮生长因子、成纤维细胞生长因子-2、HER-2和bc l-2，被预测比其他mRNAs需要更高水平的4E(一种限速启动因子)。这一预测得到了模型系统试验的支持。逆转录病毒已将PI3K和AKT突变为癌基因，使4E水平结构性增加，mTOR(雷帕霉素靶标)通过释放抑制蛋白而增加4E水平。雷帕霉素抑制mTOR可逆转PI3K或AKT癌基因转化细胞的表型，但不能逆转其他细胞的表型。4E本身也是一种癌基因，在乳腺癌和上皮性癌中增加，并与肿瘤的进展和侵袭有关。然而，4E效应的机制尚不清楚。我的实验室已经克隆了表达4E突变体的致瘤细胞系，该突变体可以减少它们在软琼脂中的菌落大小。利用这个和其他系统，我的团队将进行研究，以了解4E的数量如何改变癌细胞表型的机制。我假设：a)表达改变乳腺癌细胞表型的突变体4E会削弱对VEGF、HER-2、Bc l-2、FGF-2、低氧诱导因子(HIF-α)和COX-2 mRNAs的翻译启动；b)在人乳腺上皮细胞(HMECs)中增加4E可以刺激这些mRNAs的翻译启动。具体目标是：1)测试这些mRNAs是否通过表达4E突变体在乳腺癌细胞中进行翻译抑制；2)测试这些mRNAs是否通过增加4E在HMECs中的翻译激活而被激活；3)测试增加4E是否能保护这些mRNAs免于降解；4)测试表达受损的4E突变体的模型乳腺癌细胞系在小鼠体内的致癌、转移和组织侵袭特性，并将这些终点与列出的mRNAs的表达相关联。这些研究可能确定乳腺癌治疗或化学预防的新策略。

DESCRIPTION (provided by applicant): The protein synthesis machinery is a major target of oncogenic transformation in breast and other epithelial cancers and is a target, for new therapeutics (e.g., rapamycin analogues). However, the topic remains understudied, mRNAs with 5 UTR structural features that repress translation, such as VEGF, FGF-2, HER-2, and Bcl-2, are predicted to require higher levels of 4E (a rate limiting initiation factor) than other mRNAs. This prediction is supported by tests in model systems. Retroviruses have mutated PI3K and AKT into oncogenes that constitutively increase 4E levels, mTOR (target of rapamycin) kinase increases 4E by releasing a repressor protein. Rapamycin inhibition of mTOR reverses the phenotype of PI3K- or AKT-oncogene transformed cells but not others. 4E itself is also an oncogene, is increased in breast and epithelial cancers, and is associated with tumor progression and invasion. Yet the mechanism of the 4E effect is unknown. My laboratory has cloned tumorigenic cell lines expressing a 4E mutant which decreases their colony size in soft agar. Using this and other systems my team will conduct studies to understand the mechanism of how the quantity of 4E modifies the cancer cell phenotype. I hypothesize that: a) expressing mutant 4E that alters the phenotype of breast cancer cells impairs initiation of translation for VEGF, HER-2, Bcl-2, FGF-2, hypoxia inducible factor (HIF-lalpha) and COX-2 mRNAs; and b) increasing 4E in human mammary epithelial cells (HMECs) stimulates initiation of translation for these mRNAs. Specific Aims are: 1) to test if these mRNAs are translationally repressed in breast cancer cells by expressing a 4E mutant; 2) to test if these mRNAs are translationally activated by increasing wt 4E in HMECs; 3) to test if increased 4E protects these mRNA from degradation; 4) to test the tumorigenic, metastatic, and tissue invasion properties of model breast cancer cell lines expressing an impaired mutant of 4E in mice and correlate these end points with the expression of the mRNAs listed. These studies may identify new strategies in breast cancer therapy or chemoprevention.