Breast Cancer Biology of Translational De-repression

描述（由申请人提供）：蛋白质合成机制是乳腺癌和其他上皮性癌症的主要致癌转化靶标，也是新疗法（例如雷帕霉素类似物）的靶标。然而，该主题仍有待进一步研究，具有5个UTR结构特征的mrna抑制翻译，如VEGF、FGF-2、HER-2和Bcl-2，预计比其他mrna需要更高水平的4E（一种限速起始因子）。这一预测得到了模型系统测试的支持。逆转录病毒将PI3K和AKT突变为癌基因，从而增加4E水平，mTOR（雷帕霉素靶蛋白）激酶通过释放抑制蛋白来增加4E。雷帕霉素抑制mTOR可逆转PI3K或akt癌基因转化细胞的表型，而其他细胞则不能。4E本身也是一种致癌基因，在乳腺癌和上皮癌中增加，并与肿瘤进展和侵袭有关。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，该突变体在软琼脂中减少了它们的集落大小。使用这个和其他系统，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会损害VEGF、HER-2、Bcl-2、FGF-2、缺氧诱导因子（hif - α）和COX-2 mrna的翻译起始；b)人乳腺上皮细胞（HMECs）中4E的增加刺激了这些mrna翻译的启动。具体目的是：1)通过表达4E突变体来检测这些mrna是否在乳腺癌细胞中被翻译抑制；2)检测这些mrna是否通过增加hmec中的wt 4E而被翻译激活；3)检测增加的4E是否保护这些mRNA免受降解；4)在小鼠中检测表达4E受损突变体的模型乳腺癌细胞系的致瘤性、转移性和组织侵袭特性，并将这些终点与所列mrna的表达联系起来。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.