CDK4介导的p16蛋白胞浆易位促进乳腺癌进展的机制研究

肿瘤抑制基因p16直接参与细胞周期调控，抑制细胞增殖、分裂以及肿瘤发生。申请人前期研究发现乳腺癌组织p16蛋白表达上调，同时伴随从胞核到胞浆的亚细胞定位改变，并与肿瘤的进展及预后紧密相关（BMC Cancer，2014），但p16蛋白胞浆易位的机制及其在乳腺癌进展中的作用尚不清楚。预实验表明p16蛋白在胞浆中的异常表达与CDK4密切相关，推测p16与CDK4在胞浆中形成p16/CDK4复合体而滞留于胞浆，并促进乳腺癌进展。本研究将进一步验证p16蛋白在乳腺癌组织样本及细胞系中的亚细胞定位；继而探讨内源性p16与CDK4在胞浆中是否存在共定位和相互作用；并在细胞水平以及细胞和动物水平分别检测CDK4表达沉默、过表达、CDK4突变体对p16蛋白亚细胞定位的影响以及对乳腺癌细胞增殖、侵袭、迁移能力的调控。本项目将揭示p16蛋白胞浆易位的机制及其在乳腺癌进展中的作用，为乳腺癌的治疗提供新的思路。

Tumor suppressor gene p16 can inhibit tumorigenesis of malignant tumor by directly regulating cell cycle and suppressing cell proliferation and division. However, we found in previous study that p16 protein up-regulated in breast cancer, accompanied with translocation of p16 from nucleus to cytoplasm, which closely correlated to the progression and prognosis of breast cancer (BMC Cancer，2014). And the mechanism of p16 cytoplasmic translocation and its role in the progression of breast cancer were still not clear. Preliminary experiments showed that the aberrant expression of p16 in cytoplasm had a close correlation to CDK4. And thus, we inferred that the aberrant expression of p16 in cytoplasm, resulting from its cytoplasmic sequestration induced by p16/CDK4 complex, could promote the progression of breast cancer. In this study we will verify the subcellular localization of p16 protein in breast cancer specimens and cell lines, explore the locating relationship and the interaction between endogenous p16 and CDK4 in cytoplasm, and detect the effects of gene silence, over-expression and mutant of CDK4 on the subcellular localization of p16 protein or the activity in proliferation, invasion and immigration of breast cancer cells in cell level or in both cell and animal levels, respectively. In a word, this study aims to provide a new clue to the therapy of breast cancer by revealing the mechanism of cytoplasmic translocation of p16 and its role in the progression of breast cancer.