肿瘤干细胞被认为是肿瘤耐药、复发、转移的根源，但目前对肿瘤干细胞的调控机制了解不足。CUL4A是与乳腺癌预后密切相关的癌基因，我们初步实验显示CUL4A能诱导乳腺和乳腺癌细胞EMT及其干细胞特性，使其具有多胚层分化潜能。根据前期实验结果和文献报道，我们推测CUL4A可能通过WDR5介导的组蛋白甲基化修饰调节乳腺和乳腺癌干细胞的扩增和分化潜能。本项目拟在前期研究基础上，综合运用流式细胞术、干细胞诱导分化、基因芯片、ChIP-seq、ChIP-qPCR等技术手段在分子、细胞、转基因鼠及临床标本等层面深入探讨CUL4A调控乳腺和乳腺癌干细胞增殖和分化潜能的作用及其表观遗传学机制，并分析CUL4A表达与乳腺癌病人肿瘤干细胞、临床特征的相关性。旨在通过上述研究验证我们的假设，深化对乳腺及乳腺癌干细胞的认识，揭示乳腺癌发生及耐药、复发、转移的新机制，为进一步研究乳腺癌生物治疗方案和药物提供新思路。

CUL4A, a member of an E3 ligase family, is significantly associated with prognosis of breast cancers. Our previous data showed that over-expression of CUL4A in breast and breast cancer cell lines can induce epithelial-mesenchymal transition of normal breast and breast cancer cell lines. Further preliminary experiments indicated that CUL4A induces NANOG, OCT4, SOX2 expression in normal breast and breast cancer cell lines, increases the proportion and stemness of cancer stem cells. Higher level of tri-methylation of H3K4 and enhanced bindings of H3K4me3 with promoter sequences if the above stem-related genes were also detected in breast cancer cell line. Taken together with previous reports, we postulated that CUL4A may induce self-renewal and differentiation potentials breast stem cells and breast cancer stem cells though WDR5 mediated H3K4 tri-methylation. To validate our preliminary experiments and test our hypothesis we planned to use serials of cellular, and molecular assays such as self-renewal and differentiation potential, flow cytometry, ChIP-sequencing, ChIP-qPCR etc in culture cells, transgenic mouse models to analysis the effects of CUL4A on stemness of normal breast and cancer stem cells and try to dissect the underlying epigenetic mechanisms. Finally we will examine the correlation of CUL4A with cancer stem cells from human breast cancer tissues and clinical characteristics of patients. The successful accomplishments of this project will further our understanding of generation, stemness and other properties of breast cancer stem cells and will shed lights on mechanisms of tumorigenesis, relapse and metastasis of breast cancers.