表皮鳞癌干细胞状态维持及维甲酸诱导分化机制中Bmi-1作用研究

Cancer stem cells（CSCs）are involved in cancer evolution and therapy resistant. How to select the key target to induce CSCs differentiation and enhance the sensitivity to therapy are important issues. In our previous study, we had isolated the CSCs from squamous cell carcinoma and found high expression of Bmi-1，stem renewal factor, in SCC tissues and side population cells(SP). Moreover, retinoic acid could suppress the expression of Bmi-1 in A431 cells. We speculate that Bmi-1 could be key target of CSCs. However, whether Bmi-1 involved in maintaining of CSCs and regulated by retinoic acid in SCC has not been addressed before. We aimed to construct silencing and over expressing cell of Bmi-1 to study its function in proliferation of SCC through cells and animal assay. The regulation of Bmi-1 by Retinoic acid will be confirmed in various cells. The pathway of Bmi-1 regulated by retinoic acid will be explored through RAR/RXR receptors blockage assay etc. Further, whether silencing Bmi-1 could enhance sensitivity of cancer cells to retinoic acid would be performed. We propose that the Bmi-1 plays a key role in CSCs self-renewal and pathway of cell differentiation induced by retinoic acid, which will shed light for cancer therapy.

肿瘤干细胞（CSCs）与肿瘤发展及治疗抵抗密切相关, 如何选择关键靶点诱导CSCs分化及增强治疗敏感性是目前研究重点。我们前期研究已证明表皮鳞癌干细胞的存在,并发现在鳞癌组织及侧群细胞（SP）中干细胞更新因子Bmi-1高表达,而维甲酸可抑制培养鳞癌细胞中Bmi-1表达并诱导其核转移。我们推测Bmi-1为表皮鳞癌干性状态维持的关键靶点， 而维甲酸对其调控意义国内外尚未见其他研究报道。本课题拟通过鳞癌标本、细胞培养及动物实验，利用流式分选、基因沉默及过表达技术明确Bmi-1在鳞癌干性状态维持中作用；在不同表皮细胞中检测维甲酸对Bmi-1作用共性，通过Bmi-1基因表达调控和受体阻遏实验研究维甲酸对Bmi-1作用及通路。本课题将首次深入研究维甲酸与Bmi-1间作用关系，进一步明确Bmi-1沉默是否可以增强肿瘤细胞对维甲酸作用敏感性，为探索鳞癌CSCs干性状态维持及肿瘤治疗提供新的思路。

肿瘤干性状态维持与肿瘤发展及治疗抵抗密切相关, 如何选择关键靶点诱导细胞分化及增强治疗敏感性是目前研究重点。我们通过前期研究结果推测干细胞更新因子Bmi-1为肿瘤干性状态维持的关键靶点，沉默Bmi-1可能会逆转鳞癌干细胞的生物学行为并消弱耐药，增强肿瘤细胞对治疗敏感性。本课题拟通过鳞癌标本、细胞培养及动物实验，研究Bmi-1基因沉默前后相关基因表达谱差异、细胞周期、增殖、迁移实验及小鼠成瘤能力变化，明确Bmi-1在多种鳞癌均高表达，参与肿瘤细胞增殖、耐药基因调控。EMT与肿瘤转移及耐药密切相关，研究证明Bmi-1沉默也导致黑色素瘤细胞EMT行为逆转，并降低耐药基因ABCB1和ABCC3等表达；此外，Bmi-1作为基因表达重要抑制因子，从细胞及小鼠成瘤实验证明Bmi-1基因沉默能有效促进鳞癌细胞及黑色素瘤细胞对维甲酸作用等敏感性，进一步分析其作用机制发现，在黑色素瘤细胞中Bmi-1具有表观调控维甲酸受体表达水平作用，Bmi-1沉默抑制维甲酸受体降解，维甲酸联合Bmi-1沉默可显著抑制成瘤实验中肿瘤生长。本课题通过4年研究明确Bmi-1在皮肤肿瘤干性状态维持中作用；证明Bmi-1的沉默能提高皮肤鳞癌及黑色素瘤细胞对维甲酸药物诱导敏感性，并为今后研究维甲酸在皮肤肿瘤中的表观遗传学调控机制奠定基础和研究方向，对明确Bmi-1作为皮肤肿瘤治疗靶向具有重要意义。