转录因子Six2通过假基因CYP4Z2P介导的ceRNA网络调控乳腺癌对阿霉素耐药性的机制研究

Adriamycin resistance is the main challenges during the treatment of breast cancer. Previous studies have shown that numerous genes contributed to adriamycin resistance. Notably, cancer stem cells (CSCs) are the main factor that leads to drug resistance. Our previous studies have indicated that the expression levels of CYP4Z1 and pseudogene CYP4Z2P were much higher in breast cancer compared to the normal adjacent tissues, and the competing endogenous RNA (ceRNA) network between CYP4Z1 and pseudogene CYP4Z2P promoted breast cancer angiogenesis and conferred CSCs-related traits on breast cancer cells. Tissue microarray showed that the transcriptional factor six2 expression level was higher in breast cancer tissues, and increased the expression of CYP4Z1 and pseudogene CYP4Z2P. Therefore, we speculate that six2 could confer adriamycin resistance by promoting the ceRNA network between CYP4Z1 and pseudogene CYP4Z2P, and thus enhancing cancer stem cell-related traits on breast cancer cells. Taken together, our work aims to investigate the roles of six2 and pseudogene CYP4Z2P-mediated ceRNA network in breast cancer CSCs and thus adriamycin resistance via performing gain and loss of functional experiment. We hope that our work will contribute to find novel biomarkers or provide new clues for adriamycin resistance in breast cancer treatment.

耐药性是阿霉素治疗乳腺癌面临的主要难题。研究表明阿霉素耐药过程是由多基因共同完成的，且肿瘤干细胞是造成肿瘤耐药的主要原因。申请人研究发现假基因CYPZ2P及功能基因CYP4Z1均在乳腺癌中高表达，且它们通过假基因CYP4Z2P介导的竞争性内源RNA（ceRNA）网络促进乳腺癌血管生成及肿瘤干细胞样特性；组织芯片分析发现转录因子six2也在乳腺癌中高表达，且six2可促进CYP4Z2P及CYP4Z1的表达。由此我们设想：Six2可通过增强CYP4Z2P介导的ceRNA网络发生促进乳腺癌肿瘤干细胞样特性，导致乳腺癌对阿霉素产生耐药。为此，本项目以肿瘤干细胞为研究切入点，结合阿霉素耐药的乳腺癌细胞和动物模型，拟利用正/反向遗传学手段，研究six2参与调控的、假基因CYP4Z2P介导的ceRNA网络对阿霉素耐药性的调控作用，从新的视角阐明阿霉素耐药的机制，为临床阿霉素耐药的发生提供新的理论依据。

乳腺癌是最为常见的妇科恶性肿瘤，占女性诊断的所有癌症的30％，且近年来发病率呈上升趋势。肿瘤干细胞是肿瘤中的一小部分细胞，具有自我更新能力，与肿瘤的复发，转移和耐药密切相关。CYP4Z1及假基因CYP4Z2P在乳腺癌细胞中特异性高表达，前期研究表明，假基因CYP4Z2P介导的竞争性内源性RNA网络（ceRNET-CC）可以促进乳腺癌细胞的血管生成，促进MCF-7细胞对他莫昔芬的耐药，抑制乳腺癌细胞凋亡。但ceRNET-CC在乳腺癌细胞干性的作用及其调控机制尚不清晰，该研究旨在探索该网络对乳腺癌细胞干性的调控及其机制，同时对其是否能够影响乳腺癌细胞的化疗耐药进行了初步的研究。本课题主要就ceRNET-CC对乳腺癌细胞干性的调控机制进行了探讨，我们确定了假基因CYP4Z2P介导的ceRNA可以在体内外促进乳腺癌细胞干性，同时确定了ceRNET-CC对干性的调控部分依赖于hTERT/PI3K/Akt及ERK1/2信号通路，转录因子six2可以通过直接结合CYP4Z1及CYP4Z2P的启动子促进CYP4Z1及CYP4Z2P的转录，接下来我们证实了six2/ceRNET-CC轴可以激活hTERT/PI3K/Akt及ERK1/2信号通路，从而促进乳腺癌细胞的干性。同时，也对six2/ceRNET-CC是否能够影响乳腺癌细胞对阿霉素的耐药性进行了初步的探讨。