癌基因c-Myc活化在结直肠癌骨髓源性抑制细胞浸润中的作用及其机制研究

Chronic inflammation plays a critical role in the initiation and progression of tumors. Myeloid-derived suppressor cells (MDSCs) in colorectal cancer microenvironment enhance a variety of malignant properties of tumor cells, but the recruiting mechanisms of MDSCs induced by tumor cells are still elusive. Preliminary results showed that the infiltration of MDSCs positively correlated with the expression of c-Myc antigen and the inhibition of c-Myc reduced mesenchymal phenotype and decreased the mRNA level of CSF-1, but enhanced the epithelial phenotype. Furthermore, c-Myc overexpression noticeably increased the proportion of MDSCs in the implanted colon cancer tumor in syngeneic mice. However, c-Myc is not the regulator on the expression of CSF-1 gene. Moreover, bioinformatics study revealed the binding sites of c-Myc withTwist1 molecule, and vise versa. Immunofluorescence (IHC) assay vindicated that both molecules co-located in the nuclei. Thus, we propose that c-Myc up-regulates the CSF-1 expression by interference with Twist1, thereby increasing the infiltration of MDSCs in tumor microenvironment. In the proppsed study, clinical colorectal samples and murine tumor models will be used. IHC and flow cytometry analysis will be used to detect the effect of c-Myc expression on MDSCs infiltration. Co-IP will be employed to prove the interaction between c-Myc and Twist1. EMSA, ChIP, and gene overexpression/knockout experiments will be used to demonstrate the regulatory role of c-Myc/Twist1 complex on the transcriptional regulation of CSF-1. Furthermore, small molecular drugs will be developed to rectify the findings. The proposed study tries to elucidate the unique perspective of oncogene on the regulation of MDSCs recruitment. Therapeutic strategies are proposed to reverse the tumor-promoting inflammation, which will provide a bright promise for clinical practice in future.

慢性炎症参与多种肿瘤发生演进，包括结直肠癌，浸润其中的骨髓源性抑制细胞（MDSC）影响着肿瘤诸多生物特性，瘤细胞对MDSC浸润的调节机制亟待研究。申请者初步研究发现，结肠癌中MDSC浸润与c-Myc表达正相关；c-Myc抑制剂处理显著降低间叶标志物和CSF-1的表达；过表达c-Myc增加移植瘤MDSC浸润。而c-Myc对CSF-1无直接调控作用，免疫荧光示c-Myc与Twist1呈核共定位。因此，我们推测，c-Myc通过与Twist1结合上调CSF-1表达，促进MDSC浸润。本研究拟以临床标本和小鼠结肠癌为实验材料，探讨c-Myc在MDSC浸润中的作用及临床意义；Co-IP证明c-Myc/Twist1复合体存在，基因沉默/过表达证明复合体调控CSF-1表达,促进MDSC浸润，并探讨干预机制。本项目从癌基因独特视角阐述MDSC浸润发生机制，并提出干预方案以期为逆转促瘤生长微环境提供实验依据。