代谢重编程介导大肠癌CD110+亚群肝脏转移的分子机制研究

Cancer stem cells (CSCs) are a heterogeneous subpopulation governing tumor metastasis. We previously demonstrated CD110 as the cell surface marker of colon CSCs that metastasize to liver. However, the exact mechanism underlying this process remains elusive. In our preliminary studies, a mouse model of colorectal liver metastasis (CRLM) was established. We performed a genome-wide transcriptome analysis and observed that pentose phosphate pathway was initiated while glycolysis was suppressed in the CD110+CSCs from colorectal liver metastases. Here, we attempt to reveal the critical role of pentose phosphate pathway in CRLM mediated by the CD110+CSCs both in vitro and in vivo. Utilizing promoter analysis,small RNA interference and ChIP-PCR, we aim to clarify the miR-374b-mediated epigenetic mechanism involved in metabolic reprogramming of the CD110+CSCs. Furthermore, we try to determine whether targeting pentose phosphate pathway in vivo represents a novel therapeutic approach to prevent CRLM. Therefore, further support of this program would provide theoretical basis and experimental evidence for improvement of colorectal cancer prognosis.

大肠癌干细胞（colorectal CSCs）是主导肿瘤远处转移的异质性细胞群体，其中CD110+CSCs是负责大肠癌肝转移的亚群。迄今为止，CD110+CSCs在干性维持和脏器特异性转移中的作用机制尚未阐明。我们在前期研究中利用大肠癌肝转移裸鼠模型和高通量筛选等方法，初步证实大肠癌肝转移灶内的CD110+CSCs发生了代谢重编程，即开启磷酸戊糖途径并抑制糖酵解。本项目拟利用大肠癌原代细胞、人大肠癌标本和裸鼠肝转移模型，从体内外两方面证实磷酸戊糖途径介导CD110+CSCs大肠癌肝转移的作用；采用启动子分析、小RNA干扰、染色质免疫共沉淀等方法，阐释miR-374b参与CD110+CSCs代谢重编程的表观调控机制；并通过动物实验观察靶向干扰磷酸戊糖途径对抑制大肠癌肝转移的作用，从而为有效改善大肠癌预后提供理论基础和实践依据。

肿瘤干细胞是导致肿瘤术后复发转移的重要因素。然而，肿瘤异质性决定了肿瘤干细胞本身也具有异质性的特征。肿瘤干细胞异质性对肿瘤临床治疗提出了极大的挑战。在本项研究中，我们发现CDCP1+亚群在Kras突变型大肠癌接受化疗后得到了富集，并且驱动了化疗后的复发。在机制层面，我们证实在CDCP1+亚群中，葡萄糖代谢发生了代谢流的重构，即由糖酵解流向了磷酸戊糖途径；代谢产物经由磷酸戊糖途径产生了NAPDH，用以合成谷胱甘肽来对抗化疗药物所引起的氧化应激损伤；因此，Kras突变型大肠癌中CDCP1+亚群得以逃避化疗药物的杀伤作用。上述现象是因为CDCP1+亚群中Sirt5与磷酸丙糖异构酶相互结合，使后者发生第56位赖氨酸去丙二酰化，从而酶活性失活引起的。阻断磷酸丙糖异构酶第56位赖氨酸去丙二酰化能够增加CDCP1+亚群的化疗敏感性，显著延缓Kras突变型大肠癌术后复发转移。该项研究为临床有效改善特定遗传背景大肠癌预后提供了新思路和新方法。