Department of Health Sciences, Hiroshima Shudo University, 1-1-1, Ozuka-higashi, Asaminami-ku, Hiroshima, 731-3195, Japan.
Department of General Surgery, Affiliated hospital of Xuzhou Medical University, Xuzhou, 221000, China.
Mol Cancer. 2019 Dec 18;18(1):185. doi: 10.1186/s12943-019-1116-x.
Colon cancer (CC) cells can exhibit stemness and expansion capabilities, which contribute to resistance to conventional chemotherapies. Aberrant expression of CBX8 has been identified in many types of cancer, but the cause of this aberrant CBX8 expression and whether CBX8 is associated with stemness properties in CC remain unknown.
qRT-PCR and IHC were applied to examine CBX8 levels in normal and chemoresistant CC tissues. Cancer cell stemness and chemosensitivity were evaluated by spheroid formation, colony formation, Western blot and flow cytometry assays. RNA-seq combined with ChIP-seq was used to identify target genes, and ChIP, IP and dual luciferase reporter assays were applied to explore the underlying mechanisms.
CBX8 was significantly overexpressed in chemoresistant CC tissues. In addition, CBX8 could promote stemness and suppress chemosensitivity through LGR5. Mechanistic studies revealed that CBX8 activate the transcription of LGR5 in a noncanonical manner with assistance of Pol II. CBX8 recruited KMT2b to the LGR5 promoter, which maintained H3K4me3 status to promote LGR5 expression. Moreover, mA methylation participated in the upregulation of CBX8 by maintaining CBX8 mRNA stability.
Upon mA methylation-induced upregulation, CBX8 interacts with KMT2b and Pol II to promote LGR5 expression in a noncanonical manner, which contributes to increased cancer stemness and decreased chemosensitivity in CC. This study provides potential new therapeutic targets and valuable prognostic markers for CC.
结肠癌（CC）细胞具有干性和扩增能力，这有助于其抵抗传统化疗药物。CBX8 在许多类型的癌症中都存在异常表达，但这种 CBX8 异常表达的原因以及 CBX8 是否与 CC 中的干性特性有关尚不清楚。
应用 qRT-PCR 和免疫组化检测正常和耐药 CC 组织中 CBX8 的水平。通过球体形成、集落形成、Western blot 和流式细胞术检测评估癌细胞干性和化疗敏感性。采用 RNA-seq 联合 ChIP-seq 鉴定靶基因，并应用 ChIP、IP 和双荧光素酶报告基因检测探讨其潜在机制。
CBX8 在耐药 CC 组织中显著过表达。此外，CBX8 可以通过 LGR5 促进干性并抑制化疗敏感性。机制研究表明，CBX8 以非典型方式与 Pol II 协同作用激活 LGR5 的转录。CBX8 招募 KMT2b 到 LGR5 启动子，维持 H3K4me3 状态以促进 LGR5 表达。此外，mA 甲基化通过维持 CBX8 mRNA 稳定性参与 CBX8 的上调。
在 mA 甲基化诱导的上调后，CBX8 与 KMT2b 和 Pol II 相互作用以非典型方式促进 LGR5 表达，这有助于增加 CC 中的癌症干性和降低化疗敏感性。本研究为 CC 提供了潜在的新治疗靶点和有价值的预后标志物。
