肿瘤干细胞异染色质对人结直肠癌放射敏感性的影响及探究  

Effects of heterochromatin in colorectal cancer stem cells on radiosensitivity

作　　者：陈婷[1] 张瑜[1] 郭文浩[1] 孟茂斌[1] 莫显明[2] 卢铀[3,4] 

机构地区：[1]四川大学华西医院肿瘤中心肠部肿瘤科,四川成都610041 [2]四川大学华西医院干细胞研究室,四川成都610041 [3]四川大学华西医院肿瘤中心胸部肿瘤科,四川成都610041 [4]四川大学华西医院生物治疗国家重点实验室,四川成都610041

出　　处：《癌症》2010年第3期290-297,共8页Chinese Journal of Cancer

摘　　要：背景与目的:放射治疗在结直肠腺癌综合治疗中发挥着重要的作用,与非肿瘤干细胞(non-cancer stem cells,non-CSCs)相比,肿瘤干细胞(cancer stem cells,CSCs)更具放射抵抗性,并且是影响放射治疗效果的重要因素之一。本研究旨在探讨人结直肠腺癌CSCs特征性染色体结构及组蛋白修饰方式对肿瘤放射抵抗效应的作用。方法:收集人结直肠癌手术标本并建立裸鼠皮下移植瘤模型。免疫组化检测人手术标本和异种移植动物肿瘤的组织来源。流式细胞仪分选人结直肠腺癌标本与移植瘤模型中放射干预前后CSCs(CD133+)与non-CSCs(CD133-),并检测CSCs表面标志物CD133的表达,利用免疫荧光染色检测CD133+及CD133-细胞核中异染色质标记物(H3K9me3,HP1-α,H3K4me1)和常染色质标志物(H3K4me3)的表达情况。结果:人手术标本和异种移植动物肿瘤的组织来源相同。人结直肠腺癌中CSCs与non-CSCs染色质结构存在明显差异。CD133+细胞染色质为致密斑块状结构,CD133-细胞染色质结构则明显呈疏松片状或网格状,免疫荧光染色显示CSCs细胞核中存在的致密斑块状结构为异染色质成分。行10Gy单次大剂量放射干预1h和24h后发现,结直肠腺癌CSCs异染色质区域出现明显空泡状缺损现象,non-CSCs染色质除结构稍疏松外无其他明显改变;放射后96h和144hCSCs异染色质空泡状缺损普遍得到修复,并逐渐恢复至放射干预前的致密斑块状结构。结论:CSCs在人结直肠腺癌放射抵抗效应中发挥作用,其机制可能与异染色质形成及组蛋白的甲基化修饰紧密相关。Background and Objective： Radiotherapy （RT） is a major non-surgical modality in the comprehensive treatment for colorectal adenocarcinoma. The radioresistance of cancer stem cells （CSCs） is a key factor that influences therapeutic effectiveness. This study was to investigate the effects of specific chromosome structure and histone modification in CSCs in colorectal adenocarcinoma radioresistance. Methods： Samples were collected from resected human colorectal adenocarcinomas. Subcutaneous colorectal cancer model was established in nude mice. Immunohistochemistry showed that xenografts generated from bulk colorectal cancer cells resembled the original tumor specimen. Flow cytometry was performed to sort CSCs （CD133^＋） and non-CSCs （CD133^-） from both resected samples of colorectal adenocarcinoma and xenograft before and after high single-dose radiation. The markers labeling heterochromatin （H3K9me3,HP1-α,and H3K4me1） and euchromatin （H3K4me3） in CD133^＋ and CD133^-nucleus were detected by immunoflurescence. Results： There was distinct difference in chromatin structure between colorectal CSCs （CD133^＋） and non-CSCs （CD133^-）. The chromatin displayed compact patches in CD133^＋ nucleus,but loosely latticed structure in CD133^- nucleus; immunoflurescence verified that the compact patches existing in CSCs was generated from heterochromatin construction. In addition,the vacuole-like defect in heterochromatin regions of CSCs was observed within 24 h after exposure to 10 gray （Gy） single-dose RT. Interestingly,this phenomenon was repaired from 96 h,and recovered to dense plaque structure in heterochromatin regions of CSCs after 144 h. However,no significant difference in non-CSCs was observed after RT exception for a loose chromatin structure. Conclusions： CSCs play a role in radiosensitivity in colorectal cancer. The mechanism may be related to heterchromatin formation and histone methylation.

关 键 词：结直肠癌 肿瘤干细胞 单次大剂量放射 放疗抵抗性 异染色质 

分 类 号：R735.34[医药卫生—肿瘤]