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乳腺癌是女性最常见、病死率最高的恶性肿瘤之一,其发生发展及恶性程度与许多癌基因和抑癌基因相关[1-2]。我国女性乳腺癌的发病率和病死率在全球范围内处于比较低的水平,但呈迅速增长的趋势[3]。乳腺癌的发生与环境、生活方式密切相关,营养干预、减少超重和肥胖已被证实是有效的一级预防措施[4-5]。放疗在乳腺癌的治疗策略中一直发挥着重要作用,包括根治术后补充放疗、保留乳房放疗等[6-7]。然而,在乳腺癌的放疗方面仍然存在许多争议,如:放疗对根治术后患者生存的影响,导管原位癌和小叶原位癌术后放疗的取舍等[8]。更重要的是,部分中晚期乳腺癌患者对放疗表现出耐辐射性,逐渐变得不敏感,需加大治疗的照射剂量,然而剂量的提高会给肿瘤患者带来比较严重的不良反应及引起并发症,降低患者的生活质量[9-10]。因此,有效地增加乳腺癌的放疗敏感性,减少放疗中正常组织的放射损伤,从而提升患者的放疗效果和治愈率,这是近年来乳腺癌治疗研究的热点。
人类基因组转录出的RNA只有2%左右编码合成蛋白质,剩余98%的RNA不翻译为蛋白质,被称为非编码RNA。转录片段长度大于200 bp的RNA称为长链非编码RNA(long non-coding RNA, lncRNA)。近年来,对于lncRNA的研究已成为分子生物学以及基础医学领域研究的热点。lncRNA在高等动物的发育、细胞分化以及疾病的发生发展,尤其是代谢性疾病和肿瘤的发生发展等过程中发挥着极为重要的调节功能[11-13]。
LncRNA BRCA1相邻基因2(neighbour of BRCA1 gene 2,NBR2)(BRCA1为乳腺癌易感基因1)是近几年新发现的一个重要的lncRNA,因其在染色体上与肿瘤抑制基因BRCA1相邻而得名[14]。有研究结果表明,lncRNA NBR2的表达水平与多种癌症,特别是乳腺癌的发生发展呈负相关[15]。同时,有研究者揭示了NBR2能够被腺苷酸活化蛋白激酶(adenosine monophosphate-activated protein kinase,AMPK)上调,同时反过来与AMPK相互作用进而促进AMPK的激酶活性,最终抑制肿瘤细胞的生长[16]。笔者选用乳腺癌MCF-7和MDA-MB-231细胞系为研究对象,研究lncRNA NBR2过表达对乳腺癌MCF-7和MDA-MB-231细胞放射敏感性的影响,为探索乳腺癌的放疗增敏的新途径提供实验依据和理论基础。
长链非编码RNA NBR2对乳腺癌细胞放射敏感性的影响
Effect of long non-coding RNA NBR2 on the radiosensitivity of breast cancer cells
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摘要:
目的探讨长链非编码RNA(lncRNA)BRCA1相邻基因2(NBR2)(BRCA1为乳腺癌易感基因1)对乳腺癌MCF-7和MDA-MB-231细胞放射敏感性的影响。 方法根据处理方法的不同,分别按以下方式将乳腺癌细胞MCF-7和MDA-MB-231进行分组。(1)分为3组:空白对照组、4 Gy γ射线照射组和8 Gy γ射线照射组,采用实时定量PCR检测lncRNA NBR2的表达。(2)分为4组:空白对照组、NBR2转染组、4 Gy γ射线照射组以及NBR2转染+γ射线照射联合组,采用3-(4,5-二甲基噻唑-2)-2,5-二苯基四氮唑溴盐(MTT)方法来检测细胞增殖情况。(3)分为3组:空白对照组、NBR2单独转染组、NBR2+B细胞淋巴瘤2(BCL2)共转染组,对3组细胞进行不同剂量的γ射线照射,并采用MTT和克隆形成实验方法检测细胞生长情况。采用Student t-test对数据进行统计学分析,P<0.05表示差异有统计学意义。 结果实时定量PCR结果显示,与空白对照组相比,4 Gy γ射线照射和8 Gy γ射线照射能够显著下调lncRNA NBR2的表达水平,差异有统计学意义(MCF-7:t=10.75、11.17,MDA-MB-231:t=11.22、12.31,均P<0.01)。MTT实验结果显示,与4 Gy γ射线照射组相比,NBR2转染+γ射线照射联合组的乳腺癌细胞增殖率明显降低,差异有统计学意义(MCF-7:t=10.55,MDA-MB-231:t=11.97,均P<0.01)。同时,lncRNA NBR2过表达可以明显下调BCL2的mRNA及蛋白表达水平。另外,与NBR2单独转染组相比,NBR2+BCL2共转染组中NBR2对细胞增殖的影响显著降低,差异有统计学意义(MCF-7:t=10.87,MDA-MB-231:t=11.37,均P<0.01)。 结论辐照可以诱导lncRNA NBR2的表达水平降低,人为过表达NBR2能够抑制BCL2的蛋白表达水平,进而降低乳腺癌MCF-7和MDA-MB-231细胞的增殖能力,同时增强其放射敏感性。 -
关键词:
- RNA, 长链非编码 /
- 乳腺肿瘤 /
- 细胞增殖 /
- 辐射耐受性 /
- BRCA1相邻基因2
Abstract:ObjectiveTo explore the effects of long non-coding RNA neighbour of BRCA1 gene2(NBR2) on the radiosensitivity of breast cancer MCF-7 and MDA-MB-231 cells. MethodAccording to different treatment methods, breast cancer MCF-7 and MDA-MB-231 cells were divided into the following groups:(1) three groups including control group, 4 Gy γ ray irradiation group, and 8 Gy γ ray irradiation group, then the expression level of NBR2 was tested by real-time quantitative PCR(qRT-PCR) analysis; (2) four groups including control group, NBR2 transfection group, 4 Gy γ ray irradiation group, and NBR2 transfection+γ ray irradiation group, then the proliferation of breast cancer MCF-7 and MDA-MB-231 cells was detected by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide(MTT) assays; (3) three groups including control group, NBR2 transfection group, and NBR2+B-cell lymphoma-2(BCL2) transfection group, and the cells were irradiated with different doses of γ ray, then the proliferation was detected by MTT and clonogenic assay. Statistical significance of the results was determined by SPSS statistical software and analyzed by student's t-test. P<0.05 was considered statistically significant. ResultsqRT-PCR analysis revealed that compared with that in the control group, the expression of NBR2 was decreased significantly in breast cancer MCF-7 and MDA-MB-231 cells treated with γ ray irradiation(MCF-7:t=10.75, 11.17, MDA-MB-231:t=11.22, 12.31, all P<0.01). MTT assays showed that compared with the cells irradiated alone, the breast cancer MCF-7 and MDA-MB-231 cells irradiated in the presence of NBR2 had significantly decreased proliferation (MCF-7: t=10.55, MDA-MB-231:t=11.97, both P<0.01). NBR2 could also down-regulate the mRNA and protein level of BCL2 in these cells. The enhanced BCL2 expression significantly reduced the NBR2 inhibition of breast cancer MCF-7 and MDA-MB-231 cell proliferation after irradiation as compared with that of NBR2 alone (MCF-7:t=10.87, MDA-MB-231:t=11.37, both P<0.01). ConclusionsIrradiation could decrease the expression level of NBR2. The overexpression of NBR2 could down-regulate the BCL2 level and suppress the proliferation of breast cancer MCF-7 and MDA-MB-231 cells, thus enhancing the radiosensitivity of breast cancer cells. -
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