Frequent downregulation of LRRC26 by epigenetic alterations is involved in the malignant progression of triple-negative breast cancer
Frequent downregulation of LRRC26 by epigenetic alterations is involved in the malignant progression of triple-negative breast cancer
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DOI：
10.3892/ijo.2018.4301
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发表时间：
2018-05-01
影响因子：
5.2
通讯作者：
Katagiri, Toyomasa
中科院分区：
文献类型：
--
作者：
Miyagawa, Yoshimasa;Matsushita, Yosuke;Katagiri, Toyomasa
三阴性乳腺癌 (TNBC) 被定义为缺乏雌激素和孕激素受体表达以及人表皮生长因子受体 2 (HER2) 扩增的乳腺癌，是一种异质性疾病。对 15 个 TNBC 样本的 RNA 测序分析和癌症基因组图谱-TNBC 数据集分析发现，在 TNBC 组织中，富含亮氨酸重复序列 26 (LRRC26) 频繁下调，该蛋白对核因子 B (NF-B) 信号传导产生负调节。定量聚合酶链反应和亚硫酸氢盐焦磷酸测序分析表明，由于启动子甲基化，LRRC26 在 TNBC 组织和细胞系中经常被沉默。在缺乏 LRRC26 表达的 HCC1937 TNBC 细胞中，通过 5-aza-2-脱氧胞苷 (5-aza-dC) 处理可恢复 LRRC26 表达。值得注意的是，小干扰RNA介导的LRRC26表达敲低显着增强了HCC70细胞的贴壁依赖性生长、侵袭和迁移，而BT20细胞中LRRC26的异位过度表达抑制了其侵袭和迁移。相反，在没有肿瘤坏死因子（TNF）刺激的情况下，LRRC26 的敲低和过度表达都不会对细胞活力产生影响。同时，LRRC26的过度表达导致TNF介导的NF-B荧光素酶报告活性降低，而消除LRRC26表达则导致TNF介导的NF-B下游基因[白细胞介素6（IL-6）、IL-8和C-X-C基序趋化因子配体-1]上调。总而言之，这些发现表明，由于 DNA 甲基化，LRRC26 在 TNBC 中经常下调，并且它抑制 TNBC 细胞的不依赖于贴壁的 TNF 依赖性生长、侵袭和迁移。 LRRC26 功能的丧失可能是通过 TNF-/NF-B 独立机制导致 TNBC 细胞侵袭性的关键事件。
Triple-negative breast cancer (TNBC), defined as breast cancer lacking estrogen- and progesterone-receptor expression and human epidermal growth factor receptor 2 (HER2) amplification, is a heterogeneous disease. RNA-sequencing analysis of 15 TNBC specimens and The Cancer Genome Atlas-TNBC dataset analysis identified the frequent downregulation of leucine-rich repeat-containing 26 (LRRC26), which negatively regulates nuclear factor-B (NF-B) signaling, in TNBC tissues. Quantitative polymerase chain reaction and bisulfite pyrosequencing analyses revealed that LRRC26 was frequently silenced in TNBC tissues and cell lines as a result of promoter methylation. LRRC26 expression was restored by 5-aza-2-deoxycytidine (5-aza-dC) treatment in HCC1937 TNBC cells, which lack LRRC26 expression. Notably, small interfering RNA-mediated knockdown of LRRC26 expression significantly enhanced the anchorage-independent growth, invasion and migration of HCC70 cells, whereas ectopic overexpression of LRRC26 in BT20 cells suppressed their invasion and migration. Conversely, neither knockdown nor overexpression of LRRC26 had an effect on cell viability in the absence of tumor necrosis factor- (TNF-) stimulation. Meanwhile, overexpression of LRRC26 caused the reduction of TNF--mediated NF-B luciferase reporter activity, whereas depleting LRRC26 expression resulted in the upregulation of TNF--mediated NF-B downstream genes [interleukin-6 (IL-6), IL-8 and C-X-C motif chemokine ligand-1]. Taken together, these findings demonstrate that LRRC26 is frequently downregulated in TNBC due to DNA methylation and that it suppresses the TNF--independent anchorage-independent growth, invasion and migration of TNBC cells. Loss of LRRC26 function may be a critical event in the aggressiveness of TNBC cells through a TNF-/NF-B-independent mechanism.