Department of Gastroenterology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
Cancer Biol Ther. 2009 Nov;8(22):2166-74. doi: 10.4161/cbt.8.22.9880. Epub 2009 Nov 21.
Telomere repeat binding factor 2 (TRF2) plays a key role in the protective activity of telomere and is overexpression in several kinds of solid cancer cells. However, the role of overexpressed TRF2 in colorectal carcinoma remains unclear. The aim of this study was to determine the expression of TRF2, address the mechanism of TRF2 overexpression in human colorectal carcinoma. In present study, we examined the expression of TRF2 in colorectal cancer tissues from 39 patients, peritumoral normal tissues from 21 patients, and colon carcinoma SW480 cell line by quantitative PCR, immunohistochemistry and western blot. After siRNA silencing TRF2 expression in SW480, tumorigenesis of TRF2 was tested by cell proliferation, soft agar assay, cytofluorimetric analysis and cytogenetic analysis. To discover transcription factor that mediated TRF2 expression, Chromatin Immunoprecipitation (Chip) Assay and Electrophoretic mobility shift assays (EMSA) were employed.
Overexpression of TRF2 protein was detected in SW480 cells and 19 of 39 colorectal carcinoma tissues (49%), no overexpression was observed in 21 of 21 adjacent peritumoral normal colorectal tissues. After siRNA silencing TRF2 expression, the proliferation and colony formation of SW480 cells were significantly inhibited. Defective TRF2 induced apoptosis and increased chromosomal instability in SW480 cells, in which there were more end-to-end fusions and ring chromosomes. Chip assay and EMSA showed that transcription factor Sp1 is involved in upregulation of TRF2. These results indicate that TRF2 is overexpressed in colorectal carcinoma, Sp1 upregulates TRF2 expression, TRF2 inhibition reduces tumorigenesis of colorectal cancer, which suggests that TRF2 and SP1 may become new targets for the development of anti-cancer therapy in colorectal carcinoma.
端粒重复结合因子 2（TRF2）在保护端粒的活性中起着关键作用，并且在几种实体癌细胞中过表达。然而，过表达的 TRF2 在结直肠癌中的作用尚不清楚。本研究的目的是确定 TRF2 的表达，探讨人结直肠癌中 TRF2 过表达的机制。在本研究中，我们通过定量 PCR、免疫组织化学和 Western blot 检测了 39 例结直肠癌组织、21 例癌旁正常组织和结肠癌细胞系 SW480 中 TRF2 的表达。通过 siRNA 沉默 SW480 中的 TRF2 表达后，通过细胞增殖、软琼脂测定、细胞流式分析和细胞遗传学分析测试 TRF2 的致瘤性。为了发现介导 TRF2 表达的转录因子，采用染色质免疫沉淀（Chip）测定和电泳迁移率变动分析（EMSA）。
在 SW480 细胞和 39 例结直肠癌组织中的 19 例（49%）中检测到 TRF2 蛋白过表达，在 21 例癌旁正常结直肠组织中未观察到过表达。沉默 TRF2 表达后，SW480 细胞的增殖和集落形成明显受到抑制。TRF2 缺陷诱导 SW480 细胞凋亡，并增加染色体不稳定性，其中端-端融合和环状染色体增多。Chip 测定和 EMSA 显示转录因子 Sp1 参与 TRF2 的上调。这些结果表明，TRF2 在结直肠癌中过表达，Sp1 上调 TRF2 表达，TRF2 抑制降低结直肠癌的致瘤性，提示 TRF2 和 SP1 可能成为结直肠癌抗癌治疗的新靶点。
