Experimental design: 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.
Results: 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.