TSHZ3 functions as a tumor suppressor by DNA methylation in colorectal cancer

Abstract

Objective: Teashirt zinc finger homeobox 3 (TSHZ3) is currently reported to be aberrantly expressed in several tumors, but the detailed functions and epigenetic mechanisms of TSHZ3 in colorectal cancer (CRC) remain unclear.

Materials and methods: In this study, the TSHZ3 expression in 118 CRC and normal adjacent tissues (NATs) was evaluated, and the methylation status of the TSZH3 promoter region in CRC tissues and cell lines was also analyzed.

Results: The results of PCR analysis showed that TSHZ3 was significantly down-regulated in CRC tissues, and patients with low TSHZ3 levels had a poorer 5-year overall survival (OS) rate. Analyzing the promoter sequence (-1000∼0) by MethPrimer, TSHZ3 promoter was found to harbor abundant of CpG islands. The methylation specific PCR (MSP) analysis presented a relatively hypermethylated status of THSZ3 promoter in CRC samples. The data of MSP and bisulfite sequencing PCR (BSP) also confirmed that CpG sites of TSHZ3 promoter were methylated in CRC cells, and the DNA methyltransferase (DNMT) inhibitor 5-aza-2'-deoxycytidine (5-Aza) could effectively restored the TSHZ3 expression in vitro. Functionally, the proliferation, apoptosis and metastasis of CRC cells were regulated by TSZH3 over-expression, and the suppressing effects of TSHZ3 in CRC were also confirmed in a xenograft mouse model.

Conlusions: Our results indicated that promoter methylation was one of the mechanisms contributing to the down-regulation of TSHZ3 in CRC, and TSZH3 might served as a potential tumor suppressor gene in the development and progression of CRC.

Keywords: Colorectal cancer; DNA methylation; Overall survival; TSHZ3; Tumor suppressor gene.