Role of FBXL20 in human colorectal adenocarcinoma.

In the present study, in order to determine whether the FBXL20 gene plays a role in the carcinogenesis of human colorectal adenocarcinoma, the mRNA expression levels of FBXL20 were examined in 30 pairs of human colorectal adenocarcinoma tissues and corresponding adjacent normal colorectal tissues by quantitative real-time PCR (qRT-PCR). The pGPU/GFP/Neo-FBXL20 siRNA expression vector was transfected into the human colon carcinoma cell lines, SW480 and SW620. The mRNA levels of β-catenin, c-Myc, cyclin D1, p53, PP2A, SET and E-cadherin were determined by qRT-PCR, whereas the protein levels of β-catenin, c-Myc, caspase-3 and SET were examined by western blot analysis. MTT assay and flow cytometry were employed to assess cell proliferation, apoptosis and the cell cycle. As shown by qRT-PCR, FBXL20 mRNA expression was upregulated in 76.7% of the tumor samples. Cell proliferation was inhibited by 33.3% in the SW480-FBXL20 cells and by 22.7% in the SW620-FBXL20 cells, compared to the corresponding control cells. Furthermore, the percentages of apoptotic cells were 21.3 and 17.1% in the SW480-FBXL20 and SW620-FBXL20 cells, whereas the percentages of G1 phase cells in the two cell lines were 90.13 and 78.13%, respectively. In addition, the mRNA expression of SET and E-cadherin was upregulated in the SW480-FBXL20 and SW620-FBXL20 cells, whereas that of β-catenin, c-Myc, cyclin D1, p53 and PP2A was downregulated. Consistently, the protein expression of β-catenin and c-Myc was downregulated, whereas that of SET and caspase-3 was upregulated. Based on these results, we can conclude that FBXL20 plays an essential role in the carcinogenesis of human colorectal adenocarcinoma. Moreover, our data suggest that FBXL20 promotes carcinogenesis through the regulation of the Wnt signaling pathway and caspase activation.