Co-expression of Axin and APC gene fragments inhibits colorectal cancer cell growth via regulation of the Wnt signaling pathway

Adenomatous polyposis coli (APC) and Axin interactions serve an important role in colorectal cancer (CRC) pathogenesis. The aim of the present study was to assess the combined effects of Axin and APC co-expression in CRC cells, and to determine the underlying mechanisms involved. SW480 cells were divided into the following groups: Untransfected (SW480 group), transfected with pEGFP-N(3)plus pCS2-MT (SW480/vector-vector), transfected with pEGFP-N-3-APC5 (SW480/APC5), and transfected with pEGFP-N-3-APC5 pluspCS2-MT-Axin (SW480/APC5-Axin). APC5 and Axin mRNA levels were determined by reverse transcription-polymerase chain reaction. MTT assays and flow cytometry analysis were performed to assess cell growth and cell cycle distribution, respectively. Quantitative PCR and western blot analyses were conducted to evaluate the mRNA and protein levels, respectively, of Wnt signaling effectors, including beta-catenin, c-myc and survivin. Successful transfection of SW480 cells was determined with APC and APC-Axin plasmids as indicated by the green fluorescence signals. Notably, SW480 /APC5 cell growth was inhibited by 40.33%, and cells co-expressing APC5 and Axin demonstrated 61.27% inhibition of cell growth compared with SW480 control cells. The results demonstrate that APC5 may induce G1/S arrest in SW480 cells, and Axin may enhance cell growth arrest induced by APC5. The mRNA and protein levels of beta-catenin, c-myc and survivin were significantly reduced in SW480/APC-Axin cells when compared with the SW480/APC group. In conclusion, co-expression of APC5 and Axin genes significantly downregulated Wnt signaling in human SW480 CRC cells and inhibited cell growth, when compared with cells transfected with APC5 alone. These results may provide experimental evidence to support combined gene therapy in CRC.