The Effect of Overexpression of Homeodomain Protein TGIF2LX on the Expression of Oncogenic miRNAs in Colorectal Cancer Cell Line SW1116

Transforming growth factor-beta-induced factor X-linked (TGIF2LX) as a homeodomain protein and TGF-βcorepressor, could regulate proliferation of some cancer cells including colorectal cancer by some signaling pathways. Small non-coding RNAs (microRNA; miRNA) are known as molecular regulators of colorectal cancer that are involved in the processes of cell growth, proliferation, differentiation and apoptosis. The aim of this study was to evaluate the biological significance of TGIF2LX protein and its effect on the expression of oncogenic miRNAs miR-34a, miR-20a and miR-21 in colorectal cancer cells SW1116.

Human SW1116 cell line and cell line transfected with cDNA encoding TGIF2LX gene were cultured in RPMI 1640 medium under appropriate conditions. MTT assay was used to assess cell viability in vitro. After RNA extraction from all cell groups and cDNA synthesis, miRNA expression analysis was performed using qReal-time PCR technique.

The results showed that the increased expression of TGIF2LX could reduce the proliferation of SW1116 cell line. Gene expression analysis showed that increased expression of TGIF2LX could significantly reduce the expression level of miR-21 (P<0.038). However, the expression levels of miR-34a and miR-20a in SW1116 cells transfected with TGIF2LX did not show a significant change compared to non-transfected cells (P>0.05).

Our findings provide evidence of molecular mechanisms that the homeodomain protein TGIF2LX can act as a tumor suppressor in colorectal cancer cells by reducing miR-21 expression. Therefore, this protein can potentially be considered as a promising option for gene-based therapeutic strategies in this cancer.