Paired-like homeodomain transcription factor 2 strengthens chemoresistance in colorectal cancer by activating the Wnt/β-catenin axis.

The purpose of this study was to determine the mechanism of paired-like homeodomain transcription factor 2 (PITX2) in the chemoresistance of colorectal cancer (CRC) via the upregulation of the Wnt/β-catenin axis. CRC cells were persistently exposed to increasing 5-fluorouracil (5-FU) concentrations to establish 5-FU-resistant cells. Functional assays were conducted to examine cell viability, proliferation, and cell cycle. After the transfection of small interfering (si)-negative control and si-PITX2 in 5-FU-resistant cells, the effects of PITX2 depletion in these cells were assessed. Notably, expression of PITX2, Wnt-3a, and β-catenin, and the relation between PITX2 and Wnt-3a were verified. Additionally, an inhibitor or an activator of the Wnt/β-catenin axis was added into cells to detect the variance of the 5-FU-resistant cells. Eventually, xenograft transplantation was applied to confirm the effect of PITX2 knockdown on CRC chemoresistance to 5-FU. 5-FU-resistant CRC cells were successfully established, in which CRC cell viability, proliferation, and cell cycle were all enhanced, while PITX2 knockout led to reversed results, indicating that resistance to 5-FU in CRC was restricted. Furthermore, our findings revealed that PITX2 upregulated the Wnt/β-catenin axis. The inactivation of the Wnt/β-catenin axis resulted in the reduction of resistance to 5-FU in CRC cells; while activation of the Wnt/β-catenin axis reversed the reduced resistance to 5-FU in CRC cells caused by PITX2 knockout. Additionally, xenograft transplantation further confirmed that PITX2 knockdown reduced the resistance of HCT-116 cells to 5-FU. This study clarified that PITX2 enhanced resistance to 5-FU in CRC upregulating the Wnt/β-catenin axis.