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 HCT116 cells to 5-FU. This study clarified that PITX2 enhanced resistance to 5-FU in CRC upregulating the Wnt/β-catenin axis.

中文翻译：

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成对的同源结构域转录因子2通过激活Wnt /β-catenin轴增强结直肠癌的化学耐药性。

这项研究的目的是通过Wnt /β-catenin轴的上调来确定成对的同源结构域转录因子2（PITX2）在结直肠癌（CRC）的化学耐药性中的机制。CRC细胞持续暴露于不断增加的5-氟尿嘧啶（5-FU）浓度，以建立5-FU耐药细胞。进行功能测定以检查细胞活力，增殖和细胞周期。在5-FU耐药细胞中转染小干扰（si）阴性对照和si-PITX2后，评估了PITX2耗竭在这些细胞中的作用。值得注意的是，证实了PITX2，Wnt-3a和β-连环蛋白的表达以及PITX2和Wnt-3a之间的关系。另外，将Wnt /β-连环蛋白轴的抑制剂或活化剂加入细胞中以检测5-FU抗性细胞的变异。最终，异种移植用于证实PITX2敲低对CRC对5-FU的化学耐药性的影响。成功建立了5-FU耐药的CRC细胞，其中CRC细胞的活力，增殖和细胞周期均得到增强，而PITX2敲除导致结果相反，表明CRC对5-FU的耐药性受到限制。此外，我们的发现表明PITX2上调了Wnt /β-catenin轴。Wnt /β-catenin轴失活导致CRC细胞对5-FU的耐药性降低；而Wnt /β-catenin轴的激活逆转了PITX2敲除导致的CRC细胞对5-FU的耐药性降低。此外，异种移植进一步证实，PITX2敲低降低了HCT116细胞对5-FU的抗性。