Institute of Physiology, Pathophysiology and Toxicology, Centre of Biomedical Education and Research (ZBAF), Witten/Herdecke University, Stockumer Strasse 12, Witten, Germany.
Cancer Lett. 2019 May 1;449:237-251. doi: 10.1016/j.canlet.2019.01.044. Epub 2019 Feb 10.
Oncogenic pituitary homeobox 2 (PITX2), a de facto master regulator of developmental organ asymmetry, previously upregulated multidrug resistance (MDR) P-glycoprotein ABCB1 in A498 renal cell carcinoma (RCC) cells. The role of PITX2 isoforms in MDR cancers was investigated. Data mining correlated elevated PITX2 in >30% of cancers analyzed, maximally in colon (4.4-fold), confirmed in co-immunostaining of colon and renal cancer microarrays wherein ABCB1 concomitantly increased in RCC. Drug-resistant colorectal adenocarcinoma Colo320DM cells exhibited increased nuclear PITX2 (40-fold), PITX2 promoter activity (27-fold) and ABCB1 (8000-fold) compared to drug-sensitive Colo205. ABCB1 inhibitor PSC833/valspodar or PITX2 siRNA reversed doxorubicin resistance. Nuclei from Colo320DM and A498 cells harbored PITX2A/B1 and PITX2A/B1/B2/Cα/Cβ, respectively. ChIP-qPCR evidenced PITX2 promoter binding in drug exporters ABCB1, ABCC1, ABCG2 and importer hOCT3/SLC22A3. In A498, 786-O, Caki-1, Colo320DM, and Caco2 cells, PITX2 siRNA diminished exporters, increased hOCT3/SLC22A3 expression and activity, and reverted vincristine resistance. Heterologous PITX2 expression induced ABCB1, repressed hOCT3/SLC22A3, enhanced vincristine resistance and diminished proliferation inhibition wherein PITX2A and PITX2C were most effective. Furthermore, PITX2 activity and MDR depended on phosphorylation by GSK3 in A498 cells. Conclusively, oncogenic PITX2 limits sensitizing drug uptake and potentiates cytoprotective drug efflux, contributing to MDR phenotype.
癌基因垂体同源盒 2 (PITX2) 是发育器官不对称的实际主调控因子，先前在 A498 肾癌细胞 (RCC) 中上调多药耐药 (MDR) P-糖蛋白 ABCB1。研究了 PITX2 异构体在 MDR 癌症中的作用。数据分析表明，在分析的 >30%的癌症中，PITX2 升高，在结肠癌中最高 (4.4 倍)，在结肠癌和肾癌微阵列的共免疫染色中得到证实，其中 ABCB1 在 RCC 中同时升高。与药物敏感的 Colo205 相比，耐药性结直肠腺癌 Colo320DM 细胞表现出核 PITX2 (40 倍)、PITX2 启动子活性 (27 倍) 和 ABCB1 (8000 倍) 的增加。ABCB1 抑制剂 PSC833/valspodar 或 PITX2 siRNA 逆转了阿霉素耐药。Colo320DM 和 A498 细胞的核中分别含有 PITX2A/B1 和 PITX2A/B1/B2/Cα/Cβ。ChIP-qPCR 证明了药物外排泵 ABCB1、ABCC1、ABCG2 和内吞体 hOCT3/SLC22A3 上的 PITX2 启动子结合。在 A498、786-O、Caki-1、Colo320DM 和 Caco2 细胞中，PITX2 siRNA 减少了外排泵，增加了 hOCT3/SLC22A3 的表达和活性，并逆转了长春新碱耐药性。异源 PITX2 表达诱导 ABCB1，抑制 hOCT3/SLC22A3，增强长春新碱耐药性，减少增殖抑制，其中 PITX2A 和 PITX2C 最有效。此外，A498 细胞中 PITX2 的活性和 MDR 取决于 GSK3 的磷酸化。总之，癌基因 PITX2 限制了增敏药物摄取并增强了细胞保护药物外排，导致 MDR 表型。
