Aldonza Mark Borris D, Hong Ji-Young, Alinsug Malona V, Song Jayoung, Lee Sang Kook
College of Pharmacy, Seoul National University, Seoul 151-742, Korea.
Department of Biochemistry, College of Veterinary Medicine, Seoul National University, Seoul 151-742, Korea.
Oncotarget. 2016 Jun 7;7(23):34395-419. doi: 10.18632/oncotarget.9118.
Acquired drug resistance is a primary obstacle for effective cancer therapy. The correlation of point mutations in class III β-tubulin (TUBB3) and the prominent overexpression of ATP-binding cassette P-glycoprotein (ABCB1), a multidrug resistance gene, have been protruding mechanisms of resistance to microtubule disruptors such as paclitaxel (PTX) for many cancers. However, the precise underlying mechanism of the rapid onset of cross-resistance to an array of structurally and functionally unrelated drugs in PTX-resistant cancers has been poorly understood. We determined that our established PTX-resistant cancer cells display ABCB1/ABCC1-associated cross-resistance to chemically different drugs such as 5-fluorouracil, docetaxel, and cisplatin. We found that feedback activation of TUBB3 can be triggered through the FOXO3a-dependent regulation of ABCB1, which resulted in the accentuation of induced PTX resistance and encouraged multiplicity in acquired cross-resistance. FOXO3a-directed regulation of P-glycoprotein (P-gp) function suggests that control of ABCB1 involves methylation-dependent activation. Consistently, transcriptional overexpression or downregulation of FOXO3a directs inhibitor-controlled protease-degradation of TUBB3. The functional PI3K/Akt signaling is tightly responsive to FOXO3a activation alongside doxorubicin treatment, which directs FOXO3a arginine hypermethylation. In addition, we found that secretome factors from PTX-resistant cancer cells with acquired cross-resistance support a P-gp-dependent association in multidrug resistance (MDR) development, which assisted the FOXO3a-mediated control of TUBB3 feedback. The direct silencing of TUBB3 reverses induced multiple cross-resistance, reduces drug-resistant tumor mass, and suppresses the impaired microtubule stability status of PTX-resistant cells with transient cross-resistance. These findings highlight the control of the TUBB3 response to ABCB1 genetic suppressors as a mechanism to reverse the profuse development of multidrug resistance in cancer.
获得性耐药是有效癌症治疗的主要障碍。III类β-微管蛋白（TUBB3）中的点突变与多药耐药基因ATP结合盒P-糖蛋白（ABCB1）的显著过表达之间的相关性，一直是许多癌症对微管破坏剂（如紫杉醇（PTX））产生耐药性的突出机制。然而，PTX耐药性癌症对一系列结构和功能不相关药物快速产生交叉耐药的确切潜在机制尚不清楚。我们确定，我们建立的PTX耐药癌细胞对化学性质不同的药物（如5-氟尿嘧啶、多西他赛和顺铂）表现出与ABCB1/ABCC1相关的交叉耐药性。我们发现，TUBB3的反馈激活可通过FOXO3a对ABCB1的依赖性调节触发，这导致诱导的PTX耐药性加剧，并促进获得性交叉耐药的多样性。FOXO3a对P-糖蛋白（P-gp）功能的定向调节表明，对ABCB1的控制涉及甲基化依赖性激活。一致地，FOXO3a的转录过表达或下调指导抑制剂控制的TUBB3蛋白酶降解。功能性PI3K/Akt信号通路对FOXO3a激活以及阿霉素治疗有紧密反应，这指导FOXO3a精氨酸高甲基化。此外，我们发现，具有获得性交叉耐药性的PTX耐药癌细胞的分泌组因子在多药耐药（MDR）发展中支持P-gp依赖性关联，这有助于FOXO3a介导的TUBB3反馈控制。TUBB3的直接沉默可逆转诱导的多重交叉耐药性，减少耐药肿瘤块，并抑制具有短暂交叉耐药性的PTX耐药细胞受损的微管稳定性状态。这些发现突出了对TUBB3对ABCB1基因抑制因子反应的控制，作为一种逆转癌症中多药耐药大量发展的机制。
