Irwin Mary E, Johnson Blake P, Manshouri Roxsan, Amin Hesham M, Chandra Joya
Department of Pediatrics Research, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
University of Texas Graduate School of Biomedical Sciences at Houston, Houston, TX, USA.
Oncotarget. 2015 Sep 15;6(27):23631-46. doi: 10.18632/oncotarget.4604.
Tyrosine kinase inhibitors (TKI) have improved CML response rates, and some are effective against resistance-promoting point mutations in BCR-ABL1. However, in the absence of point mutations, resistance still occurs. Here, we identify a novel pathway mediating resistance which connects p47phox, the organizer subunit of NADPH oxidase-2 (NOX2), with early growth response-1 (Egr-1) and the Src family kinase Fyn. We found up-regulation of p47phox, Egr-1, and Fyn mRNA and protein using paired isogenic CML cell lines and mined data. Isolation of CD34+ cells and tissue microarray staining from blast crisis CML patients confirmed in vivo over-expression of components of this pathway. Knockdown studies revealed that p47phox modulated reactive oxygen species and Egr-1 expression, which, in turn, controlled Fyn expression. Interestingly, Fyn knockdown sensitized TKI-resistant cells to dasatinib, a dual BCR-ABL1/Src inhibitor. Egr-1 knockdown had similar effects, indicating the utility of targeting Fyn expression over activation. Pointedly, p47phox knockdown also restored TKI-sensitivity, indicating that targeting the NOX2 complex can overcome resistance. The NOX2/Egr-1/Fyn pathway was also conserved within TKI-resistant EGFRΔIII-expressing glioblastoma and patient-derived glioblastoma stem cells. Thus, our findings suggest that targeting the NOX2/Egr-1/Fyn pathway may have clinical implications within multiple cancer types; particularly where efficacy of TKI is compromised.
酪氨酸激酶抑制剂（TKI）提高了慢性粒细胞白血病（CML）的缓解率，并且有些药物对BCR-ABL1中促进耐药的点突变有效。然而，在不存在点突变的情况下，耐药性仍然会出现。在此，我们确定了一条介导耐药性的新途径，该途径将NADPH氧化酶-2（NOX2）的组织者亚基p47phox与早期生长反应-1（Egr-1）和Src家族激酶Fyn联系起来。我们使用配对的同基因CML细胞系并挖掘数据，发现p47phox、Egr-1和Fyn的mRNA及蛋白表达上调。对CML急变期患者的CD34+细胞进行分离以及组织微阵列染色，证实了该途径各组分在体内的过表达。敲低研究表明，p47phox调节活性氧和Egr-1表达，而Egr-1表达又控制Fyn表达。有趣的是，敲低Fyn使TKI耐药细胞对达沙替尼（一种双重BCR-ABL1/Src抑制剂）敏感。敲低Egr-1也有类似效果，表明靶向Fyn表达而非激活具有实用性。值得注意的是，敲低p47phox也恢复了TKI敏感性，表明靶向NOX2复合物可以克服耐药性。NOX2/Egr-1/Fyn途径在表达TKI耐药的EGFRΔIII的胶质母细胞瘤和患者来源的胶质母细胞瘤干细胞中也保守存在。因此，我们的研究结果表明，靶向NOX2/Egr-1/Fyn途径可能在多种癌症类型中具有临床意义；特别是在TKI疗效受损的情况下。
