Divisions of Radiation Cancer Research, Korea Institute of Radiological and Medical Sciences, Seoul, Korea.
Oncogene. 2013 Jan 10;32(2):209-21. doi: 10.1038/onc.2012.37. Epub 2012 Feb 27.
The hypothesis of cancer stem cells has been proposed to explain the therapeutic failure in a variety of cancers including lung cancers. Previously, we demonstrated acquisition of epithelial-mesenchymal transition, a feature highly reminiscent of cancer stem-like cells, in gefitinib-resistant A549 cells (A549/GR). Here, we show that A549/GR cells contain a high proportion of CXCR4+ cells that are responsible for having high potential of self-renewal activity in vitro and tumorigenicity in vivo. A549/GR cells exhibited strong sphere-forming activity and high CXCR4 expression and SDF-1α secretion compared with parent cells. Pharmacological inhibition (AMD3100) and/or siRNA transfection targeting CXCR4 significantly suppressed sphere-forming activity in A549 and A549/GR cells, and in various non-small cell lung cancer (NSCLC) cell lines. A549/GR cells showed enhanced Akt, mTOR and STAT3 (Y705) phosphorylation. Pharmacological inhibition of phosphatidyl inositol 3-kinase or transfection with wild-type PTEN suppressed phosphorylation of Akt, mTOR and STAT3 (Y705), sphere formation, and CXCR4 expression in A549/GR cells, whereas mutant PTEN enhanced these events. Inhibition of STAT3 by WP1066 or siSTAT3 significantly suppressed the sphere formation, but not CXCR4 expression, indicating that STAT3 is a downstream effector of CXCR4-mediated signaling. FACS-sorted CXCR4+ A549/GR cells formed many large spheres, had self-renewal capacity, demonstrated radiation resistance in vitro and exhibited stronger tumorigenic potential in vivo than CXCR4- cells. Lentiviral-transduction of CXCR4 enhanced sphere formation and tumorigenicity in H460 and A549 cells, whereas introduction of siCXCR4 suppressed these activities in A549/GR cells. Our data indicate that CXCR4+ NSCLC cells are strong candidates for tumorigenic stem-like cancer cells that maintain stemness through a CXCR4-medated STAT3 pathway and provide a potential therapeutic target for eliminating these malignant cells in NSCLC.
癌症干细胞假说被提出，以解释多种癌症（包括肺癌）的治疗失败。先前，我们证明了表皮-间质转化的获得，这一特征非常类似于癌症干细胞样细胞，在吉非替尼耐药的 A549 细胞（A549/GR）中。在这里，我们表明 A549/GR 细胞含有高比例的 CXCR4+细胞，这些细胞在体外具有高自我更新活性和体内致瘤性的潜力。与亲本细胞相比，A549/GR 细胞表现出强烈的球体形成活性和高 CXCR4 表达和 SDF-1α 分泌。CXCR4 的药理学抑制（AMD3100）和/或 siRNA 转染靶向显著抑制 A549 和 A549/GR 细胞以及各种非小细胞肺癌（NSCLC）细胞系中的球体形成活性。A549/GR 细胞表现出增强的 Akt、mTOR 和 STAT3（Y705）磷酸化。PI3K 药理学抑制或野生型 PTEN 转染抑制 Akt、mTOR 和 STAT3（Y705）的磷酸化、球体形成和 CXCR4 的表达，而突变型 PTEN 增强了这些事件。STAT3 的 WP1066 或 siSTAT3 抑制显著抑制球体形成，但不抑制 CXCR4 的表达，表明 STAT3 是 CXCR4 介导的信号通路的下游效应物。FACS 分选的 CXCR4+ A549/GR 细胞形成许多大球体，具有自我更新能力，在体外表现出辐射抗性，并在体内显示出比 CXCR4-细胞更强的致瘤潜能。CXCR4 的慢病毒转导增强了 H460 和 A549 细胞的球体形成和致瘤性，而 siCXCR4 的引入抑制了 A549/GR 细胞中的这些活性。我们的数据表明，CXCR4+NSCLC 细胞是具有成瘤性的干细胞样癌细胞的强有力候选者，它们通过 CXCR4 介导的 STAT3 途径维持干细胞特性，并为消除 NSCLC 中的这些恶性细胞提供了一个潜在的治疗靶点。
