Section of Otolaryngology, Department of Surgery, Yale School of Medicine, New Haven, CT 06519-1369, USA.
Oncogene. 2013 Aug 8;32(32):3698-710. doi: 10.1038/onc.2012.377. Epub 2012 Oct 1.
Treatment options for adenoid cystic carcinoma (ACC) of the salivary gland, a slowly growing tumor with propensity for neuroinvasion and late recurrence, are limited to surgery and radiotherapy. Based on expression analysis performed on clinical specimens of salivary cancers, we identified in ACC expression of the neurotrophin-3 receptor TrkC/NTRK3, neural crest marker SOX10, and other neurologic genes. Here, we characterize TrkC as a novel ACC marker, which was highly expressed in 17 out of 18 ACC primary-tumor specimens, but not in mucoepidermoid salivary carcinomas or head and neck squamous cell carcinoma. Expression of the TrkC ligand NT-3 and Tyr-phosphorylation of TrkC detected in our study suggested the existence of an autocrine signaling loop in ACC with potential therapeutic significance. NT-3 stimulation of U2OS cells with ectopic TrkC expression triggered TrkC phosphorylation and resulted in Ras, Erk 1/2 and Akt activation, as well as VEGFR1 phosphorylation. Without NT-3, TrkC remained unphosphorylated, stimulated accumulation of phospho-p53 and had opposite effects on p-Akt and p-Erk 1/2. NT-3 promoted motility, migration, invasion, soft-agar colony growth and cytoskeleton restructuring in TrkC-expressing U2OS cells. Immunohistochemical analysis demonstrated that TrkC-positive ACC specimens also show high expression of Bcl2, a Trk target regulated via Erk 1/2, in agreement with activation of the TrkC pathway in real tumors. In normal salivary gland tissue, both TrkC and Bcl2 were expressed in myoepithelial cells, suggesting a principal role for this cell lineage in the ACC origin and progression. Sub-micromolar concentrations of a novel potent Trk inhibitor AZD7451 completely blocked TrkC activation and associated tumorigenic behaviors. Pre-clinical studies on ACC tumors engrafted in mice showed efficacy and low toxicity of AZD7451, validating our in vitro data and stimulating more research into its clinical application. In summary, we describe in ACC a previously unrecognized pro-survival neurotrophin signaling pathway and link it with cancer progression.
治疗涎腺腺样囊性癌（ACC）的选择有限，这种缓慢生长的肿瘤倾向于神经侵袭和晚期复发，仅限于手术和放疗。基于对涎腺癌临床标本的表达分析，我们在 ACC 中鉴定出神经营养因子-3 受体 TrkC/NTRK3、神经嵴标记物 SOX10 和其他神经基因的表达。在这里，我们将 TrkC 描述为一种新型的 ACC 标志物，在 18 个 ACC 原发性肿瘤标本中的 17 个中高度表达，但不在黏液表皮样癌或头颈部鳞状细胞癌中表达。我们的研究中检测到 TrkC 配体 NT-3 和 TrkC 的 Tyr 磷酸化表明在 ACC 中存在潜在治疗意义的自分泌信号环路。NT-3 刺激具有异位 TrkC 表达的 U2OS 细胞触发 TrkC 磷酸化，并导致 Ras、Erk1/2 和 Akt 激活以及 VEGFR1 磷酸化。没有 NT-3，TrkC 保持非磷酸化，刺激磷酸化 p53 的积累，并对 p-Akt 和 p-Erk1/2 产生相反的影响。NT-3 促进 TrkC 表达的 U2OS 细胞的运动、迁移、侵袭、软琼脂集落生长和细胞骨架重构。免疫组织化学分析表明，TrkC 阳性 ACC 标本还表现出高表达 Trk 靶标 Bcl2，Bcl2 通过 Erk1/2 调节，与真实肿瘤中 TrkC 途径的激活一致。在正常涎腺组织中，TrkC 和 Bcl2 均在肌上皮细胞中表达，这表明该细胞谱系在 ACC 的起源和进展中具有主要作用。新型强效 Trk 抑制剂 AZD7451 的亚微摩尔浓度完全阻断了 TrkC 的激活和相关的肿瘤发生行为。在小鼠中植入的 ACC 肿瘤的临床前研究显示 AZD7451 的疗效和低毒性，验证了我们的体外数据并激发了对其临床应用的更多研究。总之，我们在 ACC 中描述了一种以前未被认识的促生存神经营养因子信号通路，并将其与癌症进展联系起来。
