Mechanistic Insights into ALK Fusion Biology Through Investigation of the Fusion Partner

摘要 涉及间变性淋巴瘤激酶（ALK）的基因重排代表了一类独特的 治疗靶向的癌基因越来越多地在许多上皮细胞中被检测到， 间叶性、造血系统和神经系统恶性肿瘤1。重要的是，ALK融合已在多达 8%的非小细胞肺癌（NSCLC）和50%的炎性肌纤维母细胞瘤（IMT）2，3。的 ALK融合的流行突出了理解融合激酶生物学的重要性， 最有效的治疗策略。 虽然由ALK易位产生的致癌融合蛋白是癌症治疗的有效靶点，但我们的研究发现， 与其他致癌基因相比，缺乏对如何最有效地靶向这些融合的理解。 司机例如，在EGFR突变型NSCLC中，不同的EGFR改变赋予不同程度的敏感性 或对EGFR导向疗法的抗性4 -8。此外，对于其他致癌融合，如视黄酸， 受体α（RARα）融合在白血病亚型中发现，已知特定基因融合到 RARα不仅影响对治疗的反应，而且本身也可以成为治疗靶点8。虽然许多不同 已报告ALK融合的5'伴侣基因，决定ALK融合阳性癌症的治疗 不考虑哪一个5'伙伴存在。例如，在NSCLC中，患有EML 4-ALK、KIF 5 B-ALK或 TFG-ALK融合均使用ALK酪氨酸激酶抑制剂（TKI）克唑替尼治疗。 在临床上，ALK TKI对ALK融合阳性肿瘤有效;然而，几乎没有数据说明 不同融合伴侣如何影响治疗前临床特征、疾病 对靶向治疗的反应性或获得性耐药性。此外，每个5'伙伴的作用没有 进行了系统的调查。总的来说，我们假设5'伙伴影响内在性质 ALK融合蛋白以及影响整体致癌潜力的细胞功能，导致 疾病表型的变异性和对靶向治疗的反应。为了验证我们的假设，我们将进行 使用在NSCLC和IMT中检测到的已知ALK融合的实验，以：1）确定5'配偶体是否改变 ALK TKI的激酶活性和疗效，以及2）确定ALK融合的5'配偶体是否影响致癌性 细胞功能和探索可能赋予差异致癌性的机制。因为更复杂的 下一代测序技术正在进入临床诊断的最前沿，临床医生不会 不仅知道存在酪氨酸激酶融合，而且知道激酶与哪个特定的5'配偶体融合。 因此，这些研究的结果有望改善ALK融合阳性癌症的治疗 以便更有效地抑制肿瘤生长并了解潜在的治疗抗性机制。 此外，由于激酶融合在许多恶性肿瘤中被发现，这些研究也可能具有潜在的 对其他激酶驱动的癌症的影响。

ABSTRACT Gene rearrangements involving the anaplastic lymphoma kinase (ALK) represent a unique class of therapeutically targetable oncogenes that are increasingly being detected in numerous epithelial, mesenchymal, hematopoietic, and neural malignancies1. Importantly, ALK fusions have been identified in up to 8% of non-small cell lung cancer (NSCLC) and 50% of inflammatory myofibroblastic tumor (IMT)2,3. The prevalence of ALK fusions highlights the importance of understanding fusion kinase biology in order to develop the most effective therapeutic strategies. While the oncogenic fusion proteins resulting from ALK translocations are valid targets for cancer therapy, our understanding of how to most effectively target these fusions is lacking in comparison to other oncogenic drivers. For example, in EGFR-mutant NSCLC, different EGFR alterations confer varying degrees of sensitivity or resistance to EGFR directed therapies4-8. In addition, for other oncogenic fusions, such as the retinoic acid receptor alpha (RARα) fusions found in subtypes of leukemia, it is known that the particular gene fused to RARα not only affects response to therapy but also can be a therapeutic target itself8. Although many different 5' partner genes have been reported for ALK fusions, treatment of ALK fusion positive cancers is decided without regard to which 5' partner is present. For example, in NSCLC, patients with EML4-ALK, KIF5B-ALK, or TFG-ALK fusions are all treated with the ALK tyrosine kinase inhibitor (TKI), crizotinib. Clinically, ALK TKIs are effective for ALK fusion positive tumors; however, there is little data to address the question of how a different fusion partner may affect pretreatment clinical characteristics, disease responsiveness to targeted therapies, or acquired resistance. Additionally, the role of each 5' partner has not been systematically investigated. Overall, we hypothesize that the 5' partner influences the intrinsic properties of the ALK fusion protein as well as the cellular functions that impact overall oncogenic potential, resulting in variability in disease phenotypes and response to targeted therapies. To test our hypothesis, we will carry out experiments using known ALK fusions detected in NSCLC and IMT to: 1) determine if the 5' partner alters kinase activity and efficacy of ALK TKIs, and 2) determine if the 5' partner of ALK fusions affects oncogenic cellular functions and explore mechanisms that may confer differential oncogenicity. Since more sophisticated next-generation sequencing technologies are coming to the forefront of clinical diagnostics, clinicians will not only know that a tyrosine kinase fusion is present, but also to which specific 5' partner the kinase is fused. Therefore, the findings from these studies are expected to refine the treatment of ALK fusion positive cancers in order to more effectively inhibit tumor growth and understand potential therapeutic resistance mechanisms. Furthermore, as kinase fusions are found in numerous malignancies, these studies may also have potential implications for other kinase-driven cancers.