Developing a novel therapeutic strategy for overcoming TKI resistance in ALL

近三分之一的成人急性淋巴细胞白血病（ALL）患者与 t（9;22）染色体易位，形成BCR-ABL癌基因。BCR-ABL诱导B细胞急性 淋巴母细胞白血病（B-ALL）直接或从慢性期髓系进展为急性母细胞期 白血病与其他类型的B-ALL相比，BCR-ABL阳性B-ALL预后差， 即使在不存在BCR-ABL激酶突变的情况下，对酪氨酸激酶抑制剂（TKI）的敏感性也较低， 这种TKI抗性的潜在机制在很大程度上是未知的。我们假设 B-ALL需要BCR-ABL激活的关键下游通路 发展，但不能通过TKI抑制BCR-ABL激酶活性而完全关闭， 提示BCR-ABL激酶非依赖性机制不同于BCR-ABL诱导的TKI耐药。 ABL激酶结构域突变。我们的初步研究结果支持了这一新颖的想法， 15-脂氧合酶（Alox 15）被BCR-ABL上调，并且是小鼠B-ALL发展所必需的，但这一点在BCR-ABL中并不重要。 用伊马替尼（一种TKI）抑制BCR-ABL激酶活性不会逆转Alox 15上调。这些 初步发现将Alox 15与B-ALL细胞中的TKI耐药性联系起来，为克服TKI耐药性提供了新的策略。 TKI耐药治疗BCR-ABL阳性B-ALL和其他策略性致癌诱导的白血病 酪氨酸激酶我们应该提到，关于Alox 15通路如何介导TKI是完全未知的 B-ALL的耐药性，更好地理解这种Alox 15介导的TKI耐药机制需要 证明Alox 15在BCR-ABL诱导的B-ALL中的重要作用，并深入研究其机制。 导致全面了解Alox 15相关通路及其对B-ALL的贡献的研究 发展毫无疑问，这些研究将有助于开发一种新的治疗策略， 通过靶向Alox 15途径克服TKI耐药性治疗BCR-ABL阳性B-ALL。 具体来说，主要采取基因敲除小鼠和CRISPR-Cas9技术的遗传方法， 我们将通过揭示Alox 15及其相关通路在B-ALL发展中的作用来验证我们的假设 以及B-ALL细胞对TKI的反应。如果成功的话，结果将对我们产生巨大的影响， 了解B-ALL的疾病机制，并帮助确定治疗TKI不敏感的 人类B-ALL仍然缺乏有效的治疗方法。具体目的是：1）研究Alox 15在肿瘤细胞中的作用 脂质代谢产物在促进B-ALL细胞生长和诱导TKI耐药中的作用 Alox 15调控BCR-ABL诱导的B淋巴细胞转化中的关键配偶体基因和耐药性 白血病细胞对TKI的耐受性;以及3）开发用于规避人类TKI耐受性的治疗策略 通过抑制Alox 15途径治疗B-ALL。

Nearly one-third of adult patients with acute lymphoblastic leukemia (ALL) are associated with the t(9;22) chromosomal translocation that forms the BCR-ABL oncogene. BCR-ABL induces B-cell acute lymphoblastic leukemia (B-ALL) directly or in acute blastic phase advanced from chronic phase myeloid leukemia. Compared to other types of B-ALL, BCR-ABL-positive B-ALL has a poor prognosis and is much less sensitive to tyrosine kinase inhibitors (TKIs) even in the absence of BCR-ABL kinase mutations, and the underlying mechanisms for this type of the TKI-resistance are largely unknown. We hypothesize that there must be critical downstream pathways whose activation by BCR-ABL is required for B-ALL development but cannot be completely shut down through inhibition of BCR-ABL kinase activity by TKIs, suggesting a BCR-ABL kinase-independent mechanism different from the TKI resistance induced by BCR- ABL kinase domain mutations. This novel idea is supported by our preliminary findings that arachidonate 15-lipoxygenase (Alox15) is upregulated by BCR-ABL and required for B-ALL development in mice but this Alox15 upregulation is not reversed by inhibiting BCR-ABL kinase activity with imatinib (a TKI). These preliminary findings link Alox15 to TKI resistance in B-ALL cells, providing a new strategy for overcoming TKI resistance in treating BCR-ABL-positive B-ALL and strategically other leukemias induced by oncogenic tyrosine kinases. We should mention that it is totally unknown about how the Alox15 pathway mediates TKI resistance in B-ALL, and a better understanding of this Alox15-mediated TKI resistant mechanism requires demonstration of an essential role of Alox15 in B-ALL induced by BCR-ABL and in-depth mechanistic studies that lead to a full understanding of Alox15-associated pathways and their contributions to B-ALL development. Without any doubt, these studies will help to develop a new therapeutic strategy for overcoming TKI resistance in treating BCR-ABL-positive B-ALL by targeting the Alox15 pathway. Specifically, by mainly taking a genetic approach using gene knockout mice and CRISPR-Cas9 technology, we will test our hypothesis by revealing the roles of Alox15 and its related pathways in B-ALL development and in the response of B-ALL cells to TKIs. If successful, the results will have a huge impact on our better understanding of disease mechanisms for B-ALL and help to identify novel targets in treating TKI-insensitive human B-ALL that still lacks effective therapies. The specific aims are: 1) To investigate the role of Alox15 lipid metabolites in promoting growth and inducing TKI resistance of B-ALL cells; 2) To study the roles of Alox15-regulated key partner genes in BCR-ABL-induced B-lymphoid transformation and resistance of leukemia cells to TKIs; and 3) To develop a therapeutic strategy for circumventing TKI resistance in human B-ALL by inhibiting the Alox15 pathway.