Tyrosine kinase inhibitors (TKIs) such as imatinib, nilotinib, dasatinib, and ponatinib have significantly improved the life expectancy of Philadelphia chromosome-positive (Ph⁺) acute lymphocytic leukemia (ALL) patients; however, resistance to TKIs remains a major clinical challenge. Point mutations in the tyrosine kinase domain (TKD) of BCR-ABL1 have emerged as the predominant cause of acquired resistance. In approximately 30% of patients, the mechanism of resistance to TKIs remains elusive. This study aimed to investigate mechanisms of nonmutational resistance in Ph⁺ ALL. Here we report the development of a nonmutational resistance cell line SupB15-RT; conferring resistance to approved ABL kinase inhibitors (AKIs) and allosteric inhibitors GNF-2, ABL001, and crizotinib, except for dasatinib (IC90 50nM), a multitarget kinase inhibitor. We found that the AKT/mTOR pathway is activated in these cells and their proliferation inhibited by Torin-1 with an IC50 of 24.7 nM. These observations were confirmed using 3 different ALL patient-derived long term cultures (PDLTCs): (1) HP (BCR-ABL1 negative), (2) PH (BCR-ABL1 positive and responsive to TKIs) and (3) BV (BCR-ABL1 positive and nonmutational resistant to TKIs). Furthermore, Torin-1 and NVP-BEZ235 induced apoptosis in PH and BV cells but not in HP cells.

Our experiments provide evidence of the involvement of AKT/mTOR pathway in the evolution of nonmutational resistance in Ph⁺ ALL which will assist in developing novel targeted therapy for Ph⁺ ALL patients with BCR-ABL1 independent nonmutational resistance.

^{伊马替尼、尼罗替尼、达沙替尼和普纳替尼等酪氨酸激酶抑制剂（TKI）显着提高了费城染色体阳性（Ph +}）急性淋巴细胞白血病（ALL）患者的预期寿命；然而，对 TKI 的耐药性仍然是一个主要的临床挑战。BCR-ABL1 酪氨酸激酶结构域 (TKD) 的点突变已成为获得性耐药的主要原因。在大约 30% 的患者中，对 TKI 的耐药机制仍然难以捉摸。本研究旨在探讨 Ph ^{+非突变抗性的机制}全部。在这里，我们报告了非突变抗性细胞系 SupB15-RT 的开发。赋予对已批准的 ABL 激酶抑制剂 (AKI) 和变构抑制剂 GNF-2、ABL001 和克唑替尼的耐药性，但多靶点激酶抑制剂达沙替尼 (IC90 50nM) 除外。我们发现 AKT/mTOR 通路在这些细胞中被激活，并且它们的增殖被 Torin-1 抑制，IC50 为 24.7 nM。使用 3 种不同的 ALL 患者衍生的长期培养物 (PDLTC) 证实了这些观察结果：(1) HP (BCR-ABL1 阴性)，(2) PH (BCR-ABL1 阳性并对 TKI 有反应) 和 (3) BV (BCR -ABL1 阳性且对 TKI 无突变抗性）。此外，Torin-1 和 NVP-BEZ235 在 PH 和 BV 细胞中诱导细胞凋亡，但在 HP 细胞中不诱导。

我们的实验提供了 AKT/mTOR 通路参与 Ph + ALL 非突变耐药性演变的证据，^这将有助于为具有 BCR-ABL1 独立非突变耐药性的 Ph ⁺ ALL 患者开发新的靶向治疗。