Dataset Information

Early BCR-ABL1 decline in imatinib-treated patients with chronic myeloid leukemia: results from a multicenter study of the Chinese CML alliance.

ABSTRACT: An early molecular response is spectacularly predictive of outcome in chronic myeloid leukemia (CML) and early response landmarks may identify the high-risk patients likely to be benefit from an early therapy switch. In this study, we evaluated the most relevant cutoffs for early molecular response markers (BCR-ABL1 values at 3 months, log reduction and halving time between diagnosis and 3 months) in 476 first-line imatinib-treated Chinese patients with chronic phase CML. All outcomes were significantly superior for the 324 patients with 3-month BCR-ABL1 ?10%, so did for the 270 patients with BCR-ABL1 >0.61 log reduction. BCR-ABL1 halving time ?22 days was identified for patients with the most favorable outcome. Moreover, the prognosis was significantly poorest for patients with both halving time >44 days and BCR-ABL1 >10%. Importantly, multivariate regression analysis demonstrated that a BCR-ABL1 log reduction calculated at 3 months of 0.61 was the only variable that significantly predicted for OS. Our results highlight the importance of rapid initial decline of BCR-ABL1 in predicting satisfactory outcome. Our data support the evidence that monitoring BCR-ABL1 values at an early time point could contribute to accurately assess response and ultimately guide clinical decisions regarding the timing of therapeutic intervention.

SUBMITTER: Zhang J

PROVIDER: S-EPMC6006175 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature

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Early BCR-ABL1 decline in imatinib-treated patients with chronic myeloid leukemia: results from a multicenter study of the Chinese CML alliance.

Zhang Jingru J Wang Yingqiao Y Wang Jianxiang J Hu Jianda J Chen Suning S Jin Jie J Liu Ting T Zhou Jianfeng J Hu Yu Y Ma Daoxin D Huang Xiaojun X Ji Chunyan C Hou Ming M

Blood cancer journal 20180615 7

An early molecular response is spectacularly predictive of outcome in chronic myeloid leukemia (CML) and early response landmarks may identify the high-risk patients likely to be benefit from an early therapy switch. In this study, we evaluated the most relevant cutoffs for early molecular response markers (BCR-ABL1 values at 3 months, log reduction and halving time between diagnosis and 3 months) in 476 first-line imatinib-treated Chinese patients with chronic phase CML. All outcomes were signi ...[more]

PMID: 29915172

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Project description:BackgroundThe BCR-ABL1 translocation occurs in chronic myeloid leukemia (CML) and in 25% of cases with acute lymphoblastic leukemia (ALL). The advent of tyrosine kinase inhibitors (TKI) has fundamentally changed the treatment of CML. However, TKI are not equally effective for treating ALL. Furthermore, de novo or secondary TKI-resistance is a significant problem in CML. We screened a panel of BCR-ABL1 positive ALL and CML cell lines to find models for imatinib-resistance.ResultsFive of 19 BCR-ABL1 positive cell lines were resistant to imatinib-induced apoptosis (KCL-22, MHH-TALL1, NALM-1, SD-1, SUP-B15). None of the resistant cell lines carried mutations in the kinase domain of BCR-ABL1 and all showed resistance to second generation TKI, nilotinib or dasatinib. STAT5, ERK1/2 and the ribosomal S6 protein (RPS6) are BCR-ABL1 downstream effectors, and all three proteins are dephosphorylated by imatinib in sensitive cell lines. TKI-resistant phosphorylation of RPS6, but responsiveness as regards JAK/STAT5 and ERK1/2 signalling were characteristic for resistant cell lines. PI3K pathway inhibitors effected dephosphorylation of RPS6 in imatinib-resistant cell lines suggesting that an oncogene other than BCR-ABL1 might be responsible for activation of the PI3K/AKT1/mTOR pathway, which would explain the TKI resistance of these cells. We show that the TKI-resistant cell line KCL-22 carries a PI3K? E545G mutation, a site critical for the constitutive activation of the PI3K/AKT1 pathway. Apoptosis in TKI-resistant cells could be induced by inhibition of AKT1, but not of mTOR.ConclusionWe introduce five Philadelphia-chromosome positive cell lines as TKI-resistance models. None of these cell lines carries mutations in the kinase domain of BCR-ABL1 or other molecular aberrations previously indicted in the context of imatinib-resistance. These cell lines are unique as they dephosphorylate ERK1/2 and STAT5 after treatment with imatinib, while PI3K/AKT1/mTOR activity remains unaffected. Inhibition of AKT1 leads to apoptosis in the imatinib-resistant cell lines. In conclusion, Ph+ cell lines show a form of imatinib-resistance attributable to constitutive activation of the PI3K/AKT1 pathway. Mutations in PIK3CA, as observed in cell line KCL-22, or PI3K activating oncogenes may undelie TKI-resistance in these cell lines.

Project description:Although the use of ATP-competitive tyrosine kinase inhibitors of oncoprotein BCR-ABL1 has enabled durable responses in patients with chronic myeloid leukemia (CML), issues of drug resistance and residual leukemic stem cells remain. To test whether the degradation of BCR-ABL1 kinase could offer improved response, we developed a series of proteolysis-targeting chimera (PROTAC) that allosterically target BCR-ABL1 protein and recruit the E3 ligase Von Hippel-Lindau, resulting in ubiquitination and subsequent degradation of the oncogenic fusion protein. In both human CML K562 cells and murine Ba/F3 cells expressing BCR-ABL1, lead compound GMB-475 induced rapid proteasomal degradation and inhibition of downstream biomarkers, such as STAT5, and showed increased sensitivity compared with diastereomeric controls lacking degradation activity. Notably, GMB-475 inhibited the proliferation of certain clinically relevant BCR-ABL1 kinase domain point mutants and further sensitized Ba/F3 BCR-ABL1 cells to inhibition by imatinib, while demonstrating no toxicity toward Ba/F3 parental cells. Reverse phase protein array analysis suggested additional differences in levels of phosphorylated SHP2, GAB2, and SHC associated with BCR-ABL1 degradation. Importantly, GMB-475 reduced viability and increased apoptosis in primary CML CD34+ cells, with no effect on healthy CD34+ cells at identical concentrations. GMB-475 degraded BCR-ABL1 and reduced cell viability in primary CML stem cells. Together, these findings suggest that combined BCR-ABL1 kinase inhibition and protein degradation may represent a strategy to address BCR-ABL1-dependent drug resistance, and warrant further investigation into the eradication of persistent leukemic stem cells, which rely on neither the presence nor the activity of the BCR-ABL1 protein for survival. SIGNIFICANCE: Small-molecule-induced degradation of BCR-ABL1 in CML provides an advantage over inhibition and provides insights into CML stem cell biology. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/79/18/4744/F1.large.jpg.

Dataset Information

Early BCR-ABL1 decline in imatinib-treated patients with chronic myeloid leukemia: results from a multicenter study of the Chinese CML alliance.

Publications

Early BCR-ABL1 decline in imatinib-treated patients with chronic myeloid leukemia: results from a multicenter study of the Chinese CML alliance.

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