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e13a2 and e14a2 are the most frequent transcript types of the BCR::ABL1 fusion gene in chronic myeloid leukemia (CML). The current goal with tyrosine kinase inhibitors (TKI) is to achieve sustained deep molecular response (DMR) in order to discontinue TKI treatment and remain in the so-called treatment-free remission (TFR) phase, but biological factors associated with these goals are not well established. This study aimed to determine the effect of transcript type on TFR in patients receiving frontline treatment with imatinib (IM) or second-generation TKI (2G-TKI). Patients treated at least 119 months with IM presented less post-discontinuation relapse than those that discontinued IM before 119 months (p = 0.005). In addition, cases with the e14a2 transcript type treated at least 119 months with IM presented a better TFR (p = 0.024). On the other hand, the type of transcript did not affect the cytogenetic or molecular response in 2G-TKI treated patients; however, the use of 2G-TKI may be associated with higher and earlier DMR in patients with the e14a2 transcript.

Abstract Haematopoietic malignancies are frequently characterized by karyotypic abnormalities. The development of targeted drugs has been pioneered with compounds against gene products of fusion genes caused by chromosomal translocations. While polysomies are equally frequent as translocations, for many of them we are lacking therapeutic approaches aimed at synthetic lethality. Here, we report two new cell lines, named MBU-7 and MBU-8, that differ in complete trisomy of chromosome18, a partial trisomy of chromosome 7 and a tetrasomy of the p-arm of chromosome 8, but otherwise share the same mutational pattern and complex karyotype. Both cell lines are divergent clones of U-937 cells and have the morphology and immunoprofile of monocytic cells. The distinct karyotypic differences between MBU-7 and MBU-8 are associated with a difference in the specific response to nucleoside analogues. Taken together, we propose the MBU-7 and MBU-8 cell lines described here as suitable in vitro models for screening and testing vulnerabilities that are associated with the disease-relevant polysomies of chromosome 7, 8 and 18.