Assessment of Chronic Myeloid Leukaemia In Vitro Models Variability: Insights Into Extracellular Vesicles.

Chronic Myeloid Leukaemia is driven by the BCR::ABL1 fusion gene. Although Tyrosine Kinase Inhibitors have significantly improved patient outcomes, drug resistance and disease persistence remain challenges, highlighting the need for effective preclinical models. We observed cellular heterogeneity among CML models in response to TKIs, influencing viability, metabolism, and molecular markers. With growing interest in extracellular vesicles as mediators of leukaemia progression via oncogenic cargo like BCR::ABL1, we explored whether EVs from different CML cell lines exhibit distinct features. EVs from K562 and KCL22 cells were characterised under basal conditions using Fourier Transform Infrared spectroscopy, Atomic Force Microscopy, dot blotting, and Nanoparticle Tracking Analysis. We assessed EV release and BCR::ABL1 content before and after treatment with imatinib, nilotinib, or dasatinib, alongside Ki67 expression to gauge proliferation. Fourier Transform Infrared Spectroscopy with Principal Component Analysis revealed distinct clustering of EVs by cell line. While untreated K562 and KCL22 cells showed similar EV output and BCR::ABL1 content, post-treatment K562 cells released more EVs with elevated BCR::ABL1 transcripts. KCL22 cells showed earlier reduction in Ki67 expression. These findings highlight model-dependent EV behaviour, reflecting patient heterogeneity and reinforcing the need for careful model selection in CML research.