P-gp quantification for cell resistance studies in leukemia cells using the innovative LightSpot-FL-1 fluorescent conjugate.

Multidrug resistance proteins contribute to chemotherapy resistance in various cancers. Among them, the P-glycoprotein (P-gp) has been the most investigated. These works aim to evaluate the efficacy of the new fluorescent tracer LightSpot-FL-1 for quantifying P-gp in CCRF-CEM and KG-1a acute leukemia cell lines, as well as in blood samples from healthy donors and leukemic patients. First, The P-gp quantity in CCRF-CEM and KG-1a cells measured by LightSpot-FL-1, was 7052 ± 2789 FU and 27,666 ± 6706 FU, respectively. Then, cells exposure to 10 µM daunorubicin (DNR) for 3 h reduced P-gp expression by 54% in CCRF-CEM cells and by 62% in KG-1a cells. Moreover, this decrease preceded a dose-dependent reduction in cell viability detected after 24 h of exposure to 10 µM DNR, with 46.6% and 72.2% viable cells for CCRF-CEM and KG-1a, respectively. These findings suggest that P-gp downregulation could serve as a potential biomarker of treatment efficacy. Additionally, LightSpot-FL-1 analysis of six acute myeloid leukemia patient blood samples allowed the identification of 14 distinct blast subpopulations, revealing substantial inter- and intra-individual heterogeneity in P-gp expression. Thus, these findings underscore the potential of LightSpot-FL-1 as a valuable tool for re-evaluating the clinical relevance of P-gp in tumor resistance diagnosis.