Analyzing and disrupting leukemic stem cell adhesion to bone-marrow stromal cells by single molecule tracking nanoscopy

Abstract

Leukemic stem cells (LSC) adhere to bone niches by adhesion molecules. These interactions, deeply reorganized in tumors, contribute to LSC resistance and leukemia relapse. However, LSC adhesion mechanisms and potential therapeutic disruption using blocking antibodies remain largely unknown. Junctional adhesion molecule JAM-C over-expression by LSC correlates with increased leukemia severity, constituting a putative therapeutic target. Here, we took advantage of nanoscopy ability to detect single molecules with nanometric accuracy to characterize JAM dynamics at leuko-stromal contacts. Videonanoscopy trajectories were reconstructed using our dedicated Multi-Target Tracing algorithm, pipelined with dual-color analyses (MTT2col). JAM-C expressed by LSCs engaged transient interactions with JAM-B expressed by stromal cells. JAM recruitment and colocalization at cell contacts were proportional to JAM-C level and reduced by a blocking anti-JAM-C antibody. MTT2col revealed at single-molecule resolution the modalities of blocking antibodies to destabilize LSC binding to their niches, opening opportunities for disrupting LSC resistance mechanisms.