The bone marrow microenvironment (BME) drives drug resistance in acute lymphoblastic leukemia (ALL) through leukemic cell interactions with bone marrow (BM) niches, but the underlying mechanisms remain unclear. Here, we show that the interaction between ALL and mesenchymal stem cells (MSCs) through integrin β1 induces an epithelial-mesenchymal transition (EMT)-like program in MSC-adherent ALL cells, resulting in drug resistance and enhanced survival. Moreover, single-cell RNA sequencing analysis of ALL-MSC co-culture identifies a hybrid cluster of MSC-adherent ALL cells expressing both B-ALL and MSC signature genes, orchestrated by a WNT/β-catenin-mediated EMT-like program. Blockade of interaction between β-catenin and CREB binding protein impairs the survival and drug resistance of MSC-adherent ALL cells in vitro and results in a reduction in leukemic burden in vivo. Targeting of this WNT/β-catenin-mediated EMT-like program is a potential therapeutic approach to overcome cell extrinsically acquired drug resistance in ALL.
Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.

Peripheral lymphoid organs (PLOs), the primary sites of development of adaptive immune responses, display a complex structural organization reflecting separation of cellular subsets (e.g., T and B lymphocytes) and functional compartments which is critical for immune function. The generation of in vitro culture systems capable of recapitulating salient features of PLOs for experimental, biotechnological, and clinical applications would be highly desirable, but has been hampered so far by the complexity of these systems. We have previously developed a three-dimensional bioreactor system for long-term, functional culture of human bone marrow cells on macroporous microspheres in a packed-bed bioreactor with frequent medium change. Here we adapt the same system for culture of human primary cells from PLOs (tonsil) in the absence of specific exogenous growth factors or activators. Cells in this system displayed higher viability over several weeks, and maintain population diversity and cell surface markers largely comparable to primary cells. Light microscopy showed cells organizing in large diverse clusters within the scaffold pores and presence of B cell-enriched areas. Strikingly, these cultures generated a significant number of antibody-producing B cells when challenged with a panel of diverse antigens, as expected from a lymphoid tissue. Thus the three-dimensional tonsil bioreactor culture system may serve as a useful model of PLOs by recapitulating their structural organization and function ex vivo.
Copyright © 2011 Wiley Periodicals, Inc.