Distinct stromal cell populations define the B-cell acute lymphoblastic leukemia microenvironment

Area of Science:

• Hematology and Oncology
• Cell Biology
• Cancer Microenvironment Research

Background:

• The bone marrow microenvironment is crucial for B-cell acute lymphoblastic leukemia (B-ALL) progression.
• The cellular diversity within the B-ALL bone marrow microenvironment is not well understood.

Purpose of the Study:

• To investigate the cellular heterogeneity of mesenchymal stromal cells (MSCs) in the B-ALL bone marrow microenvironment.
• To understand how different stromal cell populations interact with and support leukemic cells.
• To explore the role of stromal cell differentiation in B-ALL progression and relapse.

Main Methods:

• Single-cell RNA sequencing of patient-derived bone marrow aspirates from pediatric B-ALL patients.
• Spatial transcriptomic analysis to determine cell localization.
• Ex vivo functional assays using sorted stromal populations.
• Co-culture experiments to assess cell-cell interactions and differentiation.

Main Results:

• Identified two distinct MSC populations: early mesenchymal progenitors and adipogenic progenitors.
• Discovered osteogenic-lineage cells exclusively in bone biopsies.
• Both progenitor types secrete supportive factors (CXCL12, Osteopontin) aiding leukemic cell survival and chemoresistance.
• Adipogenic progenitors, but not early mesenchymal progenitors, support leukemic cells via IL-7 and VCAM1 signaling.
• B-ALL cells induce adipogenic differentiation in healthy MSCs via cell contact.
• Adipogenic progenitors are enriched in relapse samples and show enhanced differentiation capacity in B-ALL patients.

Conclusions:

• The B-ALL microenvironment comprises specialized stromal niches with distinct functions.
• Leukemic cells actively engage with and manipulate stromal cell populations, particularly inducing adipogenesis.
• Adipogenic progenitors play a significant role in B-ALL progression and relapse.