Stem cell-like reprogramming is required for leukemia-initiating activity in B-ALL.

Area of Science:

• Hematology
• Cancer Biology
• Molecular Oncology

Background:

• B cell acute lymphoblastic leukemia (B-ALL) arises from genetic alterations in B cells.
• The reprogramming of stem cell-like properties by oncogenes in committed B cells is not fully understood.

Purpose of the Study:

• To investigate the role of the PAX5::ELN oncogene in B-ALL development.
• To elucidate the mechanisms by which oncogenes induce preleukemic stem cells (pre-LSCs) and their properties.

Main Methods:

• Utilized the PAX5::ELN mouse model to study B-ALL pathogenesis.
• Employed the H2B-GFP system to assess leukemia-initiating activity.
• Integrated transcriptomic and chromatin accessibility data analysis.
• Constructed transcriptional regulatory networks.

Main Results:

• Demonstrated a causal link between differentiation blockade, self-renewal, and pre-LSC emergence in the PAX5::ELN model.
• Showed that PAX5::ELN enforces the IL7r/JAK-STAT pathway, disrupting differentiation and inducing quiescent pre-LSCs.
• Identified that these quiescent pre-LSCs exhibit a dedifferentiated, immature molecular program, similar to human B-ALL chemo-resistant cells.
• Revealed EGR1 as a potential regulator of quiescence and resistance in pre-LSCs and human B-ALL blasts.

Conclusions:

• The PAX5::ELN oncogene drives B-ALL by creating a population of quiescent, leukemia-initiating pre-LSCs.
• These pre-LSCs lose B cell identity and adopt an immature, chemo-resistant phenotype.
• EGR1 is a critical transcription factor implicated in the control of quiescence and chemo-resistance in B-ALL.