Ablation of miR-146b in mice causes hematopoietic malignancy

Area of Science:

• Molecular Biology
• Immunology
• Genetics

Background:

• Aberrant nuclear factor-κB (NF-κB) activation is implicated in malignant tumor development, including lymphoma.
• MicroRNA 146a (miR-146a) and miR-146b are known regulators of NF-κB signaling, potentially impacting inflammatory diseases and cancer.
• The distinct roles of miR-146a and miR-146b in disease pathogenesis remain incompletely understood.

Purpose of the Study:

• To investigate the specific contributions of miR-146a and miR-146b to hematopoietic malignancies.
• To elucidate the functional and physiological differences between miR-146a and miR-146b in the context of NF-κB-driven diseases.
• To analyze the impact of miR-146a and miR-146b deficiency on B-cell lymphoma and acute myeloid leukemia development.

Main Methods:

• Generation of miR-146b-knockout (KO) and miR-146a-KO mice using genome editing.
• Histopathological analysis of hematopoietic malignancies in aged KO mice.
• Assessment of microRNA expression levels upon mitogenic stimulation.
• Evaluation of microRNA targeting of NF-κB pathway components, including TRAF6, using a microRNA target screening system.
• Analysis of B-cell proliferation capacity in KO mice.

Main Results:

• Both miR-146a-KO and miR-146b-KO mice developed hematopoietic malignancies, including B-cell lymphoma and acute myeloid leukemia, during aging.
• Histological examination revealed distinct morphologies of B-cell lymphomas between miR-146a-KO and miR-146b-KO mice.
• The overall malignancy rate was lower in miR-146b-KO mice compared to miR-146a-KO mice.
• miR-146a and miR-146b were found to target common mRNAs, such as TRAF6, and inhibit NF-κB activity.
• B cells from both miR-146a-KO and miR-146b-KO mice exhibited increased proliferative capacity.

Conclusions:

• Sustained NF-κB activation, resulting from the absence of miR-146b, contributes to the development of aging-associated hematopoietic malignancies.
• miR-146a and miR-146b play crucial, albeit partially distinct, roles in suppressing NF-κB-driven hematopoietic malignancies.
• These findings highlight the therapeutic potential of targeting the miR-146a/146b-NF-κB axis in lymphoma and related cancers.