Breakage-Fusion-Bridge Events Trigger Complex Genome Rearrangements and Amplifications in Developmentally Arrested T...

Area of Science:

• Genetics
• Cancer Biology
• Immunology

Background:

• Lymphomagenesis involves complex genetic alterations.
• The role of recombination activating genes (RAG) in T-cell lymphoma development is not fully understood.
• p53 deficiency is a known factor in cancer development.

Purpose of the Study:

• To investigate the contribution of RAG1/2 nuclease to lymphomagenesis.
• To compare genomic alterations in T-cell lymphomas with and without RAG2 expression in a p53-deficient background.
• To identify distinct genome architectural routes in lymphocyte malignant transformation.

Main Methods:

• Genome-wide analysis of T-cell lymphomas from p53-deficient mice.
• Comparison of lymphomas from mice expressing RAG2 versus those lacking RAG2.
• Analysis of genomic rearrangements, DNA deletions, and gene amplifications.

Main Results:

• p53-/- lymphoblastic T-cells primarily exhibit ectopic DNA deletions.
• Rag2-/-p53-/- T-cell lymphomas show complex genomic rearrangements and amplification of chromosomal region 9qA4-5.3.
• Amplification of 9qA4-5.3 is generated by breakage-fusion-bridge during mitosis and originates from an early progenitor stage.
• The syntenic region 11q23 is amplified in human leukemia, leading to overexpression of cancer genes like MLL/KMT2A.

Conclusions:

• Lymphocyte malignant transformation follows distinct genome architectural routes.
• These routes are influenced by both RAG-dependent and RAG-independent DNA damage.
• A block in cell development contributes to distinct cancer development pathways in T-cell lymphomas.