Continuous DNA methylation deconvolution-based surrogate for B-cell differentiation state in chronic lymphocytic...

Area of Science:

• Hematology
• Epigenetics
• Cancer Biology

Background:

• Chronic lymphocytic leukemia (CLL) is clinically classified into mutated (M-CLL) and unmutated (U-CLL) subtypes based on IGHV mutation status.
• These subtypes represent distinct B-cell differentiation pathways, but a continuous epigenetic metric is lacking.

Purpose of the Study:

• To develop a continuous metric of epigenetic states in CLL.
• To correlate epigenetic states with B-cell differentiation and clinical subtypes.
• To identify epigenetic correlates of tumor burden in CLL.

Main Methods:

• Genome-scale DNA methylation was measured in 89 CLL samples.
• Reference-based cell deconvolution was used to create a B-cell epigenetic similarity scale (B-Index).
• B-Index was analyzed for classification accuracy, comparison with IGHV, and correlation with tumor burden.

Main Results:

• The B-Index accurately classifies CLL subtypes (98.8%) and shows a stronger epigenetic signal than IGHV percent identity.
• Unmutated CLL (U-CLL) is epigenetically similar to B-memory cells, with programs enriched for germinal center activation.
• An epigenetic signal associated with tumor burden, enriched for Epstein-Barr Virus transcription factors, was identified.

Conclusions:

• CLL neoplasms exhibit more epigenetic heterogeneity than current clinical classifications suggest.
• The B-Index provides a continuous epigenetic metric applicable to other neoplasms.
• This approach refines understanding of CLL pathogenesis and B-cell differentiation.