363: cfDNA size deconvolution reveals a 159‑bp nucleosomal pivot and tumor fragmentomic signatures

Zhou Z et al., Nature Communications - This study develops a Lorentzian deconvolution model of cfDNA fragment length distributions across bodily fluids, identifies a ~159 bp component that demarcates intra- vs inter-nucleosomal fragments, and shows that intra-nucleosomal fragmentation entropy distinguishes tumor-derived ctDNA from non-tumor shortening. Key terms: cell-free DNA, fragmentomics, nucleosome, ctDNA, size deconvolution.

Study Highlights:
The authors modeled cfDNA size profiles as sums of Cauchy–Lorentz distributions with ~10 bp periodicity and applied deconvolution across plasma, saliva, urine, CSF and lymphatic fluid. A distinct ~159 bp component emerged as a pivot between intra- and inter-nucleosomal fragments. Tumor-derived ctDNA shows increased intra-nucleosomal fragmentation entropy and inverse amplitude changes across the 159 bp boundary, whereas phagocytosis-associated shortening increases intra-nucleosomal amplitude without raising entropy. The intra/inter-nucleosomal entropy ratio improved cancer detection performance relative to standard size-ratio metrics across multiple cohorts.

Conclusion:
Size deconvolution using Lorentzian components reveals nucleosomal structure in cfDNA, identifies a 159 bp demarcation between fragmentation regimes, and provides an entropy-based metric that enhances ctDNA detection while separating tumor-associated fragmentation from phagocyte-related signals.

Music:
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Article title:
Cell-free DNA size deconvolution resolves nucleosomal origins and reveals tumor-associated fragmentomic alterations

First author:
Zhou Z

Journal:
Nature Communications

DOI:
10.1038/s41467-026-72925-4

Reference:
Zhou Z, Cooper WN, Cheng Z, et al. Cell-free DNA size deconvolution resolves nucleosomal origins and reveals tumor-associated fragmentomic alterations. Nat Commun (2026). https://doi.org/10.1038/s41467-026-72925-4

License:
This episode is based on an open-access article published under the Creative Commons Attribution 4.0 International License (CC BY 4.0) – https://creativecommons.org/licenses/by/4.0/

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Episode link: https://basebybase.com/episodes/cfdna-size-deconvolution-nucleosomal-origins

QC:
This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-05-09.

QC Scope:
- article metadata and core scientific claims from the narration
- excludes analogies, intro/outro, and music
- transcript coverage: Substantive auditing of the transcript's discussion of cfDNA fragmentology, Lorentzian deconvolution, the 159 bp pivot, entropy vs amplitude distinctions, Li-Fraumeni context, phagocytosis vs tumor fragmentation, and diagnostic performance metrics.
- transcript topics: cfDNA fragmentomics basics; Lorentzian size deconvolution and nucleosome structure; 159 bp boundary between intra- and inter-nucleosomal cfDNA; intra-/inter-nucleosomal amplitude and entropy ratios; ctDNA fragmentation entropy as cancer signature; phagocytosis vs tumor-derived fragmentation

QC Summary:
- factual score: 10/10
- metadata score: 10/10
- supported core claims: 7
- claims flagged for review: 0
- metadata checks passed: 4
- metadata issues found: 0

Metadata Audited:
- article_doi
- article_title
- article_journal
- license

Factual Items Audited:
- cfDNA size profiles deconvoluted into Lorentzian components across multiple fluids with ~10 bp periodicity
- a ~159 bp component demarcates intra- vs inter-nucleosomal cfDNA
- intra-nucleosomal fragmentation entropy is elevated in ctDNA; phagocytosis-associated shortening increases amplitude but not entropy
- intra-/inter-nucleosomal entropy ratio improves cancer detection performance (gastric cancer AUC ~0.87; multi-cancer AUC ~0.81–0.85; stage-specific AUCs up to ~0.91)
- radiotherapy and organ transplantation contexts show short-fragment enrichment with amplitude changes but entropy changes are not increased in non-tumor scenarios
- dd-cfDNA analyses show differences in amplitude but not entropy between high vs low donor-derived DNA groups

QC result: Pass.