Simulating cell-free chromatin using preclinical cancer models for liquid biopsy applications
Bibliographic record
Abstract
Cell-free DNA circulates in blood bound to nucleosomes, forming cell-free chromatin (cfChromatin) that retains epigenetic features, including nucleosome positioning and histone modifications. cfChromatin provides a rich source of cancer biomarkers; however, low abundance of tumor-derived cfChromatin and limited availability of clinical samples pose challenges for liquid biopsy research. To address this, we developed a framework to simulate cfChromatin nucleosomal distributions using nuclease-treated conditioned media from tissue cultures. Whole-genome sequencing confirmed that inferred nucleosome positioning reflected cell-type-specific gene expression and chromatin accessibility patterns, and comparisons with plasma cfChromatin from xenografted mice revealed concordant nucleosome profiles. Notably, simulated cfChromatin displayed stronger tumor-specific nucleosome profiles than patient plasma, where hematopoietic-derived cfChromatin dilutes signal. We further leveraged simulated cfChromatin to advance cell-free chromatin immunoprecipitation and sequencing methods, identifying repressive and bivalent chromatin domains predictive of transcriptional activity. Altogether, our results demonstrate the utility of simulated cfChromatin as a scalable preclinical tool for liquid biopsy research.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".