Structural Alterations in Breast Stromal and Epithelial DNA: The Influence of 8,5-cyclo-2-Deoxyadenosine
Bibliographic record
Abstract
(5'S)-8,5'-Cyclo-2'-deoxyadenosine (S-cdA), which arises from the reaction of the hydroxyl radical (*OH) with 2'-deoxyadenosine in DNA, is a lesion comprising a base-sugar linkage that distorts the DNA backbone. This structure impedes transcription and blocks polymerase action. Further, a single S-cdA lesion in the TATA box reduces gene expression. Considering the ability of S-cdA to disrupt DNA structure, which is likely associated with increased cancer risk, we determined S-cdA concentrations in the DNA of stroma, epithelium, and myoepithelium from normal breast tissues using liquid chromatography/mass spectrometry (LC/MS). We also identified differences in the base and backbone structures using Fourier transform-infrared (FT-IR) spectroscopy. LC/MS revealed that the lowest concentration of S-cdA in the stroma (0.04 +/- 0.02 lesions/10(6) bases) occurred in women ages 17 to 30. The highest concentration (0.13 +/- 0.07 lesions/10(6) bases) was found in women 33 to 46. FT-IR spectroscopy showed significant base and backbone differences in the stromal DNA between the women under 30 and those over 50. These findings imply that distortions in the geometry of the helix increase with age, reaching significant proportions in older women. No differences were found in the S-cdA concentrations between the three cell types, suggesting that the *OH attack on the base structure may be essentially random. Initial insight is provided on changes in DNA structure that potentially affect gene expression and increase breast cancer risk.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".