Hypoxia Provokes Base Excision Repair Changes and a Repair-Deficient, Mutator Phenotype in Colorectal Cancer Cells
Why this work is in the frame
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Bibliographic record
Abstract
UNLABELLED: Regions of acute and chronic hypoxia exist within solid tumors and can lead to increased rates of mutagenesis and/or altered DNA damage and repair protein expression. Base excision repair (BER) is responsible for resolving small, non-helix-distorting lesions from the genome that potentially cause mutations by mispairing or promoting DNA breaks during replication. Germline and somatic mutations in BER genes, such as MutY Homolog (MUTYH/MYH) and DNA-directed polymerase (POLB), are associated with increased risk of colorectal cancer. However, very little is known about the expression and function of BER proteins under hypoxic stress. Using conditions of chronic hypoxia, decreased expression of BER proteins was observed because of a mechanism involving suppressed BER protein synthesis in multiple colorectal cancer cell lines. Functional BER was impaired as determined by MYH- and 8-oxoguanine (OGG1)-specific glycosylase assays. A formamidopyrimidine-DNA glycosylase (Fpg) Comet assay revealed elevated residual DNA base damage in hypoxic cells 24 hours after H2O2 treatment as compared with normoxic controls. Similarly, high-performance liquid chromatography analysis demonstrated that 8-oxo-2'-deoxyguanosine lesions were elevated in hypoxic cells 3 and 24 hours after potassium bromate (KBrO3) treatment when compared with aerobic cells. Correspondingly, decreased clonogenic survival was observed following exposure to the DNA base damaging agents H2O2 and MMS, but not to the microtubule interfering agent paclitaxel. Thus, a persistent downregulation of BER components by the microenvironment modifies and facilitates a mutator phenotype, driving genetic instability and cancer progression. IMPLICATIONS: Aberrant BER is a contributing factor for the observed genetic instability in hypoxic tumor cells.
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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 | 0.001 | 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 it