Role of Smad1 and Smad4 proteins in the induction of p21WAF1,Cip1 during bone morphogenetic protein-induced growth arrest in human breast cancer cells
Bibliographic record
Abstract
Bone morphogenetic proteins (BMPs) are members of the transforming growth factor-beta family of cytokines. The recent observation that BMPs can inhibit breast cancer cell proliferation in vitro suggests that BMPs or the BMP pathway may hold promise as therapeutic targets for the control of breast tumor growth in women. Better to understand the mechanism of BMP-induced growth arrest we examined the effect of BMP-2 and mediators of BMP-2 action on cell proliferation and p21(Cip1) expression in breast cancer cell lines. We show here that BMP-2 potently inhibited the proliferation of breast cancer cell lines that express both Smad1 and Smad4 (CAMA-1, MCF7, MDA-MB-231, T-47D, ZR-75-1), but not that of cells that only express Smad1 (MDA-MB-468). Growth inhibition correlated with up-regulation of p21 mRNA and protein levels. Up-regulation of p21 was resistant to cycloheximide but not to actinomycin D, suggesting that it occurred at the transcriptional level. Using p21 promoter-luciferase reporter constructs we mapped the BMP-responsive region of the p21 promoter to within 211 base pairs of the transcription start site. Induction of p21 promoter activity was rapid and coincided with up-regulation of p21 mRNA and protein levels. p21 promoter activity required both Smad1 and Smad4 and was induced by either BMP-2 or constitutively active type I BMP receptors. Moreover, the C-terminal SSVS region of Smad1 was necessary for activation of the p21 promoter by BMP-2. Taken together, these results indicate that the mechanism of BMP-induced p21 promoter activation involves BMP receptors and BMP Smads.
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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 | 0.001 | 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) | 0.002 | 0.001 |
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".