Radioimmunoimaging of p21(WAF-1/CIP-1) intracellular epitopes in breast cancer
Bibliographic record
Abstract
Radioimmunoimaging of intracellular epitopes in tumours is restricted by the inability of most immunoglobuline (IgG) to traverse the cell membrane. It was hypothesized that 13-mer peptides [GRKKRRQRRRPPQ] harboring the membrane translocation and nuclear import sequences of HIV-1 tat protein (underlined) site-specifically linked to the Fc-domain of monoclonal antibodies would be able to image intracellular epitopes such as the cyclindependent kinase inhibitor, p21WAF-1/CIP-1, in breast cancer xenografts in athymic mice. The response of the p21WAF-1/CIP-1 gene in MDA-MB-468 and MCF-7 breast cancer cells to selected treatments [gamma-radiation, campotothecin, or human epidermal growth factor (hEGF)J was studied. Moderate (up to 2-5-fold) increase in p21WAF-1/CIP-1 was detected by Western blot. Prototypic immunoconjugates were constructed by conjugating the tat peptides to periodate-oxidized mouse IgG (mIgG) through a Shiff base linkage. Tat-mIgG was labeled with 123I. Tat-mIgG showed a 15-fold decrease in binding affinity for anti-mouse IgG (Fab specific) antibodies (alpha-mFab) compared to mIgG. The binding of 123I-alpha-mFab to lysate from MDA-MB-468 cells importing tat-mIgG was 17-fold higher than to lysate from unexposed cells. Imported tat-mlgG competed with tat-mIgG for displacement of binding of 123I-mIgG to alpha-mFab. Nuclear localization was observed in vitro for 123I-tat-mIgG, which was significantly higher than 123I-mlgG in three phenotypically different human breast cancer cell lines (MCF-7, MDA-MB-231 and MDA-MB468). Nuclear localization was also found in vivo in MDA-MB-468 tumour xenografts and in cells of the liver, spleen, and kidneys of athymic mice following intravenous injection of 123I-tatmIgG. Conjugation of mIgG to tat peptides had no effect on its biodistribution. Specific tat-antip21 WAF-1/CIP-1 monoclonal antibodies (tat-alpha-p21WAF-1/CIP-1) immunoconjugates were then constructed. Nuclear localization of 123I-tat-alpha-p21WAF-1/CIP-1 in MDA-MB-468 cells was significantly higher than for 123I-alpha-p21WAF-I/CIP-1 . Imported tat-alpha-p21WAF-1/CIP-1 blocked G 1 arrest in MDA-MB-468 cells caused by hEGF-induced p21WAF-1/CIP-1 Tumour uptake of 123I-tat-alphap21WAF-1/CIP-1 24 hours after intravenous injection in athymic mice was significantly higher following intratumoural injections of hEGF to induce p21WAF-1/CIP-1 than in mice not receiving hEGF or mice injected with 123 I-alpha-p21WAF-l/C1P-1 and receiving hEGF. 123I-tat-alpha-p21WAF-1/CIP-1 showed increased tumour uptake on images of hEGF-injected mice compared to control mice. Further optimization of the tumour signal is required. I conclude that tat-immunoconjugates are promising vehicles for radioimmunoimaging of p21WAF-l/CIP-1 intracellular epitopes in breast cancer.
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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) | 0.001 | 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 | 0.001 | 0.001 |
| 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".