A truncated cytoplasmic topoisomerase IIα in a drug-resistant lung cancer cell line is encoded by aTOP2A allele with a partial deletion of exon 34
Bibliographic record
Abstract
To study the problem of acquired resistance to widely used anti-cancer drugs that target the 170 kDa topoisomerase IIalpha (topo IIalpha), a drug-resistant human small-cell lung cancer cell line, H209/VP, was selected in VP-16. H209/VP cells express reduced levels of the 170 kDa topo IIalpha that is localized normally in the nucleus and also express lower levels of a 160 kDa topo IIalpha-related protein that is located predominantly in the cytoplasm. Band depletion immunoblotting experiments suggest that the H209/VP nuclear 170 kDa topo IIalpha is able to form ternary complexes with DNA and VP-16 in intact cells, but the ability of the cytoplasmic 160 kDa protein to do so is greatly diminished. Sequence analysis of the 3; end of the H209/VP mutant topo IIalpha mRNA and the TOP2A gene indicates that the mRNA is missing 200 nt that corresponds to exon 34 because the partial loss of the minimal 3; splice-acceptor sequence at the beginning of exon 34 results in splicing of exon 33 to exon 35. The protein predicted to be encoded by this mutant mRNA does not contain the COOH-terminal 109 amino acids of the wild-type enzyme that we have demonstrated contain a strongly functional nuclear localization signal sequence. Consequently, our data explain both the size and the cytoplasmic localization of the H209/VP mutant topo IIalpha. The mutant TOP2A allele in H209/VP cells differs from those in previously characterized cell lines with cytoplasmic topo IIalpha and extends the number of types of resistance-associated deletions in this region to 4. These findings indicate that this region of the TOP2A gene may be a hot spot for mutations.
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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) | 0.001 | 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 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".