High Expression of MDR1 and BCRP1 in Leukemic Stem Cells Correlates with Reversible Drug Resistance Ex Vivo and Predicts Failure of Remission Induction Chemotherapy in Patients with Acute Myeloid Leukemia.
Bibliographic record
Abstract
Abstract Although overexpression of members of the ATP-Binding-Cassette (ABC) transporter superfamily has been implicated in chemotherapy failure in acute myeloid leukemia (AML) in some studies, results have been conflicting. Previously we found no consistent difference in pre-treatment ABC transporter expression when comparing total blasts of 18 patients achieving complete remission (CR) and 13 patients who were refractory to induction chemotherapy (NR). However, among the CD34+CD38− AML cells (enriched for candidate “leukemic stem cells” which engraft in immunodeficient mice), as assessed by quantitative RT-PCR, elevated expression of MDR1 and/or BCRP1, two ABC transporters associated with drug resistance, was found in 8/10 NR patients as compared to 0/7 CR patients. No difference between CR and NR samples was observed in the more differentiated CD34+CD38+ or CD34− AML cells while none of the subpopulations showed a significant difference in MRP1 expression between CR and NR patient samples. To determine if this difference in gene expression was associated with altered functional activity of MDR1/BCRP1, the relative sensitivity of subpopulations of AML cells to induction of apoptosis following ex vivo treatment with daunorubicin with or without ABC inhibitors (PSC-833 and Verapamil) was assessed. All subpopulations of AML cells isolated from 2 CR patients showed similar drug sensitivity profiles (IC50 <0.04 μg/ml). In contrast, CD34+CD38− cells from 6 NR patients were more resistant to daunorubicin-induced apoptosis (p<0.05 for comparison of IC50s between CR and NR samples). ABC transporter inhibition in CD34+CD38− cells did not change daunorubicin sensitivity in CR samples, but increased drug sensitivity in a dose-dependent manner in NR samples, particularly in the CD34+CD38− fraction. This suggests a role for ABC transporters in sustaining a population of chemotherapy resistant leukemic stem cells which may allow survival of the malignant clone in patients following induction therapy. If the value of measuring MDR1/BCRP1 expression among these cells in predicting chemotherapy outcome is confirmed in a larger patient population, it may be possible to use such analysis to modify therapy for individual AML patients to overcome drug resistance.
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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 | 0.001 |
| 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".