ARNT Mediates Chemotherapy Resistance by Modulating the Response to Oxidative Stress in AML Cells.
Bibliographic record
Abstract
Abstract Abstract 2737 Poster Board II-713 Background Although patients with acute myelogenous leukaemia (AML) typically respond well to initial therapy, with over 75% of patients achieving complete remission, in the great majority the disease ultimately relapses. This is thought to be due to the inherent resistance of leukaemia stem cells to the effects of chemotherapy. While some mechanisms of chemoresistance, e.g. TP53 mutation and upregulation of P-glycoprotein expression, have been well characterized, this phenomenon remains incompletely understood and is a significant barrier to improving patient outcomes. Methods and results The thiazolidindione drug troglitazone (TG) induces apoptosis in AML cells via generation of intracellular reactive oxygen species (ROS), but the degree of sensitivity to TG is highly heterogeneous among AML cell lines. We studied expression of the transcription factor ARNT (aryl hydrocarbon nuclear translocator) in TG-sensitive and TG-resistant AML cell lines following TG treatment. In HL-60 cells, which are highly sensitive to induction of apoptosis by TG, ARNT mRNA levels remained constant following TG treatment and ARNT protein levels markedly decreased, while in U937 cells, which are TG resistant, ARNT mRNA levels increased and ARNT protein levels remained constant. We then tested the effect of exogenous expression of ARNT on the sensitivity of HL-60 cells to TG-induced apoptosis. HL-60 cells transduced with a retrovirus expressing ARNT became TG-resistant. Exogenous expression of ARNT also conferred resistance to induction of apoptosis by hydrogen peroxide, daunorubicin and etoposide. The cellular response to oxidative stress is governed by intracellular signaling pathways and through a transcriptional response through which expression of antioxidant genes is coordinated. HL-60 cells expressing ARNT had striking constitutive activation of AKT signaling, and treatment of these cells with a specific inhibitor of AKT signaling reversed their resistance to TG-induced apoptosis. The activation of AKT signaling by ARNT appears to be mediated by downregulation of expression of PP2A and alpha4, two key negative regulators of AKT phosphorylation. In addition, ARNT-transduced HL-60 cells showed increased expression of Nrf2, a key transcriptional regulator of the antioxidant response, and its target genes SOD2 and CAT. Conclusions The response to oxidative stress is heterogeneous in AML cells lines, and varies with expression of ARNT. ARNT activates expression of Nrf2, which stimulates expression of antioxidant genes resulting in an augmented adaptive response to ROS. Unexpectedly, ARNT also activates AKT signaling by repressing expression of the regulatory phosphatases PP2A and alpha4. These activities of ARNT result in increased resistance to the induction of apoptosis by TG, hydrogen peroxide, and chemotherapy. ARNT may play an important role in chemoresistance in and may be useful as a predictive or prognostic biomarker. Disclosures: No relevant conflicts of interest to declare.
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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 | 0.000 | 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 | 0.001 |
| 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".