Small-Molecule XIAP Inhibitors Derepress Downstream Effector Caspases and Induce Apoptosis of Leukemia Cell Lines and Patient Samples.
Notice bibliographique
Résumé
Abstract XIAP is a potent inhibitor of caspases 3, 7, and 9 and its over-expression renders malignant cells resistant to chemotherapy. Through an enzymatic derepression assay, we identified chemical XIAP antagonists, including 1396-12, based on a polyphenylurea pharmacophore (Cancer Cell, 1:25–35;2004). This compound binds and inhibits the caspase 3/7 inhibitory BIR2 domain of XIAP. Given the potential therapeutic utility of IAP inhibitors, we tested this XIAP antagonist in leukemia cell lines and primary patient samples. The XIAP antagonist 1396-12, but not the structurally related control compound, directly induced apoptosis in leukemia cell lines at low micromolar concentrations and sensitized leukemia cells to cytarabine. 1396-12 activated downstream caspases 3/7 prior to the activation of upstream caspases 8 and 9, and independent of Bcl-2 or caspase-8, consistent with the inhibition of the BIR2 domain of XIAP. To evaluate this XIAP antagonist as a potential novel therapy for acute myeloid leukemia (AML), primary AML blasts (n= 27), normal bone marrow mononuclear cells (n =1), or normal mobilized peripheral blood stem cells (PBSC) (n =6) were treated with increasing concentrations of 1396-12. Apoptosis was measured 24 hours after treatment by Annexin V staining. Median LD50 among the AML patient samples tested was 6 μM (range: 2μM to >40μM). The XIAP antagonist 1396-12 induced apoptosis of primary AML samples with a LD50 ≥ 10μM in 16 of 27 (60%) samples and with a LD50 >40μM in 7 of 27 (26%) samples. In contrast, 1396-12 was less toxic to the normal PBSC or marrow with a LD50>40μM in all normal samples tested. As a comparison, the inactive control compound was not toxic to any of the AML or normal samples at concentrations up to 40μM. In addition to the short-term cytotoxicity assays, the effects of 1396-12 on AML and normal samples were evaluated in colony formation assays. The XIAP antagonist inhibited clonogenic survival in 4 AML samples tested with a mean LD50 of 4 ± 0.8μM. Treatment with 1396-12 also reduced colony formation by 2 normal PBSC samples with LD50’s of 8.5 ± 0.3μM and 5.6 ± 0.4μM. In the normal PBSC samples, both BFU-E and CFU-GM lineages were equally reduced after treatment with the XIAP antagonist. Treatment with the control compound did not reduce colony growth in the AML or normal samples. Among the primary AML samples, response to the XIAP inhibitors correlated with XIAP protein levels. Low to absent levels of XIAP were associated with a higher probability of resistance to treatment with XIAP inhibitors (p =0.04, by logistic regression analysis). In conclusion, polyphenylurea-based XIAP antagonists directly induce apoptosis in leukemia cells and patient samples at low micromolar concentrations through a mechanism of action distinct from conventional chemotherapeutic agents. These antagonists can be used as biological tools to understand the role of IAPs in normal and malignant hematopoietic cells. They may also serve as lead compounds for the development of useful therapies for the treatment of leukemia and other malignancies, but their potential hematologic toxicity will have to be carefully evaluated in phase I clinical trials.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 0,001 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».