AML Cells Have Increased Mitochondrial Mass but Less Reserve in Their Respiratory Chain Complexes Leading to Heightened Sensitivity to Inhibition of Mitochondrial Protein Translation,
Notice bibliographique
Résumé
Abstract Abstract 3585 Recent studies suggest that dysregulated mitochondrial oxygen consumption promotes the growth of AML cells. Therefore, we characterized the structure and metabolic function of the mitochondria in AML and normal G-CSF-mobilized hematopoietic mononuclear cells (PBSCs). Compared to PBSCs, 1o AML cells had increased mitochondrial mass as demonstrated by an increased mitochondrial DNA copy number and increased activity of matrix enzyme citrate synthase. The increased mitochondrial mass observed in 1o AML cells may represent larger mitochondria and/or more numerous mitochondria. Therefore, we evaluated the mitochondria of 1o AML and normal CD34+ hematopoietic cells by electron microscopy. The mitochondria in 1o AML cells were larger in area, but fewer in number compared to normal CD34+ cells. Mitochondria contain the respiratory chain complexes that promote oxidative phosphorylation. Given the dysregulated mitochondrial biogenesis in 1o AML cells, we examined the levels and capacity of the respiratory complexes in 1o AML and normal PBSCs. When normalized for mitochondrial mass, 1o AML cells (n = 12) had reduced activity of respiratory complexes III and IV compared to PBSCs (n = 10) (Mean complex III activity AML vs PBSC: 0.32 ± 0.04 RU vs 0.66 ± 0.11 RU p = 0.0063; Mean complex IV activity AML vs PBSC: 0.13 ± 0.01 RU vs 0.24 ± 0.02 RU, p= 0.0003). We evaluated the capacity of the respiratory complexes in AML cells and PBSCs by treating with increasing concentrations of the complex III inhibitor antimycin, and measuring the changes in oxygen consumption. AML cells displayed heightened sensitivity to the complex III inhibitor and less reserve capacity in the respiratory complex compared to PBSCs (mean concentration of antimycin required to reduce oxygen consumption by 50%: AML (n = 11) vs PBSC (n = 3): 13.7 ± 1.6 nM vs 29.0 ± 2.4 nM; p = 0.0007). AML cell lines were similar to 1o AML cells with decreased basal respiratory complex activity and reserve capacity compared to PBSCs. Given the reduced levels and reserve in the respiratory chain complexes in AML cells, we evaluated the effects of inhibiting mitochondrial protein translation in AML cells and PBSCs. Chemical (tigecycline, and chloramphenicol) and genetic (RNAi knockdown of the EF-Tu) inhibition of mitochondrial translation reduced the levels and function of the respiratory complexes that contain proteins encoded by mitochondrial DNA. Consistent with the reduced reserve capacity, inhibiting mitochondrial translation preferentially reduced oxygen consumption and viability of 1o AML cells and AML cell lines over PBSCs and normal CD34+ cells. To understand the molecular basis for the abnormal mitochondrial biogenesis in 1o AML cells, we measured levels of the NRF-1, TFAM and EF-Tu, genes known to positively regulate mitochondrial biogenesis. Compared to PBSCs, AML samples showed at least a 3-fold increase in mRNA expression of these genes. Myc is a positive regulator of NRF-1, TFAM and EF-Tu. Therefore, we measured levels of myc in 1o AML cells and PBSCs by Q-RT-PCR. Compared to PBSCs, myc was increased in 1o AML cells and positively correlated with expression of NRF-1, TFAM and EF-Tu as well as with mitochondrial mass. To determine whether increased myc expression is functionally related to the increased mitochondrial biogenesis and decreased reserve in respiratory capacity, we employed P493 Burkitt's cells with inducible myc knockdown. P493 cells expressing myc had increased mitochondrial mass, larger mitochondria, and increased basal oxygen consumption compared to the myc knockdown cells. When normalized for mitochondrial mass, myc expressing cells had reduced activity of respiratory complexes III and IV compared to myc knockdown cells. In addition, myc expressing cells had less reserve in respiratory complex III (concentration of antimycin required to reduce oxygen consumption by 50% –+ myc P493 vs –myc P493: 6.580 ± 0.393 nM vs 12.87 ± 1.97 nM p =0.0352). Thus, compared to normal hematopoietic cells, AML cells have greater mitochondrial mass but reduced reserve in their respiratory complexes. As a result of this decreased reserve, AML cells have a heightened sensitivity to inhibition of mitochondrial translation which reduces respiratory chain complex levels and activity. Genetically, the abnormal mitochondrial structure and function appears related to dysregulated myc and its influence on genes promoting increased mitochondrial biogenesis. Disclosures: No relevant conflicts of interest to declare.
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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 | 0,001 | 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 | 0,000 |
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 ».