Lenalidomide Suppresses 5′-Cap-Independent C-MYC Translation in Multiple Myeloma Cells
Notice bibliographique
Résumé
Abstract Abstract 3943 Background: Immunomodulatory drugs (IMiDs) are highly active in the treatment of multiple myeloma (MM). Blockade of the Wnt-GSK3β-beta catenin axis and suppression of eIF4E-C/EBPβ-dependent IRF4 expression were previously shown to mediate some of the IMiDs cytotoxic effects. In particular, cereblon (CRBN), an adaptor protein of the Cul4A-DDB1-ROC1 ubiquitin E3 ligase complex, was recently identified as an essential requirement for IMiDs anti-MM activity. In the present study, we examined how lenalidomide treatment modifies MM cells ubiquitome downstream of the Cul4A-DDB1-CRBN E3 ligase complex with the intent to identify novel molecular targets mediating IMiDs anti-MM effects. Methods and Results: Ubiquitin-proteome pull-down using Tandem Ubiquitin Binding Entity (TUBE, Lifesensors) coupled with quantitative mass-spectroscopy based proteomics (iTRAQ) was performed to identify modification to OPM2 cells ubiquitin-proteome induced by lenalidomide (10 μM for 24 hours) versus vehicle control treatment. Among the differentially modified ubiquitilated targets, histone family members H4, H2A.Z, H2B (known substrates of the Cullin-Ring Ub E3 ligases) and the 40S ribosomal proteins RPS25 and RPS26 were more than 2 fold increased in lenalidomide treated samples. Ribosomal protein RPS25 is required for internal ribosomal entry site (IRES) and 5′-cap-independent proteosynthesis. To examine the function of RPS25 in MM, siRNA-KD experiments were carried out in 2 human MM cell lines (OPM2 and MM1S). RPS25 silencing significantly (30–40%) reduced MM cells viability (MTT assay) when compared to non-targeting siRNA controls. Of interest, MM cells surviving RPS25 silencing were more resistant to IMIDs with approximately 20 to 30% reduction in lenalidomide induced cells death (Annexin V staining and MTT assay). Since, the 5′ UTR of c-myc is known to contain an IRES segement and c-myc translation can therefore be initiated by internal ribosome entry (RPS25 mediated) as well as by cap-dependent mechanisms, we next examined whether lenalidomide may downregulate c-myc through an IRF4-independent and rather RPS25-IRES dependent mechanism. Following 4 hours exposure to lenalidomide, C-MYC protein was significantly downregulated (western blot analysis) in OPM2 and MM1S cells, with no changes to IRF4 (protein or mRNA) or c-myc mRNA (qRT-PCR) at this early time point. No changes were observed in IRF4 until 24–48 hours of treatment with lenalidomide, findings consistent with an IRF4-independent C-MYC downregulation. Using the bicistronic (pRMF) luciferase reporter plasmid in which the upstream cistron encodes a Renilla luciferase translated in a cap-dependent manner, and the downstream cistron encoding a firefly luciferase translated in a cap-independent manner because of c-myc IRES insertion between the two cistrons, we examined whether treatment with lenalidomide modifies c-myc IRES ribosomal entry and translation. Following lenalidomide treatment, MM1S-pRMF transfected cells had a significant reduction in c-myc cap-independent translation as indicated by the reduction in the firely/renilla luminescence ratio. These findings were further supported by the use of the m-TOR inhibitor Rapamycin, an inhibitor of cap-dependent protein translation. Co-treatment of MM1S and OPM2 cells for 4 hours with the combination of Rapamycin (10 nM) and lenalidomide (10 μM) resulted in further reduction in C-MYC protein levels compared to either drugs alone. These results are consistent with an independent and additive (5′-cap-dependent with Rapamycin and independent with lenalidomide) rather than epistatic (both 5′-cap dependent) effects on c-myc translation. Conclusions: Taken together our data indicate that treatment with lenalidomide suppresses c-myc translation in an IRF4/5′-cap-translation independent mechanism (early time point), an effect possibly resulting from a Cul4a-CRBN regulation of RPS25, a key protein-mediating ribosomal entry. Disclosures: Neri: Johnson ans Johnson: Research Funding. Bahlis:Johnson and Johnson: Honoraria, Research Funding; Celgene: Honoraria.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
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 | 0,000 |
| 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 ».