Triptolide and its prodrug Minnelide target high-risk MYC-amplified medulloblastoma in preclinical models
Jezabel Rodriguez-Blanco, … , Nagi G. Ayad, David J. Robbins
Jezabel Rodriguez-Blanco, … , Nagi G. Ayad, David J. Robbins
Published June 17, 2024
Citation Information: J Clin Invest. 2024;134(15):e171136. https://doi.org/10.1172/JCI171136.
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Research Article Oncology

Triptolide and its prodrug Minnelide target high-risk MYC-amplified medulloblastoma in preclinical models

Abstract

Most children with medulloblastoma (MB) achieve remission, but some face very aggressive metastatic tumors. Their dismal outcome highlights the critical need to advance therapeutic approaches that benefit such high-risk patients. Minnelide, a clinically relevant analog of the natural product triptolide, has oncostatic activity in both preclinical and early clinical settings. Despite its efficacy and tolerable toxicity, this compound has not been evaluated in MB. Utilizing a bioinformatic data set that integrates cellular drug response data with gene expression, we predicted that Group 3 (G3) MB, which has a poor 5-year survival, would be sensitive to triptolide/Minnelide. We subsequently showed that both triptolide and Minnelide attenuate the viability of G3 MB cells ex vivo. Transcriptomic analyses identified MYC signaling, a pathologically relevant driver of G3 MB, as a downstream target of this class of drugs. We validated this MYC dependency in G3 MB cells and showed that triptolide exerts its efficacy by reducing both MYC transcription and MYC protein stability. Importantly, Minnelide acted on MYC to reduce tumor growth and leptomeningeal spread, which resulted in improved survival of G3 MB animal models. Moreover, Minnelide improved the efficacy of adjuvant chemotherapy, further highlighting its potential for the treatment of MYC-driven G3 MB.

Authors

Jezabel Rodriguez-Blanco, April D. Salvador, Robert K. Suter, Marzena Swiderska-Syn, Isabel Palomo-Caturla, Valentin Kliebe, Pritika Shahani, Kendell Peterson, Maria Turos-Cabal, Megan E. Vieira, Daniel T. Wynn, Ashley J. Howell, Fan Yang, Yuguang Ban, Heather J. McCrea, Frederique Zindy, Etienne Danis, Rajeev Vibhakar, Anna Jermakowicz, Vanesa Martin, Christopher C. Coss, Brent T. Harris, Aguirre de Cubas, X. Steven Chen, Thibaut Barnoud, Martine F. Roussel, Nagi G. Ayad, David J. Robbins

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Figure 8

Minnelide shows translational potential.

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Minnelide shows translational potential. (A) RCMB28 PDOX cells were impl...
(A) RCMB28 PDOX cells were implanted into mice 3 weeks before vehicle or Minnelide (0.4 mg/kg, i.p., daily) dosing. Five days later, tumor areas in their brains were measured (vehicle n = 4, Minnelide n = 5). (B) Numbers of Ki67- and C-Casp3–positive cells in brains from similarly treated mice were quantified by IHC analyses (vehicle n = 4, Minnelide n = 5). (C) Metastatic lesions of mice harboring RCMB28-derived tumors and similarly dosed were measured (vehicle n = 4, Minnelide n = 5). (D) RCMB28 were orthotopically implanted 3 days before starting similar vehicle or Minnelide dosing. Symptom-free survival was determined and analyzed using log-rank (Mantel-Cox) tests (n = 10). (E) mG3-2929 cultures were exposed to triptolide alone or in combination with indicated compounds. Cell viability was determined by MTT reduction, and SynergyFinder was used to generate 3D surface plots and obtain synergy scores (cisplatin n = 4, lomustine n = 3, cyclophosphamide n = 5). An HSA score of greater than 10 indicates synergy. (F) Mice were implanted with mG3-2929 cells 8 days before daily dosing with cyclophosphamide (65 mg/kg, i.p.), alone or with Minnelide (0.4 mg/kg, i.p.). Tumor burden was determined by IVIS imaging 8 days later (vehicle/Minnelide n = 5, cyclophosphamide/combination n = 4), and analyzed using 1-way ANOVA followed by Newman-Keuls post hoc test. (G) mG3-2929 were allowed to form tumors for 8 days before starting similar dosing. Symptom-free survival data were analyzed using a log-rank (Mantel-Cox) test (vehicle/cyclophosphamide/combination n = 9, Minnelide n = 10). All tumor area measurements were performed in ×2.5-magnified H&E-stained slides. All images are representative. Arrows indicate tumor presence. All tissues were harvested 6 hours after the last injection. Results are presented as mean ± SEM of data normalized to 1 vehicle-treated animal. Scale bars: 400 μm (A and C) and 50 μm (B). Statistical significance was assessed using unpaired, 1-tailed Student’s t test. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001.