Neuronal differentiation and cell-cycle programs mediate response to BET-bromodomain inhibition in MYC-driven medulloblastoma

June 3, 2019

rimental details: Cell lines were seeded into 384-well, white-walled, clear bottom plates at a density of 500 cells/well. Twenty-four hours after seeding, combination drugs were administered using an HP D300 Digital Dispenser in matrix format. Drug was administered such that the final volume of DMSO did not exceed 0.5%. The cells were then incubated for seven days and cell luminescence was measure

BET-bromodomain inhibition (BETi) has shown pre-clinical promise for MYC-amplified medulloblastoma. However, the mechanisms for its action, and ultimately for resistance, have not been fully defined. Here, using a combination of expression profiling, genome-scale CRISPR/Cas9-mediated loss of function and ORF/cDNA driven rescue screens, and cell-based models of spontaneous resistance, we identify bHLH/homeobox transcription factors and cell-cycle regulators as key genes mediating BETi's response and resistance. Cells that acquire drug tolerance exhibit a more neuronally differentiated cell-state and expression of lineage-specific bHLH/homeobox transcription factors. However, they do not terminally differentiate, maintain expression of CCND2, and continue to cycle through S-phase. Moreover, CDK4/CDK6 inhibition delays acquisition of resistance. Therefore, our data provide insights about the mechanisms underlying BETi effects and the appearance of resistance and support the therapeutic use of combined cell-cycle inhibitors with BETi in MYC-amplified medulloblastoma.

Bandopadhayay, P; Piccioni, F; O'Rourke, R; Ho, P; Gonzalez, EM; Buchan, G; Qian, K; Gionet, G; Girard, E; Coxon, M; Rees, MG; Brenan, L; Dubois, F; Shapira, O; Greenwald, NF; Pages, M; Balboni Iniguez, A; Paolella, BR; Meng, A; Sinai, C; Roti, G; Dharia, NV; Creech, A; Tanenbaum, B; Khadka, P; Tracy, A; Tiv, HL; Hong, AL; Coy, S; Rashid, R; Lin, JR; Cowley, GS; Lam, FC; Goodale, A; Lee, Y; Schoolcraft, K; Vazquez, F; Hahn, WC; Tsherniak, A; Bradner, JE; Yaffe, MB; Milde, T; Pfister, SM; Qi, J; Schenone, M; Carr, SA; Ligon, KL; Kieran, MW; Santagata, S; Olson, JM; Gokhale, PC; Jaffe, JD; Root, DE; Stegmaier, K; Johannessen, CM; Beroukhim, R;

Journal: Nat Commun Pages: 2400

Original article (31160565)