Differentiation of NUT Midline Carcinoma in Humans and Mice by Epigenomic Reprogramming.
Brian Schwartz, Matthias Hofer, Madeleine Lemieux, Daniel Bauer, Michael Cameron, Nathan West, Elin Agoston, Tan Ince, Katherine Janeway, Sara Vargas, Antonio Perez-Atayde, Jon Aster, Stephen Sallan, Andrew Kung, James Bradner, Christopher French. Brigham and Women's Hospital, Boston, MA; Dana-Farber Cancer Institute, Boston, MA; Children's Hospital, Boston, MA
Background: NUT midline carcinoma (NMC) is a lethal tumor defined by the presence of BRD-NUT fusion proteins that act by arresting differentiation. Here, we explore the mechanisms underlying the ability of BRD4-NUT to prevent squamous differentiation.
Design: In vitro studies were conducted with five NMC cell lines, 797, per403, 690, 143, and 10326, and primary cells derived from the index patient. In vivo studies were conducted with three NMC cell lines, 797, per403, and patient-derived cells. Knockdown of BRD-NUT was used as a positive control.
Results: We find that overexpression of the twin bromodomains of BRD4 or a portion of NUT that binds the histone acetyltransferase (HAT) p300 induces NMC cells to differentiate, suggesting a model in which BRD4-NUT sequesters HATs in areas of acetylated chromatin. Consistent with this idea, knockdown of BRD4-NUT caused global increases in histone acetylation, whereas enforced expression of BRD4-NUT had the opposite effect. Sequestration of HATs appears to occur in nuclear BRD4-NUT foci, which correspond to specific genomic regions that are rich in acetylated histones but transcriptionally inactive. Of therapeutic interest, treatment of NMC cells with histone deacetylase inhibitors (HDACi) dispersed nuclear foci, restored histone acetylation, induced NMC cells to differentiate in vitro, and had anti-tumor effects in NMC xenograft models. Based on these data, a child with NMC was treated with the FDA-approved HDAC inhibitor vorinostat. An objective response was obtained after five weeks of therapy, suggesting that this rational therapeutic approach merits further evaluation in patients with NMC.
Conclusions: In summary, we describe: 1) the rationale for targeted use of HDAC inhibitors in NMC; 2) the utility of a pharmacodynamic drug response (acetylation) as a mechanism of oncoprotein redistribution; and 3) the first example (to our knowledge) of true differentiation therapy since the seminal studies of retinoic acid in the treatment of acute promyelocytic leukemia.
Wednesday, March 2, 2011 9:30 AM
Poster Session V # 257, Wednesday Morning