Dual inhibition of DNMTs and EZH2 can overcome both intrinsic and acquired resistance of myeloma cells to IMiDs in a Cereblon-independent manner

Konstantinos Dimopoulos, Alexandra Søgaard Helbo, Helga Fibiger Munch-Petersen, Lene Sjö, Jesper Christensen, Lasse Sommer Kristensen, Fazila Asmar, Emil Hermansen, Casey O'Connel, Peter Gimsing, Gangning Liang, Kirsten Grønbaek

66 Citations (Scopus)

Abstract

Thalidomide and its derivatives, lenalidomide and pomalidomide (also known as IMiDs), have significantly changed the treatment landscape of multiple myeloma, and the recent discovery of cereblon (CRBN) as their direct biological target has led to a deeper understanding of their complex mechanism of action. In an effort to comprehend the precise mechanisms behind the development of IMiD resistance and examine whether it is potentially reversible, we established lenalidomide- (-LR) and pomalidomide-resistant (-PR) human myeloma cell lines from two IMiD-sensitive cell lines, OPM2 and NCI-H929, by continuous culture in the presence of lenalidomide or pomalidomide for 4-6 months, until acquirement of stable resistance. By assessing genome-wide DNA methylation and chromatin accessibility in these cell lines, we found that acquired IMiD-resistance is associated with an increase of genome-wide DNA methylation and an even greater reduction of chromatin accessibility. Transcriptome analysis confirmed that resistant cell lines are mainly characterized by a reduction in gene expression, identifying SMAD3 as a commonly downregulated gene in IMiD-resistant cell lines. Moreover, we show that these changes are potentially reversible, since combination of 5-Azacytidine and EPZ-6438 not only restored the observed accessibility changes and the expression of SMAD3, but also resensitized the resistant cells to both lenalidomide and pomalidomide. Interestingly, the resensitization process was independent of CRBN. Our data suggest that simultaneous inhibition of DNA methyl-transferases (DNMTs) and EZH2 leads to an extensive epigenetic reprogramming which allows myeloma cells to (re)gain sensitivity to IMiDs.

Original languageEnglish
JournalMolecular Oncology
Volume12
Issue number2
Pages (from-to)180-195
ISSN1574-7891
DOIs
Publication statusPublished - 2017

Keywords

  • Journal Article

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