Deciphering the oncogenic network of PRC-2 loss guided leukemogenesis

Introduction:

Mutations leading to the loss of PRC2 activity – including -7/-7q deletions – frequently occur in adult AML, MDS, and pediatric ML-DS and JMML. Leukemogenesis is orchestrated by the cooperation of multiple mutations, which we aimed to decipher in the context of PRC2 loss, to gain molecular insights enabling development of novel therapeutic strategies.

Results:

A 96-well based CRISPR-Cas9 in vitro cooperation screening enabled us to efficiently screen for the transforming capacity of 148 different combinations of gRNAs targets in addition to Ezh2.

Amongst the most potent transformative, cooperating events were mutations in epigenetic modifiers (Bcor, Tet2), and growth factor regulators (Cbl, Nf1), whereas Cohesin mutations seemed to be dispensable. Subsequent in vivo leukemogenesis assessment widely reproduced these results. Global gene expression analysis identified an overlapping Ezh2 loss -and cooperation- signature of 178 genes differentially regulated by the three most potent gRNA pools, which may contain valuable therapeutic targets.

Conclusions:

CRISPR-Cas9 cooperation screenings in vivo and in vitro were powerful to probe oncogenic interactions. Both assays unraveled cooperating mutations for the Ezh2-loss and provided valuable cellular resources. Molecularly, potential oncogenic synergies and dependencies were uncovered, which may be exploited for therapeutic approaches in the future.