A novel CRISPR activation mouse enables modelling of aggressive lymphoma and interrogation of venetoclax resistance.

Abstract

CRISPR technologies have advanced cancer modelling in mice, but CRISPR activation (CRISPRa) methods have not been thoroughly exploited in this context. Here we establish a CRISPRa mouse (dCas9a-SAMKI/+) for inducing gene expression in vivo and in vitro. Using dCas9a-SAMKI/KI primary lymphocytes, we induced B cell restricted genes in the T cell lineage and vice versa, demonstrating the power of this system. Next, to model double hit lymphoma (DHL), we transactivated pro-survival BCL-2 in Eµ-MycT/+;dCas9a-SAMKI/+ haematopoietic stem and progenitor cells. Lethally-irradiated mice transplanted with these cells rapidly developed lymphomas expressing high BCL-2. Unlike standard Eµ-Myc lymphomas, BCL-2-expressing lymphomas were highly sensitive to the BCL-2 inhibitor venetoclax. Finally, we performed genome-wide activation screens in these lymphoma cells and found a dominant role for the BCL-2 family protein A1 in venetoclax resistance. This demonstrates the power of our CRISPRa model for mimicking disease and provides insights into potential resistance mechanisms towards targeted therapies.

Last but not least: BFL-1 as an emerging target for anti-cancer therapies

“…When cyclin-dependent kinase 9 (CDK9) inhibitors were applied to down-regulate both BFL-1 and MCL-1, an induction of apoptosis in BH3-mimetic–resistant lymphoma cells was observed, and regression of BFL-1 + DLBCL was achieved in patient-derived xenograft (PDX) models [ 56 ]. Recently, unbiased genome wide CRISPR activation screens revealed a dominant role for A1 in venetoclax resistance in a novel model of aggressive lymphoma [ 57 ]. Furthermore, high BFL-1 levels were reported in ALCL cell lines which are resistant to MCL-1 or BCL-XL inhibitors, and siRNA knockdown of BCL2A1 induced apoptosis in drug resistant cells [ 58 ].…”