Poster Presentation 35th Lorne Cancer Conference 2023

Genome wide in vivo CRISPR activation screen identifies oncogenes that cooperate with TRP53 deficiency to drive blood cancer (#303)

Margaret A Potts 1 2 , Yexuan Deng 2 , Andrew J Kueh 1 2 , Geraldine Healey 2 , Andreas Strasser 1 2 , Marco J Herold 1 2
  1. Department of Medical Biology, University of Melbourne, Melbourne, Victoria, Australia
  2. Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia

To develop new and improved therapeutics for cancer, we must identify cancer driving genes and understand functionally how they promote tumorigenesis. Deep sequencing analysis of human tumours have identified several tumour driving genes but also suggest that many more exist.

 

The tumour suppressor TP53, which is mutated in 50% of human cancers, regulates several cellular processes including DNA repair, apoptosis, cell cycle arrest and senescence. We aimed to identify oncogenes that cooperate with TRP53 deficiency to drive blood cancer development and skew the cancer development towards a certain haematopoietic lineage.

 

We performed a functional CRISPR activation screen in the haematopoietic compartment employing primary foetal liver derived CRISPR activation enabled Trp53 knockout (dCas9aKI/+/Trp53-/-) haematopoietic stem and progenitor cells (HSPCs). These HSPCs were transduced with a genome-wide sgRNA library and injected into lethally irradiated wildtype recipient mice whereby we proposed that activation of an oncogene that cooperates with Trp53 deficiency would accelerate tumorigenesis. 

 

Library recipient mice developed cancer at a seemingly accelerated rate (median survival 105 days) compared to recipient mice transplanted with non-targeting sgRNA transduced HSPCs (median survival 203 days). Thymic T cell lymphoma accounts for ~70% of the tumour spectrum in mice where TRP53 is deleted in the haematopoietic compartment. Interestingly, only 8% of library recipient mice that developed cancer prior to 100 days post reconstitution developed thymic T cell lymphoma versus 56% of library recipient mice that developed cancer post 100 days. This suggests CRISPR activated target genes that strongly accelerated TRP53 deficient malignancy created a bias away from T lymphoid cancers towards B lymphoid or myeloid cancers. Deep sequence analysis of accelerated tumours revealed enrichment of sgRNAs targeting genes, of which some were previously implicated in acute myeloid leukemia (e.g. Fli1 and Cbfb).

 

This study identifies oncogenes that accelerate TRP53 deficient driven blood cancers. Additionally, it provides insights into oncogenes that might skew cancer development towards a particular blood lineage.