Award Title: Targeting RNA metabolism to expand haematopoietic stem cells and eredicate acute myeloid leukaemia
Funder: Cancer Research UK

Abstract: Background
Lifelong haematopoiesis critically depends on haematopoietic stem cells (HSCs) which possess unique self-renewal capacity and multilineage differentiation potential. Due to these properties, allogeneic HSC transplantation, in which HSCs are sourced from adult donors or cord blood (CB), offers optimal treatment for many diseases, including blood malignancies. Given the shortage of suitable donors and low HSC yield from CB, it is essential to efficiently expand HSCs for widespread applications.

 In acute myeloid leukaemia (AML), HSCs/progenitors acquire mutations disrupting the balance between self-renewal and differentiation, often resulting in the formation of treatment-resistant leukaemic stem cells (LSCs), which initiate and propagate leukaemia. Since current therapies often fail to eradicate LSCs, the surviving LSCs cause severe disease relapses. It is therefore essential to identify efficient means of LSC elimination.

 Aims
We investigated methylation- and uridylation-dependent regulation of RNA metabolism, whose role in haematopoiesis remains unknown. N6-methyladenosine methylation (m6A) and 3’-uridylation are widespread RNA modifications which control transcript degradation. We found that conditional deletion of YTHDF2, an m6A reader which recognises m6A-modified transcripts and accelerates their degradation, or inactivation of terminal uridylyl transferases (TUT4/7) which catalyse RNA 3’-uridylation thus promoting its decay, results in HSC expansion. We discovered that YTHDF2 is highly expressed in AML and is essential for disease initiation. We intend to address the hypothesis that m6A- and 3’-uridylation-dependent regulation of RNA metabolism orchestrates normal and leukaemic/cancer stem cell functions, and target these pathways to expand HSCs and eliminate LSCs.

Methods
Firstly, using genetic and functional approaches in mouse and human HSCs we will identify the key features of HSCs which are dependent on YTHDF2 and TUT4/7, and establish the therapeutic potential of their inactivation in expanding HSCs. Secondly, we will systematically dissect the requirement for YTHDF2 and TUT4/7 at distinct stages of leukaemogenesis in clinically-relevant mouse AML models and validate them as therapeutic targets in diverse AML subtypes with distinct prognoses. Finally, we will employ state-of-the-art molecular approaches to identify mechanisms through which YTHDF2 and TUT4/7 function and dissect their impact on HSC biology and AML leukaemogenesis.

 How the results will be used
This research programme will establish the therapeutic potential of inactivating YTHDF2, TUT4/7 or their downstream pathways in expanding clinically-relevant HSCs and targeting LSCs in different AML subtypes. We will next launch drug discovery programmes and subsequent clinical trials for HSC expansion and AML therapies. Finally, these investigations will reach beyond haematopoiesis and inform novel therapies for other cancers.


Research Activity Codes: 2.1 BIOLOGICAL AND ENDOGENOUS FACTORS;5.1 PHARMACEUTICALS
Health Categories: CANCER AND NEOPLASMS;BLOOD