Sphingosine Kinases in B-lineage Acute Lymphoblastic Leukaemia

Abstract

The work presented in this thesis examines firstly, the effects of the sphingosine like immunomodulatory drug FTY720 on B-lineage acute lymphoblastic leukaemia (ALL) cells. Secondly, the research focuses on a related area, namely, the intra-cellular enzymes called sphingosine kinases (SphKs). FTY720 resulted in cytotoxic effects and the induction of autophagy, in vitro in ALL cells. However, disparate in vivo effects were seen in Ph+ and Ph- ALL with a reduction in disease burden seen only in the former, highlighting the importance of pharmacological testing in both in vitro and in vivo settings. Sphingosine kinase 1 (SphK1) and sphingosine kinase 2 (SphK2) are over-expressed in ALL with inhibition producing cytotoxic effects, autophagy and predominantly caspase-independent cell death. SphK1 and SphK2 gene deletion resulted in reduced leukaemia penetrance in a murine Ph+ ALL disease model and SphK2 inhibition reduced the growth of human ALL xenografts. SphK2 inhibition resulted in lower MYC gene and protein expression through reduced association of acetylated histone H3 with the MYC promoter. This establishes a completely novel insight into the interactions of SphK2 in ALL and signifies the importance of sphingolipid signalling in this aggressive malignancy