HEMOGENIC ENDOTHELIUM – THE MISSING LINK BETWEEN ANTI-ANGIOGENICS AND THEIR EFFECTIVENESS IN LEUKAEMIA — The Association Specialists
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  3. HEMOGENIC ENDOTHELIUM – THE MISSING LINK BETWEEN ANTI-ANGIOGENICS AND THEIR EFFECTIVENESS IN LEUKAEMIA

HEMOGENIC ENDOTHELIUM – THE MISSING LINK BETWEEN ANTI-ANGIOGENICS AND THEIR EFFECTIVENESS IN LEUKAEMIA (284)

Indhu Subramanian 1 2 , Emily S Fuller 1 , Katie Powell 2 , Rolfe Howlett 3 , Anthony W Ashton 2 , Viive M Howell 1
  1. Bill Walsh Translational Cancer Research Laboratory, Kolling Institute of Medical Research, St Leonards, NSW, Australia
  2. Perinatal Research Laboratory, Kolling Institute of Medical Research, St Leonards, NSW, Australia
  3. Department of Pathology, University of New South Wales, Kensington, NSW, Australia

Background

The most pronounced micro-environmental changes observed in the bone marrow of leukaemia patients are endothelial proliferation and angiogenesis. How blood vessels sustain/initiate leukaemia is unknown; however, this may explain why anti-angiogenic agents are effective treatments for leukaemia.

Aim

To define whether perturbation of the endothelium initiates/perpetuates leukaemia and determine the genes responsible.

Methods

Sleeping Beauty (SB) is a mutagenesis system that randomly integrates transposons into genomic DNA. Endothelial-specific SB activation was achieved by driving CRE-recombinase expression via Tie-2 promoter/enhancer. Tissues were analysed for histology, immune profiles and genes with insertional mutations.

Results

Over 50 weeks all CRE+ mice (n=106), but none of the WT mice (n=35), became moribund and were sacrificed. At necropsy >70% of CRE+ mice displayed peripheral leukocytosis and gross anatomical/histological modifications in spleens, livers and thymus. Molecular analyses showed amplifications of either T cell  (CD3; 49%) or macrophage (CD14; 28%) populations or both (23%) in the spleen and bone marrow of CRE+ mice. These leukocytes were SB positive indicating they originated from endothelial cells, and not haematopoietic stem cells, which was confirmed using in vitro assays. Deep sequencing identified genes related to cytokine mediated signalling and transcriptional control (including Notch1, Erg, Flt3, and Pard3b). Many of the identified genes are already implicated in human disease.  This not only validates our model but also has provided additional, previously unrecognised genes that contribute significantly to the development of leukaemia and may offer new therapeutic targets to treat disease.

Conclusions

Targeting SB insertional mutagenesis to the endothelium resulted in haematological malignancy in mice indicating direct impact of endothelial cells over both myeloid and lymphoid differentiation.  These data, for the first time, provide clear evidence for the endothelium in the regulation of post-natal haematopoiesis and provide a rationale for the use of anti-angiogenic therapy in the treatment of leukaemia.