Myeloproliferative neoplasms, JAK/STAT signalling and stem cell subversion
The JAK/STAT pathway has essential roles in several aspects of metazoan biology including haematopoiesis and stem cell function. JAK/STAT signalling is essential for maintenance of several Drosophila stem cell populations and influences the behaviour of mammalian ES cells and adult stem cells (e.g. haematopoietic stem cells (HSCs) and neural stem cells). Somatic mutations affecting this pathway occur in multiple tumour types and are especially common in human myeloproliferative neoplasms (MPNs). The Green lab is integrating multiple approaches (genomics, patient samples, mouse models, stem/progenitor cell biology, signalling and transcriptional programmes) to study the mechanisms whereby aberrant JAK/STAT signalling subverts haematopoiesis and results in a myeloproliferative neoplasm.
Human myeloproliferative neoplasms arise from the HSC compartment and are associated with overproduction of specific lineages. Their study is providing powerful insights into the earliest stages of tumorigenesis and has broad relevance for cancer and stem cell biology. The BCR-ABL negative MPNs represent a spectrum of clonal disorders, with three main members: polycythaemia vera (PV), essential thrombocythaemia (ET) and primary myelofibrosis (PMF). In 2005 several groups, including our own, reported that the majority of patients harbor a single acquired gain-of-function mutation in JAK2, and mouse models have subsequently demonstrated that JAK2 is sufficient to give rise to an MPN.
The discovery of the JAK2 mutation has revolutionized research into the MPNs and has allowed us to provide multiple insights into the molecular and cellular mechanisms by which JAK2 mutations subvert haematopoiesis and result in the various clinical phenotypes associated with human MPNs. These studies have had direct clinical impact with new approaches to classification and diagnosis already embedded in international guidelines. Moreover dissection of the molecular consequences of JAK2 mutations has also provided unexpected insights into fundamental biological mechanisms, including chromatin biology, cytokine signalling and cellular responses to DNA damage.
A major question for the MPN field has been the cause of JAK2 mutation-negative MPNs. We have recently identified unusual mutations in CALR (an ER chaperone) in most JAK2 mutation-negative patients (Nangalia et al. NEJM 2013). CALR mutations all give rise to a novel C-terminus and occur in the HSC compartment early in disease evolution. Our data reveal a novel biological pathway as a target for tumorigenic mutations, will greatly simplify patient diagnosis and open up the possibility of tumour-specific therapy.
Selected recent highlights from the Green lab include:
- Discovery of JAK2 exon12 mutations which revealed a clinically distinct subtype of PV (Scott et al. NEJM 2007).
- Demonstration that JAK2 mutation promotes survival of DNA-damaged cells by inhibiting the BCL-xL deamidation pathway (Zhao et al. NEJM 2008).
- Unexpected nuclear role for JAK2 as a histone kinase which regulates transcription of target genes and can drive factor-independent ES cell self-renewal (Dawson et al. Nature 2009; Griffiths et al. Nature Cell Biol. 2011).
- Demonstration that JAK2 V617F mutation inhibits the function of single haematopoietic stem cells (Li et al. Blood 2010; Kent et al. PLoS Biol. 2013).
- Finding that development of PV but not ET is associated with an unexpected defect in STAT1 signalling (Chen et al. Cancer Cell 2010).
- Description of a novel pathogenetic consequence of acquired chromosome deletion — cooperative inactivation of imprinted genes (Aziz et al. J. Clin. Invest. 2013).
- Description of the genomic landscape of the MPNs and discovery of CALR mutations in most JAK2-unmutated MPN patients (Nangalia et al. NEJM 2013).
MPN resources in Cambridge
Over the past decade, we have established a powerful combination of clinical resources and research expertise. Tony Green is Chief Investigator for the PT-1 suite of clinical studies (>1200 patients; largest randomized study of any MPN; has been running since 1997; unique prospective dataset and samples), and directs a specialist MPN clinic. The ability to study fresh samples from well characterized patients greatly facilitates much of our research. Cambridge also houses the UK MPN sample bank. Importantly, the interaction with the clinical service is two-way: assays for JAK2V617F, JAK2 exon 12 and MPL mutations have all been transferred to our Regional Diagnostic Service and are already in routine use.
Haematopoiesis in Cambridge
The Green lab is based solely at CIMR but Professor Green is also a member of the Cambridge Stem Cell Institute.
The Green lab is part of a consortium of Cambridge University groups, largely in the CIMR and adjacent buildings, that share a focus on normal and/or leukaemic haematopoiesis. Current programmes include transcriptional networks of haematopoietic stem cells (Bertie Göttgens), leukaemic stem cells (Brian Huntly), ribosome biology and bone marrow failure syndromes (Alan Warren, LMB), zebrafish haematopoiesis (Ana Cvejc), megakaryocyte and platelet biology (Willem Ouwehand and Cedric Ghevaert) and the pathogenesis of the myeloproliferative neoplasms (Tony Green). In addition, the Green lab has close interactions with: the Wellcome Trust Sanger Institute (e.g. Peter Campbell, George Vassiliou, David Adams, Pentao Liu); the Wellcome Trust/MRC Stem Cell Institute (e.g. Ben Simons, Brian Hendrich); the Cambridge epigenetics community (e.g. Anne Ferguson-Smith, Wolf Reik); and the Addenbrooke’s Department of Haematology (e.g. regional haemato-oncology diagnostic service and clinical haemato-oncology service).
Potential post-docs, clinical fellows and students:
We are always keen to hear from good people. Please e-mail me (firstname.lastname@example.org) with a copy of your CV including the details of two referees.
Nangalia, J., Massie, C. E., Baxter, E. J,. Nice, F. L., Gunes, G., Wedge, D. C. ……. Papaemmanuil, E., Campbell, P. J. and Green, A. R. Somatic CALR mutations in myeloproliferative neoplasasms with nonmutated JAK2. N. Engl. J. Med. 369, 2391–2405 (2013).
Aziz, A.*, Baxter, E. J.*, Edwards, C., Ito, M., Cheong, C. Y., Bench, A. …….Campbell, P. J., Ferguson-Smith, A. C.$ and Green, A. R$. *Joint first authors, $joint last authors. Cooperativity of imprinted genes inactivated by acquired chromosome 20 deletions. J. Clin. Invest. 123, 2169–2182 (2013).
Kent, D. G., Li, J., Tanna, H., Fink, J., Kirschner, K., Pask, D. C., Silber, Y., Hamilton, T. L., Sneade, R., Simons, B. D. and Green, A. R. Self-renewal of single mouse hematopoietic stem cells is reduced by JAK2V617F without compromising progenitor cell expansion. PLoS Biol. 11, e1001576 (2013).
Griffiths, D. S., Li, J., Dawson, M. A., Trotter, M., Cheng, Y. H., Smith, A., Mansfield, W., Liu, P., Kouzarides, T., Nichols, J., Bannister, A., Green, A. R. and Göttgens, B. LIF independent JAK signalling to chromatin in embryonic stem cells uncovered from an adult stem cell disease. Nature Cell Biol. 13, 13–21 (2011).
Chen, E., Beer, P. A., Godfrey, A. L., Ortmann, C. A., Li, J., Costa-Pereira, A. P., Ingle, C. E., Dermitzakis, E. T., Campbell, P. J. and Green, A. R. Distinct clinical phenotypes associated with JAK2V617F reflect differential STAT1 signaling. Cancer Cell 18, 524–535 (2010).
Dawson, M. A.†, Bannister, A. J.†, Gottgens, B., Foster, S. D., Bartke, T., Green, A. R.* and Kouzarides, T.* (*joint senior authors; †joint first author). JAK2 phosphorylates histone H3Y41 and excludes HP1a from chromatin. Nature 461, 819–822 (2009).
Zhao, R., Follows, G. A., Beer, P. A., Scott, L. M., Huntly, B. J. P., Green, A. R.* and Alexander, D. R.* (*joint senior authors). Inhibition of the Bcl-xL deamidation pathway in myeloproliferative disorders. N. Engl. J. Med. 359, 2778–2789 (2008).
Scott, L. M., Tong, W., Levine, R. L., Scott, M. A., Beer, P. A., Stratton, M. R., Futreal, P. A., Erber, W. N., McMullin, M. F., Harrison, C. N., Warren, A. J., Gilliland, D. G., Lodish, H. F. and Green, A. R. JAK2 exon 12 mutations in polycythemia vera and idiopathic erythrocytosis. N. Engl. J. Med. 356, 459–468 (2007).
Baxter, E. J., Scott, L. M., Campbell, P. J., East. C., Fourouclas, N., Swanton, S., Vassiliou, G. S., Bench, A. J., Boyd, E. M., Curtin, N., Scott, M. and Erber, W. N., Cancer Genome Project, Green, A. R. Acquired mutation of the tyrosine kinase JAK2 in human myeloproliferative disorders. Lancet 365, 1054–1061 (2005).
Harrison, C. N., Campbell, P. J., Buck, G., Wheatley, K., East, C. L., Bareford, D., Wilkins, B. S., van der Walt, J. D., Reilly, J. T., Grigg, A. P., Revell, P., Woodcock, B. E. and Green, A. R. Hydroxyurea compared with anagrelide in high-risk essential thrombocythemia. N. Engl. J. Med. 353, 33–45 (2005).