Leukaemogenesis induced by an activating β-catenin mutation in osteoblasts

Abstract

A mouse model shows that osteoblast activating β-catenin mutations alone are sufficient to initiate the development of acute myeloid leukaemia acting through increased Notch signalling. The tumour microenvironment has profound influences on tumorigenesis, and genetic alterations in stromal cells can contribute to the development of cancer. Stavroula Kousteni and colleagues show in a mouse model that activating mutations in β-catenin in osteoblasts are sufficient to initiate the development of acute myeloid leukaemia (AML). These mutations trigger the release of ligands from osteoblasts that activate the Notch signalling pathway in haematopoietic cells; inhibition of the Notch pathway ameliorates the disease. The observation of increased β-catenin signalling in osteoblasts in patients with myeloproliferative disease and AML suggests that a similar mechanism may contribute to leukaemia in humans. Cells of the osteoblast lineage affect the homing1,2 and the number of long-term repopulating haematopoietic stem cells3,4, haematopoietic stem cell mobilization and lineage determination and B cell lymphopoiesis5,6,7. Osteoblasts were recently implicated in pre-leukaemic conditions in mice8,9. However, a single genetic change in osteoblasts that can induce leukaemogenesis has not been shown. Here we show that an activating mutation of β-catenin in mouse osteoblasts alters the differentiation potential of myeloid and lymphoid progenitors leading to development of acute myeloid leukaemia with common chromosomal aberrations and cell autonomous progression. Activated β-catenin stimulates expression of the Notch ligand jagged 1 in osteoblasts. Subsequent activation of Notch signalling in haematopoietic stem cell progenitors induces the malignant changes. Genetic or pharmacological inhibition of Notch signalling ameliorates acute myeloid leukaemia and demonstrates the pathogenic role of the Notch pathway. In 38% of patients with myelodysplastic syndromes or acute myeloid leukaemia, increased β-catenin signalling and nuclear accumulation was identified in osteoblasts and these patients showed increased Notch signalling in haematopoietic cells. These findings demonstrate that genetic alterations in osteoblasts can induce acute myeloid leukaemia, identify molecular signals leading to this transformation and suggest a potential novel pharmacotherapeutic approach to acute myeloid leukaemia.