Differential inflammatory conditioning of the bone marrow by acute myeloid leukemia and its impact on progression

• An inflammatory bone marrow microenvironment with elevated levels of PGE2 accelerates the progression of PGE2-sensitive AML.

• A specific subset of patients with AML may benefit from combination treatment with COX2 inhibition and standard chemotherapy.

Inflammation promotes solid tumor progression, but how regulatory mechanisms of inflammation may impact leukemia is less well studied. Using annexin A5 (ANXA 5), a calcium-binding protein known for apoptosis, which we discovered to be differentially expressed in the bone marrow microenvironment (BMM) of mice with acute myeloid (AML) versus chronic myeloid leukemia, as a model system, we unravel here a circuit in which AML-derived tumor necrosis factor (TNF)α dose-dependently reduces ANXA5 in the BMM. This creates an inflammatory BMM via elevated levels of prostaglandin E2 (PGE2). Via binding to its EP4 receptor, PGE2 increases -catenin and hypoxia-inducible factor (HIF) 1 α signaling in AML cells, thereby accelerating PGE2-sensitive AML. Human trephine biopsies may show lower ANXA5 expression and higher PGE2 expression in AML compared to other hematological malignancies. Further, syngeneic and xenogeneic transplantation models suggest a survival benefit after treatment with the inhibitor of prostaglandin-endoperoxide synthase 2 (cyclooxygenase 2 (COX2)), celecoxib, plus cytarabine in those AML types highly sensitive to PGE2 compared to cytarabine alone. Taken together, TNFα/ANXA5/NF-kB/COX2/PGE2-mediated inflammation influences AML course in a highly differential and circular manner, and AML patients with 'inflammatory AML' may benefit from antiphlogistic agents as adjunct therapy.