Autotaxin is expressed in FLT3-ITD positive acute myeloid leukemia and hematopoietic stem cells and promotes cell migration and proliferation

Abstract

Autotaxin (ATX) has been reported to act as a motility and growth factor in a variety of cancer cells. The ATX protein acts as a secreted lysophospholipase D by converting lysophosphatidylcholine (LPC) to lysophosphatidic acid (LPA), which signals via G-protein-coupled receptors and has important functions in cell migration and proliferation. This study demonstrates that ATX expression is specifically upregulated and functionally active in acute myeloid leukemia (AML) harboring an internal tandem duplication (ITD) mutation of the FLT3 receptor gene. Moreover, ATX expression was also found in normal human CD34+ progenitor cells and selected myeloid and lymphoid subpopulations. Enforced expression of mutant FLT3-ITD by retroviral vector transduction increased ATX mRNA in selected cell lines, whereas inhibition of FLT3-ITD signaling by sublethal doses of PKC412 or SU5614 led to a significant downregulation of ATX mRNA and protein levels. In the presence of LPC, ATX expression significantly increased proliferation. LPA induced proliferation, regardless of ATX expression, and induced chemotaxis in all tested human leukemic cell lines and human CD34(+) progenitors. LPC increased chemotaxis only in cells with high expression of endogenous ATX by at least 80%, demonstrating the autocrine action of ATX. Inhibition of ATX using a small molecule inhibitor selectively induced killing of ATX-expressing cell lines and reduced motility in these cells. Our data suggest that the production of bioactive LPA through ATX is involved in controlling proliferation and migration during hematopoiesis and that deregulation of ATX contributes to the pathogenesis of AML.