Aberrant Expression of Hepatocyte Growth Factor Induces Autocrine MET Activation Providing a Novel Therapeutic Target In Acute Myeloid Leukemia.

Abstract 1042

Despite improvements in the treatment of acute myeloid leukemia (AML), high risk disease such as complex aberrant karyotype AML remains largely refractory to current therapy, and is mostly fatal. Identification of effective therapeutic targets by using candidate gene approaches has been limited by the number and variety of genetic defects associated with AML. Thus, we carried out a genome-wide functional screen in complex karyotype AML using a retroviral library of short hairpin RNAs (shRNAs), and discovered that shRNA-mediated depletion of hepatocyte growth factor (HGF) specifically inhibits growth of AML cells but not a panel of lymphoid cancer cells. HGF was to found to be aberrantly expressed in about 15% of patients with AML, including most patients with complex karyotype disease. In contrast to normal CD34+ cells that express MET (but not HGF), 5 of 7 cell lines derived from patients with complex karyotype AML exhibited aberrant expression of HGF that was associated with autocrine activation of its receptor MET. Depletion of HGF or MET using multiple independent shRNAs profoundly reduced proliferation and induced cell death in AML cells lines that express HGF but not those that lack HGF expression. Inhibition of MET using the tyrosine kinase inhibitor (SU11274) or HGF using neutralizing anti-HGF antibody (R&D Systems) also inhibited growth and induced apoptosis in AML cell lines dependent on HGF/MET activation but not those that lack HGF expression. Thus, aberrant HGF expression causes autocrine MET activation and oncogene dependence in a subset of patients with AML, confers sensitivity to HGF/MET inhibition, and provides a novel therapeutic target for this otherwise lethal disease.