EFFECT OF HEPATOCYTE GROWTH-FACTOR ON EARLY HUMAN HEMATOPOIETIC-CELL DEVELOPMENT

Hepatocyte growth factor (HGF) stimulates cell proliferation, differen tiation and migration by binding to its receptor, MET R. Whether the H GF/MET R axis plays an important regulatory role in human haemopoietic cell growth is an unresolved issue. To investigate this situation, we employed several complementary strategies including RT-PCR, FAGS anal ysis, and mRNA perturbation with oligodeoxynucleotides (ODN). We found that very primitive, FACS sorted, CD34(+) Kit(+) marrow mononuclear c ells (MNC) failed to express RT-PCR detectable MET R mRNA. In contrast , MET R expression was easily detectable by RT-PCR in marrow stroma fi broblasts, in cells isolated from BFU-E and CPU-GM colonies, and in un selected normal MNC. Subsequent FAGS analysis revealed that MET R prot ein was detectable on similar to 5% of the latter cells. HGE at concen trations of 1-50 ng/ml, had no demonstrable effect on survival or clon ing efficiency of normal CD34(+) MNC in serum-free cultures. Antisense ODN mediated perturbation of MET R mRNA expression in normal CD34(+) MNC, with FAGS documented decline in protein expression, had no effect an the ability of these cells to give rise to haemopoietic colonies o f any lineage. We also examined the biology of HGF/MET R expression in malignant haemopoietic cells. Using the strategies described above, w e found that MET R mRNA was expressed in many human haemopoietic cell lines, and that the protein was expressed at high levels on HTLV trans formed T lymphocytes. Wild-type CML and AML blast cells also expressed MET mRNA, and HGF was able to co-stimulate CFU-GM colony formation in similar to 20% of cases studied. Therefore, although the HGF/MET R ax is appears to be dispensable for normal haemopoietic cell growth, it m ay play a role in the growth of malignant haemopoietic progenitor cell s.