ACUTE LEUKEMIAS EXPRESS A FUNCTIONAL RECEPTOR FOR THE HUMAN GROWTH-HORMONE

The potential influence of the human growth hormone (hGH) on the behav ior of acute leukemias is a matter of controversy. We investigated pri mary childhood and adult leukemias (n=44) and leukemic cell lines (n=1 3) for the expression of the hGH receptor (hGHR) by immunohistochemist ry and flow cytometry. All leukemias expressed the hGHR in the cytopla sm; expression on the surface was undetectable in some of the leukemia s. In leukemic cell lines, hGHR expression on the surface was demonstr ated in a dose-dependent manner after incubation with rhGH. Physiologi c concentrations of hGH were more efficient than higher doses in incre asing hGHR surface expression, A proliferative response to hGH was acc omplished in cell lines REH, Molt4, and K562. However, only one of 19 primary leukemias (ALL, n=12; AML, n=7) showed increased cell counts a fter the addition of 50-800 ng/ml recombinant hGH (rhGH). These cells were of an immature T-cell phenotype. We thus conclude that acute leuk emias can be stimulated by hGH to up-regulate its receptor, but that m ost primary leukemias may require additional signals for the induction of proliferation.