TNF-alpha-induced growth suppression of CD34(+) myeloid leukemic cell lines signals through TNF receptor type I and is associated with NF-kappa B activation

Conflicting results have been reported regarding the effect of TNF-alpha on the growth of human primitive hemopoietic cells, In this study, we have ex amined the effect of TNF-alpha on the proliferation of several CD34(+)/CD38 (+) (KG-1, TF-1) and CD34(+)/CD38 (KG-1a, TF-1a) myeloid leukemic progenito r cell lines. Our data show that TNF-alpha markedly inhibits the growth of these cells in both liquid and soft agar cultures, Addition of GM-CSF or IL -3 does not prevent TNF-alpha-induced growth inhibition, Flow cytometry ana lyses of propidium iodide-stained cells demonstrated cell death of all four cell lines, as judged by the presence of cells with hypodiploid DNA conten t after exposure of cells to TNF-alpha for 4 days. Annexin V assays detecte d apoptosis in TF-1, but not in TF-1a, KG-1, and KG-1a cells in terms of tr anslocation of phosphatidylserine shortly after TNF-alpha treatment. Neutra lizing anti-TNF receptor type I (TNFR-I; p55) Ab almost completely reversed TNF-alpha-induced growth inhibition in both liquid and soft agar cultures, whereas anti-TNFR-II (p75) Ab had only a marginal effect, TNF-alpha rapidl y induced marked activation of nuclear transcription: factor NF-kappa B in all 4 cell lines, The majority of this effect was abolished by the type I r eceptor Ab, whereas the type II receptor neutralizing Ab had no effect, Our data also show that TNF-alpha is incapable of inducing activation of the m itogen-activated protein kinase pathway in these leukemic cell lines.