Autocrine regulation of erythropoietin gene expression in human hepatocellular carcinoma cells.
We have previously reported that a marked increase in erythropoietin (Epo) production can be demonstrated in Hep3B cell cultures in response to hypoxia (1). In order to determine whether this increase involves an autocrine mechanism, we have investigated the effects of purified human recombinant Epo (rHuEpo) on Epo production. Purified rHuEpo (5-80 mU/ml) produced a significant increase above control levels of Epo in Hep3B cell cultures under normoxic (20% O2) conditions. Hypoxic (1% o2) incubation of Hep3B cells with rHuEpo caused an increase over control levels of EpomRNA. Hep3B cells also expressed Epo receptor (Epo-R) transcripts. Binding studies [125I]Epo revealed that Hep3B cells contain a single class of binding site (kd=2.9 nmol/L and Bmax=1760 sites/cell). Antierythropoietin receptor monoclonal antibody inhibited the rHuEpo induced elevation in medium levels of Epo and blocked [125I]-Epo binding to Hep3B cell membranes. These results demonstrate that the expression of EpomRNA may be controlled, at least in part, by an autocrine mechanism.
Ohigashi
T
T
Department of Pharmacology, Tulane University School of Medicine, New Orleans, Louisiana 70112, USA.
Yoshioka
K
K
Fisher
J W
JW
D000332:Aerobiosis; D006528:Carcinoma, Hepatocellular; D015687:Cell Hypoxia; D004305:Dose-Response Relationship, Drug; D004921:Erythropoietin / Q000096:biosynthesis* / Q000378:metabolism / Q000494:pharmacology*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D007700:Kinetics; D008113:Liver Neoplasms; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D017467:Receptors, Erythropoietin / Q000096:biosynthesis* / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D012333:RNA, Messenger; D017467:Receptors, Erythropoietin; D011994:Recombinant Proteins; D004921:Erythropoietin