Regulation of heparin-binding EGF-like growth factor expression by phorbol ester in a human hepatoma-derived cell line

摘要

Heparin-bingding EGF-like growth factor (HB-EGF) is a recently identified potent mitogen for smooth muscle cells and fibroblasts. HB-EGF has been shown to be an hXIF receptor ligand, inn also to stimulate epithelial cell growth. A human hepatoma-derived cell line, Mulilavu, was analyzed for the production ol'IIB-UGF inRNA and active HB-EGI: protein. It was found that the cell line synthesized very low or umleleembie basal level of I IB liGF niRNA. However, the addition of 12-0-tetr;uleeanoyipliorbol-l3aeetate (TPA) led to a rapid and tnuisieiu rise in HB-HCil1' mRNA level. 111S-I-XJJ in Mahlavu cells appears to be regulated by a protein kinusu C (PKC) pathway, since PKC inhibitors, 117, slauiosporin, and calphostin C, abrogated the induction of HB-KGF mRNA by TPA. Unlike vascular smooth muscle cells, induction of llll"KCil; gene iranseription by TPA was blocked completely by incubation with cycloheximide, suggesting that protein synthesis, may be a prerequisite for MB-MiF gene transcription in Mahlavu cells. Mahlavu cells were also found to release a hioaetive 111) HUI; like protein into conditioned medium which stimulates DNA synthesis in UP 170.7 cells. This activity was neutralized by an anii-HH H(il; antibody. These results indicate thai HB-HCil' gene transcription is regulated via a PKC pathway, resulting in secretion of active I1B HCiI; into the culture medium of hepatoma-derived Mahlavu cells.