Expression and regulation of the meprin beta gene in human cancer cells

A novel mRNA isoform (meprin beta') of the cell-surface protease subunit me prin beta was previously identified in human colon cancer cells. The study reported here revealed that this mRNA isoform was identical within the prot ein coding region and at the 3' end to the beta isoform of normal intestine but that it contained an extended 5' untranslated region. Meprin beta' mRN A was expressed in the human breast cancer cell lines MCF-7 and SK-BR-3, in the human osteosarcoma cell line U2 Os, and in the human pancreatic cancer cell line BxPC-3. Meprin beta mRNA, but not beta' mRNA, was expressed in h uman fetal kidney cells. We cloned and sequenced genomic DNA encoding porti ons of the promoter region of the meprin beta gene. The unique sequences pr esent in the beta' mRNA were present in the human genomic DNA immediately u pstream of the transcription start site for the beta mRNA. The human meprin promoter sequence was searched for potential transcription-factor binding sites, and putative activator protein-1, polyoma enhancer activator 3 (PEA3 ), CCAAT enhancer-binding protein beta, and estrogen-receptor binding sites were identified along with binding sites for the intestine-specific cdx-2 transcription factor. The activity of meprin promoter/luciferase reporter g ene constructs transfected into U2 Os cells was highest with constructs con taining 83 and 639 bp of promoter DNA. These regions of the promoter each c ontain a putative PEA3 element. Treatment of the human colon adenocarcinoma cell line HT29-18C(1) with 50 or 100 ng/mL phorbol myristal acetate for 8 h increased meprin beta' mRNA levels. Likewise, U2 Os cells transfected wit h the -639/luciferase or -1800/luciferase constructs showed a phorbol myris tal acetate-inducible increase in reporter gene activity, indicating that t he PEA3 element within the -639 construct or other elements further upstrea m respond to phorbol ester. (C) 1999 Wiley-Liss, inc.