Cell surface localization and release of the candidate tumor suppressor Ecrg4 from polymorphonuclear cells and monocytes activate macrophages.

ABSTRACT: We identified fresh human leukocytes as an abundant source of the candidate epithelial tumor suppressor gene, Ecrg4, an epigenetically regulated gene, which unlike other tumor suppressor genes, encodes an orphan-secreted, ligand-like protein. In human cell lines, Ecrg4 gene expression was low, Ecrg4 protein undetectable, and Ecrg4 promoter hypermethylation high (45-90%) and reversible by the methylation inhibitor 5-AzaC. In contrast, Ecrg4 gene expression in fresh, normal human PBMCs and PMNs was 600-800 times higher than in cultured cell lines, methylation of the Ecrg4 promoter was low (<3%), and protein levels were readily detectable in lysates and on the cell surface. Flow cytometry, immunofluorescent staining, and cell surface biotinylation established that full-length, 14-kDa Ecrg4 wa

SUBMITTER: Baird A 

PROVIDER: S-EPMC3336773 | biostudies-literature | 2012 May

REPOSITORIES: biostudies-literature