Syndecan-1 is a transmembrane proteoglycan expressed predominantly in epithelial cells. Studies with immunohistochemistry have shown that syndecan-1 expression is reduced in carcinoma derived from human epidermis. Here we show that syndecan-1 mRNA, which is abundant in human primary keratinocyte (HK) and HaCaT spontaneous immortalized keratinocyte, is decreased in cervical-carcinoma cell lines. Further, in relation to a long and well-conserved 3' untranslated region (3' UTR) of syndecan-1 cDNA, we examined whether 3' UTR is involved with syndecan-1-mRNA reduction in cervical-carcinoma cells. A stable transfection experiment showed that addition of the 3' UTR does not affect expression in HaCaT, but that syndecan-1 cDNA containing the 3' UTR is not expressed efficiently selectively in cervical-carcinoma cell lines. The transient assay with CAT reporter plasmids linking the 3' UTR confirmed this, and indicated that the 3' end of the 3' UTR (nt 2285-2410) is required to influence expression in cervical-carcinoma cells. Further excessive expression of syndecan-1 suppressed growth in cervical-carcinoma cells. These results demonstrate that the reduction of syndecan-1 mRNA involved with the 3' untranslated region gives growth advantage to cervical-carcinoma cells.