BACKGROUND: D-glucuronyl C5-epimerase (GLCE) is one of the key enzymes in the biosynthesis of heparansulfate proteoglycans. Down-regulation of GLCE expression in human breast tumours suggests a possible involvement of the gene in carcinogenesis. In this study, an effect of GLCE ectopic expression on cell proliferation and viability of breast carcinoma cells MCF7 in vitro and its potential molecular mechanisms were investigated. RESULTS: D-glucuronyl C5-epimerase expression was significantly decreased in MCF7 cells compared to normal human breast tissue. Re-expression of GLCE inhibited proliferative activity of MCF7 cells according to CyQUANT NF Cell Proliferation Assay, while it did not affect their viability in Colony Formation Test. According to Cancer PathFinder RT Profiler PCR Array, antiproliferative effect of GLCE in vitro could be related to the enhanced expression of tumour suppressor genes р53 (+3.3 fold), E2F1 (+3.00 fold), BRCA1 (+3.5 fold), SYK (+8.1 fold) and apoptosis-related genes BCL2 (+4.2 fold) and NFKB1 (+2.6 fold). Also, GLCE re-expression in MCF7 cells considerably changed the expression of some genes involved in angiogenesis (IL8, +4.6 fold; IFNB1, +3.9 fold; TNF, +4.6 fold and TGFB1, -5.7 fold) and invasion/metastasis (SYK, +8.1 fold; NME1, +3.96 fold; S100A4, -4.6 fold). CONCLUSIONS: The ability of D-glucuronyl С5-epimerase to suppress proliferation of breast cancer cells MCF7 through the attenuated expression of different key genes involved in cell cycle regulation, angiogenesis and metastasis molecular pathways supports the idea on the involvement of the gene in regulation of breast cancer cell proliferation.