The ability of D-glucuronyl C5-epimerase to affect simultaneously several different key genes of the cell cycle regulation (р53, E2F1, BRCA1), angiogenesis (IL8, IFNB1, TNF, TGFB1) and metastasis (SYK, NME1, S100A4, TGFb) supports the idea on the involvement of the gene in regulation of breast cancer cell proliferation. The gene discussed is BRCA1; the disease is breast carcinoma.