We performed quantitative real-time PCR (qPCR) to measure the relative gene expression of the respective glypicans, GPC1, GPC2, GPC3, GPC4, GPC5 and GPC6 in seven breast cancer cell lines; MCF-7 and T47D as representatives of the luminal molecular subtype, SKBR3 and BT-474 as representatives of the HER2 subtype and MDA-MB-231, MDA-MB-453, MDA-MB-468 as representatives of the basal subtype. The gene discussed is GPC4; the disease is breast carcinoma.