GPC3 and breast cancer: Two studies have shown that in breast cancer, GPC3 is downregulated by means of hypermethylation of the GPC3-promoter (Xiang et al. 2001; Yan et al. 2001) and Yan et al. have described that the silencing of GPC3 by means of promoter hypermethylation is more predominant in hormone-receptor negative patients, implying that GPC3 is expressed less in those patients.