SFRP1 and glioblastoma: In this regard, Foltz et al. (2010) showed that, among three Wnt antagonist genes, DKK1, SFRP1, and WIF-1, only DKK1 expression was restored by treatment with DNA demethylating agent 5-azacytidine in T98 glioblastoma cells, suggesting the presence of promoter hypermethylation.