Previous studies have shown that 5-aza-deoxycytidine treatment of a variety of tumor (glioma, choriocarcinoma, B-lymphoma and melanoma) cell lines results in significant hypomethylation of a CpG-rich region located within 450 bp 5' of the HLA-G start codon and correlates with a significant increase in HLA-G expression [15]. The gene discussed is HLA-G; the disease is choriocarcinoma.