Sowinska [4] demonstrated that combined DNMT1 and DNMT3b siRNAs could enhance promoter demethylation and re-expression of CXCL12 in MCF-7 breast cancer as well as AsPC1 in pancreatic carcinoma cell lines, and suggested that they acted synergistically in inhibiting CpG island hypermethylation of tumor suppressor genes. The gene discussed is DNMT3B; the disease is breast carcinoma.