Specifically, transfection of each miR-29 member into A549 lung cancer cells led to a reduction in DNMT3A and DNMT3B mRNA levels, which correlated with decreased global DNA methylation and the re-expression, in both A549 and H1299 lung cancer cells, of tumor suppressor genes such as FHIT and WWOX, normally silenced through promoter methylation in lung cancer. The gene discussed is DNMT3B; the disease is lung cancer.