DNMT1 and lung carcinoma: Samakoglu et al. (2012) also report that a combination therapy consisting of an EGFR antibody with cisplatin and gemcitabine induces mir-29b expression, the downregulation of DNMT3b, and the hypomethylation of tumor-suppressor genes in a lung cancer xenograft model. mir-29b has also been shown to down-regulate DNMT1, an enzyme involved in the maintenance of DNA methylation, indirectly by targeting Sp1, a transactivator of the DNMT1 gene in leukemia (Garzon et al., 2009).