PTPN6 and acute myeloid leukemia: Promoter methylation of PTPN6 occurs in acute myeloid leukemia (AML) cells; indeed, treatment with 5-Azacytidine (5-AZA), an inhibitor of the DNA methyltransferase (DNMT) 1, upregulated PTPN6, thereby resulting in STAT3 inhibition.