DNMT1 inhibition results in the suppression of STAT3 activation. (A, left) Two T-cell lymphoma cell lines (PB-1 and 2A) treated with the DNMT inhibitor DAC were examined for expression of the noninhibited DNMT1 protein (upper lane) and STAT3 phosphorylation at Tyr705 (upper middle lane) and Ser727 (lower middle lane) and for expression of total STAT3 (lower lane). Untreated cells served as a control. (A, right) Expression of noninhibited DNMT1, p-Y705STAT3, and total STAT3 in the additional T-cell lymphoma cell line, 2B, before and after treatment with DAC. (B, left) 2A cells were treated for 72 hours with 2 fluorescein-labeled DNMT1 antisense DNA oligonucleotides, designated DNMT1 AS-ON(1) and DNMT1 AS-ON(2), and non–sense DNA oligonucleotide (NS-ON) as control. Flow cytometry analysis showed efficiency of the uptake of FITC-labeled DNMT1 AS-ON(1). (B, right) Western blot expression of DNMT1, phospho-STAT3, and total STAT3 after treatment with control NS-ON, DNMT1 AS-ON(1), and AS-ON(2).