TBr down regulated STAT3 target genes and promoted ubiquitin dependent degradation of activated STAT3.

<p>(A) HL-60, MOLT-4 and K-562 cells were treated with TBr at indicated concentrations for 6 h. Lysates were prepared and immunoblotting of indicated proteins were performed. β actin was used as the loading control. (B) HL-60 cells were treated with TBr at 2 and 3 µM concentrations along with the proteasomal inhibitor MG132 (0.07 µM) for 6 h. Protein lysates were prepared and p-STAT3 (Y705) was immunoprecipitated with its respective antibody. Immunoblotting was used to detect antiubiquitin (P4D1, Santacruz) and p-STAT3 (Y705) antibodies. A predominant ubiquitination of the tyrosine705 phosphorylated STAT3 is seen in the TBr treated cells under proteasomal inhibition. (C) MG132 pre-treatment rescued decreased p-STAT3 expression in TBr treated HL-60 cells. Data are mean ± SD of three similar experiments, *p<0.05, **p<0.01 for TBr vs TBr with MG132.