Bcl6 plays a key role in cellular senescence.

<p>Bcl6 siRNA(siBcl6) significantly increases the number of SA-b-gal positive cells in both unstressed and in 0.1 µM doxorubicin-treated cells, and it completely abolishes the anti-senescent effect of pre-treatment with L-165041 (L-165). siPPARδ completely abolishes the pro-senescent effect of 0.1 µM doxorubicin. H9c2 cells were transfected with Bcl6-, PPARδ specific or control (siCT) siRNA for 48 h before treatment with or without L-165041 for 2 h followed by treatment with or without 0.1 µM doxorubicin (Dox 0.1) for 3 h. Cells were assayed for protein amount (after 24 h), premature senescence (after 3 days) and apoptosis (after 24 h). (A) Western blot analysis with Bcl6 and PPARδ antibodies. (B) SA-b-gal activity (magnification ×200). (C) Bar graph illustrating the percentage of SA-b-gal positive cells. *<i>p</i><0.05 versus corresponding siCT of the same treatment condition, (D) Bar graph illustrating the percentage of caspase-3 positive cells.