Figure 1.

Combination of different p53 activators led increased cell death in cancer cells carrying WT p53. (A) Plk1 was acetylated by HDAC I/II but not SIRT family deacetylases. A375 cells were treated with either NAM (N) or TSA (T) alone or both, and harvested 24 hours post-treatment for anti-Plk1 IP, followed by IB against acetylated lysine. (B) Inhibition of SIRT deacetylases led to increased p53 level and decreased Plk1 level. A375 cells were treated with tenovin-1 for 24 hours, harvested for IB against Plk1 and p53. Lysates were also subjected to anti-Plk1 IP, followed by IB. (C) Combing Plk1 inhibitor or DNA damage agent with SIRT inhibitor led to an increase of cell death in A375 cells. A375 cells were treated with BI2536 or doxorubincin either alone or with Tenovin-1 for 24 hours, and harvested for IB with antibodies indicated. (D, E) Plk1 inhibitor and SIRT inhibitor together induced an increase of cell death in p53-positive LNCaP and C4-2 cells. Cells were treated with BI2536 or Tenovin-1 alone or together for 24 hours, and harvested for IB. (F) Plk1 inhibitor plus SIRT inhibitor did not induce an increase of cell death in p53-null PC-3 cells. Cells were treated with BI2536 or Tenovin-1 alone or together for 24 hours, and harvested for IB. (G, H) Knock-down of Plk1 sensitized p53-positive cancer cells to Tenovin-1. LNCaP (G) and C4-2 (H) were treated with either control or Plk1-shRNA lentivirus for 2 days, incubated with Tenovin-1 for 24 hours, and harvested for IB. (I, J) Knock-down of p53 antagonized BI2536-induced cell death. LNCaP (I) and C4-2 (J) cells were treated with either control or p53-shRNA lentivirus for 2 days, incubated with BI2536 for 24 hours, and harvested for IB.