PTTG1 and Drug-Induced Senescence Figure 3. PTTG1 down regulates p21 in colon cancer cells. a) HCT116 WT and PTTG12/2 cells were treated with control vehicle (C), doxorubicin (Dox, 0.02 uM) or TSA (0.005 uM), and proteins analyzed by Western blotting to assess histone H3 and H4 acetylation; b) PTTG12/2 cells were transfected with scrambled siRNA (C), or siRNA targeting p21, p53 or Sp1 respectively and treated with doxorubicin (0.02 uM) for 48 hours. Protein levels were evaluated by Western blotting and senescence evaluated with b-gal staining; c) HCT116 or SW620 cells were transfected with empty vector or scrambled siRNA (C) or PTTG1 plasmids or siRNA as indicated, proteins were extracted and PTTG1 and p21 levels evaluated by PLoS ONE | www.plosone.org 7 August 2011 | Volume 6 | Issue 8 | e23754