p16 modulates apoptosis through E2F1.

<p>(A) Western blots showing the expression of the indicated pro-and anti-apoptotic proteins in U2OS and EHI. (B) Western blots showing the expression of the indicated proteins in U2OS, U2OS cells stably transfected with plasmids encoding either scrambled sequence (ctl) or E2F1 (+). The numbers below the bands indicate the corresponding expression levels. (C) U2OS, EH1 and E2F1-expressing U2OS cells were either mock-treated or challenged with doxorubicin (2 µM) and then re-incubated for 72 hrs. Cells were then divided into two groups; one was used to analyze cell death by annexinV/PI flow cytometry. The numbers in the charts indicate the proportions of early and late apoptosis. (D) Histogram showing the proportions of apoptosis (early+late) induced by different doses of doxorubicin. The error bars represent standard deviation of three different experiments. (E) The second group of cells was used to assess the level of the indicated proteins by immunoblotting. (F) Graph showing the Bax/Bcl-2 ratio in the indicated cells after treatment with doxorubicin. Error bars represent standard deviation of at least three different experiments.