TP53 and cancer: Figure 5D shows that ATR inhibition reduced TERT protein levels in p53− RKO, NCI-H522 and NCI-H1299 cells but not in p53+ RKO, A549 and NCI-H460 cells Moreover, addition of an ATR inhibitor reduced ETV1 levels to varying extents in all cell lines. TERT protein levels were also reduced following knockdown of ATR or ETV1 in NCI-H522 cells and two additional human cancer cell lines that express mutant p53 (Figure S9A), as well as in HeLa cells, which lack p53 activity due to expression of the human papilloma virus E6 protein (Figure S9B).