Expression of E6 sensitizes human keratinocytes to therapeutic agents. NIKS-E6 and vector control cells were treated with DMSO, MMC (5 μg/ml), paclitaxel (10 μM), etoposide (50 μM), or cisplatin (100 μM) for 48 hours. Cells were fixed, stained with propidium iodide (PI) or PI plus Annexin V-FITC, and analyzed by flow cytometry. Representative histograms of PI-stained, etoposide- or DMSO-treated cells from three experiments are shown in A. Quantification of sub-G1 populaiton of PI-stained cells is summarized in B. The results of a representative experiment (of 3) of etoposide/DMSO-treated, Annexin V-FITC/PI-stained cells are shown in C.