In vitro cellular cytotoxicity on p53/p21-expressing or deficient HCT116 cell lines. The activity of 5 μg/ml (black bars), 20 μg/ml (grey bars) Antp-p21 fusion protein and chemotherapy alone (white bars) in the absence of chemotherapy or in the presence of 10 μg/ml cisplatin and 8.5 μg/ml paclitaxel was investigated in a series of human colon carcinoma cell lines. The cell lines used were: (A) HCT116, p53 parental p21+/+, p53+/+. (B) HCT116, p53 knock-out p21+/+, p53−/−, (C) HCT116, p21 parental p21+/+, p53+/+, (D) HCT116, p21 knock-out p21-/-, p53+/+, (E) RKO p53+/+, (F) RKO E6 (pCMV-E6-transfected RKO)-lacks appreciable functional p53, (G) Caco-2 (colon adenocarcinoma line used as control). Bars grouped with a single star (*) are statistically significantly different (=p < 0.05) and bars grouped with a double star (**) are highly statistically significantly different (=p < 0.005) using the student’s T-test.