TP53 and small cell lung carcinoma: To evaluate the ability of the TAT and Pep1 peptide sequences to deliver the E1A peptide into cells, immunofluorescence (IF) using an anti‐FLAG antibody was used to monitor peptide internalization in two human cancer cell lines, the p53‐deficient H1299 non‐small cell lung cancer cells (Fig. 2) and the p53 WT A375 melanoma cells (Fig. S1A).