DHTKD1 and infection: The ED50 of Ad-TERTp-E1A-1504 for C4-2B was 1/3.5 as much as that of Ad-TERTp-E1A-NC, and was 1/1400 as much as that of Ad-ΔE1A-1504 and this antitumor potential difference increased with prolonged infection (Table 1).