Evaluation of the antineoplastic activity of adozelesin alone and in combination with 5-aza-2'-deoxycytidine and cytosine arabinoside on DLD-1 human colon carcinoma cells.

Adozelesin (Ado), a CC-1065 analog, shows significant antineoplastic activity in vivo against several types of murine tumors and human tumor xenografts. Ado is a DNA alkylating agent. One objective of this study was to investigate the cytotoxic action of Ado against the human colon (HT-29, DLD-1) and the lung (SK) carcinoma cell lines. The concentrations of Ado that produced 50% cell kill for a 4 and 24 h exposure were in the range of 0.001-0.02 ng/ml for both colon and lung carcinoma cells, indicating that this analog was a very potent cytotoxic agent. Since most clinical regimens for tumor therapy consist of several drugs, we investigated the antineoplastic action of Ado in combination with 5-aza-2'-deoxycytidine (5-Aza-CdR), a potent inhibitor of DNA methylation or cytosine arabinoside (Ara-C), a potent inhibitor of DNA synthesis. The Ado plus 5-Aza-CdR combination showed a synergistic effect on cytotoxicity of DLD-1 colon carcinoma cells for both a 6 and 24 h exposure. However, combination of Ado and Ara-C for a 6 h exposure showed an antagonistic effect, whereas a 24 h exposure showed a synergistic effect. These preclinical results provide some preliminary data on possible drugs that can be selected for use in combination with Ado in future clinical trials in patients with cancer.