adozelesin and Colonic-Neoplasms

The pleiotrophic cellular response to DNA damage includes activation of cell cycle checkpoints, induction of DNA repair pathways, and initiation of programmed cell death among others. The fate of cells with damaged DNA depends on the coordination of these different responses. The clinical efficacy of genotoxic therapies is influenced by cell fate and thus by how the DNA damage response is coordinated. While a great deal has been learned about how different DNA lesions activate distinct cell cycle checkpoints and DNA repair pathways, less is known about whether the type of DNA lesion influences the qualitative and quantitative nature of the cell death response. To address this question, HCT116 colon carcinoma cells have been treated with equally cytotoxic doses of the antitumor DNA alkylating agents adozelesin or bizelesin or the DNA strand scission agent C-1027. The relative contribution of cell cycle arrest and cell death to measured cytotoxicity varied among the three drugs. Apoptotic cell death accounts for most C-1027 cytotoxicity while cell cycle arrest and cell death both contribute to the cytotoxicity of the alkylating agents. Each of the drugs induces a distinct but overlapping pattern of caspase activation. In addition, the cell death response to these drugs is differentially dependent on p53 and p21. These observations suggest that the type of DNA lesion influences not only the relative extent of apoptotic cell death at a given cytotoxic dose but also the qualitative nature of that response.

Topics: Aminoglycosides; Antibiotics, Antineoplastic; Antineoplastic Agents, Alkylating; Benzofurans; Cell Cycle; Cell Death; Cell Proliferation; Colonic Neoplasms; Cyclohexanecarboxylic Acids; Cyclohexenes; DNA Damage; Dose-Response Relationship, Drug; Duocarmycins; Enediynes; HCT116 Cells; Humans; Indoles; Inhibitory Concentration 50; Urea

As members of the cyclopropylpyrroloindole family, adozelesin and bizelesin cause genomic DNA lesions by alkylating DNA. Adozelesin induces single-strand DNA lesions, whereas bizelesin induces both single-strand lesions and double-strand DNA cross-links. At equivalent cytotoxic concentrations, these agents caused different biological responses. Low adozelesin concentrations (e.g., 0.5 nM) induced a transient S-phase block and cell cycle arrest in G(2)-M, as well as increased induction of p53 and p21, whereas a high drug concentration (e.g., 2.5 nM) caused apoptosis but no p21 induction. In contrast, both low and high bizelesin concentrations enhanced p53 and p21 induction and triggered G(2)-M cell cycle arrest and eventual senescence without significant apoptotic cell death. However, in cells lacking p21, bizelesin, as well as adozelesin, triggered apoptosis, indicating that p21 was crucial to sustained bizelesin-induced G(2)-M arrest. Thus, despite similar abilities to alkylate DNA, the chemotherapeutic agents adozelesin and bizelesin caused a decrease in HCT116 tumor cell proliferation by different pathways (i.e., adozelesin induced apoptosis, and bizelesin induced senescence).

Topics: Antineoplastic Agents, Alkylating; Apoptosis; Benzofurans; Cell Cycle; Cellular Senescence; Colonic Neoplasms; Cyclin-Dependent Kinase Inhibitor p21; Cyclins; Cyclohexanecarboxylic Acids; Cyclohexenes; DNA Damage; DNA, Neoplasm; Dose-Response Relationship, Drug; Duocarmycins; Humans; Indoles; Signal Transduction; Tumor Cells, Cultured; Tumor Suppressor Protein p53; Urea

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.

Topics: Adenocarcinoma; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Azacitidine; Benzofurans; Carcinoma, Squamous Cell; Cell Division; Colonic Neoplasms; Cyclohexanecarboxylic Acids; Cyclohexenes; Cytarabine; Decitabine; DNA, Neoplasm; Drug Screening Assays, Antitumor; Duocarmycins; Humans; Indoles; Lung Neoplasms; Time Factors; Tumor Cells, Cultured

U-73,975 (U-73) and U-77,779 (U-77), two analogues of the cyclopropylpyrroloindole antitumor antibiotic CC-1065, are promising novel chemotherapeutic agents which are known to alkylate the N3 position of adenine in a sequence-selective manner. The concentration of U-73 required to produce a 1 log cell kill in 6 human tumor cell lines varied from 20-60 pM. U-77 was more cytotoxic than U-73, with the concentrations required for a 1 log cell kill ranging from 1-20 pM. The cytotoxicity of U-73 and U-77 was found to be independent of the guanine O6-alkyltransferase phenotype. The sensitivity of the BE and HT-29 human colon carcinoma cells was increased when the time of drug exposure was increased from 2 to 6 h. DNA interstrand cross-links, as measured by the technique of alkaline elution, could only be detected when HT-29 or BE cells were exposed to extremely high concentrations of U-77 for 6 h. No other forms of DNA damage were detected in genomic DNA with either compound. U-77 was also found to induce DNA interstrand cross-links in naked DNA, as measured by an agarose gel method. The rate of interstrand cross-linking was extremely rapid with the "second-arm" of the cross-link being completed within 2 h. The mechanism by which these cyclopropylpyrroloindole compounds elicit their cytotoxicity, however, remains to be elucidated.

Topics: Antibiotics, Antineoplastic; Benzofurans; Carcinoma; Cell Death; Colonic Neoplasms; Cross-Linking Reagents; Cyclohexanecarboxylic Acids; Cyclohexenes; DNA Damage; Dose-Response Relationship, Drug; Duocarmycins; Humans; Indoles; Leucomycins; Lung Neoplasms; Plasmids; Tumor Cells, Cultured; Urea

Adozelesin (U-73975) is a potent synthetic cyclopropylpyrroloindole (CPI) analog of the cytotoxic DNA-binding antibiotic, CC-1065. In contrast to the natural product, adozelesin and related CPI analogs do not cause delayed death in non-tumored mice. Adozelesin, selected from a series of analogs for its superior in vivo antitumor activity and ease of formulation, is highly active when administered i.v. against i.p. - or s.c.- implanted murine tumors, including L1210 leukemia, B16 melanoma, M5076 sarcoma, and colon 38 carcinoma, and produces long-term survivors in mice bearing i.v.-inoculated L1210 and Lewis lung carcinoma. Modest activity is shown against the highly drug-resistant pancreas 02 carcinoma. Adozelesin is also highly effective against human tumor xenografts s.c.-implanted in athymic (nude) mice, including colon CX-1 adenocarcinoma, lung LX-1 tumor, clear cell Caki-1 carcinoma, and ovarian 2780 carcinoma. Its broad spectrum of in vivo activity compares favorably with three widely used antitumor drugs, i.e. cisplatin, cyclophosphamide, and doxorubicin. Adozelesin appears to be more effective than these drugs in the treatment of very resistant tumors such as s.c.-implanted mouse B16 melanoma, pancreatic 02 carcinoma, and human colon CX-1 and human lung LX-1 tumor xenografts. Based on its high potency and high efficacy against a broad spectrum of experimental tumors, adozelesin was chosen for clinical investigation and development.

Topics: Animals; Antineoplastic Agents; Benzofurans; Colonic Neoplasms; Cyclohexanecarboxylic Acids; Cyclohexenes; DNA, Neoplasm; Duocarmycins; Female; Humans; Indoles; Leukemia L1210; Leukemia, Experimental; Lung Neoplasms; Male; Melanoma, Experimental; Mice; Mice, Nude; Molecular Structure; Neoplasm Transplantation; Pancreatic Neoplasms; Sarcoma, Experimental