soblidotin and Colonic-Neoplasms

TZT-1027 (Soblidotin), a microtubule-depolymerizing agent exerts both a direct cytotoxic activity against cancer cells and an indirect antivascular activity against tumor vascular endothelial cells. We compared both activities of TZT-1027 with those of various anticancer agents having different mechanisms of action, including vinca alkaloids, a vascular targeting agent, a taxane and nonmicrotubule-binding agents. In the MTT assay, TZT-1027 most potently inhibited the growth of both murine colon C26 cancer cells and human umbilical vein endothelial cells, implying its potent antivascular activity against tumor vasculature in addition to its cytotoxic activity against cancer cells. Treatment with 0.1 microg/ml TZT-1027 significantly enhanced vascular permeability in human umbilical vein endothelial cell monolayers and a single intravenous administration of 2 mg/kg TZT-1027 significantly reduced the perfusion of Colon26 tumors implanted into mice, with efficacies superior to vinca alkaloids and comparable to a known vascular targeting agent. These results strongly suggest that TZT-1027 exerts marked antivascular activity. Next, to clarify the mechanism of the antivascular activity, we have taken a novel approach, and analyzed the relationships among human umbilical vein endothelial cells cytotoxicity, vascular permeability and tumor perfusion, on the basis of efficacies of each agent. Analyses revealed strong and significant correlations, and indicated that the vascular endothelial cell damage leads to endothelial barrier dysfunction and, thereby, tumor vascular shutdown. In summary, TZT-1027 was verified to have not only an excellent cytotoxic activity, but also an attractive antivascular activity through the induction of damage to vascular endothelial cells. We believe that these dual activities may make TZT-1027 useful for treating solid tumors.

Topics: Adenocarcinoma; Angiogenesis Inhibitors; Animals; Antineoplastic Agents; Cell Line, Tumor; Cell Membrane Permeability; Cell Survival; Colonic Neoplasms; Dextrans; Diffusion; Endothelial Cells; Endothelium, Vascular; Female; Fluorescein-5-isothiocyanate; Humans; Indicators and Reagents; Mice; Mice, Inbred BALB C; Oligopeptides; Tetrazolium Salts; Thiazoles; Umbilical Veins

We investigated the ability of TZT-1027 (Soblidotin), a novel antimicrotubule agent, to induce antivascular effects, because most vascular targeting agents that selectively disrupt tumor vasculature also inhibit tubulin polymerization. Treatment with 10(-7) g/mL TZT-1027 rapidly disrupted the microtubule cytoskeleton in human umbilical vascular endothelial cells (HUVEC), and significantly enhanced vascular permeability in HUVEC monolayers. In addition, single intravenous administration of 2 mg/kg TZT-1027 to mice bearing Colon26 tumors significantly reduced tumor perfusion and caused extravascular leakage of erythrocytes 1 h after administration. Subsequently, thrombus formation with deposition of fibrin and tumor necrosis was observed 3 and 24 h after administration, respectively. These results strongly suggest that TZT-1027 possesses antivascular effects. TZT-1027 induced apoptosis not only in HUVEC but also in C26 cancer cells (cell line of Colon26 solid tumor) in vitro, suggesting it exerts direct cytotoxicity against tumor cells in addition to its antivascular effects. A single intravenous administration of 1, 2 and 4 mg/kg TZT-1027 significantly prolonged the survival of mice with advanced-stage Colon26 tumors in a dose-dependent manner. Furthermore, TZT-1027 itself less markedly enhanced the permeability of normal vessels, but was additive with vascular endothelial growth factor, indicating the possibility that TZT-1027 selectively exerts its activity on tumor vessels. In summary, these results suggest that TZT-1027 exerts both an indirect antivascular effect and a direct cytotoxic effect, resulting in strong antitumor activity against advanced-stage tumors, and that TZT-1027 may be useful clinically for treating solid tumors.

Topics: Adenocarcinoma; Animals; Antineoplastic Agents; Cell Division; Cells, Cultured; Colonic Neoplasms; Endothelium, Vascular; Female; Fluorescent Antibody Technique; Guinea Pigs; Humans; Mice; Mice, Inbred BALB C; Microtubules; Neovascularization, Pathologic; Oligopeptides; Skin; Umbilical Veins

TZT-1027 was evaluated for its antitumor effects in sixteen human tumors xenografted in nude mice from gastric (H-81, H-106, H-30, H-154), breast (H-31, H-62), colon (H-110, H-143), lung (LC-376, H-74, Mqnu-1, LC-351), liver (H-181), renal cell (H-12) and ovarian (H-OC-3, SOC-4) cancer lines. In the latter three and lung (Mqnu-1, LC-351) cancers the results were compared with those obtained with CPT-11, VCR, CDDP, ADM. TZT-1027 showed effective antitumor activity (IR > or = 58%) against fifteen of the tumor lines, all but LC-351, and showed markedly effective activity (IR > or = 80%) against twelve tumor lines, including drug-resistant colon (H-110), lung (H-74) and ovarian (SOC-4) cancer lines. The complete regression was shown in five H-OC-3 tumor-bearing mice out of seven. Moreover, TZT-1027 was shown to be more potent in three cancer models (Mqnu-1, H-81, SOC-4) than CPT-11, and to have markedly effective antitumor activity in two cancers (H-12, H-OC-3) in which VCR was ineffective and in ovarian cancer (SOC-4) in which CPT-11, CDDP and ADM were ineffective. The administration of TZT-1027 induced fewer side effects; transient reduction of body weight was observed in four lines out of sixteen tested. These results suggest that TZT-1027 is an excellent candidate for clinical trials for the treatment of cancer.

Topics: Animals; Antineoplastic Agents; Body Weight; Breast Neoplasms; Colonic Neoplasms; Humans; Lung Neoplasms; Mice; Mice, Nude; Neoplasm Transplantation; Oligopeptides; Stomach Neoplasms

TZT-1027, a dolastatin 10 derivative, is an antimicrotubule agent with potent antitumor activity both in vitro and in vivo. In this study, we performed biochemical and histopathological examinations, and evaluated TZT-1027-induced tumoral vascular collapse and tumor cell death in an advanced tumor model, murine colon 26 adenocarcinoma. In addition, we studied the effects of TZT-1027 on cultured human umbilical vein endothelial cells (HUVEC). Tolerable doses of TZT-1027 induced tumor-selective hemorrhage within 1 h. This hemorrhage occurred mainly in the peripheral area of the tumor mass. Measurements of tumoral hemoglobin content and dye permeation revealed that the hemorrhage occurred firstly and tumor blood flow stopped secondarily. The vascular damage was followed by continuous induction of apoptosis of the tumor cells, tumor tissue necrosis, and tumor regression. In cultured HUVEC, TZT-1027 induced marked cell contraction with membrane blebbing in 30 min. These cell changes were completely inhibited by K252a, a broad-spectrum inhibitor of protein kinases. These effects of TZT-1027 on both tumor vasculature and HUVEC were greater than those of vincristine. In conclusion, TZT-1027 quickly attacked the well-developed vascular system of advanced tumors by a putative protein kinase-dependent mechanism, and then blocked tumor blood flow. Therefore, TZT-1027 has both a conventional antitumor activity and a unique anti-tumoral vascular activity, making it a potentially powerful tool for clinical cancer therapy.

Topics: Animals; Antineoplastic Agents; Cell Survival; Colonic Neoplasms; Disease Models, Animal; DNA Fragmentation; Endothelium, Vascular; Female; Hemoglobins; Humans; Mice; Mice, Inbred BALB C; Microtubules; Neoplasm Transplantation; Neovascularization, Pathologic; Oligopeptides; Permeability; Tumor Cells, Cultured