soblidotin and thiazolyl-blue

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

TZT-1027, an antimicrotubule agent that inhibits the polymerization of tubulin, shows potent antitumor activity in various transplantable tumor models in vivo. The high antitumor activity of TZT-1027 prompted us to speculate that this compound may have a mode of action other than its antimicrotubule and antimitotic activities. To elucidate the interaction of antitumor cytokines with TZT-1027 in tumors in vivo, we examined the antitumor activity of this agent against various cytokine gene-transfected Lewis lung carcinoma (LLC) cells inoculated into C57BL/6 mice.. In vitro growth inhibition was evaluated using the MTT assay, and in vivo activity was evaluated in subcutaneous models in C57BL/6 mice. The status of the vasculature in tumor tissues was evaluated immunohistochemically using anti-CD31 antibody. We used a cDNA macroarray to examine the gene expression profiles in tumor tissues removed from mice.. TZT-1027 at 3 mg/kg showed potent antitumor activity in Mock (LLC-Neo cells) inoculated mice with a T/C% value of 16%. TZT-1027 at 3 mg/kg showed more potent antitumor activity in LLC-TNF cells and LLC-IL6 cells with T/C% values of 4% and 3%, respectively. TZT-1027 treatment destroyed the tumor vasculature as well as tumor cells in LLC-TNF and LLC-IL6 tissues of mice treated with TZT-1027. The LLC-TNF and LLC-IL6 tissues of mice treated with TZT-1027 had in common the independent alteration of the non-histone chromosomal protein HMG-14 and transcription factor 1 for heat shock gene. Focusing on the gene regulation related to angiogenesis, the alteration in transcriptional factors such as ets family genes and homeobox family genes was remarkable.. These factors are candidates as determinants of the enhanced TZT-1027 antitumor activity in relation to these cytokines.

Topics: Animals; Antineoplastic Agents; Carcinoma, Lewis Lung; DNA, Complementary; Gene Expression Regulation, Neoplastic; Immunohistochemistry; Interleukin-6; LLC-PK1 Cells; Mice; Mice, Inbred C57BL; Oligonucleotide Array Sequence Analysis; Oligopeptides; RNA, Neoplasm; Tetrazolium Salts; Thiazoles; Transfection; Tumor Necrosis Factor-alpha