TZT-1027, an Antimicrotubule Agent, Attacks Tumor Vasculature and Induces Tumor Cell Death

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.     

Blue laser imaging identifies endoscopic findings corresponding to metachronous esophageal squamous cell carcinoma

Esophagus - This study aimed to evaluate endoscopic findings using non-magnifying blue laser imaging (BLI) to determine the risk factors for metachronous esophageal squamous cell carcinoma (ESCC)....     

Characterization of the Interaction of TZT-1027, a Potent Antitumor Agent, with Tubulin

TZT‐1027, a derivative of dolastatin 10 isolated from the Indian Ocean sea hare Dolabella auricularia in 1987 by Pettit et al., is a potent antimicrotubule agent. We have compared the activity of TZT‐1027 with that of dolastatin 10 as well as the vinca alkaloids vinblastine (VLB), vincristine (VCR) and vindesine (VDS). TZT‐1027 and dolastatin 10 inhibited microtubule polymerization concentration‐dependently at 1–100 μM with IC₅₀ values of 2.2±0.6 and 2.3±0.7 μM, respectively. VLB, VCR and VDS inhibited microtubule polymerization at 1–3 μM with IC₅₀ values of 2.7±0.6, 1.6±0.4 and 1.6±0.2 μM, respectively, but showed a slight decrease in inhibitory effect at concentrations of 10 μM or more. TZT‐1027 also inhibited monosodium glutamate‐induced tubulin polymerization concentration‐dependently at 0.3–10 μM, with an IC₅₀ of 1.2 μM, whereas VLB was only effective at 0.3–3 μM, with an IC₅₀ of 0.6 μM, and caused so‐called “aggregation” of tubulin at 10 μM. Scatchard analysis of the binding data for [³H]VLB suggested one binding site (K_d 0.2±0.04 μM and B_max 6.0±0.26 nM/mg protein), while that for [³H]TZT‐1027 suggested two binding sites, one of high affinity (K_d 0.2±0.01 μM and B_max 1.7±0.012 nM/mg protein) and the other of low affinity (K_d 10.3±1.46 μM, and B_max 11.6±0.83 nM/mg protein). [³H]TZT‐1027 was completely displaced by dolastatin 10 but only incompletely by VLB. [³H]VLB was completely displaced by dolastatin 10 and TZT‐1027. Furthermore, TZT‐1027 prevented [³H]VLB from binding to tubulin in a non‐competitive manner according to Lineweaver‐Burk analysis. TZT‐1027 concentrationdependently inhibited both [³H]guanosine 5′‐triphosphate (GTP) binding to and GTP hydrolysis on tubulin. VLB inhibited the hydrolysis of GTP on tubulin concentration‐dependently to a lesser extent than TZT‐1027, but no inhibitory effect of VLB on [³H]GTP binding to tubulin was evident even at 100 μM. Thus, TZT‐1027 affected the binding of VLB to tubulin, but its binding site was not completely identical to that of VLB. TZT‐1027 had a potent inhibitory effect on tubulin polymerization and differed from vinca alkaloids in its mode of action against tubulin polymerization.     

Complete one-to-one correspondence between magnifying endoscopic and histopathologic images: the KOTO method II

Recent advances in magnifying endoscopy with narrow-band imaging/blue laser imaging have aided in the diagnosis of gastrointestinal lesions. However, it requires knowledge of the relationship between magnifying endoscopic and histopathological images. We propose a novel method which makes possible a complete correspondence between magnifying endoscopic and histopathological images at the single glandular duct level. The KOTO method II enables three-dimensional visualization of the correlation between the endoscopic surface pattern of the mucosa and histopathological images. This method may be helpful in the development of diagnosis using magnifying endoscopy.

     

Antivascular effects of TZT-1027 (Soblidotin) on murine Colon26 adenocarcinoma

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.     

Can image-enhanced endoscopy improve the diagnosis of Kyoto classification of gastritis in the clinical setting?

Endoscopic diagnosis of Helicobacter pylori (H. pylori) infection, the most common cause of gastric cancer, is very important to clarify high-risk patients of gastric cancer for reducing morbidity and mortality of gastric cancer. Recently, the Kyoto classification of gastritis was developed based on the endoscopic characteristics of H. pylori infection-associated gastritis for clarifying H. pylori infection status and evaluating risk factors of gastric cancer. Recently, magnifying endoscopy with narrow-band imaging (NBI) has reported benefits of the accuracy and reproducibility of endoscopic diagnosis for H. pylori-related premalignant lesions. In addition to NBI, various types of image-enhanced endoscopies (IEEs) are available including autofluorescence imaging, blue laser imaging, and linked color imaging. This review focuses on understanding the clinical applications and the corresponding evidences shown to improve the diagnosis of gastritis based on Kyoto classification using currently available advanced technologies of IEEs.     

Efficacy of scissor-type knives for endoscopic mucosal dissection of superficial gastrointestinal neoplasms

Endoscopic submucosal dissection (ESD) for superficial gastrointestinal neoplasms has become widespread. However, certain aspects of the procedure remain difficult to manage, such as intraoperative bleeding and perforation. There are two kinds of scissor-type knife: the Clutch Cutter (Fujifilm Co., Tokyo, Japan) and the SB knife (Sumitomo Bakelite Co., Tokyo, Japan). These knives have different features from other types of ESD knives and enable the performance of all ESD procedures, including mucosal incision, submucosal dissection, and hemostasis. The standard approach with scissor-type knives involves first grabbing the tissue and then incising or dissecting it. Theoretically, perforation as a result of unintentional movement should never happen with scissor-type knives compared to needle- or blade-type knives, which may induce perforation through unintentional movement. Moreover, the rates of severe bleeding and self-completion of ESD with scissor-type knives by non-experts were reported to be significantly better than for other knives. Thus, scissor-type knives can resolve these problems and help to further standardize ESD globally. In this review, we summarize reports on the efficacy of such scissor-type knives for ESD of gastrointestinal tumors. We also present the pocket-creation method and the application of traction devices, such as dental floss and S-O clips (Zeon Medical Co., Tokyo, Japan) for improving the performance of ESD with a Clutch Cutter.     

Antitumor activity of TZT-1027 (Soblidotin) against vascular endothelial growth factor-secreting human lung cancer in vivo

TZT-1027 (Soblidotin), an antimicrotubule agent, has been demonstrated to show potent antitumor effects, though the relationships among antitumor effect, cytotoxicity and anti-vascular effect of TZT-1027 have not been studied. We established in vivo human lung vascular-rich tumor models using a vascular endothelial growth factor-secreting tumor (SBC-3/VEGF). SBC-3/VEGF tumors exhibited a high degree of angiogenesis in comparison with the mock transfectant (SBC-3/Neo) tumors in a dorsal skinfold chamber model and grew much faster and larger than SBC-3/Neo tumors in the tumor growth study. The antitumor activity of antimicrotubule agents, including TZT-1027, was evaluated in both early- and advanced-stage SBC-3/Neo and SBC-3/VEGF tumor models to elucidate the relationship between the antitumor activity and anti-vascular effect of these agents. TZT-1027 exhibited potent antitumor activity against both early- and advanced-stage SBC-3/Neo and SBC-3/VEGF tumors, whereas combretastatin A4 phosphate did not. Vincristine and docetaxel exhibited potent antitumor activity against early-stage SBC-3/Neo and SBC-3/VEGF tumors, and advanced-stage SBC-3/Neo tumors, but did not exhibit activity against advanced-stage SBC-3/VEGF tumors. The difference in antitumor activity between these agents could be ascribed to differences in direct cytotoxicity and anti-vascular effect. Furthermore, a prominent accumulation of erythrocytes in the tumor vasculature, followed by leakage and scattering of these erythrocytes from the tumor vasculature, was observed after TZT-1027 administration to mice bearing advanced-stage SBC-3/VEGF tumors. These findings strongly suggest that TZT-1027 has a potent anti-vascular effect, in addition to direct cytotoxicity.