Masanori Murakoshi

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.

An antimicrotubule agent, TZT-1027, does not induce neuropathologic alterations which are detected after administration of vincristine or paclitaxel in animal models

One of the major dose-limiting toxicities induced by antimicrotubule antitumor agents such as vinca alkaloids and taxanes is peripheral neuropathy. The neurotoxicity of TZT-1027 (a dolastatin 10 derivative antimicrotubule agent) was thus assessed using the animal models for antimicrotubule agent-induced neurotoxicity. Rabbits were intravenously given TZT-1027 or vincristine weekly for 5 weeks. In the mouse study, TZT-1027, vincristine or paclitaxel was intravenously given every 2 days and/or weekly. Despite the neuropathologic evidence such as myelinated axonal and fiber degeneration in the peripheral nerves and in the sensory tracts of the spinal cord following the treatment with vincristine or paclitaxel, no drug-induced alteration was observed in the TZT-1027 groups. Although there are reports that some other dolastatin derivatives with antimicrotubule activity showed no neurotoxic potential in humans, the present study represents the first demonstration in experimental animals that a dolastatin derivative has no, or at least a lower, neurotoxic potential compared to other antimicrotubule agents.

Effect of anti-androgen (TZP-4238) on steroid-induced canine prostatic hyperplasia. Light and electron microscopic investigations.

The effect of a synthetic steroidal anti‐androgen, TZP‐4238, on steroid‐induced canine prostatic hyperplasia was studied by light and electron microscopy. Male beagle dogs (1–2 years old) were divided into four experimental groups. Group 1 consisted of intact controls. The other animals were castrated. The castrated animals were treated for 25 weeks with 1) 5α‐androstane‐3α, 17β‐diol (A‐diol) plus 17β‐estradiol (E2)(Group2), 2) A‐diol plus E2+ TZP 4238 0.5mg/kg (Group 3) and 3) A‐diol plus E2+ chlormadinone acetate (CMA) 2.5 mg/kg (Group 4). TZP‐4238 and CMA were administered orally for 21 weeks after 4 weeks treatment with A‐diol plus E., In group 2, glandular hyperplasia of the prostate was clearly noted. In contrast, combined treatment with TZP‐4238 (Group 3) or CMA (Group 4) produced marked atrophy of the glandular epithelium. Loss of secretory and metabolic activities was confirmed by ultrastructural investigations. Our data indicate that TZP‐4238 is a potent anti‐androgen for the prevention of canine prostatic hyperplasia in the steroid‐induced benign prostatic hyperplasia (BPH) model. Acta Pathol Jpn 40: 871–879, 1990.

Inhibitory Influence of a New Steroidal Anti‐androgen, TZP‐4238, on Prostatic Hyperplasia in the Beagle Dog

The effect of a synthetic steroidal anti‐androgen, TZP‐4238, on spontaneous benign prostatic hyperplasia (BPH) in dogs was investigated. Old male beagle dogs (5–9 years old) were divided into three experimental groups. Group 1 consisted of BPH controls. Groups 2 and 3 received TZP‐4238 0.1 mg/kg/day and chlormadinone acetate (CMA) 0.3 mg/kg/day P.o., respectively, for 5 months. In group 1, glandular hyperplasia of the prostate was clearly detected. In contrast, TZP‐4238 (Group 2) or CMA (Group 3) produced marked atrophy of the glandular epithelium. In addition, a histopathological study showed that TZP‐4238 or CMA medication for 5 months exerted no effect on the testes and the pituitary luteinizing hormone (LH) cells. Therefore, it is suggested that TZP 4238 (0.1 mg/kg) or CMA (0.3 mg/kg) causes regression of spontaneous canine BPH without any histopathological effects on the testes and pituitary LH cells. However, slightly decreased serum testosterone levels were found in TZP 4238 treated animals, due apparently to a direct and/or indirect effect on the testes. Thus, it is suggested that a marginal antigonadotrophic effect cannot be excluded. It is concluded that TZP‐4238 is a potent anti‐androgen for the treatment of spontaneous canine BPH, without any negative influence on the function of the testes and the pituitary LH cells. Acta Pathol Jpn 42: 151–157, 1992.

Biological Aspects of Pituitary Tumors Induced by Synthetic Salmon Calcitonin (TZ–CT) in Sprague-Dawley Rats

Rat pituitary tumors induced by synthetic salmon calcitonin (TZ–CT) were studied by the indirect peroxidase‐labeled antibody method, together with ultrastructure and serum hormone measurement. Immunohistochemically, TZ–CT‐induced pituitary tumors showed staining for only rLHα subunit, and were negative for other peptide hormones including GH, PRL, αMSH and ACTH, and the α subunit of glycoprotein hormones. Electron microscopic examination showed that the majority of tumor cells possessed numerous small secretory granules, 100 to 200 nm in diameter. The serum PRL concentrations of rats with TZ–CT induced pituitary tumors were markedly elevated, but not beyond 130 ng/ml. From our data, TZ–CT‐induced pituitary tumors are considered to be endocrinologically inactive and to produce α subunit. Furthermore, these tumors are thought to be potentially useful models of α subunit producing pituitary tumors in humans. This is the first report to document the tumorigenesis of α subunit producing pituitary tumors in rats after long‐term treatment with calcitonin.

A Case of Testosterone-secreting Adrenal Cortical Adenoma with Spironolactone Body-like Inclusion

Testosterone secreting adrenal adenoma is rare. We recently experienced a 17‐year‐old pubertal girl who showed signs of virilization and a high serum level of testosterone. The excised adrenal gland showed a 3.5 × 3 × 3‐cm cortical adenoma. Light and electron microscopic findings together with the high serum level and high tumor tissue contents of testosterone and dehydroepiandrosterone (DHA) indicated that the tumor was a testosterone‐secreting adrenal cortical adenoma. This appears to be a rather rare tumor from a review of the literature. Interestingly, in this case, the cytoplasm of the tumor cells contained structures resembling spironolactone bodies. From the results of enzyme histo‐chemistry, the steroidogenetic pathways in this tumor were speculated. Acta Pathol Jpn 40: 67–72, 1990.

Immunolocalization of Glutathione-Peroxidase (GPx1) in the Rat Adrenal Cortex: Correlation between Steroidogenesis and Lipid Peroxidation

In order to confirm the relationship between glutathione-peroxidase (GPx1) and biological significance on steroidogenesis, we have studied the immunocytochemical localization of GPx1 in the rat adrenal cortical cells. GPx1 was observed not only in cytoplasm (cytosol GPx1) but in mitochondria (mitochondrial GPx1). The staining intensity was altered by the functional state of the adrenal cortical cells. Furthermore, cytosol- and mitochondrial-GPx1 was modified by lipoperoxidative damage in the adrenal cortical cells. Therefore, we proposed that the pattern of GPx1 staining should be a more sensitive and specific indicator of oxidative damage in cells. Thus, the staining pattern of GPx1 is thought to be a useful marker for lipid peroxidation in the adrenal cortical cells.