Ichiro Urushizaki

Circulating transferrin receptor in human serum

Circulating transferrin receptor has been detected in human serum with a sensitive immunoassay. The mean concentrations of the serum transferrin receptor in healthy males and females were 251 +/- 94 (mean +/- SD) ng/ml and 256 +/- 99 ng/ml, respectively. The serum receptor concentration in patients with haematological malignancies, including acute leukaemia, multiple myeloma and malignant lymphoma, varied widely, from normal to 1100 ng/ml. A single band with an approximate molecular weight between 80,000 and 100,000 daltons was obtained by polyacrylamide gel electrophoresis-immunoblotting analysis of serum.

Release of tumor necrosis factor (TNF) into mouse peritoneal fluids by OK-432, a streptococcal preparation.

A cytotoxic factor was induced in peritoneal fluid by injection of OK-432 in mice which had been primed with OK-432. Two-step stimulation (priming and eliciting) was always necessary to induce the cytotoxic factor. OK-432-primed mice did not produce soluble cytotoxic factor spontaneously and no cytotoxic activity was detected in the mice treated by a single injection of OK-432 as an eliciting agent. This observation was also confirmed by in vitro experiments. Only when activated macrophages were incubated with OK-432 (or with lipopolysaccharide) was cytotoxin released into medium supernatant. High doses of OK-432 were required to prime mice for the production of cytotoxic factor, whereas a small amount was enough to elicit. The peritoneal cytotoxic factor obtained by OK-432 injection appears to be identical to tumor necrosis factor in the serum for the following reasons: The two factors are similar in mode of cytotoxic action. Both are produced from macrophages. They are similar in physicochemical characteristics. The cytotoxicity of the peritoneal cytotoxic factor was totally abolished by anti-TNF serum.

Microheterogeneity of horse spleen ferritin and apoferritin

Abstract In the present experiments we attemped to fractionate horse spleen ferritin and apoferritin on an electrofocusing column and obtained eight or nine heterogenous peaks in a pH range of 4.22 to 4.6, which were grouped into three main components. There was no significant difference between the fraction patterns of horse spleen ferritin, monomeric ferritin and apoferritin. The heterogeneity demonstrated in the present paper represents polymorphic forms of ferritin rather than polymeric forms as hitherto described.

Cytotocidal Mechanism of TNF: Effects of Lysosomal Enzyme and Hydroxyl Radical Inhibitors on Cytotoxicity

The participation of lysosomal enzymes, hydroxyl radicals, and mitochondrial respiration in the cytocidal effect of TNF on tumor cells was investigated. The cytotoxicity of TNF on L-M cells was clearly reduced by lysosomotropic agents, DMSO (hydroxyl radical scavenger), NDGA (lipoxygenase inhibitor), and sodium azide (mitochondrial respiration inhibitor). The results suggest that lysosomal enzyme and hydroxyl radicals play an important triggering role in the destruction of tumor cells by TNF, and that the process of destruction might require ATP.

Synergistic Cytotoxicity of Recombinant Human TNF and Various Anti-Cancer Drugs

A synergistic increase in the cytotoxic effects of recombinant human tumor necrosis factor (rH-TNF) and anti-cancer drugs was demonstrated in vitro. The cytotoxicity of rH-TNF against L-M cells in combination with Mitomycin C (MMC), Adriamycin (ADM), Cytosine arabinoside (Ara-C), Actinomycin D (ACD), Daunomycin (DM), Cisplatin (CDDP), Vincristine (VCR), and 5-Fluorouracil (5FU), based on the concentration necessary for 50% inhibition of cell growth (IC50), was 4 to 347 times as high as that of rH-TNF alone. The results suggest that combination therapy including rH-TNF and anti-cancer drugs may be of value in the treatment of malignancy in human patients.

Immunoreactive transferrin receptor in sera of pregnant women

Abstract Immunoreactive transferrin receptors in sera of 90 pregnant women of various gestational periods were investigated. The mean concentrations of the serum transferrin receptor in normal males and females were 251 ± 94 ng/ml and 256 ± 99 ng/ml, respectively. Serum transferrin receptor levels in pregnant women did not show a significant increase in the early stage of gestation. However, a rapid elevation of the mean concentration of transferrin receptor was observered after 20 weeks of pregnancy. The apparent increase with gestation period suggests that this immunoreactive receptor in the sera of pregnant women is derived from the placental syncytiotrophoblast and reflects the activity of maternofetal iron transport.

Externalization of transferrin receptor in established human cell lines

The externalization of transferrin receptors was found in established human tumor cell lines at the rate of 10-35 ng/hour/10(6) cells, when they were incubated with transferrin at 37 degrees C. This externalization is inhibited by lowering the incubation temperature to 4 degrees C or eliminating the ligand from the culture medium. Metabolic inhibitors such as sodium azide, colchicine, cytochalasin B and chloroquine also decreased the rate of externalization. Almost 95% of released transferrin receptors were precipitated by centrifugation at 100,000 x g for 30 min, suggesting that transferrin receptor is externalized into the medium as a vesicular form.

Microheterogeneity of rat liver ferritin: comparison of electrofocusing and chromatographic fractions.

Abstract Isoelectric fractionation of rat liver ferritin showed three heterogeneous peaks. The isoelectric points of three peaks were pI 5.16, 5.24, and 5.29. Using CM-cellulose column chromatography, heat supernatant of rat liver homogenate was separated to six fractions by a stepwise elution. Among them, three fractions which are eluted by acetate buffer with pH 5.1, 5.2, and 5.3 were shown to be ferritin electrophoretically and immunologically. Three ferritin fractions eluted by CM-cellulose column chromatography were applied to electrofocusing columns. The ferritin fraction which was eluted by a acetate buffer, pH 5.1, gave a single peak with isoelectric point of 5.16. The ferritin fraction which was eluted by a acetate buffer pH 5.2 gave also a single peak with isoelectric point of 5.24. The last ferritin fraction could not be applied to electrofocusing column because of a small amount of protein concentration. Microheterogeneity of rat liver ferritin on isoelectric fractionation corresponds to it on CM-cellulose column chromatography.

Therapeutic Effect of Endogenous Tumor Necrosis Factor on Ascites Meth A Sarcoma

The therapeutic effect of endogenous tumor necrosis factor (TNF) on Meth A ascites fibrosarcoma in mice was investigated. Serum and peritoneal fluid from tumor bearing mice treated with OK-432 and LPS were cytotoxic to tumor cells in vitro. The peak of cytotoxicity in both the serum and peritoneal fluid was found in the fraction corresponding to a molecular weight of approximately 54,000-56,000 on HPLC and the pI was found to be 4.9-5.1 by isoelectric focusing. These results are consistent with previously reported findings on TNF, and indicate that endogenous TNF has a satisfactory life-prolonging effect. The tumor necrosis factor (TNF) is considered to be one of the clinically most promising anti-cancer cytokines because of its potent and very specific antitumor effect on target cells (Carswell, Old, Kassel, Green, Fiore & Williamson, 1975; Matthews & Watkins, 1978; Niitsu, Watanabe & Urushizaki, 1984). TNF as an anti-cancer cytokine for the treatment of cancer may be applied in one of the two following ways: by administration of purified TNF or by endogenously inducing TNF in cancer bearing individuals. The antitumor effects of TNF administered exogenously have been examined using crude preparations or serum containing TNF (tumor necrosis serum, TNS) (Carswell et al., 1975; Watanabe, Niitsu, Sone, Neda, Ishigaki & Urushizaki, 1984). In a previous paper we reported that mice primed with OK-432 and challenged with endotoxin produced a soluble cytotoxic factor in peritoneal fluids (Yamamoto, Nagamuta, Usami, Sugawara, Watanabe, Niitsu & Urushizaki, 1985; Nagamuta, Yamamoto, Usami, Sugawara, Watanabe, Niitsu & Urushizaki, 1985). Ths peritoneal cytotoxic factor (PCF) had cytostatic and/or cytotoxic effect not only on mouse tumor cell lines but also on human tumor cell lines without species specificity. Normal cell lines were not affected. Here we report the endogenous production of TNF in tumor bearing mice and its antitumor effects.

Production of cytotoxic factor into mouse peritoneal fluid by OK-432, a streptococcal preparation

A cytotoxic factor was induced by the injection of LPS into the peritoneal fluids of mice which had been previously primed with a streptococcal antitumor preparation, OK-432. No cytotoxic effect on L-929 cells was observed in the peritoneal fluids of mice singly treated with OK-432 or LPS. Various mouse and human tumor cell lines were effectively killed by this peritoneal cytotoxic factor, though normal cell lines were insensitive, which indicates that this factor is not species-specific. The highest level of cytotoxic activity was obtained when LPS was given to mice 5 days after the injection of OK-432. The optimal time for collection of peritoneal fluids for the cytotoxic factor was 2 h following the LPS injection. Interferon activity was found to be negative by the plaque reduction test using L-929 cells with vesicular stomatitis virus. These results suggest that this cytotoxic factor is similar to the tumor necrosis factor (TNF) in the mouse serum.