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Biomedical subjects

T Shirasaka

Publications and source records attributed to T Shirasaka.

At least 127 records · Page 7Linked to original sources
PubMed1988

Combined therapy of mice bearing a lymphokine-activated killer-resistant tumor with recombinant interleukin 2 and an antitumor monoclonal antibody capable of inducing antibody-dependent cellular cytotoxicity.

The ability of lymphokine-activated killer (LAK) cells to mediate antibody-dependent cellular cytotoxicity and its efficacy against a LAK-resistant tumor were investigated. Cells of the MH134 murine hepatoma line are scarcely lysed by LAK cells generated in vitro by incubation of C3H/HeN mouse spleen cells with human recombinant interleukin 2 (rIL 2). However, the splenic LAK cells potently lysed the LAK-resistant tumor cells in the presence of 11G2, a monoclonal antibody (MAb) of the IgG1 isotype reactive with a part of MM antigen. Peritoneal cells induced by daily i.p. injections of rIL 2 not only exhibited LAK activity but also mediated antibody-dependent cellular cytotoxicity against MH134 tumor cells in the presence of 11G2. The peritoneal cells exhibiting these cytotoxic activities were found to be nonadherent and nonphagocytic mononuclear cells possessing a similar cell surface phenotype as that of splenic LAK cells, that is Thy-1.2+ approximately -, Lyt-1.1-, Lyt-2.1-, and asialo GM1+. Treatment of spleen cells with antibodies and complement before culture with rIL 2 revealed that the phenotype of splenic LAK precursors is Thy-1.2- and asialo GM1+. The in vivo induction of peritoneal LAK cells in response to i.p. injections of rIL 2 was markedly depressed in C57BL/6 beige mice but was normally accomplished in BALB/c nude mice. Combined therapy of C3H/HeN mice bearing MH134 ascitic tumor with i.p. injection of rIL 2 and 11G2 brought about potent suppression of the tumor growth, resulting in the significant increase in the number of tumor-free mice, whereas neither rIL 2 nor the MAb could exhibit such a potent antitumor effect when used alone. Injection (i.v.) of anti-asialo GM1 antibody not only blocked the induction of peritoneal LAK cells by rIL 2 but also abrogated the development of the antitumor effect of the combined therapy. These results strongly suggest that combination of antitumor MAbs capable of inducing antibody-dependent cellular cytotoxicity with rIL 2 therapy could result in the generation of potent antitumor effects against LAK-resistant tumors and that asialo GM1-positive non-T-cell populations including cells of the natural killer cell lineage are essential, at least in part, for development of the antitumor effects of the combined therapy with rIL 2 and MAbs.

Animals↗
PubMed1988

Augmentative effect of Nocardia rubra cell-wall skeleton (N-CWS) on lymphokine-activated killer (LAK) cell induction.

The present study elucidated that N-CWS augments the cytolytic activity against 3LL tumor cells of LAK cells from N-CWS-immunized mice administered i.p. with rIL-2. This augmentative effect of N-CWS was not seen when the LAK cells were prepared from normal mice. The cytolytic activity was predominantly expressed in the NAPC prepared from the site of injection of rIL-2, and repeated administrations of rIL-2 were required to induce and maintain this potent cytolytic activity in vivo. Serological analysis revealed that the LAK cells were positive for Thy 1.2 and asialo GM1 antigens and that they were not classical CTL or NK cells. The administration of rIL-2 statistically prolonged the MST of mice bearing LAK-sensitive 3LL cells but not the MST of mice bearing LAK-resistant EL-4 leukemia. Furthermore, combination therapy with N-CWS and rIL-2 prolonged the MST of the mice more than the therapy with rIL-2 alone. These results suggest that LAK cells potentiated with N-CWS would be useful for immunotherapy of malignant neoplasms.

Animals↗
PubMed1987

Synergistic antitumor effects of BCG and monoclonal antibodies capable of inducing antibody-dependent cell-mediated cytotoxicity.

Three monoclonal antibodies (MAbs) of different immunoglobulin subclasses against MH134 murine ascitic hepatoma cells, detecting the same antigenic determinant of tumor-associated antigen of the tumor cells, were tested for their ability to produce a synergistic antitumor effect with Mycobacterium bovis BCG in C3H/HeN mice. 12A2 (IgG2a) induced both antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) against the tumor cells. C3H/HeN mice were inoculated ip with MH134 tumor cells (day 0), and received an ip injection of BCG (day 1) and/or 12A2 (day 5). The combined therapy with BCG and 12A2 brought about a significant prolongation of the survival period, whereas either BCG or the MAb alone exhibited poor therapeutic effectiveness. 11G2 (IgG1), inducing ADCC but not CDC against MH134 tumor cells, was shown to exhibit antitumor effects as potent as those of 12A2, when used in combination with BCG. However, 7C2 (IgM), capable of inducing CDC but not ADCC to the tumor cells, produced no apparent synergistic effect with BCG. ADCC of BCG-induced peritoneal cells was mediated by the adherent cell population of the cells and abolished by the addition of carrageenan, suggesting that the effector cells of the cytotoxicity were macrophages. Moreover, carrageenan abolished the combined antitumor effect of BCG and these MAbs in the serological Winn assay. These results suggest that activated macrophages play a major role in the synergistic antitumor effect of BCG and MAbs capable of inducing ADCC against MH134 tumor.

Animals↗
PubMed1987

Inhibitory effects of pyrimidine, barbituric acid and pyridine derivatives on 5-fluorouracil degradation in rat liver extracts.

The inhibitory effects of about 30 compounds, mainly pyrimidine and pyridine derivatives, on 5-fluorouracil degradation catalyzed by dihydrouracil dehydrogenase (DHU dehydrogenase) were investigated. The inhibitory activities of 5-substituted uracil derivatives decreased time-dependently during preincubation with liver extracts, indicating that these compounds are substrates of DHU dehydrogenase. During preincubation, 4,6-dihydroxypyrimidine derivatives were found to be converted to barbituric acid derivatives, which have stronger activities. The inhibitory activity of 2,4-dihydroxypyridine (3-deazauracil), which was stronger than that of uracil, did not change during preincubation, indicating that this compound is not a substrate but is an inhibitor of DHU dehydrogenase, and suggesting that 2,6-dihydroxypyridine (1-deazauracil) could be a potent inhibitor. In the light of these findings, we examined various derivatives of barbituric acid, 2,4-dihydroxypyridine and 2,6-dihydroxypyridine. Among these compounds, 3-cyano-2,6-dihydroxypyridine and 5-chloro-2,4-dihydroxypyridine were the strongest inhibitors with Ki values for DHU dehydrogenase of 2.3 X 10(-7) M and 3.6 X 10(-7) M, respectively.

Animals↗
PubMed1986

[Studies of the antitumor activity and enzymology of 2'-deoxy-5-fluorouridine (FdUrd) derivatives].

The antitumor activity and enzymology of 2'-deoxy-3', 5'-bis-O-(4-methoxyphenoxycarbonyl)-5-fluoro-3-(4-n-Propoxybenz oyl uridine (FF-707) were examined. It was found that stability in small intestine homogenate of FF-707 was higher than that of FF-705 [2'-deoxy-3', 5'-O-diacetyl-5-fluoro-3-(3 methylbenzoyl) uridine]. Reduction of the tumor weight was greater in mice bearing sarcoma-180 and rats bearing Yoshida sarcoma treated with the oral administration of FF-707 than that FF-705. The relationship between the antitumor activity and the inhibition of thymidylate synthase after the oral administration of FF-707 was examined. The extent of the inhibition of thymidylate synthase seemed to be parallel to that of the inhibition of the tumor growth.

Animals↗
PubMed1986

[Thymidylate synthase inhibition in malignant tumors after oral administration of UFT].

Surgical resection of solid tumors was undertaken five to six hours after the oral administration of UFT (300-500 mg/body) in five patients, who were (then) assayed for 5-fluorodeoxyuridylate (FdUMP), total dTMP synthase (TS) and non-FdUMP-bound, free enzyme. Three patients had gastric cancer, and two had mammary cancer. Control solid tumors were obtained without, the drug in eight patients. Six patients had gastric cancer. Eight had mammary cancer. Total TS averaged 2.04 p mol/g in the malignant tissues. TS inhibition averaged 40.1% to 57.1% in gastric cancer and 17.1% to 52.7% in mammary cancer. These data suggest that TS inhibition after oral administration of 5FU derivatives may be usefully studied for biochemical parameters of mechanisms of drug resistance.

Administration, Oral↗
PubMed1984

[Development of fluoropyrimidine derivatives].

5-Fluorouracil (5-FU), first synthesized by Heidelberger et al. in 1957 has been used extensively in the treatment of cancer. In the process of development antitumor drugs in fluoropyrimidine, 5-FU and 5-fluorodeoxyuridine (FdUrd) were chosen because these two drugs relatively were incorporated into tumor tissues more than into normal tissues. The toxicity of 5-FU seems to be proportional to its concentration in blood. To be effective clinically, the concentration of a therapeutic drugs (5-FU and FdUrd) should be high in the tumor and low in the blood. In this paper, the characterization of masked forms of 5-FU and FdUrd were described as follows: Metabolism of 5-FU and uracil. Conversion of FT-207 to 5-FU (P-450). Prove in chemotherapy of cancer by oral administration of FT-207. Theory of co-administration of FT-207 with uracil (UFT-therapy). Conversion of 5'DFUR (5'deoxy-5-fluorouridine) to 5-FU (Pyrimidine nucleoside phosphorylase). Conversion of FF-705a 2'-deoxy-3', 5'-O- diacetyl-5-fluoro-3-(3-methylbenzoyl)-uridine to FdUrd and 5-FU, and fluctuation of 5-FU and FdUrd levels in the blood after oral administration of FF-705a.

Animals↗
PubMed1984

[Regulation of enzyme activities involved in pyrimidine synthesis and its application to cancer chemotherapy].

We examined the enhancing effect of antitumor activity by co-administration of 5-FU or its masked form (FT-207) with bases or nucleosides of purine and pyrimidine. It was found that the antitumor activity of 5-FU or FT-207 on sarcoma-180 and AH-130 tumor was oral administration of uracil, deoxyuridine, uridine, thymine or thymidine. Uracil had more effect than other pyrimidine nucleotides in enhancing antitumor effect of these drug to FT-207 without toxicity. In contrast to the results with FT-207, co-administration of uracil with 5-FU increased its antitumor activity and also the toxicity of 5-FU. On the ther hand, no enhancing antitumor activity of dRib-1-P, Rib-1-P, Ado, Xao, Guo, Ino, dAdo, dIno and dGuo to FT-207 was observed. Concentration of 5-FU in the tumor, blood and various organs of AH-130-bearing rats after oral administration of clinical doses of FT-270 and uracil was examined. On oral administration of FT-207 plus uracil in various combinations, the highest T/B (ratio of concentration of 5-FU in the tumor to that in blood) value was obtained at a ratio of uracil to FT-207 of 4. Moreover, it was found that 5-FU was mainly phosphorylated in the tumor tissues whereas it was mainly degraded in liver slices. Degradation of 5-FU in vitro was inhibited more by thymine than by uracil. Phosphorylation of 5-FU, however, was not inhibited by uracil, thymine or thymidine, even times the concentration of 5-FU. These findings suggest that the enhancement of antitumor activity of 5-FU-masked form is more important the inhibition of 5-FU degradation than the stimulation of 5-FU phosphorylation.

Administration, Oral↗
PubMed1984

[Studies on the mechanism of antitumor activity of 5-FU and its derivatives--relationship between the inhibition of tumor growth and the inhibition of thymidylate synthetase in vivo].

The relationship between the antitumor activity and the inhibition of thymidylate synthase after oral administration of 5-FU, FT-207 or UFT was examined. The inhibition of tumor growth on sarcoma-180 after oral administration of 5-FU (20 mg/kg), FT-207 (120 mg/kg) or UFT (30 mg/kg) was 40%, 50% or 70%, respectively. It was found that the inhibition of thymidylate synthase in sarcoma-180 tumor tissue after single oral administration of 5-FU (20 mg/kg), FT-207 (30 or 120 mg/kg) or UFT (30 mg/kg) were about 45%, 20%, 50% or 65%, respectively, but the activities of other enzymes involved in DNA synthesis were not almost inhibited. Thymidylate synthase was inhibited more severely by oral administration of UFT (30 mg/kg). The activities of other enzymes were not inhibited even by continuous oral administration of these drugs for 6 or 11 days. The extent of inhibition of thymidylate synthase seemed to be parallel to that of inhibition of tumor growth. These results suggest that the inhibition of thymidylate synthase by FdUMP converted from 5-FU, FT-207 or UFT plays a major role in their antitumor actions.

Animals↗
PubMed1984

Characterization of the activity of growth factor from AH-130 tumor cells.

The activation of DNA synthesis induced by growth factor from the cytosol of AH-130 tumor cells (AH-130GF) was inhibited by alkylamines (methylamine, ethylamine, and dansylcadaverine), which inhibit the intracellular processing of hormone-receptor complexes. Calmodulin inhibitors (trifluoperazine and W-7) also inhibited the mitogenic action of AH-130GF, suggesting that the Ca-calmodulin system and proteolytic processing in lysosomes are necessary for stimulation of DNA synthesis by AH-130GF after its binding to the cell surface. Membrane phosphorylation induced by AH-130GF or epidermal growth factor (EGF) was investigated by using rat liver plasma membranes and 3T3 cell membranes in vitro. EGF increased the phosphorylation of two protein components with molecular weights of 160K and 130K in rat plasma membranes, but AH-130GF increased the phosphorylation of only the 130K protein. No specific phosphorylation induced by AH-130GF was detected in 3T3 cell membranes, but EGF induced phosphorylation of the 160K receptor protein.

Animals↗
PubMed1983

Effect of an exogenous energy source and amino acids on DNA synthesis in regenerating rat liver.

Rats on a protein-free diet synthesized less DNA after partial hepatectomy than rats on a normal diet. In regenerating livers of animals on the protein-free diet, induction of several enzymes involved in the DNA precursor synthetic pathway, and especially ribonucleotide reductase, were depressed. When young rats were maintained solely by parenteral nutrition after partial hepatectomy, exogenous amino acids were more important than the exogenous energy source for induction of enzymes involved in synthesis of DNA and its pyrimidine nucleotide precursors. In particular, induction of ribonucleotide reductase appeared to be controlled by exogenous amino acids. Tryptophan, methionine, phenylalanine, leucine, valine, isoleucine and threonine seemed to stimulate the induction of this enzyme most after partial hepatectomy.

Amino Acids↗
PubMed1983

[Studies on the mechanism of cytotoxicity of 5-fluorouracil--through impairment of metabolism].

Mechanism of cytotoxicity of 5-fluorouracil (5-FU) in relation to impairment of RNA metabolism was studied. 5-FU depressed the levels of ribonucleotide reductase and thymidine kinase, which are two key enzymes in DNA synthesis, in solid AH-130 tumor when given intraperitoneally at a dose of 60 mg/kg, and this inhibition seemed to be very toxic against cells. But this dose of 5-FU exceeded the amount that could be degraded by the liver, which was much higher than the clinical dose. We concluded that the impairment of RNA metabolism caused by 5-FU played a minor role in its anti-tumor actions.

Animals↗
PubMed1982

Activities of various enzymes of pyrimidine nucleotide and DNA syntheses in normal and neoplastic human tissues.

The activities of the key enzymes of pyrimidine nucleotide and DNA syntheses in 43 human tumors and 28 normal human tissues were investigated. The activities of cytidine triphosphate synthetase, deoxycytidine monophosphate deaminase, uridine kinase, thymidine kinase, thymidine monophosphate kinase and DNA polymerase were markedly increased in tumor tissues, compared with those in the corresponding normal tissues, while the activities of deoxycytidine kinase, cytidine deaminase and deoxycytidine deaminase were only slightly increased. The use of thymidine and deoxyuridine as substrates of human pyrimidine nucleoside phosphorylase gave 1 to 2 orders of magnitude higher activity than that of uridine.

Carbon-Nitrogen Ligases↗
PubMed1982

Growth factor from tumor cells.

Suitable conditions for assay of the growth factor from Yoshida sarcoma and AH-130 tumor cells were investigated using three different cell lines: baby hamster kidney cells, human embryonic lung cells and Swiss Albino mouse 3T3 embryo fibroblast cells. The results indicated that the 3T3 cell line was more sensitive to the growth stimulating activity than the other two lines. A fraction of Yoshida sarcoma tumor cells containing the growth factor showed less growth stimulating activity than a fraction of AH-130 tumor cells prepared by the same method. Using the 3T3 cell line for assay of activity, the growth factor was partially purified from AH-130 tumor cells by ammonium sulfate fractionation, DEAE-cellulose column chromatography and gel filtration on a Sephacryl S-300 column. It appeared to be thermolabile, and its molecular weight was estimated as about 80,000 by gel filtration on Sephacryl S-300. These findings suggest that it is a high-molecular-weight substance.

Animals↗
PubMed1981

Metabolism of 5-fluorouracil in various human normal and tumor tissues.

The metabolism of 5-fluorouracil (5-FU) in tumors and normal tissues of humans was investigated in vitro. Phosphorylation of 5-FU was faster in tumor tissues than in normal tissues. Phosphorylating activity with 2-deoxy-alpha-D-ribose 1-phosphate (dRiblP) and ATP as cofactors was more active than that with alpha D-ribose 1-phosphate (RiblP) and ATP, or 5-phospho-alpha-D-ribosyldiphosphate (PPRibP) as cofactors. Phosphorylating activity in squamous cell carcinoma of the lung was similar to that in adenocarcinomas. Degradation of 5-FU was much faster in the liver than in other tissues including tumor tissues.

Adenocarcinoma↗
PubMed1981

Metabolism of pyrimidine nucleotides in various tissues and tumor cells from rodents.

The metabolism of pyrimidine nucleotides in various tissues and tumor cells of rodents was investigated. Ribonucleoside diphosphate reductase, thymidine monophosphate kinase and DNA polymerase (alpha, beta) were specifically localized in tumor cells, i.e., the activities of these enzymes in tumor cells were at least three times higher than those in normal tissues, including rapidly growing tissues, such as bone marrow, thymus, and spleen. The activities of deoxycytidine monophosphate deaminase and all the nucleoside kinase were high not only in tumor cells, but also in rapidly growing normal tissues, so that these enzymes are unsuitable as targets for cancer chemotherapy. The tissue distribution of other enzymes, including orotate phosphoribosyltransferases, cytidine triphosphate synthetase, thymidine monophosphate synthase, nucleoside phosphorylases and cytidine deaminase had no relation with the cell growth rate. AH130 tumor cells and the thymus showed specific increases in the activities of enzymes involved in de novo DNA synthesis. In contrast, Yoshida sarcoma and bone marrow showed high activities of enzymes in the salvage pathway of DNA synthesis, which suggested that the two tumors have different patterns of nucleotide metabolism.

Animals↗
PubMed1981

Possible regulation of ribonucleoside diphosphate reductase.

Two inhibitors of ribonucleoside diphosphate reductase (RR) (EC 1.17.4.1) in vitro were isolated from normal rat liver: they were a nondialyzable, heat-labile, high-molecular-weight ribonucleoside diphosphate reductase inhibitor (HRRI, and a dialyzable, heat-stable, low-molecular-weight ribonucleoside diphosphate reductase inhibitor (LRRI). The activities of both inhibitors varied inversely with the cell growth rate. HRRI from the cytosol fraction of rat liver was partially purified by ammonium sulfate fractionation (0 - 50%), and gel filtration on a Sepharose 6B column. It was eluted in the void volume from this column, together with ATP-hydrolyzing activity. The HRRI fraction also contained CDP kinase and CDPase activities, suggesting that HRRI is a complex of several enzymes that reduce the concentrations of the substrate of RR, CDP, and of the allosteric activator, ATP. LRRI was extracted from the cytosol of rat liver with ethanol (80% final concentration) and purified further by washing with organic solvent, and be chromatographies of Amberlite IR-45 and Dowex 50. Finally, it was identified as glucose, which was phosphorylated to glucose 6-phosphate by hexokinase present tin the RR enzyme solution ( 0 - 35% ammonium sulfate fraction of AH-130 cytosol), thus causing ATP depletion. Thus, neither inhibitor reacted directly with the RR enzyme, but both may regulate the enzyme activity in vivo by reducing the intracellular levels of substrates or cofactors.

Animals↗