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Biomedical subjects

T Tsuruo

Publications and source records attributed to T Tsuruo.

At least 307 records · Page 17Linked to original sources
PubMed1993

Differential expression of protein tyrosine phosphatase genes during phorbol ester-induced differentiation of human leukemia U937 cells.

Some human leukemia cell lines, such as HL-60 and U937, differentiate to monocyte/macrophage by treatment with chemicals such as phorbol ester or 1,25-dihydroxy vitamin D3. In this report, we demonstrate that cellular protein tyrosine phosphatase (PTPase) activity (especially in cytosol) in monoblastoid leukemia U937 cells increased up to 2-fold during the course of monocytic differentiation. We have cloned 13 PTPase-related gene fragments from the differentiated U937 cells using the reverse transcription-polymerase chain reaction method. Two of these were found to be genes of novel isozymes, PTP-U1 and PTP-U2. We investigated the changes in expression of each isozyme during the differentiation of the cells and found that nine isozymes (both cytosolic and transmembranous) were expressed more in the differentiated cells than in the undifferentiated cells. Among them, PTP-U1 and PTP-U2 were greatly induced by phorbol ester. Interestingly, there were two cytosolic isozymes that were down-regulated during the course of differentiation. Our present data suggest that the functions of the PTPase isozyme during monocytic maturation are not always equivalent to each other, and tyrosine dephosphorylation may participate in several different pathways of signal transduction during the differentiation of leukemia cells.

Base Sequence↗
PubMed1993

[Signal transduction of insulin-like growth factor I in a highly metastatic tumor cell line].

Insulin-like growth factor I (IGF-I) exists in the blood at a high concentration and in various tissues. IGF-I may positively participate in the process of tumor metastasis, since it has various biological activities in addition to growth promoting activity for many cell types including malignant cells. We found a highly metastatic cell line (colon 26 NL-17) the growth of which IGF-I strongly promoted. Investigation of the mechanism of signal transduction of IGF-I in the NL-17 cells revealed two cytoplasmic proteins (pp150 and pp160) which were immediately tyrosine-phosphorylated upon IGF-I stimulation and enabled to bind to phosphatidyl inositol 3-kinase. The pp150 and pp160 may be important mediators of IGF-I signal.

Animals↗
PubMed1993

[Regulation of tumor metastasis and extracellular matrix degradative enzyme production by microenvironments].

We have recently established human tumor cell lines which metastasize to specific organs from orthotopic implantation sites but not from ectopic sites in nude mice. Using these tumor cell lines we have been studying the mechanisms of the regulation of tumor metastasis by organ specific microenvironments. Here, we discuss the mechanisms of the regulation of extracellular matrix degrading enzyme production by interactions between tumor cells and tissue specific fibroblasts.

Animals↗
PubMed1993

[Lymphatic metastasis and cell adhesion, growth and growth inhibition].

Malignant tumor cells often metastasize to regional and distant lymph nodes. The mechanisms of lymphatic metastasis, however, have not been well understood. To investigate these mechanisms, we used mouse CS-21 malignant T lymphoma cells which form tumors at subcutaneous sites and metastasize to lymph nodes with a high incidence. In contrast, CS-21 cells do not metastasize to other organs following intravenous injection. CS-21 lymphoma cells continuously grew in vitro when the cells were cocultured with CA-12 stromal cells isolated from lymph nodes. However, when CS-21 cells were separated from the stromal cells, they underwent apoptosis which was characterized by nucleus condensation and DNA fragmentation. We have developed monoclonal antibodies against CS-21 cell surface molecules by intrasplenic injection of the cell membranes. Several clones of monoclonal antibodies were able to partially inhibit adhesion of CS-21 cells to a monolayer of CA-12 stromal cells. Treatment of CS-21 cells with the monoclonal antibodies which specifically bind to the cell surface components of M(r) -168K and -23K prevented the apoptosis of CS-21 cells after separation from the stromal cells. In the experiments using Transwell chambers we found that the growth of CS-21 cells was also supported by soluble factors secreted from CA-12 stromal cells. The secreted factors were, however, not sufficient to prevent CS-21 cell apoptosis. The result suggested that the stromal cells of lymph nodes play an important role in lymphatic metastasis of CS-21 lymphoma cells by cell-cell adhesion and secretion of soluble factors that prevent apoptosis of lymphoma cells and enhance their growth in concert.

Animals↗
PubMed1992

Purification and characterization of NF-R1 that regulates the expression of the human multidrug resistance (MDR1) gene.

We have purified a protein, NF-R1, that specifically binds to two unrelated motifs--the ATTCAGTCA motif and the GC-box motif--on the MDR1 proximal promoter. Purified NF-R1 has been confirmed by southwestern blotting to be a 110-kDa protein. Methylation interference analysis revealed that the nucleotides were in close contact with purified NF-R1 on the ATTCAGTCA and GC-box motifs. The nucleotides were required for the binding of NF-R1, as seen by competition gel mobility shift assay using point mutated oligonucleotides. In a CAT expression assay using the corresponding point-mutated MDR1 promoter fused to a CAT gene, binding inhibition of NF-R1 to the promoter resulted in 2- to 3-fold increases of CAT activity, as compared to the intact promoter in Adriamycin-resistant K562 cells. Thus NF-R1 has a relation to the negative regulation of the MDR1 gene transcription.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

Functional involvement of P-glycoprotein in blood-brain barrier.

P-glycoprotein, an active efflux pump of antitumor agents in multidrug-resistant tumor cells, exists in various normal tissues, including brain capillaries. To study the physiological function of P-glycoprotein expressed in brain capillary endothelium, we established nine mouse brain capillary endothelial cell (MBEC) lines and examined the transport of antitumor agents across the monolayer of MBEC epithelia. In the MBECs, the activities of alkaline phosphatase and gamma-glutamyl transpeptidase, specific markers for brain capillary endothelial cells, were about three times higher than those in other cells including human umbilical vein endothelial cells. By immunoblot analysis, P-glycoprotein was detected in all of the nine MBEC clones. The P-glycoprotein expressed in MBECs specifically bound [125I]iodoaryl azidoprazosin as that in multidrug-resistant cells, and efflux of vincristine was observed in the MBECs. When MBECs were grown on a porous filter membrane, they formed a monolayer of epithelium. By immunoelectron microscopic analysis, P-glycoprotein in MBEC epithelia was shown to be localized to the apical surface of the cells. Moreover, the unidirectional transepithelial transport of vincristine from basal side to apical side was demonstrated in vitro. These observations indicate that P-glycoprotein in brain capillary endothelium prevents vincristine from entering the central nervous system and thus may be one of the functional components of the blood-brain barrier.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

Inhibition of different steps of the ubiquitin system by cisplatin and aclarubicin.

Ubiquitin is involved in such fundamental cellular processes as cell cycle control, DNA repair, protein degradation and stress responses. We previously reported that cisplatin could inhibit the ubiquitin-ATP-dependent proteolysis and ubiquitination. We further investigated the effect of various antitumor agents on the ubiquitin system and found that aclarubicin (ACR) inhibits the ubiquitin-ATP-dependent proteolysis but not the ubiquitination process. We found that ACR as well as cisplatin inhibited the ubiquitin-ATP-dependent proteolytic activity of rabbit reticulocytes. The IC50 values of these agents were 52 and 90 microM, respectively. Although cisplatin inhibits the conjugation of ubiquitin to proteins through the inhibition of a ubiquitin-activating enzyme, ACR, at 120 microM, does not. Thus, the antitumor agents affecting the ubiquitin system could be classified into two groups; one is represented by cisplatin, which inhibits the ubiquitination of the proteins, and the other is ACR, which does not inhibit the ubiquitination but does inhibit the ubiquitin-ATP-dependent proteolysis. Mitomycin C belongs to the latter group.

Aclarubicin↗
PubMed1992

Human immunodeficiency virus type 1 induces 1-beta-D-arabinofuranosylcytosine resistance in human H9 cell line.

We have found that chronically HIV-1(IIIB)-infected H9 cells showed 21-fold resistance to 1-beta-D-arabinofuranosylcytosine (ARA-C) compared with uninfected H9 cells. In the infected H9 cells, a 37% increase of dCTP pool and a 34% increase of dATP were observed, and no alteration of dTTP and dGTP was observed, compared with the uninfected H9 cells. A marked decrease of ARA-CTP generation was observed in the infected H9 cells after 3-h incubation with 0.1-10 microM ARA-C. The level of deoxycytidine kinase activity with ARA-C as substrate was similar in both the infected and the uninfected cells; however, a 37-fold increase of cytidine deaminase activity was observed in the infected H9 cells. These results indicate that the induction of cytidine deaminase activity by HIV-1(IIIB) infection conferred ARA-C resistance to H9 cells. This conclusion was supported by the observation that a marked reversal of ARA-C resistance in the infected H9 cells occurred after treatment with the inhibitor of cytidine deaminase, 3,4,5,6-tetrahydrouridine. The understanding of these cellular alterations in drug sensitivity may facilitate the development of effective therapeutic strategies against HIV-1-infected cells.

Arabinofuranosylcytosine Triphosphate↗
PubMed1992

Immunohistochemical identification of P-glycoprotein in previously untreated, diffuse large cell and immunoblastic lymphomas.

Expression of P-glycoprotein has been linked to multidrug resistance in cancer cell lines and human tumors. We investigated the frequency and clinical significance of P-glycoprotein immunoreactivity in 57 previously untreated diffuse large cell and immunoblastic lymphomas. Banked frozen tissue, which had been obtained prior to chemotherapy, was tested for reactivity with 2 monoclonal antibodies (MRK16 and C219) that recognize different domains of P-glycoprotein, using an immunoperoxidase technique. Thirteen of 57 lymphomas (23%) showed strong staining of greater than 50% of neoplastic cells; 15 of 57 (26%) showed labeling of a minority (11-50%) of neoplastic lymphocytes; 14 of 57 (25%) yielded equivocal results (reactivity in less than 10% of cells); and 15 of 57 (26%) were negative for P-glycoprotein. The 2 monoclonal antibodies were comparable in reactivity. Expression of MDR-1 mRNA was determined in 6 cases with sufficient available tissue, and did not correlate well with the percentages of cells reactive for P-glycoprotein by immunohistochemistry. Thirty-nine of our 57 patients completed multiagent chemotherapy. Contrary to our expectations, we found that P-glycoprotein immunoreactivity did not decrease the likelihood of response to induction chemotherapy. Median survival also was not adversely affected.

ABO Blood-Group System↗
PubMed1992

Functionally active homodimer of P-glycoprotein in multidrug-resistant tumor cells.

P-glycoprotein plays a key role in multidrug resistance of tumor cells. In order to elucidate the possible quarternary structure/function relationship of P-glycoprotein, we treated multidrug-resistant human leukemia K562/ADM cells with the crosslinking reagent, disuccinimidyl suberate. In addition to 180K P-glycoprotein, a 340K protein was immunoprecipitated with an anti-P-glycoprotein monoclonal antibody, MRK-16. The 340K protein is most probably a dimeric P-glycoprotein, since only the 180K P-glycoprotein was immunoprecipitated with MRK-16 when K562/ADM cells were treated with the cleavable crosslinking reagent, dithiobis(succinimidylpropionate), and analysed under reduced conditions. The dimeric P-glycoprotein was photolabeled with [3H]azidopine like the 180K monomeric P-glycoprotein and the photolabeling was inhibited by excess amount of vincristine and verapamil. The dimeric P-glycoprotein could be a functionally active form of the protein involved in the transport of antitumor agents.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

Synthesis and anti-HIV activity of 9-[c-4,t-5-bis(hydroxymethyl)cyclopent-2-en-r-1-yl]-9H-adenine.

The synthesis and in vitro anti-HIV activity of two new racemic nucleoside analogues are described; namely, 9-[c-4,t-5-bis(hydroxymethyl)cyclopent-2-en-r-1-yl]-9H-adenine (12) and its guanine analogue 18. While the latter (18) showed no activity, the therapeutic index of the former (12) was 200 and comparable to that (400) of carbovir. One enantiomer of 12 may be viewed as an analogue of carbocyclic oxetanocin and the other as an analogue of carbovir. Hence, these results indicate that one or both of the individual enantiomers of 12 could serve as candidates or lead compounds for the development of anti-AIDS agents.

Adenine↗
PubMed1992

Differential expression of DNA topoisomerase I gene between CPT-11 acquired- and native-resistant human pancreatic tumor cell lines: detected by RNA/PCR-based quantitation assay.

RNA/PCR quantitation method was developed to determine DNA Topoisomerase I(Topo I)-specific mRNA in order to study its gene expression in CPT-11 sensitive, acquired- or native-resistant human pancreatic tumor cell lines. The results were supported by Northern blotting and Western blotting analyses. Acquired-resistant cells have shown decreased levels of Topo I mRNA, compared with their parental cells. On the contrary, in the wild type cells no correlation was shown between sensitivity and gene expression. On the other, specific Topo I activity of the native resistant cell lines was fairly lower than that of sensitive cell lines, suggesting that immunoreactive Topo I protein contains low levels of active form enzyme which could be targets of CPT-11 in these native-resistant ones. Finally, the different mechanisms might be operative between acquired- and native-resistant tumor cells.

Antineoplastic Agents, Phytogenic↗
PubMed1992

Resolution of 9-(c-4,t-5-bishydroxymethylcyclopent-2-en-r-1-yl)-9H-adenine and selective inhibition of human immunodeficiency virus by the (-) enantiomer.

Two enantiomers of 9-(c-4,t-5-bishydroxymethylcyclopent-2-en-r-1-yl)-9H- adenine (BCA) which showed a potent and selective anti-HIV effects have been synthesized and evaluated against human immunodeficiency virus type 1. The result demonstrated that the potent-HIV activity of racemic BCA is expressed solely by the (-) isomer.

Adenine↗
PubMed1992

Synthesis and antitumor activity of tropolone derivatives. 7. Bistropolones containing connecting methylene chains.

Bistropolone derivatives (4-12) containing differing lengths of linkage between the two tropolone rings were prepared and examined for their antitumor activity in in vitro (KB cell) and in vivo (leukemia P388 in mice) systems. Parent compound 3, related compounds previously prepared, and the new compounds 4-12 were evaluated for inhibitory activity against ribonucleotide reductase by indirect means to measure their effects on the dNTP pool imbalance. Present structure-activity relationship results would suggest that potently active bistropolones in vivo inhibit intracellular ribonucleotide reductase through chelating with the two irons at the two active sites of the enzyme.

Animals↗
PubMed1992

Clinical significance of multidrug resistance P-glycoprotein expression on acute nonlymphoblastic leukemia cells at diagnosis.

To evaluate the clinical value of the expression of multidrug resistance P-glycoprotein (P-170) on the surface of acute nonlymphoblastic leukemia (ANLL) cells, we analyzed specimens from 150 newly diagnosed patients for staining with MRK16, a monoclonal antibody (MoAb) that binds to an external epitope of P-170. Other surface markers (CD13, CD14, CD15, and CD34) were studied by the same technique. A marker was considered positive when 20% or more cells were stained. Of 150 samples, 71 were P-170-positive. These cases did not differ from P-170-negative cases with regard to age, sex, initial white blood cell (WBC) counts, or French-American-British (FAB) type (except for M3 ANLL, which were more frequently negative). However, leukemias arising from previous myelodysplastic syndrome (MDS) and therapy-induced leukemias were more frequently P-170-positive. CD34 and P-170 expression were significantly associated. All patients were treated by intensive chemotherapy. Complete remission (CR) rates were significantly lower in P-170-positive (23/71, 32%) than in P-170-negative cases (64/79, 81%) (P less than 10(-5)). CD34 positivity was also associated with a low remission rate (P less than 10(-5)). Survival was shorter for P-170- and CD34-positive patients (P less than 10(-5)). The prognostic value of both markers was confirmed in multivariate analysis. CR duration was also shorter for P-170-positive cases, but the difference is less significant (P = .05). It is concluded that P-170 analysis may be an important tool for predicting the outcome of intensive chemotherapy in ANLL patients.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

Reversal of multidrug resistance by an immunosuppressive agent FK-506.

FK-506, a novel immunosuppressive agent, was examined for its reversing effect on multidrug-resistant tumor cells. FK-506 at 3 microM completely reversed the resistance against vincristine (VCR) in vitro in VCR-resistant mouse leukemia P388 cells (P388/VCR). FK-506 also enhanced the cytotoxicity of VCR in Adriamycin(ADM)-resistant human ovarian cancer A2780 cells (AD10) and ADM-resistant human myelogenous leukemia K562 cells (K562/ADM) in vitro. FK-506 was also effective in modulating sensitivity to ADM in AD10 cells in vitro. FK-506 enhanced the chemotherapeutic effect of VCR in P388/VCR-bearing mice. When 20 mg/kg FK-506 was combined with 200 micrograms/kg VCR, a T/C value of 151% was obtained. Under the protocol used in this study, FK-506 was more potent than cyclosporin A (CsA) and verapamil. FK-506 inhibited [3H]azidopine binding to P-glycoprotein efficiently. The binding of VCR to K562/ADM plasma membrane was inhibited by FK-506 as effectively as by CsA. Moreover, the accumulation of VCR in AD10 cells was increased by FK-506 as efficiently as that of CsA and verapamil. These results indicate that FK-506 directly interacts with P-glycoprotein like CsA and verapamil, inhibits the active efflux of vincristine from resistant cells, increases the vincristine accumulation in resistant cells, and thus overcomes multidrug resistance in vitro and in vivo.

ATP Binding Cassette Transporter, Subfamily B, Mem↗