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T Suda

Publications and source records attributed to T Suda.

At least 19 recordsLinked to original sources
PubMed1992

In vivo and in vitro stem cell function of c-kit- and Sca-1-positive murine hematopoietic cells.

c-kit is expressed on hematopoietic stem cells and progenitor cells, but not on lymphohematopoietic differentiated cells. Lineage marker-negative, c-kit-positive (Lin-c-kit+) bone marrow cells were fractionated by means of Ly6A/E or Sca-1 expression. Lin-c-kit+Sca-1+ cells, which consisted of 0.08% of bone marrow nucleated cells, did not contain day-8 colony-forming units-spleen (CFU-S), but 80% were day-12 CFU-S. One hundred cells rescued the lethally irradiated mice and reconstituted hematopoiesis. On the other hand, 2 x 10(3) of Lin-c-kit+Sca-1- cells formed 20 day-8 and 11 day-12 spleen colonies, but they could not rescue the lethally irradiated mice. These data indicate that Lin-c-kit+Sca-1+ cells are primitive hematopoietic stem cells and that Sca-1-cells do not contain stem cells that reconstitute hematopoiesis. Lin-c-kit+Sca-1+ cells formed no colonies in the presence of stem cell factor (SCF) or interleukin-6 (IL-6), and only 10% of them formed colonies in the presence of IL-3. However, approximately 50% of them formed large colonies in the presence of IL-3, IL-6, and SCF. Moreover, when single cells were deposited into culture medium by fluorescence-activated cell sorter clone sorting system, 40% of them proliferated on a stromal cell line (PA-6) and proliferated for more than 2 weeks. In contrast, 15% of the Lin-c-kit+Sca-1-cells formed colonies in the presence of IL-3, but no synergistic effects were observed in combination with SCF plus IL-6 and/or IL-3. Approximately 10% proliferated on PA-6, but most of them degenerated within 2 weeks. The population ratio of c-kit+Sca-1+ to c-kit+Sca-1- increased 2 and 4 days after exposure to 5-fluorouracil (5-FU). These results are consistent with the relative enrichment of highly proliferative colony-forming cells by 5-FU. These data show that, although c-kit is found both on the primitive hematopoietic stem cells and progenitors, Sca-1+ cells are more primitive and respond better than Sca-1- cells to a combination of hematopoietic factors, including SCF and stromal cells.

Animals↗
PubMed1992

Granulocyte-macrophage colony-stimulating factor and erythropoietin act competitively to induce two different programs of differentiation in the human pluripotent cell line UT-7.

The UT-7 cell line was established from a patient with a megakaryoblastic leukemia (Komatsu et al, Cancer Res 51: 341, 1991). Its proliferation is strictly dependent on the presence of hematopoietic growth factors including erythropoietin (Epo), granulocyte-macrophage colony-stimulating factor (GM-CSF), and interleukin-3 (IL-3). We investigated the differentiation capacities of this cell line under the action of several growth factors, using immunomarkers, flow cytometry, and ultrastructural techniques. In the presence of GM-CSF and IL-3, eosinophil and basophil promyelocytes were detected, as well as a few cells with erythroid and megakaryocytic (MK) differentiation features. In contrast, Epo induced a marked erythroid differentiation with an increase of glycophorin A expression, accompanied by a few hemoglobinized cells. Differentiation induced by the growth factors took 24 to 48 hours to begin, and increased with cell passages to a plateau at 2 weeks of culture. However, this was not only due to a cell selection because the differential effects of Epo and GM-CSF were observed from a single cell clone and the phenotype could be reversed by opposite growth factors, even after a long period of culture. We subsequently investigated the phenotype of UT-7 in the presence of combinations of Epo, IL-3, and GM-CSF, and showed that GM-CSF and IL-3 act predominantly over Epo. This effect was mediated by a rapid downmodulation of Epo receptors by GM-CSF at messenger RNA and binding sites levels, without a change in receptor affinities. On the other hand, Epo had no effect on number and affinity of GM-CSF receptors. This study shows that UT-7 is a growth factor-dependent pluripotent cell line in which commitment may be directed by a hierarchical action of growth factors through an early and rapid transmodulation of growth factor receptors.

Basophils↗
PubMed1992

Osteoclasts express high levels of p60c-src, preferentially on ruffled border membranes.

Expression of p60c-src, the normal cellular counterpart of the transforming protein of Rous sarcoma virus (RSV), p60v-src, was examined in mouse and rat authentic osteoclasts and mouse osteoclast-like multinucleated cells (MNCs) formed in vitro. In co-cultures of mouse osteoblastic cells and spleen cells, the expression of p60c-src strikingly increased on day 5 in parallel with the appearance of MNCs in the presence of 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25(OH)2D3). Immunohistochemical examination confirmed the high level expression of p60c-src in both mouse authentic osteoclasts and MNCs. Electron microscopic examination revealed that p60c-src was primarily localized on ruffled border membranes and vacuoles, but not on the clear zone in rat authentic osteoclasts. These results suggest that p60c-src is important in osteoclastic bone resorption.

Animals↗
PubMed1992

A synthetic peptide corresponding to 86-93 of the human type I IL-1 receptor binds human recombinant IL-1 (alpha and beta) and inhibits IL-1 actions in vitro and in vivo.

A synthetic peptide corresponding to 86-93 of the human type I IL-1 receptor and its analogues bound human recombinant (hr) IL-1 (alpha and beta) and inhibited dose-dependently both Con A-stimulated proliferation of mouse spleen cells and hrIL-1 beta-stimulated formation of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells in rat bone marrow cell cultures. Furthermore, hrIL-1 beta-induced mouse paw edema was dose-dependently inhibited by systemic administration (ip) of the synthetic peptide. These results suggest that one of the IL-1 binding sites of the human type I IL-1 receptor comes to the region of 86-93 and the synthetic peptide having the ability to bind hrIL-1 (alpha and beta) blocks the biological activities of exogenous hrIL-1 beta and endogenous mouse IL-1.

Amino Acid Sequence↗
PubMed1992

Phenotypic and functional characterization of c-kit expression during intrathymic T cell development.

We have studied the expression and function of c-kit on subsets of mouse thymocytes. c-kit was primarily expressed on subpopulations of CD4-CD8-CD3- triple negative (TN) cells. The strongest c-kit expression was associated with subsets that represent the least mature TN cells, including CD44+CD25- TN, and a subpopulation of CD25+ TN. These cells were also Thy-1lo, H-2Khi TSA-1hi, HSAlo, B220-, Mac-1-, and Gr-1-. Additionally, the recently described pre-TN thymocyte population (CD4loCD3-CD8-) was also c-kit+. CD25+ TN thymocytes proliferated in the presence of IL-7 and stem cell factor (the ligand for c-kit), and this proliferation was completely inhibited in the presence of anti-c-kit. Furthermore, the addition of anti-c-kit to 2-deoxyguanosine-treated fetal thymic lobes undergoing reconstitution with fetal liver-derived precursor cells inhibited their T cell differentiation potential. These observations indicate an important role for c-kit/stem cell factor interactions during early thymocyte development.

Animals↗
PubMed1992

Cytokine production by mature and immature CD4-CD8- T cells. Alpha beta-T cell receptor+ CD4-CD8- T cells produce IL-4.

This study follows our previous investigation describing the production of four cytokines (IL-2, IL-4, IFN-gamma, and TNF-alpha) by subsets of thymocytes defined by the expression of CD3, 4, 8, and 25. Here we investigate in greater detail subpopulations of CD4-CD8- double negative (DN) thymocytes. First we divided immature CD25-CD4-CD8-CD3- (CD25- triple negative) (TN) thymocytes into CD44+ and CD44- subsets. The CD44+ population includes very immature precursor T cells and produced high titers of IL-2, TNF-alpha, and IFN-gamma upon activation with calcium ionophore and phorbol ester. In contrast, the CD44- subset of CD25- TN thymocytes did not produce any of the cytokines studied under similar activation conditions. This observation indicates that the latter subset, which differentiates spontaneously in vitro into CD4+CD8+, already resembles CD4+CD8+ thymocytes (which do not produce any of the tested cytokines). We also subdivided the more mature CD3+ DN thymocytes into TCR-alpha beta- and TCR-gamma delta-bearing subsets. These cells produced cytokines upon activation with solid phase anti-CD3 mAb. gamma delta TCR+ DN thymocytes produced IL-2, IFN-gamma and TNF-alpha, whereas alpha beta TCR+ DN thymocytes produced IL-4, IFN-gamma, and TNF-alpha but not IL-2. We then studied alpha beta TCR+ DN T cells isolated from the spleen and found a similar cytokine production profile. Furthermore, splenic alpha beta TCR+ DN cells showed a TCR V beta gene expression profile reminiscent of alpha beta TCR+ DN thymocytes (predominant use of V beta 8.2). These observations suggest that at least some alpha beta TCR+ DN splenocytes are derived from alpha beta TCR+ DN thymocytes and also raises the possibility that these cells may play a role in the development of Th2 responses through their production of IL-4.

Animals↗
PubMed1992

In vitro proliferation of primitive hemopoietic stem cells supported by stromal cells: evidence for the presence of a mechanism(s) other than that involving c-kit receptor and its ligand.

The preadipose cell line, PA6, can support long-term hemopoiesis. Frequency of the hemopoietic stem cells capable of sustaining hemopoiesis in cocultures of bone marrow cells and PA6 cells for 6 wk was 1/5.3 x 10(4) bone marrow cells. In the group of dishes into which bone marrow cells had been inoculated at 2.5 x 10(4) cells/dish, 3 of 19 dishes (16%) contained stem cells capable of reconstituting erythropoiesis of WBB6F1-W/Wv mice, indicating that PA6 cells can support the proliferation of primitive hemopoietic stem cells. When the cocultures were treated with an antagonistic anti-c-kit monoclonal antibody, ACK2, only a small number of day 12 spleen colony-forming units survived; and hemopoiesis was severely reduced. However, when the cocultures were continued with antibody-free medium, hemopoiesis dramatically recovered. To examine the proliferative properties of the ACK2-resistant stem cells, we developed a colony assay system by modifying our coculture system. Sequential observations of the development of individual colonies and their disappearance demonstrated that the stem cells having higher proliferative capacity preferentially survive the ACK2 treatment. Furthermore, cells of subclones of the PA6 clone that were incapable of supporting long-term hemopoiesis expressed mRNA for the c-kit ligand. These results suggest that a mechanism(s) other than that involving c-kit receptor and its ligand plays an important role in the survival and proliferation of primitive hemopoietic stem cells.

Animals↗
PubMed1992

Herbimycin A, an inhibitor of tyrosine kinase, prolongs survival of mice inoculated with myeloid leukemia C1 cells with high expression of v-abl tyrosine kinase.

Herbimycin A, a benzoquinonoid ansamycin antibiotic, reduces intracellular phosphorylation by some tyrosine kinases, including v-abl. The mouse megakaryoblastic cell line C1 expresses v-abl protein at high levels. Herbimycin A at about 20 ng/ml caused 50% inhibition of growth of C1 cells but at 100 ng/ml scarcely affected the growth of another mouse leukemia cell line, M1 cells, or of normal bone marrow cells. Injection of 10(6) C1 cells into nude mice resulted in death of all the mice within 30 days. Administration of herbimycin A significantly enhanced the survival of mice inoculated with C1 cells but scarcely affected the survival of mice inoculated with M1 cells. These results suggest that herbimycin A and/or related compounds may be useful for treatment of some types of leukemia in which tyrosine kinase activity is implicated as a determinant of the oncogenic state.

Animals↗
PubMed1992

Parathyroid hormone inhibits 25-hydroxyvitamin D3-24-hydroxylase mRNA expression stimulated by 1 alpha,25-dihydroxyvitamin D3 in rat kidney but not in intestine.

Using a cDNA probe for rat renal 24-hydroxylase, expression of its mRNA was compared in the rat kidney and intestine. Vitamin D-deficient rats received a single injection of 1 alpha,25-dihydroxyvitamin D3. Expression of 24-hydroxylase mRNA was first detected in the kidney at 3-h post-injection and increased thereafter. Similarly, 24-hydroxylase mRNA was expressed in the intestine after 1 alpha,25-dihydroxyvitamin D3 injection. However, the dose level of 1 alpha,25-dihydroxyvitamin D3 required to induce the intestinal 24-hydroxylase mRNA expression was only 1/100 the amount required to induce renal 24-hydroxylase mRNA. Induction of intestinal 24-hydroxylase mRNA expression by 1 alpha,25-dihydroxyvitamin D3 was far more rapid than that of renal 24-hydroxylase mRNA. Thyroparathyroidectomy shortened the time required to induce expression of renal, but not intestinal, 24-hydroxylase mRNA. Administration of either parathyroid hormone or cAMP to vitamin D-deficient rats greatly reduced the expression of 24-hydroxylase mRNA in the kidney but not in the intestine. When rats were fed a vitamin D-repleted diet containing 0.7% (adequate) or 0.03% (low) calcium for 2 weeks, intestinal expression of 24-hydroxylase mRNA could be induced only in the low calcium group. In contrast, renal mRNA expression was preferentially stimulated in the adequate calcium group. These results clearly demonstrate that the expression of 24-hydroxylase mRNA is down-regulated by parathyroid hormone in the kidney but not in the intestine.

Animals↗
PubMed1992

In vitro induction of CD8 expression on thymic pre-T cells. II. Characterization of CD3-CD4-CD8 alpha + cells generated in vitro by culturing CD25+CD3-CD4-CD8- thymocytes with T cell growth factor-beta and tumor necrosis factor-alpha.

We previously reported that CD25 (IL-2R p55)-positive CD3-CD4-CD8- murine thymocytes can be induced to express CD8 alpha (Lyt-2) by transforming growth factor-beta plus TNF-alpha in the presence of IL-7 (which is necessary to maintain the viability and differentiation capacity of CD25+CD3-CD4-CD8- thymocytes in vitro). The majority of cells recovered after 2 to 3 days from these cultures expressed CD8 alpha (but not CD3 or CD4). In this study, we have characterized these in vitro generated CD3-CD4-CD8 alpha + thymocytes and compared them with normal CD3-CD4-CD8+ thymocytes. Unlike normal CD3-CD4-CD8+ thymocytes that express CD8 alpha and CD8 beta (Lyt-3-chain) simultaneously, only a fraction of in vitro generated CD3-CD4-CD8 alpha + cells expressed CD8 beta. However, along with the induction of CD8 alpha and CD8 beta expression, the expression of other T cell differentiation markers (including CD2, CD25, and CD44) also changed in a manner corresponding to physiologic differentiation. Cell-surface phenotyping suggests that CD8 alpha + beta - cells are less mature than CD8 alpha + beta + cells. These in vitro generated CD3-CD4-CD8 alpha + thymocytes expanded and differentiated into the CD4+CD8+ stage as well as mature (CD3+) single positive (CD4+CD8-) and CD4-CD8+) stages in fetal thymus organ culture that had been depleted of lymphoid cells by treatment with 2-deoxyguanosine. The latter observation indicates that these in vitro generated CD3-CD4-CD8 alpha + thymocytes are responsive to other differentiation-inducing signals (including those that induce CD4) that exist in fetal thymus organ culture. These results suggest that in vitro generated CD3-CD4-CD8 alpha + thymocytes represent intermediate differentiation stages between CD25+CD3-CD4-CD8- and CD3-CD4-CD8+ cells found in normal thymus.

Animals↗
PubMed1992

The role of corticotropin-releasing factor and vasopressin in hypoglycemia-induced proopiomelanocortin gene expression in the rat anterior pituitary gland.

In this study, we examined the effect of passive immunization of endogenous corticotropin-releasing factor (CRF) and arginine vasopressin (AVP) on hypoglycemia-induced adrenocorticotropic hormone (ACTH) secretion and determined proopiomelanocortin messenger RNA (POMC mRNA) levels in the anterior pituitary as well as hypothalamic CRF mRNA levels in pentobarbital anesthetized rats. The response of plasma ACTH to hypoglycemia was partially inhibited by the administration of CRF-antiserum (CRF-As) or AVP-antiserum (AVP-As) alone, but was found to be completely abolished by the administration of CRF-As + AVP-As as compared to the response in normal rabbit serum-treated rats. The hypoglycemia-induced POMC mRNA level in the anterior pituitary was completely inhibited by the administration of CRF-As alone and CRF-As + AVP-As, but was not inhibited by AVP-As alone as compared to the response in normal rabbit serum-treated rats. The administration of CRF-As and/or AVP-As did not affect hypoglycemia-induced CRF mRNA levels in the hypothalamus. These results indicate that the synergistic effect of CRF and AVP is important for hypoglycemia-induced ACTH secretion, but CRF is essential and indispensable for hypoglycemia-induced POMC gene expression in the anterior pituitary (AP).

Animals↗
PubMed1992

Two types of murine CD34 mRNA generated by alternative splicing.

To characterize and clarify the function of CD34 antigen experimentally, we isolated two types of CD34 mRNA from a cDNA library of murine stromal cell line, PA-6 stimulated with lipopolysaccharide (LPS) and 12-o-tetra-decanoylphorbol 13-acetate (TPA) using a human CD34 probe. In addition to the clone (open reading frame [ORF]:1149bp) reported by Brown et al, a novel clone (ORF:978 bp) was obtained. The difference between the two clones was in the cytoplasmic portion of CD34; the former has 73 amino acids, while the latter has 16. We investigated the genomic sequence of cytoplasmic portion and found conserved nucleotide sequences at the exon-intron junction (GT ... AG). Thus, it was concluded that alternative splicing gave two types of CD34 mRNA. A novel clone contains the longer cDNA, including a insert of 156 bp, but results in a shorter predicted coding sequence because of the introduction of an inframe stop codon. Northern blot analysis using a murine cDNA probe (HindIII fragment, 900 bp) showed that CD34 was highly expressed in the brain and testis, and moderately in the thymus, spleen, and bone marrow, but not in adult liver. However, day 12 to 14 fetal liver cells showed significant expression of CD34. Quantitative reverse transcription polymerase chain reaction showed that spleen, thymus, bone marrow, and testis RNA gave two bands of almost equal intensity, but in the brain a novel clone was expressed three times more than the other clone. Furthermore, Northern blot analysis using a probe (156 bp) specific for the spliced intracellular region confirmed the significant mRNA expression of a novel clone. Although the biologic significance of alternative splicing remains to be elucidated, it is suggested that a different carboxyterminal tail causes a change in signal transduction.

Amino Acid Sequence↗
PubMed1992

Lack of bone resorption in osteosclerotic (oc/oc) mice is due to a defect in osteoclast progenitors rather than the local microenvironment provided by osteoblastic cells.

In a co-culture system of mouse spleen cells and osteoblastic cells, we have demonstrated that a suitable microenvironment must be provided by osteoblastic cells in order for osteoclast-like multinucleated cell (MNC) formation. Using this co-culture system, we examined the pathogenetic mechanism underlying the lack of bone resorption in osteosclerotic oc/oc mice. Numerous tartrate-resistant acid phosphatase (TRAP, an osteoclast marker enzyme)-positive MNCs were formed in response to 1 alpha,25-dihydroxyvitamin D3 [1 alpha,25(OH)2D3] both in co-cultures of oc/oc spleen cells and normal osteoblastic cells and in those of normal spleen cells and oc/oc osteoblastic cells. TRAP-positive MNCs derived from normal spleen cells tended to spread out on culture dishes, whereas those from oc/oc spleen cells remained as small, compact MNCs. When TRAP-positive MNCs enriched from co-cultures of normal spleen cells and oc/oc osteoblastic cells were cultured on dentine slices, they formed numerous resorption pits with ruffled borders and clear zones. In contrast, none of the TRAP-positive MNCs derived from oc/oc spleen cells formed either ruffled borders or resorption pits. These results indicate that the lack of bone resorption in oc/oc mice is due to a defect in osteoclast progenitors rather than the local microenvironment provided by osteoblastic cells.

Acid Phosphatase↗
PubMed1992

In vitro induction of CD8 expression on thymic pre-T cells. I. Transforming growth factor-beta and tumor necrosis factor-alpha induce CD8 expression on CD8- thymic subsets including the CD25+CD3-CD4-CD8- pre-T cell subset.

We previously reported that IL-7 maintains the viability and differentiation potential of CD25 (IL-2R p55) positive CD3-CD4-CD8- thymic pre-T cells in vitro. This culture system is suitable for studying signals that regulate differentiation of T cell precursors in the thymus. In this study, we screened cytokines for their capacity to induce CD4 or CD8 in murine thymic pre-T cells cultured with IL-7. Of 15 cytokines tested, only transforming growth factor (TGF-beta) and TNF-alpha induced CD8 (Lyt-2), while no cytokine was able to induce CD4 on CD25+CD3-CD4-CD8- thymocytes. The combination of TGF-beta and TNF-alpha was synergistic, and the majority of cells recovered after 2 to 3 days in culture expressed CD8 (but not CD3 or CD4). A similar effect of TGF-beta and TNF-alpha was observed using day-15 fetal thymocytes, CD3+CD4-CD8- or CD3+CD4+CD8- adult thymocytes, although the combination of these cytokines resulted in an additive rather than a synergistic effect in these subsets. In contrast, neither TGF-beta nor TNF-alpha induced CD8 expression on splenic CD4+CD8- T cells. These observations suggest a role for these cytokines in the induction of CD8 expression in CD8- thymocyte subsets including CD3-CD4-CD8- thymic pre-T cells.

Animals↗
PubMed1992

Reactivity profiles of leukemic myeloblasts with monoclonal antibodies directed to sialosyl-Le(x) and other lacto-series type 2 chain antigens:absence of reactivity with normal hematopoietic progenitor cells.

We investigated the expression profiles of lacto-series type 2 antigens in hematopoietic cells and their progenitors, in comparison with leukemic leukocytes. Reactivity profiles of various anti-type 2 chain monoclonal antibodies (MoAbs) with leukemic blasts from 12 patients with acute myeloblastic leukemia (AML) and those from two patients with acute unclassified leukemia (AUL) show that anti-sialosyl-Le(x) MoAb SNH3 reacted strongly with greater than 95% of leukemic blast leukocyte populations from all patients (14 of 14). Another anti-sialosyl-Le(x) MoAb, FH6, showed less reactivity than SNH3 (12 of 14 patients), while anti-Le(y) MoAb AH6 showed reactivity with only 8 of 14 patients. On the other hand, none of the anti-type 2 chain MoAbs reacted with CD34+ normal adult bone marrow (BM) mononuclear cells obtained independently from three healthy volunteers. MoAb SNH3, but not FH6 or AH6, showed complement-mediated cytotoxicity to leukemic blasts from these patients, as well as to myelogenous leukemia cell line HL60. Colony-forming unit granulocyte-macrophage (CFU-GM), but not burst-forming unit-erythroid (BFU-E), was incompletely inhibited by treatment of normal BM mononuclear cells with SNH3 and complement. The absence of type 2 chain antigen expression in hematopoietic progenitor cells and in in vitro hematopoietic colonies (CFU-GM and BFU-E) strongly suggests that application of anti-carbohydrate MoAbs, particularly anti-sialosyl-Le(x) could be useful for elimination of leukemic myeloblasts infiltrating in BM, for purging of leukemic blasts in BM, and for facilitation of autologous BM transplantation.

Antibodies, Monoclonal↗
PubMed1992

In vitro reconstitution of an erythropoietin gene transcription system using its 5'-flanking sequence and a nuclear extract from anemic kidney.

We have developed an in vitro transcription system for the erythropoietin (Epo) gene. This system uses a plasmid carrying 0.2 kb of 5'-flanking sequence from the human Epo gene, rNTPs and a nuclear extract from mouse kidney. The transcribed RNA was assayed by primer extension with an end-labeled primer complementary to the sequence of the plasmid, dNTPs and reverse transcriptase. The primer extension product corresponding to the transcript was detected on a sequencing gel. The in vitro promoter activity of the Epo 5'-flanking sequence was observed with a nuclear extract from anemic kidney but not with that from normal kidney.

Anemia↗
PubMed1992

Prolonged decrease of serum calcium concentration by murine gamma-interferon in hypercalcemic, human tumor (EC-GI)-bearing nude mice.

Murine gamma-interferon (MuIFN-gamma) is a potent inhibitor of bone resorption induced by interleukin 1 and parathyroid hormone-related protein in vitro. To investigate whether MuIFN-gamma is also effective in vivo, the cytokine was injected s.c. into hypercalcemic, tumor (EC-GI)-bearing nude mice, in which parathyroid hormone-related protein and interleukin 1 alpha are synergistically responsible for causing humoral hypercalcemia. When MuIFN-gamma was injected s.c. at a dose of 1 to 20 x 10(4) units for 5 days consecutively, serum calcium concentrations in the tumor-bearing mice decreased in a dose-dependent manner. The minimal effective dose was 5 x 10(4) units/mouse. Unlike calcitonin, which decreased the serum calcium concentration for only 1 to 2 days despite continuous daily injections, MuIFN-gamma decreased it for more than 7 days even after the injections had been stopped. Human gamma-interferon was completely ineffective. The decrease in serum calcium concentration was accompanied by a decrease in urinary calcium excretion. Histological examination of the femur revealed a decreased number of osteoclasts in the MuIFN-gamma-treated mice. Furthermore, MuIFN-gamma, when injected into nude mice or normal mice at a dose of 15 x 10(4) units for 3 days, almost completely abolished the formation of multinucleated osteoclast-like cells in vitro. These findings suggest that MuIFN-gamma suppresses the formation and maturation of osteoclasts and inhibits osteoclastic bone resorption, resulting in the prolonged decrease of serum calcium concentration seen in hypercalcemic, tumor-bearing nude mice. Therefore, bone resorption inhibitors like MuIFN-gamma, which ameliorate humoral hypercalcemia without an escape phenomenon, are potentially useful for the treatment of malignancy-associated hypercalcemia.

Animals↗