Regulation of normal hemopoiesis in the acute leukemia L5222

Normal hemopoiesis becomes markedly depressed in rats during the development of the rat leukemia L5222. Whether this could be due to the influence of a circulating humoral factor was investigated by comparing the growth of normal bone marrow cells in diffusion chambers implanted into the peritoneal cavity of normal or leukemic hosts. Similar growth in total cell numbers was observed in both groups of hosts, and no significant difference could be detected between them. In an attempt to exclude the possibility that an inhibitor either did not penetrate to the peritoneum or was inactivated by the chamber membrane, normal serum, or serum from a highly leukemic rat was mixed with the bone marrow cell suspension in the chambers. Again, no difference in growth between the 2 groups could be detected. Therefore, the influence of a circulating humoral factor in the depression of normal bone marrow hemopoiesis in this experimental leukemia seems to be ruled out, and the decrease may be attributable to local events in the bone marrow such as short-range factors or cellular interaction between the leukemic and normal hemopoietic cell populations.

Differentiation of Friend virus-induced leukemia cells

A long-term cultured Friend leukemia cell is able to differentiate along the erythrocytic series following treatment with some substances and that can be demonstrated by a conjugated erythrocyte membrane-specific antibody technique. Differentiation is induced by inhibition of DNA synthesis and by dimethylsulfoxide (DMSO), erythropoietin (EP) and Vitamin B12 (B12), and other agents. The effective substances were divided into 2 groups by the mode of differentiation of Friend cells. A differentiated state continues for several days when cells are re-cultured in the medium without substances. The decreased tumorigenecity of differentiated cells is proved by back transplantation to mice.

Phenethyl isothiocyanate promotes immune responses in normal BALB/c mice, inhibits murine leukemia WEHI-3 cells, and stimulates immunomodulations in vivo

Enhanced cruciferous vegetable consumption is associated with the reduction of cancer incidence as shown in epidemiological studies. Phenethyl isothiocyanate (PEITC), one of the important compounds in cruciferous vegetables, has been shown to induce apoptosis in many types of human cancer cell lines, but there is no available information addressing the effects on normal and leukemia mice in vivo. The purpose of this study is to focus on the in vivo effects of PEITC on immune responses of normal and WEHI-3 leukemia BALB/c mice in vivo. Influences of PEITC on BALB/c mice after intraperitoneal (i.p.) injection with WEHI-3 cells and normal mice were investigated. In normal BALB/c mice, PEITC did not affect the body weight when compared to the olive oil treated animals. Moreover, PEITC promoted phagocytosis by macrophages from peripheral blood mononuclear cells (PBMC) and peritoneal cavity, increased the levels of CD11b and Mac-3, decreased the level of CD19 and promoted natural killer (NK) cell cytotoxic activity, but it did not alter the level of CD3. Also, PEITC enhanced T cell proliferation after concanavalin A (Con A) stimulation. Otherwise, PEITC increased the body weight, but decreased the weight of liver and spleen as compared to the olive oil-treated WEHI-3 leukemia mice. PEITC also increased the level of CD19, decreased the levels of CD3 and Mac-3 rather than influence in the level of CD11b, suggesting that the differentiation of the precursor of macrophages and T cells was inhibited, but the differentiation of the precursor of B cells was promoted in leukemia mice. Furthermore, PEITC enhanced phagocytosis by monocytes and macrophages from PBMC and peritoneal cavity, and also promoted the NK cell cytotoxic activity in comparison with the group of leukemia mice. Based on these observations, the biological properties of PEITC can promote immune responses in normal and WEHI-3 leukemia mice in vivo. © 2011 Wiley Periodicals, Inc. Environ Toxicol, 2013.

Evidence for an association of high levels of endogenous Acetyl-Ser-Asp-Lys-Pro, a potent mediator of angiogenesis, with acute myeloid leukemia development

Evidence from clinical and laboratory studies suggests that angiogenesis is important in the progression of solid tumours and hematologic malignancies. We have shown that the naturally occurring tetrapeptide Acetyl-Ser-Asp-Lys-Pro (AcSDKP) is a potent angiogenic factor normally present at nanomolar concentrations in the blood. A murine leukemia model was used to assess whether there was a correlation between levels of endogenous AcSDKP and the development of disease. Levels of AcSDKP in the plasma and bone marrow (BM) cells from mice bearing an acute myeloid leukemia (AML) were five- to ten-fold greater than those in non-leukemic mice. Furthermore, a strong correlation between the concentration of endogenous AcSDKP and the progression of AML was demonstrated. These results are consistent with the marked increase in BM vascularity observed in leukemic mice. The physiologic relevance of these findings awaits further studies and the contribution of AcSDKP to the pathogenesis of leukemia is under investigation.

Cooperative antitumor effects of vitamin D3 derivatives and rosemary preparations in a mouse model of myeloid leukemia

1alpha,25-dihydroxyvitamin D(3) (1,25D(3)) is a powerful differentiation agent, which has potential for treatment of myeloid leukemias and other types of cancer, but the calcemia produced by pharmacologically active doses precludes the use of this agent in the clinic. We have shown that carnosic acid, the major rosemary polyphenol, enhances the differentiating and antiproliferative effects of low concentrations of 1,25D(3) in human myeloid leukemia cell lines (HL60, U937). Here we translated these findings to in vivo conditions using a syngeneic mouse leukemia tumor model. To this end, we first demonstrated that as in HL60 cells, differentiation of WEHI-3B D(-) murine myelomonocytic leukemia cells induced by 1 nM 1,25D(3) or its low-calcemic analog, 1,25-dihydroxy-16-ene-5,6-trans-cholecalciferol (Ro25-4020), can be synergistically potentiated by carnosic acid (10 microM) or the carnosic acid-rich ethanolic extract of rosemary leaves. This effect was accompanied by cell cycle arrest in G0 + G1 phase and a marked inhibition of cell growth. In the in vivo studies, i.p. injections of 2 microg Ro25-4020 in Balb/c mice bearing WEHI-3B D(-) tumors produced a significant delay in tumor appearance and reduction in tumor size, without significant toxicity. Another analog, 1,25-dihydroxy-16,23Z-diene-20-epi-26,27-hexafluoro-19-nor-cholecalciferol (Ro26-3884) administered at the same dose was less effective than Ro25-4020 and profoundly toxic. Importantly, combined treatment with 1% dry rosemary extract (mixed with food) and 1 microg Ro25-4020 resulted in a strong cooperative antitumor effect, without inducing hypercalcemia. These results indicate for the first time that a plant polyphenolic preparation and a vitamin D derivative can cooperate not only in inducing leukemia cell differentiation in vitro, but also in the antileukemic activity in vivo. These data may suggest novel protocols for chemoprevention or differentiation therapy of myeloid leukemia.

Establishment of a transplantable human myeloid BALB/c nude mouse model

To establish a mouse model bearing transplantable human chronic myeloid leukemia for hematopoietic stem cell transplantation to treat leukemia, 4 - 5-week-old female BALB/c nude mice were given cyclophosphamide 2 mg/mouse at day -2, -1, and then the human chronic myeloid leukemia K562 cells were engrafted into the mice at day 0 by injection via tail vein or peritoneal cavity. PB and BM cells were collected, the CD45, CD13, and CD33 antigens were delected by using FCM, the bcr/abl fusion gene mRNA was examined by RT-PCR. The results showed that transplantable leukemic mice could be yielded from 4 - 5-week-old nude mice either by injection through tail vein or peritoneal cavity when the total number of inoculated tumor cells was more than 2 x 10(5) per mouse, whether being pretreated with 2 mg CTX/mouse or not. The transplanted mice could survive 30 - 60 day with leukemia. In conclusion, the mouse model bearing leukemia can be established by inoculation 2 x 10(5) K562 cells into immunodeficient BALB/c nude mice.

[Establishment and characterization of a human acute monocytic leukemic cell line, SHI-1, carrying t(6;11)(q27;23) and p53 gene alteration]

OBJECTIVE

To establish a novel human monocytic leukemic cell line and characterize its biological features.

METHODS

Mononuclear cells isolated from the bone marrow of an acute monocytic leukemia (AML-M(5b)) patient at relapse were inoculated in a liquid culture system. And the biologic features of the established cell line SHI-1 were characterized by morphology, cytochemical staining, flow cytometry, karyotypic analysis, polymerase chain reaction (PCR), reverse transcriptase PCR (RT-PCR), fluorescence in situ hybridization (FISH), tumorigenicity in nude mice, quantitative fluorescent polymerase chain reaction, broth medium culture, short tandem repeating sequences-PCR (STR-PCR), multiplex-FISH (M-FISH), and (3)H-thymidine incorporation assay.

RESULTS

A human acute monocytic leukemia cell line, SHI-1, was established and has proliferated continuously in vitro for over one year. The cell line presented typical morphology and immuno-profile of monocytic lineage with the original t(6;11)(q27;q23) and del(17)(p11) abnormalities. The MLL-AF6 fusion transcript was detected by RT-PCR. The rearrangement of MLL gene, deletion of p53 gene, and translocation between chromosomes 6 and 11 were revealed by FISH. A point mutation of ATC-->ACC at exon 6 of the p53 gene was found by sequencing of the PCR products. The clonality and the high tumorigenicity of the SHI-1 cell line were confirmed. Infections of EBV and mycoplasma were excluded. A derivative chromosome 7 resulting from a translocation between chromosomes 7 and 13, monosomy 18 and a minute derived from chromosome 8 in addition to t(6;11) and deletion(17)(p11) were detected by M-FISH in SHI-1 cells passaged to March 2003. Cell line authentication by STR-PCR confirmed the identity to the original leukemic cells of the patient. (3)H-thymidine incorporation assay showed that IL-4 and IL-15 had proliferative effects, while IFN-gamma, TNFalpha, IL-2, PDGF, and IL-7 had inhibitory effects on the cell line.

CONCLUSIONS

SHI-1 is a novel acute monocytic leukemia-derived cell line carrying t(6;11)(q27;q23) and p53 gene alteration and having high tumorigenicity in nude mice. It provides a new useful tool for leukemia research.

[Spontaneous leukosis as a model for an investigation of low and very low physical and physico-chemical effects on oncological process]

Kinetic investigation of spontaneous leukosis in AKR mice have been carried in connection with a number of indices: changes in the mass of principal organs of the immune systems (thymus, spleen, lymphatic nodes), liver, alterations of haematological data (the sum of leukocytes, the percentage composition of blood cells, the quantity of undifferentiated cells), changes of physico-chemical conditions in cells (NMR-investigation). The dynamics of some of these indices and also life-spans of animals with leukosis after irradiation with doses 1.2-2.4 cGy (dose-rate 0.6 cGy/day) have been investigated. The enhancement of the frequency of leukosis and shortening the average and maximum life-spans of irradiated mice has been found.

Suppression of retrovirus-induced immunodeficiency disease (murine AIDS) by trimidox and didox: novel ribonucleotide reductase inhibitors with less bone marrow toxicity than hydroxyurea

Recently, the use of the ribonucleotide reductase (RR) inhibitor hydroxyurea (HU) in combination with nucleoside analogs has gained attention as a potential strategy for anti-HIV-1 therapy. However, appeal for the long-term use of HU in HIV-1 infection may be limited by its propensity to induce hematopoietic toxicity. We report a comparison of the efficacy and bone marrow toxicity of HU (400 and 200 mg/kg/day) with the novel RR inhibitors and free radical-scavenging compounds didox (DX; 3,4-dihydroxybenzohydroxamic acid; 350 mg/kg/day) and trimidox (TX; 3,4,5-trihydroxybenzamidoxime; 175 mg/kg/day) in the murine AIDS (LPBM5 MuLV) model of retrovirus infection. Infected mice received daily drug treatment for 8 weeks. Efficacy was determined by measuring drug effects on retroviral-induced disease progression (i.e. development of splenomegaly and hypergammaglobulinemia) and by evaluating splenic levels of proviral DNA. Bone marrow toxicity was evaluated by measuring peripheral blood indices (WBC, hematocrit and reticulocyte counts), femoral cellularity and by determining the numbers of hematopoietic progenitor cells (CFU-GM, BFU-E) per femur and spleen. Compared to infected controls receiving no drug treatment, disease progression was significantly suppressed by TX, DX and HU. However, HU was associated with mortality and induced significant hematopoietic toxicity in a time- and dose-dependent manner. Conversely, TX and DX effectively inhibited retrovirus-induced disease but did not induce hematopoietic toxicity. These results suggest that due to their reduced hematopoietic toxicity and ability to inhibit disease progression in murine AIDS, TX and DX may offer effective alternatives to HU therapy in HIV-1 infection.

Gender-related differences in susceptibility, early virus dissemination and immunosuppression in mice infected with Friend murine leukaemia virus variant FIS-2

An emerging amount of data indicates a correlation between gender-related factors and regulation of virus infection and supports what is known in clinical circles, that these topics are of great importance in many infectious diseases. In the present study we found that young adult NMRI male mice are more susceptible to infection by a variant of Friend murine leukaemia virus, FIS-2, than are female mice. We observed that the level of virus in serum, bone marrow and spleen was initially higher in male mice. Male mice were also more susceptible to FIS-2-induced immunosuppression. These results indicate a more efficient virus replication and dissemination in male mice. Studies with recombinant viruses between FIS-2 and the prototype Friend murine leukaemia virus revealed that FIS-2 LTR is one major factor contributing to the observed gender differences. A possible sex hormone influence on FIS-2 transcription due to the presence of a glucocorticoid response element in FIS-2 LTR is discussed.

Facilitation of functional compartmentalization of bone marrow cells in leukemic mice by biological response modifiers: an immunotherapeutic approach

Biological Response Modifiers (BRMs) including interleukin-2 (IL-2), interferon-gamma (IFN-gamma) and sheep erythrocytes (SRBC) protected N,N'-ethylnitrosourea (ENU) induced leukaemic mice. Two cell types from the bone marrow were isolated in density specific gradient representing two distinct compartments, the low density cells being more CD34 positive than the high density group. Investigations with the functional efficacy of such compartments revealed significant improvement of cytotoxic efficacy and phagocytic burst at the high density compartment (HDC) level. The high density compartment was found to be more responsive towards the BRMs compared to the cells of the low density compartment (LDC). It was suggested that use of BRMs in vivo can stimulate a potent functional progenitor compartmentalization in normal as well as leukaemic mice. These observations are expected to help a logistic approach towards combined BRM therapy at the clinical level.

[Dynamic of DNAse activity induction in serum of normal animals after heterogeneous DNA injection and in hereditary pathology]

Studies of reactions in animals with hereditary diseases (Sapphire minks highly sensitive to Aleutian disease virus, ADV; CBA mice with 60-70% incidence of tumors; AKR mice with 90% incidence of leukemia) showed that serum DNAse activity in these animals dropped after injection of a foreign heterogeneous DNA and remained decreased during 72 h. By contrast, serum DNAse activity considerably and persistently increased after injection of DNA in Standard minks resistant to ADV, C57BI/6J mice with 1% tumor incidence, and random-bred albino mice. Presumably the capacity of standard minks to react to a foreign heterogeneous DNA by increase of DNAse activity ensures their resistance to DNA-containing ADV, while incapacity of Sapphire minks to respond to DNA by DNAse activity induction makes them sensitive to ADV. A similar relationship between the capacity to react to DNA by changes in serum DNAse activity and capacity to inherit a disease was detected in mouse strains.

Absence of the effects of 50 Hz magnetic fields on the progression of acute myeloid leukaemia in rats

PURPOSE

As the most recent epidemiological studies provide no definite conclusions about the effects of 50/60 Hz magnetic fields (MFs) on the incidence of leukaemia in humans, animal models in a well-controlled environment are useful for evaluating the possibility of an association between MFs and leukaemia. The present study was designed to determine whether 50 Hz magnetic fields can alter the progression of leukaemia.

MATERIALS AND METHODS

A well-characterized model of transplantable acute myeloid leukaemia in rats was used for the first time. This model is closely related to human acute myeloid leukaemia, the type most frequently reported in epidemiological studies of adults. After leukaemic cell implantation, rats were exposed to a sinusoidal 50 Hz MF of 100 microT for 18 h a day, 7 days a week, throughout leukaemia progression. The parameters investigated were: survival time, body weight, haematologic parameters, infiltration of blood, bone marrow, spleen and liver by leukaemic cells.

RESULTS

The results showed no significant changes (p > 0.05) in leukaemic MF-exposed versus unexposed rats for any of the parameters involved in leukaemia progression.

CONCLUSION

These data do not support the hypothesis that 50 Hz magnetic fields influence leukaemia progression in humans.

Alteration of cytokine levels in murine retrovirus infection: modulation by combination therapy

Immunoregulatory cytokines may regulate the resistance or susceptibility of a host to retroviral infection. These cytokines may be therapeutically modulated to prevent or limit the progression of infection. The non-progression to AIDS of some HIV+ patients has been related to a strong type 1 cytokine response (IL-2, IL-12, and IFNgamma). For this reason, we investigated the ability of combination therapeutics to modulate cytokines in vivo towards a type 1 cytokine response in a murine retroviral infection using Friend leukemia virus (FLV). BALB/c mice were infected with FLV and treated with either 3'-azido-3'-deoxythymidine (AZT), the immunomodulator methionine enkephalin (MENK), or a combination of both AZT and MENK starting 3 d post infection. Splenocytes were harvested on days 1, 3, 7, 14, 21 and 28 post treatment initiation and cultured with 1 microg/ml concanavalin A (ConA) for 24 h. Supernatants were examined for IL-2, IL-4, IL-10, IL-12, and IFNgamma cytokine production using cytokine specific ELISAs. The levels of type 2 cytokines were not significantly changed by any treatment group over the course of the disease. However, although decreased in all infected animals, type 1 cytokines were partially maintained by the combination treatment through day 21. RT-PCR for cytokine specific mRNA confirmed these results, with expression of the type 1 cytokines, especially IFNgamma, being maintained through day 21. Establishment of a treatment regime that can maintain protective cytokine activities against disease progression may prove applicable to other retroviral infections.

Identification of directly infected cells in the bone marrow of neonatal moloney murine leukemia virus-infected mice by use of a moloney murine leukemia virus-based vector

Early bone marrow infection of Moloney murine leukemia virus (M-MuLV)-infected mice was studied. Previous experiments indicated that early bone marrow infection is essential for the efficient development of T lymphoma. In order to identify the cellular pathway of infection in the bone marrow, infection of mice with a helper-free replication-defective M-MuLV-based retroviral vector was carried out. Such a vector will undergo only one round of infection, without spreading to other cells; thus, cells infected by the initially injected virus (directly infected cells) can be identified. For these experiments, the BAG vector that expresses bacterial beta-galactosidase was employed. Neonatal NIH/Swiss mice were inoculated intraperitoneally with ca. 10(6) infectious units of a BAG vector pseudotyped with M-MuLV proteins, and bone marrow cells were recovered 2 to 12 days postinfection. Single-cell suspensions were tested for infection by staining with X-Gal (5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside) or by immunofluorescence with an anti-beta-galactosidase antibody. Two sizes of infected cells were evident: large multinucleated cells and small nondescript (presumptively hematopoietic) cells. Secondary stains for lineage-specific markers indicated that the large cells were osteoclasts. Some of the small cells expressed nonspecific esterase, which placed them in the myeloid lineage, but they lacked markers for hematopoietic progenitors (mac-1, gr-1, sca-1, and CD34). These results provide evidence for primary M-MuLV infection of osteoclasts or osteoclast progenitors in the bone marrow, and they suggest that known hematopoietic progenitors are not primary targets for infection. However, the subsequent spread of infection to hematopoietic progenitors was indicated, since bone marrow from mice infected in parallel with replication-competent wild-type M-MuLV showed detectable infection in small cells positive for mac-1 or CD34, as well as in osteoclasts.

G-CSF mobilization of haemopoietic cell populations in SCID mice engrafted with human leukaemia

We have studied granulocyte colony-stimulating factor (G-CSF)-induced mobilization of haemopoietic cells in severe combined immune-deficient (SCID) mice engrafted with human leukaemia. Three leukaemia cell lines were investigated: the HL60 myeloblastic cell line, a chronic myeloid leukaemia (CML) xenograft cell line and an acute myeloid leukaemia (AML) xenograft line. Engraftment was detected using immunofluorescent staining of class I human leukocyte antigens and flow cytometry. All the tumours grew as disseminated disease with engraftment of bone marrow preceding involvement of peripheral blood (PB). After treatment with G-CSF (250 microg/kg/day) for 5 days, mobilization of haemopoietic progenitor cells (HPCs) was observed in non-engrafted SCID mice (40-fold) and in mice engrafted with human leukaemia (20-fold). G-CSF stimulated increases in PB HPCs and total numbers of host nucleated cells in leukaemia-bearing mice but did not induce rises in numbers of circulating HL60 colony-forming cells. Similarly, in mice engrafted with human CML or AML, G-CSF did not increase the number of malignant cells in the PB. These results provided evidence that the migration of normal and malignant haemopoietic cells into the PB are controlled by different mechanisms, and that contamination of PBSC harvests with leukaemic cells in SCID-human chimaeric mice is not enhanced by G-CSF-stimulated mobilization.

Preclinical pharmacology of ecteinascidin 729, a marine natural product with potent antitumor activity

Ecteinascidins are marine natural products with potent antiproliferative activity under evaluation as chemotherapeutic agents by the National Cancer Institute. Ecteinascidins bind the minor groove of DNA and may form covalent adducts with DNA by binding the N-2 of guanine in a fashion similar to saframycin antibiotics. The most potent ecteinascidin is ET-729 with antitumor activity observed following administration of 3.8 and 10 micrograms/kg to mice bearing P388 leukemia and B16 melanoma, respectively. A reverse-phase high-performance liquid chromatography (HPLC) assay and an L1210 cell bioassay were developed for ET-729 and utilized for stability and murine pharmacokinetic studies. HPLC analysis showed that ET-729 was stable in organic solvents, mobile phase and acidic buffer (t1/2 > 100 h). Stability was diminished under neutral and basic conditions (t1/2 < 14 h). Following a 48-h incubation with L1210 cells in growth medium in the absence and presence of 2.5% murine plasma, the 50% growth inhibitory concentrations (IC50) of ET-729 were 37 and 72 pM, respectively. Following intravenous administration of ET-729 to male CD2F1 mice, the disappearance of antiproliferative activity determined by the bioassay was described by a two-compartment open model. The mean values of the elimination half-life and plasma clearance were 28 min and 39.7 ml/min per kg, respectively. Following intraperitoneal administration, peak plasma concentrations of antiproliferative activity were observed 6-15 min after injection and antiproliferative concentrations remained above 1 nM for longer than 1 h. Intraperitoneal bioavailability varied over a wide range (20-91%). Antiproliferative activity was detected in every urine sample following intravenous and intraperitoneal administration, but the total 48-h urinary recovery was less than 0.1%.

10A1 MuLV induces a murine leukemia that expresses hematopoietic stem cell markers by a mechanism that includes fli-1 integration

The 10A1 murine leukemia virus induces tumors that lack lineage-specific markers found on myeloid, T-cell, and B-cell lineages. Either erythroid or multipotent stem cells can have this phenotype; therefore we have used fluorescence-activated cell sorter analysis with either multipotent stem cell markers or markers found on lineage-restricted precursors to differentiate between these two possibilities. The results showed that tumors induced by 10A1 expressed multipotent stem cell markers as well as some lineage-restricted precursor markers. To further study the tumor phenotype, we analyzed total RNAs from 10A1-induced tumors by Northern blotting for c-kit, erythropoietin receptor, and T-cell gamma receptor mRNAs. Most of the tumors contained these mRNAs, which are characteristic of early hematopoietic cells. These results are consistent with the hypothesis that 10A1-induced tumor cells are early multipotent hematopoietic stem cells. Southern blot analysis revealed that 14 of 14 10A1-induced tumor cell DNAs examined contained MuLV integrations into the fli-1 gene. The results strongly suggested that promoter insertion into fli-1 is required for tumor formation.

Melatonin concentrations in pineal organ culture are suppressed by sera from tumor-bearing mice

The melatonin rhythm is significantly attenuated in a wide range of human and animal tumor types. Since surgical removal of the tumor has been shown to restore this rhythm, we hypothesized that a plasma borne tumor-associated factor (TAMF) could be responsible. A population of mice were injected with tumor cells and sequentially killed and bled over the following 9 days, i.e., to the maximal state of tumor growth. Pooled serum from the different collection days was added to an established pineal organ culture system, and melatonin concentrations measured. A highly significant correlation between melatonin concentrations and the stage of tumor growth was seen with maximal inhibition occurring at day 9 (P < 0.01). These findings support our hypothesis and may help to explain the mechanism whereby melatonin rhythmicity is suppressed in cancer patients.

A constitutively activated erythropoietin receptor stimulates proliferation and contributes to transformation of multipotent, committed nonerythroid and erythroid progenitor cells

If the env gene of spleen focus-forming virus (SFFV) is replaced by a cDNA encoding a constitutively active form of the erythropoietin receptor, EPO-R(R129C), the resultant recombinant virus, SFFVcEPO-R, induces transient thrombocytosis and erythrocytosis in infected mice. Clonogenic progenitor cell assays of cells from the bone marrow and spleens of these infected mice suggest that EPO-R(R129C) can stimulate proliferation of committed megakaryocytic and erythroid progenitors as well as nonerythroid multipotent progenitors. From the spleens of SFFVcEPO-R-infected mice, eight multiphenotypic immortal cell lines were isolated and characterized. These included primitive erythroid, lymphoid, and monocytic cells. Some expressed proteins characteristic of more than one lineage. All cell lines resulting from SFFVcEPO-R infection contained a mutant form of the p53 gene. However, in contrast to infection by SFFV, activation of PU.1 gene expression, by retroviral integration, was not observed. One cell line had integrated a provirus upstream of the fli-1 gene, in a location typically seen in erythroleukemic cells generated by Friend murine leukemia virus infection. This event led to increased expression of fli-1 in this cell line. Thus, infection by SFFVcEPO-R can induce proliferation and lead to transformation of nonerythroid as well as very immature erythroid progenitor cells. The sites of proviral integration in clonal cell lines are distinct from those in SFFV-derived lines.

Comparison of the effects of CD3 and CD5 donor T cell depletion on graft-versus-leukemia in a murine model for MHC-matched unrelated-donor transplantation

Studies were designed to prospectively evaluate the effects of selective depletion for donor T cells strongly expressing the CD3 and CD5 pan-T antigens on the incidence of leukemia relapse following bone marrow transplantation. This evaluation was performed under controlled conditions in a mouse model for MHC-matched unrelated-donor transplantation, employing Rauscher leukemic SJL/J mice as the recipients and leukemia-resistant B10.S mice as the donors. Selective donor cell depletion for CD3 and CD5 was accomplished ex vivo prior to transplantation by incubation with the appropriate monoclonal antibody plus complement. When untreated, Rauscher leukemia resulted in a 97% fatality incidence. This was reduced to 30% by the transplant of non-depleted B10.S cells, with another 37% recipients dying from GVHD and graft failure. CD3 depletion reduced the GVHd deaths to 6% but increased relapse to 62%. Conversely, CD5 depletion had no effect on relapse or on GVHD but did significantly increase graft failure, thus negatively affecting survival. Evaluation of the results, done in conjunction with flow cytometry analysis of the effects of CD3 versus CD5 depletion on the donor cells, suggests that the T cells involved in suppressing leukemic relapse in these studies, and hence contributing to the GVL response, most probably had a phenotype of CD3+, CD5-.

Involvement of the complement system in the pathogenesis of pulmonary leukostasis in experimental myelocytic leukemia

The role of the complement system in the pathogenesis of pulmonary leukostasis in myelocytic leukemia was studied in a rat model. Acute myelocytic leukemia was induced in six Brown-Norway rats, and complement levels were assayed during the course of the disease. Whole complement activity (CH50) and hemolytic activity of C1q, C3, and C4 decreased from day 16 after induction of the leukemia, when the rats developed pulmonary leukostasis. In addition, local complement activation was established in the lung vessels by immunofluorescence microscopy in advanced stages of pulmonary leukostasis. Finally, following systemic activation of the complement system by injection of cobra venom factor (CVF), leukemic rats (n = 6) died of pulmonary leukostasis 4.5 days earlier than did leukemic controls (n = 6). These findings suggest that, in acute myelocytic leukemia in Brown-Norway rats, pulmonary leukostasis is induced by activation of the complement system. This finding could lead to new modes of treatment for a life-threatening complication of leukemia.

Induction of Fc receptors on murine macrophages and leukemic cells by interleukin-1 beta

Recombinant human interleukin-1 beta (rhIL-1 beta) is shown to be a strong inducer of Fc receptors (FcR) on murine macrophages and not on granulocytes. Data is provided indicating that rhIL-1 beta does induce specific but not nonspecific phagocytosis. Macrophages are shown to autoinduce their FcR expression as a function of time in culture. This induction is increased by the use of exogenous rhIL-1 beta and inhibited by anti-rhIL-1 beta antibody, pointing to an autocrine regulation of FcR expression on macrophages. On the other hand the myelomonocytic cell line WEH13BD- and the macrophage like cell line WR19M.1 are also shown to be inducible for the expression of FcR by this molecule. Data is also provided showing that recombinant murine Interferon gamma (rmIFN gamma) induces FcR on both macrophages and granulocytes. Whereas polyclonal antibodies inhibit FcR induction by IL-1 on macrophages, it does not inhibit FcR induction by IFN gamma on these cells. This points to a different mechanism of induction of FcR by IFN and IL-1. Finally, the possible application of rhIL-1 beta in vivo to help the organism fight infections is discussed.

Erythroblasts as an index of initial stage of 2,7-FAA, ENU and BNU-induced rat leukemia

The appearance of orthochromatic erythroblasts in the peripheral blood was evaluated as an index of the initial stage of leukemia induced in rats by the oral administration of N,N'-2,7-fluorenylenebisacetamide, 1-ethyl-1-nitrosourea and 1-butyl-1-nitrosourea. Solitary leukemia lesions found mainly in the bone marrow and composed of one or a few nodular foci were found by using erythroblasts as an index. The time interval from the first appearance of erythroblasts to autopsy was short in solitary lesions, slightly longer in scattered lesions, and even longer in diffuse leukemia lesions. Although the appearance of orthochromatic erythroblasts in the peripheral blood was due to several causes other than leukemia, this appearance was useful as an index of the initial stage of chemically induced leukemia in rats.

Catabolism of the tetrapeptide N-Ac-Ser-Asp-Lys-Pro (AcSDKP), an inhibitor of hematopoietic stem cell (CFU-S) proliferation, following in vitro incubation with hematopoietic tissues from normal and leukemic mice

The comparative degradation of N-Ac-Ser-Asp-Lys-Pro (AcSDKP), a negative regulator controlling the proliferation of the hematopoietic pluripotent stem cell, was investigated following incubation with plasma, bone marrow and spleen cells from normal mice and mice bearing a transplantable myeloid leukemia. Using the tetrapeptide, specifically radiolabelled in the lysyl residue, degradation of [3H]AcSDKP was followed by measurement of [3H]Lys formation resulting from its catabolism. It was shown that already after 1 h the degradation of AcSDKP in plasma from leukemic mice was higher compared to that following incubation in plasma from normal mice, whereas incubation with bone marrow cells exhibits a small difference only after 4 hours incubation. However, no increase of AcSDKP catabolic activity was observed following incubation with spleen cells from leukemic animals when compared with incubation of normal spleen cells.

Chronic feline leukemia virus infection alters arachidonic acid proportions in vivo and in vitro

The polyunsaturated omega-6 fatty acid, arachidonic acid ([AA] 20:4n-6), is both the key of the immunoregulatory substances, prostaglandins, and leukotrienes, and an essential component of immune cell membrane phospholipids, providing stability and flexibility to ensure cellular function. To explore possible effects of the physiological burden of viral replication in chronic viral infections on AA availability, plasma total esterified fatty acid (FA) proportions were measured in the feline leukemia (FeLV) model. Plasma FA profiles of 12 specific-pathogen-free cats with chronic infections with Rickard strain feline leukemia virus (FeLV-R) were compared with 12 age- and sex-matched uninfected specific-pathogen-free cats at 4 months after infection. A significant decrease from normal of average AA proportion was found in FeLV-R-infected cat plasma, while other major FA (palmitic, stearic, and oleic and omega-3 FA normally remained present until near death. Since plasma FA content rapidly affects circulating immune cell membrane composition and since FeLV infection also targets immune cells, we compared FA profiles of feline T4-thymic lymphoma 3201 cell membranes that were infected with virulent FeLV-R or less virulent FeLV-A, at 20 days after viral inoculation with sham-inoculated uninfected 3201 cells. Significantly altered FA proportions and ratios of saturated to unsaturated FA found in infected cell membranes were similar to plasma FA changes and paralleled the virulence of the FeLV inoculum. Altered postinfection FA proportions may impart serious functional defects to the immune cells of chronic FeLV-infected cats, contributing to the inability of their immune systems to eliminate FeLV by depleted plasma AA stores and modified cell membrane composition. Decreased AA availability may be an important factor in the cachexia and fatal outcome of FeLV infection.

Early divergence of erythroid lineage suggested by gene rearrangements in mouse hematopoietic neoplasms

A total of 113 primary murine hematopoietic neoplasms, including those of erythroid, granulocytic, and T and B lymphoid lineages, were examined for rearrangement of immunoglobulin heavy (IgH) and kappa light chain (IgK) and T cell receptor beta and gamma (TcR-beta and TcR-gamma) genes. There was a total absence of Ig or TcR gene rearrangements in erythroid leukemias. In contrast, overlaps of IgH rearrangements were observed in myeloid and T cell as well as B cell neoplasms. In a minority of B cell lymphomas, rearrangements of TcR-beta or TcR-gamma genes were detected. This evidence of shared recombinase activity for myeloid, T cell, and B cell-lineage tumors and the absence of such activity in erythroid tumors suggest early divergence of the erythroid pathway.

Involvement of the spleen in preleukemic development of a murine retrovirus-induced promonocytic leukemia

An acute myeloid leukemia can result from the inoculation of Moloney murine leukemia virus into BALB/c mice undergoing a 2,6,10,14-tetramethylpentadecane-induced chronic inflammatory response in the peritoneal cavity. This leukemia is ultimately observed in the peritoneal cavity as an ascites with cells infiltrating the granulomatous tissue. It has been proposed, however, that hematopoietic organs such as the spleen and bone marrow are involved in preleukemic development of Moloney murine leukemia. Therefore, to determine if the spleen plays a role in this development, mice were splenectomized at various times relative to virus inoculation. When splenectomies were performed 3 days before and 2, 4, 6, and 8 weeks after virus inoculation there was, in all cases, a decreased death rate compared to sham-splenectomized controls. The greatest difference in death rate due to promonocytic leukemia was observed when mice were splenectomized at 4 weeks after virus inoculation. The decrease in disease incidence observed as a result of splenectomy was not caused by decreased virus spread in hematopoietic organs or an alteration in the profile of the cellular infiltrate in the granuloma. It was found, however, that the spleens of 2,6,10,14-tetramethylpentadecane-treated mice, relative to those of normal mice, have a significantly increased number of granulocyte-macrophage colony-forming cells and a slightly increased number of multipotential colony-forming cells. These observations suggest that a population of target cells for transformation, consisting of granulocyte-macrophage precursor cells, may reside in the spleen. Alternatively, partially transformed cells may reside temporarily in the spleen during the developmental stages of the disease process.

Induction and inhibition of bovine leukaemia virus expression in naturally infected cells

Bovine leukaemia virus (BLV) resides in infected lymphocytes in a latent, repressed state but becomes expressed a few hours after the cells are cultured in vitro. We have identified several conditions and factors affecting the expression of BLV in short-term cultures of naturally infected lymphoid cells. The presence of foetal calf serum in the culture medium greatly stimulates virus expression. This stimulation is not due to cellular proliferation. Transcription of BLV RNA and synthesis of p25 in the cultures of peripheral blood lymphocytes are preceded by a lag period of several hours. Synthesis of BLV p25 in these cultures takes place almost immediately after viral RNA synthesis. Extending previous results, we demonstrate that the plasma and lymphatic fluid of cattle contain factors that suppress and stimulate BLV expression. As a result of systematic examination of several parameters, we have developed reproducible assays for the detection of these factors. It is very likely that their relative concentration in the host is an important determinant of susceptibility and resistance to the development of lymphosarcoma and persistent lymphocytosis in BLV-infected cattle.

Hematological and clinico-biochemical characteristics of leukemia in Fischer 344 rats

Seventy-one male and 52 female F 344 rats with leukemia used as controls in the 30-month inhalation studies were characterized by hematological and clinico-biochemical findings. Hematological findings revealed that the leukocyte count, mean corpuscular volume, and mean corpuscular hemoglobin increased in both sexes of leukemic rats showing profound anemia, while the platelet count, erythrocyte count, hematocrit, and hemoglobin concentration decreased. In these rats, the serum levels of low density lipoprotein, free cholesterol, total bilirubin, blood urea nitrogen, and triglyceride and the activities of glutamic oxalacetic transaminase, glutamic pyruvic transaminase, creatine phosphokinase, alkaline phosphatase, and lactate dehydrogenase increased markedly and the level of high density lipoprotein, the oxygen partial pressure, and the cholinesterase activity decreased. Clinical signs such as decrease in redness of the eyes, decrease in body weight, abdominal distension, staining of the public region, and debility were seen in most leukemic animals. These clinical signs and hematological and clinico-biochemical findings may be helpful in diagnosis of leukemia in long-term experiments.

[Autologous blood-derived stem cell transplantation in the treatment of proliferative disorders of the hematopoietic system (I)]

Peripheral blood can be an alternative source of hematopoietic stem cells which after autografting are capable of sustaining or completely recovering of lymphopoiesis without the necessity of bone marrow harvesting. Theoretical assumptions conditioning the clinical application of circulating stem cells autotransplantation have been described. The results of experimental studies performed in animals and humans have allowed for closer characterization of these cells. However, the physiological significance of their presence in the peripheral blood still remains unknown.

Leukaemia and anaemia in AKR/O mice I. Leukaemia characteristics, haematological variables and erythropoiesis stimulating factor(s)

AKR/O mice were used as a model for studying the pathogenesis of the anaemia accompanying leukaemia/lymphoma. The leukaemia incidence was 87%. Median age at diagnosis was 11.3 months. At diagnosis most of the mice had normal leukocyte counts. Clinically the mice divided into subgroups depending on the relative organ involvement: 1) thymoma group (n = 98), 2) spleen group (n = 144), 3) combined group (n = 27) and 4) mice with moderate organ changes (n = 216). Mice of group 1 were younger than the others, had a rapidly progressive disease, normal to elevated packed cell volume (PCV), and plasma erythropoietin (Epo) was normal or increased. Mice of group 2 were usually anaemic with high plasma Epo estimates and often elevated reticulocyte counts. Group 4 was the oldest group. Some of these mice were severely affected haematologically. Overall there was an inverse relation between PCV and plasma Epo estimate, indicating a normal Epo response to anaemia. In all groups increasing spleen size was associated with increased severity of anaemia and increased reticulocyte counts. The association between anaemia, elevated reticulocyte counts and spleen enlargement suggests haemolysis as a mechanism for anaemia, and also raises the question of compensatory spleen erythropoiesis.

Impaired immune responsiveness is an essential component in persistent central nervous system infection with gross murine leukemia virus

Exposure of newborn mice to Gross murine leukemia virus (GMuLV) results in persistent viral infection of the central nervous system (CNS) white matter. Animals exposed to virus as neonates showed a marked depression in GMuLV-specific B lymphocyte function as evidenced by significant decreases in adult and neonatal anti-GMuLV antibody levels. Immunohistochemical analyses showed that the sites of GMuLV infection in the CNS were also devoid of major histocompatibility complex (MHC) class I and II protein expression, although transplantation of GMuLV-infected brain tissue to the kidney capsules of immunocompetent mice induced a potent mononuclear cell graft infiltrate. These results indicate that persistent GMuLV infection of the CNS is linked to both impairment of anti-GMuLV peripheral immune responses and deficient antigen-presenting cell function within the CNS.

[The effect of finoptin on the metabolism and pharmacological action of cyclophosphane in vivo and in vitro]

Phynoptin (Ph) and cyclophosphamide (CP) gave rise to a type I spectral changes with liver microsomal fraction. KS were 15 microM and 2150 microM, respectively. Ph increases the concentration of NBP product(s) of CP and acrolein in the blood plasma of animals. Ph increases a toxicity of CP. LD50 was 388.0 +/- 13.9 mg/kg for CP and LD50 was 342.8 +/- 16.9 mg/kg for CP in combination with Ph. Ph changes a therapeutic action of CP in mice with hemocytoblastosis La. Pharmacokinetic interactions have been demonstrated between calcium antagonists Ph and CP.

[Effect of herbal tonic on the membrane fluidity of the mice suffered from lymphatic leukemia]

By using fluorescence polarization technology, the authors have studied variations in the membrane fluidity of red blood cell and spleen lymphocytes of the mice with lymphatic leukemia (L7212) untreated or treated by the compound tonic of traditional Chinese medicine decoction of reinforcing Qi and nourishing Yin and decoction of reinforcing Qi and nourishing blood. It was not only confirmed that the membrane fluidity of malignant lymphocytes increased more greatly, but also discovered that the variations could appear in early period of leukemia. The membrane fluidity of lymphocytes of the mice with leukemia treated by the herbal tonic could drop to normal level. But the membrane fluidity of the red blood cell between the normal mice (615) and the leukemia mice (L7212), untreated or treated by the herbal tonic, had no significant difference.

RESULT

the above mentioned suggests the herbal tonic could resist leukemia by reducing the membrane fluidity of the lymphocytes and improving structure and function of the membrane.

Serum deoxythymidine-5'-triphosphatase activity in lymphoproliferative disorders of men and mice

A recently discovered enzyme of the pyrimidine pathway, deoxythymidine-5'-triphosphatase (dTTPase), was estimated in sera from leukemic mice and 64 untreated patients with non-Hodgkin's lymphoma (NHL) as well as 30 patients with plasmocytoma. At the age of 19 weeks the Mov-9 substrain of 129 mice developed leukemia in contrast to the congenic controls. Patient lymph node biopsies were classified according to the Kiel classification. The results showed a significant correlation between dTTPase activity and the onset of proliferation (studied in mice), as well as the grade of malignancy (studied in men). The more advanced the disease or the less aggressive the tumor, the higher the dTTPase activity. This gives rise to the speculation that dTTPase might be part of a control in the proliferation process.

[Synthesis and properties of new rubomycin derivatives]

Condensation of rubomycin (daunorubicin) with respective hydrazides yielded novel substituted hydrazones: 13-cyanoacetyl hydrazone rubomycin, 13-L-phenylalanyl hydrazone rubomycin, 13-BOC-3-(uracilyl-1)-DL-alanyl hydrazone rubomycin and 13-BOC-3-(adenylyl-9)-DL-alanyl hydrazone rubomycin. With successive treatment of rubomycin with hydrazine hydrate and respective ketones novel asymmetric azines were prepared: 13-cyclopentylidene hydrazone rubomycin, 13-alpha,alpha'-dimethyl-cyclopentylidene hydrazone rubomycin and 13-(1-phenylethylidene-1) hydrazone rubomycin. 14-Adenylyl-N9-rubomycin was synthesized by interaction of 14-bromorubomycin with adenine and hydrogenation of its analog, 14-N-imidazolyl rubomycin by sodium borhydrite yielded 13-dihydro-14-N-imidazolyl rubomycin. There was observed correlation between the antimicrobial activity of the derivatives against B. mycoides and their cytostatic effect on the cells of murine leukemia NK/LI. The high in vitro activity of 13-cyclopentylidene hydrazone rubomycin showed satisfactory correlation with the results of the study on the antitumor effect in animals.

Variations in erythropoiesis throughout a lifetime. Studies in a high-leukaemic mouse strain, the AKR/O strain, and a non-leukaemic strain, the WLO strain

We have studied the development of some haematological variables: erythropoiesis stimulating factor(s) (ESF), investigated with an in vitro cell culture assay; and the content of bone marrow and spleen erythroid colony forming unit(s) (CFU-E) and erythroid burst forming unit(s) (BFU-E) throughout the lifetime of 2 different mouse strains: the high-leukaemic, retrovirus infected AKR/O strain, and the non-leukaemic WLO strain. During the recovery phase of the postnatal anaemia, a peak in plasma ESF occurs in both strains. In young adult mice of both strains another peak in plasma ESF occurs at 70-110 days of age, associated with an increased number of bone marrow CFU-E, in a period when packed cell volume (PCV) remains stable. As the animals grow older PCV decreases, whereas plasma ESF and bone marrow CFU-E concentration increase. These results, together with in vitro dose-response studies, suggest reduced sensitivity to erythropoietin (Epo) of the ageing erythron. Throughout, the AKR/O strain has higher levels of plasma ESF and bone marrow CFU-E concentrations than the WLO strain, indicating both a reduced Epo responsiveness and some degree of ineffective erythropoiesis in the AKR/O strain. At all ages the AKR/O strain has a high concentration of Epo independent bone marrow CFU-E, possibly caused by the virus infection of precursor cells.

Suppression of immunological responses in rabbits experimentally infected with bovine leukemia virus

Ten 2- to 4-month-old rabbits were inoculated subcutaneously with bovine leukemia virus (BLV)-infected bovine or sheep cells. By 6 weeks after inoculation all ten rabbits had converted to BLV antibody-positive, and BLV or BLV antigen was detected in lymphocytes from most of the rabbits tested, although there were few antigen-producing cells. Three rabbits showed continuous respiratory symptoms after infection and one died with pneumonia. Humoral immune responses against mouse serum were significantly suppressed in BLV-infected rabbits compared with non-infected control rabbits. The lymphocyte blastogenesis response was also suppressed in BLV-infected rabbits. At the time of necropsy, six rabbits showed pulmonary lesions; however, none of the BLV-infected rabbits had tumors during an observation period of over 1 year.

Guanosine 5'-[gamma-thio]triphosphate-stimulated hydrolysis of phosphatidylinositol 4,5-bisphosphate in HL-60 granulocytes. Evidence that the guanine nucleotide acts by relieving phospholipase C from an inhibitory constraint

Myeloid differentiated human leukaemia (HL-60) cells contain a soluble phospholipase C that hydrolysed phosphatidylinositol 4.5-bisphosphate and was markedly stimulated by the metabolically stable GTP analogue guanosine 5'-[gamma-thio]triphosphate (GTP[S]). Half-maximal and maximal (up to 5-fold) stimulation of inositol phosphate formation by GTP[S] occurred at 1.5 microM and 30 microM respectively. Other nucleotides (GTP, GDP, GMP, guanosine 5'-[beta-thio]diphosphate. ATP, adenosine 5'-[gamma-thio]triphosphate, UTP) did not affect phospholipase C activity, GTP[S] stimulation of inositol phosphate accumulation was inhibited by excess GDP, but not by ADP. The effect of GTP[S] on inositol phosphate formation was absolutely dependent on and markedly stimulated by free Ca2+ (median effective concn. approximately 100 nM). Analysis of inositol phosphates by anion-exchange chromatography revealed InsP3 as the major product of GTP[S]-stimulated phospholipase C activity. In the absence of GTP[S], specific phospholipase C activity was markedly decreased when tested at high protein concentrations, whereas GTP[S] stimulation of the enzyme was markedly enhanced under these conditions. As both basal and GTP[S]-stimulated inositol phosphate formation were linear with time whether studied at low or high protein concentration, these results suggest that (a) phospholipase C is under an inhibitory constraint and (b) GTP[S] relieves this inhibition, most likely by activating a soluble GTP-binding protein.

Comparative levels of CALLA/neutral endopeptidase on normal granulocytes, leukemic cells, and transfected COS-1 cells

We discovered that the common acute lymphoblastic leukemia antigen, CALLA (CD10), was identical to human neutral endopeptidase 3.4.24.11 (NEP), a Zn-binding glycoprotein with an extracellular active site capable of hydrolyzing several biologically active peptides. In this study we compare the expression of CALLA/NEP in terms of antigenic density and enzymatic activity at the cell surface and of messenger RNA (mRNA) levels on granulocytes, leukemic cells, and CALLA-transfected COS-1 cells. Mature granulocytes, the only readily available source of normal human CALLA, express relatively low but constant levels of antigen, NEP activity (3.5 pmol/min/10(6) cells), and mRNA. The two major CALLA-mRNA species of 6.5 kb and 3.8 kb, observed to date in a variety of cells and tissues, were also found in four independent granulocyte preparations. With leukemia cell lines, a correlation was established between the density of CALLA antigen and the level of enzymatic activity (3.4 to 21.0 pmol/min/10(6) cells). This paper constitutes the first report of NEP activity on blast cells derived from patients with non-T acute lymphoblastic leukemia (ALL); the levels of activity were variable (1.5 to 35.9 pmol/min/10(6) cells for six cases) but correlated with the level of CALLA assessed by flow cytometry. Heterogeneous levels of expression of the CALLA-mRNA species were also observed in non-T ALL cases that correlated with the level of CALLA expression at the surface of these cells. Very high levels of NEP activity were achieved by transfecting COS-1 cells with pSV-CALLA; 20% of the transfected cells were CALLA+ and expressed 550 pmol/min/10(6) cells. Extracts prepared from COS-1 cells transfected with pSV-CALLA (carrying human NEP cDNA) and pSVENK19 (carrying rabbit NEP-cDNA), respectively, gave Michaelis constant (Km) values of 50 mumol/L and similar inhibition curves with thiorphan. Thus the recombinant proteins encoded by these two genes have similar enzymatic properties, confirming the high degree of their structural relatedness. The expression of high levels of CALLA/NEP on COS-1 cells should allow the use of this system to test the effects of specific mutations on activity and might lead to the understanding of the role of CALLA in the onset and/or progression of leukemia.

1,25-Dihydroxy-16-ene-23-yne-vitamin D3 prolongs survival time of leukemic mice

The 1,25-dihydroxy-16-ene-23-yne-vitamin D3 [1,25(OH)2-16-ene-23-yne-D3] is a vitamin D analog that is very potent in inhibiting proliferation and inducing differentiation of myeloid leukemic cells in vitro. Also, 1,25(OH)2-16-ene-23-yne-D3 is 300 times less active in mediating intestinal calcium absorption and bone calcium mobilization as compared to 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], the physiologically active metabolite. Furthermore, 1,25(OH)2-16-ene-23-yne-D3 is 10-25 times less potent than 1,25(OH)2D3 in causing hypercalcemia in BALB/c mice injected intraperitoneally (i.p.) every other day (q.o.d.) for 6 weeks. We explored the therapeutic potential of 1,25(OH)2-16-ene-23-yne-D3 by developing and using the following three leukemia models. (i) Injection of 2.5 x 10(5) myeloid leukemic cells (WEHI 3BD+) into syngeneic BALB/c mice resulted in leukemic death of all diluent-injected mice by day 26. Mice who received the same number of leukemic cells and also received 1,25(OH)2D3 (0.1 micrograms q.o.d., i.p.) had nearly an identical survival curve. Those who received the leukemic cells and 1,25(OH)2-16-ene-23-yne-D3 (1.6 micrograms q.o.d., i.p.) had a significantly (P = 0.003) longer survival, with the last mouse dying of leukemia on day 50. (ii) Injection of 50% fewer leukemic cells (1 x 10(5) cells) into syngeneic BALB/c mice resulted in 86% dead of leukemia at 51 days. Experimental mice who received the same number of leukemic cells and 1,25(OH)2-16-ene-23-yne-D3 (0.8 microgram q.o.d.) had a significantly (P = 0.0006) longer survival than controls; only 53% of the mice were dead by day 100. (iii) After injection of 1.5 x 10(4) leukemic cells, 13% of syngeneic BALB/c mice were free of disease at day 180. In contrast, 43% of mice who received leukemic cells and 1,25(OH)2-16-ene-23-yne-D3 (1.6 micrograms q.o.d.) were still free of disease at day 180. In summary, 1,25(OH)2-16-ene-23-yne-D3 is a vitamin D analog that significantly increased survival of mice who had myeloid leukemia.