Growth and biologic properties of karyotypically defined subcategories of adult acute lymphocytic leukemia in mice with severe combined immunodeficiency

Modest progress has been achieved over the past two decades in the treatment of adult acute lymphocytic leukemia (ALL). With modern therapy, response rates are 70% to 80%, but cure rates only average 25% to 30%. Improved in vivo models are needed to investigate the biology of adult ALL and to test new treatment concepts. Fresh leukemia samples from children with ALL have been successfully transplanted into mice with severe combined immunodeficiency (SCID), but no experience exists for adult ALL. We treated SCID mice with 2 mg cyclophosphamide 24 hours before intravenously injecting 20 x 10(6) viable leukemia cells obtained from 13 patients with newly diagnosed adult ALL within five defined phenotype/karyotype subcategories. Ten (76%) of 13 injected leukemia specimens representing all five categories engrafted. The median survival duration of mice was 20 weeks from the time of leukemia cell injection. The rate of engraftment by ALL subset was as follows: two of two T-cell, two of three t(11q23), two of two hyperdiploid, two of three t(9;22), and two of three diploid ALL. The pattern of organ involvement by leukemia in the mice was similar to that of the human disease. Immunohistochemistry and flow cytometry documented the stability of each leukemic phenotype after passage through SCID mice. Cells transplanted from the spleen and bone marrow of mice engrafted with ALL into recipient mice resulted in consistent engraftment. The survival duration in passage groups was similar to that in groups injected with primary cells. The high frequency of engraftment, availability of frozen original specimens, and successful passages in SCID mice provide an in vivo model of adult ALL suitable for further studies of the disease biology and for design of drug studies for the different subtypes of previously untreated adult ALL.     

Homing and progression patterns of childhood acute lymphoblastic leukemias in severe combined immunodeficiency mice

The aim of this study was to analyze the homing and progression patterns of childhood acute lymphoblastic leukemias (ALL) in mice with severe combined immunodeficiency (SCID). Upon intraperitoneal (IP) transfer, cells from relapse samples of three children with T-lineage ALL spread hematogenously and infiltrated the non-lymphoid and/or lymphoid organs with a pattern reminiscent of the human clinical disease. These mice either died or were killed in extremis at a mean of 9 weeks. Moreover, cell lines established in vitro from two of these samples manifested identical homing and progression in the SCID mouse as compared with the original patients' cells. Thus, long-term culture of the primary leukemic T cells did not alter their invasive potential and migration pattern. When engrafted IP, three cell lines established from pre-B-ALL cases displayed primarily a lymphatic spread with induction of local tumor masses and kidney/liver nodules. Mice were killed at 11 to 13 weeks, but had not developed imminently fatal leukemia. However, when transferred intravenously, one pre-B ALL cell line was able to spread hematogenously and to infiltrate both lymphoid and non-lymphoid tissues. Overall, these data demonstrate that the SCID mouse provides an efficient and reproducible model to study the pathogenesis of childhood ALL, and may be a suitable system for evaluating therapy.     

A clinically relevant SCID-hu in vivo model of human multiple myeloma

We developed a novel in vivo multiple myeloma (MM) model by engrafting the interleukin 6 (IL-6)-dependent human MM cell line INA-6 into severe combined immunodeficiency (SCID) mice previously given implants of a human fetal bone chip (SCID-hu mice). INA-6 cells require either exogenous human IL-6 (huIL-6) or bone marrow stromal cells (BMSCs) to proliferate in vitro. In this model, we monitored the in vivo growth of INA-6 cells stably transduced with a green fluorescent protein (GFP) gene (INA-6GFP+ cells). INA-6 MM cells engrafted in SCID-hu mice but not in SCID mice that had not been given implants of human fetal bone. The level of soluble human IL-6 receptor (shuIL-6R) in murine serum and fluorescence imaging of host animals were sensitive indicators of tumor growth. Dexamethasone as well as experimental drugs, such as Atiprimod and B-B4-DM1, were used to confirm the utility of the model for evaluation of anti-MM agents. We report that this model is highly reproducible and allows for evaluation of investigational drugs targeting IL-6-dependent MM cells in the human bone marrow (huBM) milieu.     

Reconstitution of SCID mice with human lymphoid and myeloid cells after transplantation with human fetal bone marrow without the requirement for exogenous human cytokines.

Investigation of human hematopoietic maturation has been hampered by the lack of in vivo models. Although engraftment of irradiated C.B-17 scid/scid (SCID) mice with human progenitor cells occurred after infusion with human pediatric bone marrow cells, significant engraftment of the mouse bone marrow with human cells was dependent upon continuous treatment with exogenous human cytokines. Furthermore, despite cytokine treatment, only minimal peripheral engraftment of these mice with human cells was observed. In the present study, after infusion of irradiated SCID mice with pre-cultured human fetal bone marrow cells (BM-SCID-hu mice), their bone marrow became significantly engrafted with human precursor cells and their peripheral lymphoid compartment became populated with human B cells and monocytes independently of the administration of extraneous human cytokines. Examination of the bone marrow of the BM-SCID-hu mice for human cytokine mRNA gene expression demonstrated human leukemia inhibitory factor mRNA and interleukin 7 mRNA in nine of nine BM-SCID-hu mice and macrophage-colony-stimulating factor mRNA in seven of eight BM-SCID-hu mice. This was an intriguing observation because these cytokines regulate different stages of human hematopoiesis. Since engraftment occurs in the absence of exogenous cytokine treatment, the BM-SCID-hu mouse model described should provide a useful in vivo system for studying factors important in the maturation of human myeloid and lymphoid cells in the bone marrow and the behavior of the mature human cells after dissemination into the peripheral lymphoid tissue.     

Growth pattern and clinical correlation of subcutaneously inoculated human primary acute leukemias in severe combined immunodeficiency mice

We examined the ability of patient-derived human leukemic blasts to generate leukemic growth and dissemination in severe combined immunodeficiency (SCID) mice by subcutaneous inoculation without conditioning treatment or administration of growth-promoting cytokines. Additionally, we correlated the growth pattern with the clinical outcome of patients from whom the leukemic cells were derived. The leukemias displayed three distinct growth patterns, ie, either aggressive, indolent, or no tumor growth. Leukemic cells from 6 of 13 patients with acute myeloid leukemia (AML), 4 of 7 T-cell acute lymphoblastic leukemia (T-ALL), and 11 of 16 patients with B-lineage ALL grew as subcutaneous tumors, with a significant number subsequently disseminating into distant organs in SCID mice. Patients whose leukemic blasts displayed an aggressive growth and dissemination pattern in SCID mice had a relatively poor clinical outcome, whereas patients with AML and T- or B-lineage ALL whose leukemic blasts grew indolently or whose cells failed to induce growth had a more favorable clinical course. Our study has shown that the subcutaneous inoculation of patient-derived human leukemic cells in SCID mice can engraft and grow as subcutaneous tumors with subsequent dissemination to distant organs in a manner analogous to their pattern of growth in humans. Additionally, these data suggest a clinical correlation to the growth and dissemination of some leukemic subtypes that may represent not only an additional prognosticator for patient outcome, but also a vehicle for the study of the biologic behavior of human leukemias and the development of novel therapeutic strategies.     

The nonobese diabetic/severe combined immunodeficient (NOD/SCID) mouse model of childhood acute lymphoblastic leukemia reveals intrinsic differences in biologic characteristics at diagnosis and relapse

Acute lymphoblastic leukemia cells from 19 children, including 7 who remain in first complete remission (CR1), were engrafted into nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice. High-level infiltration of bone marrow, spleen, and liver was observed, with variable infiltration of other organs. The immunophenotypes of xenografts were essentially unaltered compared with the original patient sample. In addition, sequencing of the entire p53 coding region revealed no mutations in 14 of 14 xenografts (10 from patients at diagnosis and 4 at relapse). Cells harvested from the spleens of engrafted mice readily transferred the leukemia to secondary and tertiary recipients. To correlate biologic characteristics of xenografts with clinical and prognostic features of the patients, the rates at which individual leukemia samples engrafted in NOD/SCID mice were analyzed. Differences in biologic correlates were encountered depending on stage of disease: a direct correlation was observed between the rate of engraftment and length of CR1 for samples harvested at relapse (r = 0.96; P =.002), but not diagnosis (r = 0.38; P =.40). In contrast, the in vivo responses of 6 xenografts to vincristine showed a direct correlation (r = 0.96; P =.002) between the length of CR1 and the rate at which the leukemia cell population recovered following vincristine treatment, regardless of whether the xenografts were derived from patients at diagnosis or relapse. This study supports previous findings that the NOD/SCID model of childhood ALL provides an accurate representation of the human disease and indicates that it may be of value to predict relapse and design alternative treatment strategies in a patient-specific manner.     

Monitoring of engraftment and progression of acute lymphoblastic leukemia in individual NOD/SCID mice

OBJECTIVE: The aim of this study was to develop an animal model for human acute lymphoblastic leukemia (ALL) in which the kinetics and characteristics of leukemia can be sequentially monitored in individual mice. MATERIALS AND METHODS: NOD/SCID mice were inoculated intravenously with primary ALL. Progression of leukemia was monitored throughout the development of disease by determination of absolute leukemic cell counts (LCC) in peripheral blood. RESULTS: LCC as low as 10(4) leukemic cells/mL blood could be detected. ALL cells from 5 of 5 patients engrafted, and after identification of the first leukemic cells in peripheral blood, LCC increased exponentially. Leukemic cells showed specificity of homing to spleen and bone marrow, and LCC strongly correlated with the level of leukemic engraftment in these organs throughout disease progression, demonstrating that LCC are representative for overall leukemic burden. Cytogenetic analysis of leukemic cells recovered after six successive in vivo transfers revealed no major karyotypic changes as compared to primary cells, and selection of the dominant clones was observed. This selection process was reflected by an increase in the rate of leukemic progression as compared to the first inoculation, demonstrating the accuracy with which kinetics of leukemic progression can be studied by determination of LCC. CONCLUSIONS: This model is suitable for detailed studies of kinetics and characteristics of ALL in vivo, and it may be useful for monitoring effects of novel therapeutic regimens.     

Interleukin-4 variant (BAY 36-1677) selectively induces apoptosis in acute lymphoblastic leukemia cells

Interleukin 4 (IL-4) suppresses the growth of acute lymphoblastic leukemia (ALL) cells, but its clinical usefulness is limited by proinflammatory activity due mainly to the interaction of cytokine with endothelial cells and fibroblasts. Stroma-supported cultures of leukemic lymphoblasts were used to test the antileukemic activity of an IL-4 variant, BAY 36-1677, in which the mutations Arg 121 to Glu and Thr 13 to Asp ensure high affinity for IL-4Ralpha/IL-2Rgamma receptors expressed by lymphoid cells, without activation of the IL-4Ralpha/IL-13Ralpha receptors mainly expressed by other cells. BAY 36-1677 (25 ng/mL) was cytotoxic in 14 of 16 cases of B-lineage ALL; the median reduction in cell recovery after 7 days of culture was 85% (range, 17%-95%) compared to results of parallel cultures not exposed to the cytokine. Twelve of the 14 sensitive cases had t(9;22) or 11q23 abnormalities; 3 were obtained at relapse. BAY 36-1677 induced apoptosis in leukemic lymphoblasts but did not substantially affect the growth of normal CD34+ cells, thus conferring a growth advantage to normal hematopoietic cells over leukemic lymphoblasts in vitro. BAY 36-1677 had antileukemic activity equal or superior to that produced by native IL-4, but it lacked any effects on the growth of endothelial cells and fibroblasts. The molecular manipulation of IL-4 to abrogate its proinflammatory activity has generated a novel and therapeutically promising cytokine for the treatment of high-risk ALL.     

Characterization of acute lymphoblastic leukemia progenitor cells

Only some acute lymphoblastic leukemia (ALL) cells are thought to be capable of proliferating to maintain the leukemic clone, and these cells may be the most relevant to target with treatment regimens. We have developed a serum-free suspension culture (SC) system that supported growth of B-ALL cells from 33 patients for up to 6 weeks. ALL cells from 28 cases (85%) were expanded in this system, and growth was superior in SC than in long-term bone marrow culture. To characterize ALL progenitors, cells were sorted for expression of CD34 and CD10 or CD19 and the subfractions assayed in SC and in nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice. Cells capable of long-term proliferation in vitro and NOD/SCID repopulation were derived only from the CD34(+)/CD10(-) and CD34(+)/CD19(-) subfractions, and these cells could engraft secondary recipients. The engrafted cells had the same immunophenotype and karyotype as was seen at diagnosis, suggesting they had differentiated in vivo. These results demonstrate that ALL cells capable of long-term proliferation in vitro and in vivo are CD34(+)/CD10(-)/CD19(-). This suggests that cells with a more immature phenotype, rather than committed B-lymphoid cells, may be the targets for transformation in B-ALL.     

Propagation of human blastic myeloid leukemias in the SCID mouse.

Existing in vitro culture technology does not permit the routine propagation of most human myeloid leukemias. Previous work has shown the usefulness of mice with severe combined immunodeficiency (SCID) for the growth of human lymphoblastic leukemia. We show here that human myeloid cell lines and bone marrow samples from patients with acute myeloid leukemia (AML) and blast crisis of chronic myeloid leukemia (CML) also grow in SCID mice. Human AML or CML cell lines (three of three lines tested) grew in the bone marrow and peripheral blood of the mice after intravenous (IV) inoculation in a pattern closely resembling human AML. To define the best conditions for the growth of primary human myeloid leukemia cells, samples were transplanted into mice at several alternative sites. Using flow cytometry and Southern analysis, mice were analyzed at defined intervals up to 36 weeks after transplantation for the presence of human cells in various tissues. For four of four patients with AML and two of two patients with blast crisis of CML, myeloblasts grew locally at the site of implantation and were detected in the murine hematopoietic tissues. In contrast, marrow implants from patients in the chronic phase of CML (six patients) showed infrequent and limited myeloid growth in the mice. These findings demonstrate that the SCID mouse is a reproducible system for the propagation of blastic human myeloid leukemias. The differential growth of early- versus late-phase CML suggests that the SCID mouse may be a useful assay for identifying biologically aggressive leukemias early in their clinical presentation.     

Inhibitory effect of interleukin-4 on the in vitro growth of Ph1-positive acute lymphoblastic leukemia cells

We investigated the effect of recombinant human interleukin-4 (rhIL-4) on the in vitro growth of human leukemia cells in liquid culture and 3H-thymidine incorporation and found inhibitory effects on the growth of leukemic cells from patients with Ph1-positive acute lymphoblastic leukemia (Ph1 ALL) and three Ph1 ALL cell lines. However, no inhibitory effects were seen in Ph1-positive leukemic cell lines derived from patients with chronic myelogenous leukemia in blast crisis and various types of Ph1-negative leukemia cells, including B-lineage leukemia cells. In a flow cytometry assay of IL-4 receptor (IL-4R), all three Ph1-positive ALL cell lines showed the presence of IL-4R on their cell surfaces, and the IL-4-dependent inhibition on the growth of Ph1-positive ALL cells was abrogated by the addition of either monoclonal or polyclonal antibodies against rhIL-4. Other cytokines, including IL-2, IL-3, granulocyte-macrophage colony-stimulating factor (CSF), granulocyte-CSF, and IL-6, showed no inhibitory effects on the growth of Ph1-ALL cells, but tumor necrosis factor-alpha (TNF-alpha) and interferon (IFN)-alpha, -beta, and -gamma displayed slight inhibitory effects in a high concentration. The growth inhibition induced by rhIL-4 in the Ph1-positive ALL cells was not abrogated by the addition of antibodies against either IFN-gamma or TNF-alpha. Furthermore, these cells showed no significant production of IFN-alpha, -beta, or -gamma or TNF-alpha after exposure to rhIL-4, thus indicating that the growth inhibition of Ph1-positive ALL cells by rhIL-4 is not associated with IL-4-stimulating production of these factors. rhIL-4 caused significant inhibition of the tyrosine kinase activity in these Ph1-positive ALL cells, similar to Herbimycin A, an inhibitor of tyrosine kinase that inhibited the tyrosine kinase activity in these cells. Our finding suggests that the clinical evaluation of rhIL-4 may offer promising therapeutic possibilities for patients with Ph1-positive ALL.     

Motility, proliferation, and egress to the circulation of human AML cells are elastase dependent in NOD/SCID chimeric mice

The role of the proteolytic enzyme elastase in motility and proliferation of leukemic human acute myeloblastic leukemia (AML) cells is currently unknown. We report a correlation between abnormally high levels of elastase in the blood of AML patients and the number of leukemic blast cells in the circulation. In AML cells, we observed expression of cell-surface elastase, which was regulated by the chemokine stromal cell-derived factor-1 (SDF-1). In vitro inhibition of elastase prevented SDF-1-induced cell polarization, podia formation, and reduced migration of human AML cells as well as their adhesion. Elastase inhibition also significantly impaired in vivo homing of most human AML cells to the bone marrow (BM) of nonobese diabetic-severe combined immunodeficient (NOD/SCID)/beta-2 microglobulin knock-out (B2m null) mice that underwent transplantation. Moreover, in vitro proliferation of AML cells was elastase dependent. In contrast, treatment with elastase inhibitor enhanced the proliferation rate of human cord blood CD34+ cells, including primitive CD34+/CD38- cells, and their in vivo homing. Finally, NOD/SCID mice previously engrafted with human AML cells and treated with elastase inhibitor had significantly reduced egress of leukemic cells into the circulation. Taken together, our data demonstrate that human AML cells constitutively secrete and express SDF-1-dependent cell-surface elastase, which regulates their migration and proliferation.     

The role of TNF-alpha in the pathogenesis of inflammation and joint destruction in rheumatoid arthritis (RA): a study using a human RA/SCID mouse chimera

OBJECTIVE: In order to elucidate which cytokine preferentially stimulates the synovium in patients with rheumatoid arthritis (RA), we investigated the roles of tumour necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6) using SCID mice engrafted with human RA tissue (SCID-HuRAg). METHODS: The SCID-HuRAg mice were prepared according to our previously described method. First, SCID-HuRAg mice were treated with chimeric anti-TNF-alpha monoclonal antibody (mAb, 100 microg/mouse) and histological changes were examined 4 weeks after the initial treatment. Secondly, a total of 100 microg of recombinant TNF-alpha or IL-6 (0.6 microg/h) was administered daily to mice using an osmium pump. The histological changes and serum cytokine levels were examined 4 weeks after the initial administration. Human immunoglobulin G (IgG) was administered to mice as a control. RESULTS: Synovial inflammatory cells were significantly decreased after the anti-TNF-alpha mAb treatment; conversely, the degree of synovial inflammation was significantly exacerbated by TNF-alpha administration. The levels of both IL-6 and TNF-alpha in sera were significantly increased by recombinant TNF-alpha administration, while TNF-alpha levels were unchanged by IL-6 administration. This suggests that TNF-alpha controls IL-6 production. Despite the profound changes in inflammation, we found no effects on bone and no articular cartilage damage was produced by TNF-alpha. CONCLUSION: This study provides strong evidence that TNF-alpha is a key molecule in the control of the inflammatory changes that occur in the RA synovium. In addition, TNF-alpha regulates IL-6 production. However, other inflammatory pathways independent of TNF-alpha may contribute to the bone and cartilage damage seen in RA.     

In vitro and in vivo activity of topotecan against human B-lineage acute lymphoblastic leukemia cells

Topotecan [(S)-9-dimethylaminomethyl-10-hydroxycamptothecin hydrochloride; SK&F 104864-A, NSC 609699], a water soluble semisynthetic analogue of the alkaloid camptothecin, is a potent topoisomerase I inhibitor. Here we show that topotecan stabilizes topoisomerase I/DNA cleavable complexes in radiation-resistant human B- lineage acute lymphoblastic leukemia (ALL) cells, causes rapid apoptotic cell death despite high-level expression of bcl-2 protein, and inhibits ALL cell in vitro clonogenic growth in a dose-dependent fashion. Furthermore, topotecan elicited potent antileukemic activity in three different severe combined immunodeficiency (SCID) mouse models of human poor prognosis ALL and markedly improved event-free survival of SCID mice challenged with otherwise fatal doses of human leukemia cells at systemic drug exposure levels that can be easily achieved in children with leukemia.     

Lineage switch in childhood leukemia with monosomy 7 and reverse of lineage switch in severe combined immunodeficient mice.

Morphophenotypic lineage switches occur in a small percentage of those with acute leukemia, and the underlying mechanisms are not clear. In this study, we attempted to induce a lineage switch in acute myelocytic leukemia (AML) with monosomy 7, whose lineage had switched from acute T-lymphocytic leukemia (T-ALL) during chemotherapy, in severe combined immunodeficient (SCID) mice. Although the transplanted myeloid cells were engrafted in SCID mice without cytokine administration, T-ALL developed in SCID mice treated with recombinant human granulocyte-macrophage colony-stimulating factor or recombinant human interleukin 3. Analysis of the nucleotide sequences of the rearranged T-cell receptor gamma-chain (TCR-gamma) gene revealed that this lineage switch resulted from the selection of the T-lineage subclone in SCID mice, which had expanded at onset. In addition, we found that the T-lineage and myeloid cells belonged to the distinct subclones, which were different in TCR-gamma gene rearrangements, but were derived from a common clone with an identical N-ras gene mutation for both subclones. In in vitro cultures, only the myeloid subclone grew; the T-lineage subclone failed to grow even in the presence of recombinant human granulocyte-macrophage colony-stimulating factor or recombinant human interleukin 3. These results suggested that the initial diagnostic T-lymphoid subclone, whose growth was dependent on these cytokines and the hematopoietic microenvironment, emerged from a bipotential T-lymphoid/myeloid leukemic stem cell, and further genetic event(s) induced the myeloid subclone, which grew independently of these cytokines and the microenvironment.     

In vivo control of acute lymphoblastic leukemia by immunostimulatory CpG oligonucleotides

Despite considerable success in treating newly diagnosed childhood acute lymphoblastic leukemia (ALL), relapsed disease remains a significant clinical challenge. Using a NOD/SCID mouse xenograft model, we report that immunostimulatory DNA oligonucleotides containing CpG motifs (CpG ODNs) stimulate significant immune activity against primary human ALL cells in vivo. The administration of CpG ODNs induced a significant reduction in systemic leukemia burden, mediated continued disease control, and significantly improved survival of mice with established human ALL. The death of leukemia cells in vivo was independent of the ability of ALL cells to respond directly to CpG ODNs and correlated with the production of IL-12p70, IFN-alpha, and IFN-gamma by the host. In addition, depletion of natural killer cells by anti-asialo-GM1 treatment significantly reduced the in vivo antileukemic activity of CpG ODN. This antileukemia effect was not limited to the xenograft model because natural killer cell-dependent killing of ALL by human peripheral blood mononuclear cells (PBMCs) was also increased by CpG ODN stimulation. These results suggest that CpG ODNs have potential as therapeutic agents for the treatment of ALL.     

Chemotherapy resistance in acute lymphoblastic leukemia requires hERG1 channels and is overcome by hERG1 blockers

Bone marrow mesenchymal cells (MSCs) can protect leukemic cells from chemotherapy, thus increasing their survival rate. We studied the potential molecular mechanisms underlying this effect in acute lymphoblastic leukemia (ALL) cells. Coculture of ALL cells with MSCs induced on the lymphoblast plasma membrane the expression of a signaling complex formed by hERG1 (human ether-à-go-go-related gene 1) channels, the β(1)-integrin subunit, and the chemokine receptor CXC chemokine receptor-4. The assembly of such a protein complex activated both the extracellular signal-related kinase 1/2 (ERK1/2) and the phosphoinositide 3-kinase (PI3K)/Akt prosurvival signaling pathways. At the same time, ALL cells became markedly resistant to chemotherapy-induced apoptosis. hERG1 channel function appeared to be important for both the initiation of prosurvival signals and the development of drug resistance, because specific channel blockers decreased the protective effect of MSCs. NOD/SCID mice engrafted with ALL cells and treated with channel blockers showed reduced leukemic infiltration and had higher survival rates. Moreover, hERG1 blockade enhanced the therapeutic effect produced by corticosteroids. Our findings provide a rationale for clinical testing of hERG1 blockers in the context of antileukemic therapy for patients with ALL.     

Responses to donor lymphocyte infusion for acute lymphoblastic leukemia may be determined by both qualitative and quantitative limitations of antileukemic T-cell responses as observed in an animal model for human leukemia

OBJECTIVE: Donor lymphocyte infusion (DLI) after allogeneic stem cell transplantation is largely unsuccessful in the treatment of acute lymphoblastic leukemia (ALL). To allow identification of the causes of this failure, we established an animal model of DLI in human ALL. METHODS: NOD/scid mice were inoculated with primary human ALL cells. Cells from five different patients were studied. After engraftment, DLI was performed by infusion of human leukocyte antigen (HLA)-identical donor T cells or HLA-disparate donor T cells. RESULTS: DLI resulted in expansion of activated, leukemia-reactive T cells in all donor-patient combinations. After 40 days of expansion, T cells abruptly declined in numbers and displayed loss of cytotoxicity. At this moment, remissions were observed in three of five donor-patient combinations. In animals engrafted with the two unresponsive ALL, remissions could be achieved when HLA-disparate DLI was given. CONCLUSION: Our results indicate that the inefficacy of DLI in ALL may be due to the limitation of the proliferative capacity of ALL-reactive T cells and that the antileukemic efficacy during the limited time span of proliferation depends on the antigenic disparity between the donor and the patient. The model can be used to study whether alternative strategies may result in more sustained antileukemic responses after DLI in ALL.     

A model of in vivo cell proliferation of adult T-cell leukemia

We have made a model of in vivo cell proliferation of leukemic cells from adult T-cell leukemia (ATL) patients using severe combined immunodeficiency (SCID) mice. Peripheral blood mononuclear cells (PBMC) or lymph node cells (LNC) depleted of B cells and monocytes were intraperitoneally injected into SCID mice treated with antimurine interleukin-2 receptor (IL-2+) beta chain monoclonal antibody (MoAb)(TM- beta 1), followed by daily injection of human recombinant IL-2 until 60 days after cell injection. SCID mice injected with ATL cells from 6 of 8 ATL patients were found to have the tumor or leukemia 5 to 7 weeks after the inoculation of cells. Serum levels of soluble form of human IL-2R alpha chain (Tac) were markedly elevated in such mice. The cells recovered from the mice injected with leukemic cells from four different ATL patients had the same cell surface phenotype as that of original leukemic cells which were CD4+Tac+. Furthermore, we detected the same integration site of human T-cell leukemia virus type I (HTLV- I) provirus and the same rearrangement pattern of human T-cell receptor (TCR) beta chain gene as those of ATL cells by Southern blot hybridization, indicating that the cells proliferating in SCID mice were derived from the original ATL cell clone. Histologic examination showed that the pattern of the infiltration of ATL cells into various organs in SCID mice was similar to that of an ATL patient. Such a model of in vivo cell proliferation of ATL cells will be useful for the study of the mechanism of neoplastic cell proliferation and for the development of a new and effective treatment of ATL.     

Elimination of human leukemia cells in NOD/SCID mice by WT1-TCR gene-transduced human T cells

Cytotoxic T lymphocytes (CTLs) specific for an HLA-A2-presented peptide epitope of the Wilms tumor antigen-1 (WT1) can selectively kill immature human leukemia progenitor and stem cells in vitro. In this study we have used retroviral gene transfer to introduce a WT1-specific T-cell receptor (TCR) into T lymphocytes obtained from patients with leukemia and from healthy donors. TCR-transduced T cells kill leukemia cells in vitro and display WT1-specific cytokine production. Intravenous injection of TCR-transduced T cells into nonobese diabetic-severe combined immunodeficiency (NOD/SCID) mice harboring human leukemia cells resulted in leukemia elimination, whereas transfer of control T cells transduced with an irrelevant TCR was ineffective. The data suggest that adoptive immunotherapy with WT1-TCR gene-modified patient T cells should be considered for the treatment of leukemia.