Biomedical subjects

R Taetle

Publications and source records attributed to R Taetle.

At least 55 records · Page 3Linked to original sources

PubMed1993

Effects of transforming growth factor beta 1 on growth and apoptosis of human acute myelogenous leukemia cells.

Because limited studies examined effects of transforming growth factor (TGF) beta 1 on growth of human acute myelogenous leukemia (AML) cells, we used factor-dependent and primary AML cells to assess TGF-beta 1 effects on human AML cell growth. OCI-AML1 cells were growth inhibited by TGF-beta 1 regardless of which growth factor was used as a stimulus. In contrast, AML-193 cells were resistant to TGF-beta 1 when grown with or without growth factors. UCSD/AML1 cells were sensitive to TGF-beta 1 inhibition when grown with most cytokines but were relatively resistant to TGF-beta 1 in the presence of macrophage colony-stimulating factor (M-CSF). Although cells grown from 5 of 6 AML patients were inhibited by TGF-beta 1, cells from 1 AML patient were growth stimulated by TGF-beta 1 in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF), M-CSF, or mast cell growth factor (kit ligand). Thus, 3 growth patterns with TGF-beta 1 were observed: (a) sensitivity to growth inhibition; (b) resistance; and (c) factor-dependent resistance. Further studies showed that AML-193 and UCSD/AML1 cells expressed type II TGF-beta 1 receptors and that ability of TGF-beta 1 to decrease GM-CSF receptors did not correlate with growth inhibition. AML-193 cells and UCSD/AML1 cells grown with M-CSF could be propagated in 1 ng/ml TGF-beta 1, but UCSD/AML1 cells grown with GM-CSF and TGF-beta 1 died. Morphology and agarose gel analysis of DNA showed UCSD/AML1 cells underwent apoptosis when grown with GM-CSF and TGF-beta 1 but not with M-CSF and TGF-beta 1. Similar studies of OCI-AML1 cells showed that TGF-beta 1 induced apoptosis of cells grown in 5637 bladder cell-conditioned medium or GM-CSF. These studies indicate that human AML cells exhibit heterogeneous growth responses to TGF-beta 1 and that some effects of TGF-beta 1 on myeloid cells occur through programmed cell death.

Apoptosis↗

PubMed1993

High-dose carboplatin chemotherapy with GM-CSF and peripheral blood progenitor cell support: a model for delivering repeated cycles of dose-intensive therapy.

High-dose chemotherapy regimens can cure a number of otherwise incurable diseases, such as Hodgkin's disease, non-Hodgkin's lymphoma, neuroblastoma, acute leukemia (in remission), and breast cancer. Trials of high-dose chemotherapy have generally used autologous bone marrow transplant or peripheral blood stem cell support to ensure hematologic recovery after intensive chemotherapy and/or radiation. This report describes an approach in which high-dose carboplatin chemotherapy was followed initially by granulocyte-macrophage colony-stimulating factor (GM-CSF; Escherichia coli. Sandoz-Schering, East Hanover and Kenilworth, NJ) and in subsequent patients, by both GM-CSF and repeated cycles of peripheral blood progenitor cell (PBPC) collection and administration. The addition of PBPC to this regimen led to significant reductions in the duration of neutropenia and thrombocytopenia, the requirement for erythrocyte and platelet transfusions, the length of hospital stay, and the use of intravenous antibiotics in this group relative to those patients who received GM-CSF alone. In addition, laboratory studies are presented that show a direct correlation between the number of progenitor cells reinfused and the duration of neutropenia and thrombocytopenia. The report also reviews data indicating that circulating progenitor cells are depleted by this approach. This suggests that the number of progenitor cells available for mobilization is finite. Finally, the magnitude of these effects, and their implications for future trials with repetitive cycles of dose-intensive therapy, are discussed.

Adult↗

PubMed1993

Retroviral gene transfer of epidermal growth factor receptor into HL60 cells results in a partial block of retinoic acid-induced granulocytic differentiation.

HL60 cells are devoid of endogenous epidermal growth factor receptor (EGFR). They respond to retinoic acid and undergo terminal granulocytic differentiation. EGFR complementary DNA was introduced into HL60 cells by retroviral gene transfer. Scatchard plot showed that the binding characteristics are identical to those of A431 cells. HL60-EGFR cells were estimated to express 34,000 EGFR/cell (Kd = 5 nM). The tyrosine phosphorylation upon ligand binding is the first step of signal transduction. The dominant phosphotyrosyl proteins in epidermal growth factor-stimulated HL60-EGFR cells include a 170 kDa protein (EGFR itself), and 125 and 53 kDa proteins. The EGFR signal results in the induction of 92 kDa gelatinase/matrix metalloproteinase in HL60-EGFR cells, thereby providing evidence of the function of the exogenous EGFR and a semiquantitative measure of the EGFR signal. These HL60-EGFR cells offer a unique opportunity to examine the potentially important role of EGFR (c-erbB) in maintaining homeostasis between self-renewal and differentiation. c-erbB has been shown to play a physiological role in the self-renewal of the very early avian stem cells which do express EGFR. The v-erbB (double truncated EGFR) has been shown to cause avian erythroblastosis. We found that these HL60-EGFR cells responded to retinoic acid differently from the HL60-control cells. A partial block of only 45% granulocytic differentiation and concomitant proliferation was noted, consistent with a shift of balance between self-renewal and differentiation toward the former.

Cell Differentiation↗

PubMed1993

Expression of the EVI1 gene in chronic myelogenous leukemia in blast crisis.

The EVI1 gene encodes a nuclear, zinc finger, DNA binding protein expressed after provirus insertion into the Fim-3 or EVI1 loci in murine leukemia myeloid cells. EVI1 is also expressed by cells from AML patients with chromosome rearrangements involving band 3q26, the putative location of the EVI1 gene, but expression of this gene is not detected in normal bone marrow. We report expression of EVI1 by cells from a patient with chronic myelogenous leukemia in blast crisis (CML/BC) whose cells showed inv(3)(q22q26). In vitro culture of these cells resulted in macrophage differentiation and loss of EVI1 expression. Results in this patient suggest EVI1 expression played a role in CML blast transformation. Patients with CML/BC and other nonrandom chromosome abnormalities involving chromosome 3q26 should be evaluated for EVI1 expression.

Adult↗

PubMed1992

Antiproliferative and antitumor activity of the 2-cyanoaziridine compound imexon on tumor cell lines and fresh tumor cells in vitro.

BACKGROUND: Imexon, a 2-cyanoaziridine, is therapeutic and reverses lymphadenopathy and splenomegaly in the LP-BM5 murine retrovirus-induced immunodeficiency disease (murine AIDS). It can restore chemotherapy-induced immunosuppression. Imexon reduced the incidence of lymphoma in severe combined immune deficient mice inoculated with human lymphocytes. PURPOSE: To determine its antitumor activity, we screened imexon against fresh human tumor cells and tumor cell lines. To determine the time-concentration relationships of its cytotoxicity, we studied the effects of imexon on macromolecular synthesis and on the cell cycle. METHODS: Imexon was incubated at 1-200 micrograms/mL with various tumor cell lines, mitogen-stimulated peripheral blood lymphocytes, and fresh tumor cells. Cell survival, macromolecular synthesis, and cell cycle progression were studied. RESULTS: The concentration of imexon that caused 50% inhibition of growth was under 10 micrograms/mL for lymphocytes stimulated with mitogens. It was about 3-10 micrograms/mL for B-cell lymphomas and both multi-drug-resistant and -sensitive myeloma cell lines. Imexon inhibited four of seven fresh lymphoma and 11 of 16 fresh myeloma biopsy specimens to less than 40% of the control. A 1-hour exposure of lymphoma cells to 50-100 microgram/mL followed by removal of drug by washing the cells and continuing culture resulted in greater than 95% inhibition during the next 48-72 hours. Imexon selectively inhibited protein synthesis during the first 24-48 hours of exposure of lymphoma and myeloma cells. Cells exposed to inhibitory concentrations of imexon were blocked in cell cycle progression. CONCLUSION: Imexon may be a potentially useful agent in the treatment of malignant disease, particularly lymphoid malignancies, and should be explored further.

Antineoplastic Agents↗

PubMed1992

Activation of EVI1 gene expression in human acute myelogenous leukemias by translocations spanning 300-400 kilobases on chromosome band 3q26.

Retroviral activation of Evi-1 gene expression is one of the most common transforming events in murine myeloid leukemias. To evaluate the role of the EVI1 gene in human acute myelogenous leukemia (AML), leukemic blasts or cell lines from 116 patients were examined. In eight patients the EVI1 gene was expressed and all but one had cytogenetically detectable translocations of chromosome 3q26 where the EVI1 gene has been localized. To identify breakpoints, a restriction map that spans 1700 kilobases (kb) of the EVI1 locus was developed by pulsed-field gel electrophoresis. In one case, t(3;3)(q21;q26), a rearrangement was localized to 170-330 kb 5' of the gene. In a second case, t(3;3)(q21;q26), there was a rearrangement 13 kb 5' of the gene. This rearrangement was cloned and shown to be due to the fusion of sequences from 3q21-22 with the EVI1 locus. In the third case, ins(3)-(q21q25q27), there was a rearrangement that mapped 150 kb downstream from the 5' end of the gene.

Base Sequence↗

PubMed1992

Sequential cycles of high-dose carboplatin administered with recombinant human granulocyte-macrophage colony-stimulating factor and repeated infusions of autologous peripheral-blood progenitor cells: a novel and effective method for delivering multiple courses of dose-intensive therapy.

PURPOSE: The trial was undertaken to study the effect of administering granulocyte-macrophage colony-stimulating factor (GM-CSF) with and without peripheral-blood progenitor cells (PBPC) on the hematologic and nonhematologic toxicity observed with multiple cycles of high-dose carboplatin chemotherapy. PATIENTS AND METHODS: Eighteen patients with a variety of solid tumors received a total of 40 cycles of carboplatin, 1,200 mg/m2 per cycle, administered by continuous infusion over 96 hours. All 40 courses were administered with a daily 4-hour intravenous (IV) infusion of either 5 or 10 micrograms/kg/d of recombinant human Escherichia coli-derived GM-CSF. The first 20 courses were administered without PBPC support (treatment A). Because of severe neutropenia and thrombocytopenia, the next 20 courses of therapy were administered with GM-CSF, PBPC, and oral antibiotic prophylaxis (treatment B). RESULTS: The addition of PBPC support led to a significant reduction in the duration of neutropenia (10.5 v 7.5 days; P = .027) and thrombocytopenia (12.4 v 5.2 days; P = .001), number of RBC transfusions (six v three; P = .01) and platelet transfusions (10.3 v 3.7; P = .013), number of hospital days (12.6 v 2.9; P = .01), and days of IV antibiotics (11.8 v 2.4; P = .007) per cycle. Significant increases in the weekly dose intensity (206 v 285 mg/m2/wk; P = .014) and total dose (2,287 v 3,600 mg/m2; P = .018) of carboplatin delivered were also observed with treatment B. The overall response rate in this study was 70%, with 11 of 16 assessable patients achieving either a complete (three patients) or partial (eight patients) remission. CONCLUSION: This combination of GM-CSF and PBPC infusion represents an effective method for delivering multiple cycles of high-dose carboplatin chemotherapy and may serve as a model for the administration of high-dose chemotherapy in future trials.

Adult↗

PubMed1992

A dose-escalation study of carboplatin/cyclophosphamide/etoposide along with autologous bone marrow or peripheral blood stem cell rescue.

Twenty patients have received 21 courses of high-dose cyclophosphamide (6 g/m2 over 4 days), etoposide (1,800 mg/m2 over 3 days), and carboplatin (800 to 1,600 mg/m2 by continuous infusion over 96 hours) and autologous bone marrow or peripheral blood stem cell rescue. The maximum tolerated dose of this regimen included these doses of cyclophosphamide and etoposide with a total of 1,600 mg/m2 carboplatin. Acute renal failure was the dose-limiting toxicity and, at the maximum tolerated dose, was observed in two patients of 14 evaluable courses. Nonhematologic toxicity was otherwise modest, and the overall response rate was 70% in patients with a wide variety of solid hematologic neoplasms.

Acute Kidney Injury↗

PubMed1992

Expression and regulation of the evi-1 gene in the human factor-dependent leukemia cell line, UCSD/AML1.

The human factor-dependent leukemia cell line UCSD/AML1 contains the t(3;3) (q21;q26) characteristic of the syndrome of acute leukemia with high platelets. The human homologue of the murine leukemia oncogene evi-1 was recently localized to chromosome 3q24-3q28 and transcription of evi-1 is a frequent event in mouse-retrovirus-induced leukemias (17). To determine whether translocations near human 3q24 might induce similar genetic changes, we examined and compared evi-1 and c-myc expression and regulation in UCSD/AML1 cells. Steady-state evi-1 transcripts were detected in UCSD/AML1 and murine leukemia M1 cells, but were not present in HL60 or Namalwa human leukemia cells. Transcription assays showed the evi-1 gene was actively transcribed in UCSD/AML1, but not HL60 nuclei. Evi-1 transcript sizes and half-life were similar in UCSD/AML1 and human HEC-1B carcinoma cells which express evi-1 transcripts, but do not have abnormalities involving chromosome 3. An alternative splice site detected by polymerase chain reaction was present in transcripts from both cell lines. Regulation of evi-1 RNA in UCSD/AML1 cells was similar to that of actin transcripts in response to cycloheximide or phorbol-ester-induced macrophage differentiation. After withdrawal of granulocyte/macrophage colony-stimulating factor (GM-CSF), evi-1, actin, and histone H3 transcripts declined in concert with exit from the cell cycle. Minor differences in rates of recovery were noted for these three genes after GM-CSF restimulation. In contrast, c-myc was expressed at high levels in UCSD/AML1 cells and showed evidence for specific regulation in response to cycloheximide, phorbol ester, and GM-CSF withdrawal and restimulation. These studies suggest the 3q translocation in UCSD/AML1 cells is associated with evi-1 transcription and expression of a potential transforming gene. In contrast to c-myc, evi-1 expression is minimally altered by biologically active chemicals or growth factor stimulation.

Animals↗

PubMed1991

Assessment of ligand effects in intracellular trafficking of ricin A chain using anti-ricin hybridomas.

Intracellular ricin and immunotoxin trafficking has been difficult to study as only one to two cytosolic ricin A chain (RTA) molecules are sufficient to cause cell death. Previous studies (R.J. Youle and M. Colombatti, J. Biol. Chem., 262: 4676-4882, 1987) using anti-ricin hybridomas identified the secretory pre-Golgi as a critical site for RTA intoxication. We used ricin and RTA immunotoxins constructed with transferrin (TF) or anti-murine TF receptor antibody (RI7/217) to compare patterns of cytotoxicity and intracellular trafficking in anti-ricin hybridomas. Anti-RTA and anti-ricin B chain (RTB) hybridomas bound similar amounts of ricin and secreted comparable amounts of anti-ricin immunoglobulin. Anti-RTA hybridomas were 50- to 500-fold more resistant to ricin than nonsecretory and anti-RTB hybridomas, defining a ricin-resistant phenotype. All hybridomas expressed similar levels of surface TF receptors. RTA immunotoxins were constructed using human TF or RI7/217 and a disulfide linker. In protein synthesis inhibition assays, ricin-resistant hybridomas were manyfold more resistant to RI7/217-RTA than were ricin-sensitive hybridomas. In contrast, all hybridomas were equally sensitive to TF-RTA. Monensin increased ricin cytotoxicity minimally against all hybridomas, but dramatically increased RI7/217-RTA cytotoxicity in ricin-resistant and ricin-sensitive hybridomas in a way that abrogated the ricin-resistant phenotype. In contrast, monensin increased TF-RTA cytotoxicity equally in all hybridomas. Ammonium chloride had little effect on ricin or RI7/217-RTA cytotoxicity, but increased TF-RTA cytotoxicity against all hybridomas. Taken together, these results suggest that RTA molecules mediating cytotoxicity pass through an anti-RTA antibody-containing pre-Golgi compartment when bound to RTB or RI7/217, but not when bound to TF. Monensin abrogates the ricin-resistant phenotype when RTA is linked to RI7/217, but not RTB. This suggests that monensin alters RI7/217-RTA processing proximal to the pre-Golgi and that passage through the pre-Golgi may not be necessary for translocation of RTA to the cytoplasm. Ammonium chloride alters toxin cytotoxicity only when RTA is linked to TF, suggesting that only TF trafficks RTA through an acid-sensitive compartment prior to cytoplasmic translocation. With the addition of potentiating agents, each toxin studied showed a unique cytotoxicity profile against the anti-ricin hybridomas, demonstrating a dominant role of the cell binding ligand in intracellular toxin trafficking.

Ammonium Chloride↗

PubMed1991

Expression of functional epidermal growth factor receptors in a human hematopoietic cell line.

To test the feasibility of using the human epidermal growth factor receptor (EGFR) as a model for growth factor receptor action in human hematopoietic cells, we infected Burkitt lymphoma cells (Namalwa) with a recombinant amphotrophic retrovirus containing a thymidine kinase promoter-driven human EGFR complementary DNA and the neomycin resistance gene. Neomycin-resistant cells expressing surface EGFR were selected by cell sorting using anti-EGFR monoclonal antibody 225. The selected cells expressed a Mr 170,000 protein immunoprecipitated by monoclonal antibody 225 and apparently identical to EGFR from A431 carcinoma cells. Infected Namalwa cells expressed 42,000 epidermal growth factor (EGF) binding sites/cell, and Scatchard analysis showed two affinities (Kd approximately 5 nM and approximately 0.5 nM). EGFR autophosphorylation was detected using antiphosphotyrosine antibodies after 5 min exposure to EGF. EGF binding induced rapid EGFR internalization (t1/2 = 9 min) and mobilization of transferrin receptors to the cell surface within 1 min. In fetal bovine serum-containing and serum-free cultures, EGF did not stimulate Namalwa cell proliferation. However, in the presence of 1.25% dimethyl sulfoxide (DMSO), EGF caused a dose-dependent increase in DNA synthesis. DMSO induced a cell cycle block in G1, which was partially reversed by EGF. DMSO induced changes in some B-cell markers suggesting cellular differentiation and increased surface EGF receptor number. Cells grown in DMSO and EGF were established as an EGF-dependent cell line for greater than 12 weeks, whereas cells grown in DMSO without EGF died within 1-2 weeks. Namalwa cells expressing EGFR demonstrated more rapid tumor growth in athymic mice. These studies demonstrate expression of functional EGFR mediating early biochemical and growth responses in a human hematopoietic cell, and indicate that EGFR can be used as an effective model in human hematopoietic cells. Results using DMSO are consistent with studies in other human leukemia cells indicating that agents inducing differentiation can restore growth factor dependence in previously factor-independent leukemia cells.

Animals↗

PubMed1991

Regulation of CD45 expression in human leukemia cells.

The CD45 antigen cluster identifies a family of transmembrane glycoprotein tyrosine phosphatases (PTPases) present on nearly all hemopoietic cells. Recent studies suggest that CD45 may play a role in the control of receptor mediated blood cell responses, and that expression of the CD45 gene varies during bone marrow cell maturation. However, relatively little is known of the mechanisms controlling CD45 expression and function. Here we show that the induction of granulocyte or monocyte differentiation of HL60 leukemia cells is accompanied by a rapid increase in CD45 antigen expression and CD45 PTPase activity. In contrast, other leukemia cell lines induced for monocyte/macrophage differentiation did not show increased CD45. Immunoprecipitation of radiolabelled CD45 glycoprotein from dimethyl sulphoxide (DMSO) treated HL60 cells indicated that the cells expressed 200 and 180 kD isoforms. Northern blots of steady-state RNA from HL60 cells showed a 4-11-fold increase in CD45 transcripts after DMSO treatment, but no alteration in the half-life of CD45 mRNA. Nuclear transcription assays showed that CD45 expression was controlled at the level of gene transcription. Namalwa Burkitt leukemia cells expressing the heterologous epidermal growth factor (EGF) receptor protein tyrosine kinase were used to assess the specificity of CD45 PTPase activity. Co-clustering of CD45 and the EGF receptor with specific monoclonal antibodies failed to alter the EGF stimulated tyrosine phosphorylation of the EGF receptor. These studies indicate that CD45 increases during myeloid maturation, and the expression of the CD45 gene is controlled at the level of gene transcription. Preliminary studies suggest that CD45 does not alter the protein tyrosine kinase activity of the EGF receptor in intact cells, suggesting substrate specificity in vivo.

Antigens, CD↗

PubMed1991

Analysis of granulocyte-macrophage colony-stimulating factor action in differentiating myeloid leukemia cells: treatment with DMSO may reveal a common pathway for growth factor gene regulation.

Previous studies showed that factor-independent, late-passage HL60 acute nonlymphocytic leukemia (ANLL) cells proliferated in response to granulocyte-macrophage colony-stimulating factor (GM-CSF) after treatment with dimethylsulfoxide (DMSO) or other agents inducing cellular differentiation. In the present studies, we examined mechanisms of this response. After treatment with DMSO, GM-CSF delayed expression of some HL60 differentiation programs (CD11b expression), but not others (nitro blue tetrazolium dye reduction), and delayed the exit of cells from the cell cycle. In the presence of DMSO, GM-CSF but not granulocyte colony-stimulating factor (G-CSF) increased expression of steady-state c-myc RNA. DMSO-treated HL60 cells expressing heterologous epidermal growth factor (EGF) receptors also proliferated in response to EGF and showed increased c-myc expression. Nuclear transcription studies showed that GM-CSF did not alter c-myc transcription in DMSO-treated cells, and studies using actinomycin-D showed no increase in steady-state c-myc RNA half-life. These studies indicate that GM-CSF increases post-deterministic proliferation and alters the phenotype of differentiating HL60 cells, and post-transcriptional alterations in c-myc expression may be responsible for some of these changes. Heterologous EGF receptors mediate similar responses, suggesting that treating HL60 cells with DMSO may reveal a common pathway of growth factor gene regulation.

Blotting, Northern↗

PubMed1990

Preclinical evaluation of illudins as anticancer agents: basis for selective cytotoxicity.

Illudins are potent natural products derived from Omphalotus illudens and related fungi. The chemical structure of illudins differs from that of other conventional chemotherapeutic agents. While illudins are toxic to most tumor cells after prolonged exposure (greater than or equal to 48 hr), with shorter exposure times (less than or equal to 2 hr), they show selective toxicity for human myelocytic leukemia and epidermoid, lung, ovarian, and breast carcinoma cells of various species of origin. The apparent histologic specificity of illudin S toxicity is based on an energy-dependent transport mechanism present in sensitive cells, but absent in cells relatively resistant to illudin S. For human myeloid leukemia HL60 cells, the Michaelis constant was 4.2 microM and the maximum velocity was 12.2 pmol/minute per 10 million cells or 730 pmol/hour per 10 million cells. The energy-dependent transport mechanism was detected in other mammalian tumor cells.

Animals↗

PubMed1990

Characterization of a factor-dependent acute leukemia cell line with translocation (3;3)(q21;q26).

A strictly factor-dependent cell line (UCSD/AML1) was established from a patient with the syndrome of multilineage acute leukemia with high platelets. The patient's cells and the cell line karyotype were 45,XX,-7,t(3;3)(q21;q26), typical of the syndrome of acute leukemia with high platelets. The cell line expresses CD34, CD7, TdT, and myeloid (CD13, CD14, CD33) and megakaryocyte/platelet (CD36, CD41, CD42b, CDw49b) antigens. In short-term culture, UCSD/AML1 cells proliferate in response to interleukin-3 (IL-3), IL-4, IL-6, macrophage colony-stimulating factor (M-CSF), and granulocyte-macrophage CSF (GM-CSF), but not IL-1, IL-2, IL-5, or G-CSF. In long-term culture, proliferation can be sustained by GM-CSF, IL-6, or M-CSF. When maintained in GM-CSF, a small percentage of cells form multinucleated megakaryocyte-like giant cells. Culture with GM-CSF combined with IL-6, but not with IL-6 alone, increased giant cell formation fourfold to sevenfold. IL-6 alone or in combination with GM-CSF increased expression of platelet-related antigens. In contrast, culture with phorbol ester induced formation of macrophage-like cells. UCSD/AML1 is the first human acute nonlymphocytic leukemia cell line established from a patient with an acute leukemia syndrome associated with a specific chromosome abnormality.

Acute Disease↗

PubMed1990

Combinations of anti-transferrin receptor monoclonal antibodies inhibit human tumor cell growth in vitro and in vivo: evidence for synergistic antiproliferative effects.

Thirty-two murine monoclonal antibodies (MAbs) against the external domain of the human transferrin (Tf) receptor have been obtained using human Tf receptor glycoprotein produced in a baculovirus expression system as immunogen. The MAbs were tested separately, and in combination, for their ability to inhibit growth of CCRF-CEM leukemic T-cells in tissue culture. One MAb, D65.30, an IgG1, inhibited growth of CCRF-CEM cells as effectively as the anti-Tf receptor MAb 42/6, an IgA, previously found to have the highest antiproliferative activity in this assay. Some combinations of two or more MAbs inhibited the in vitro growth of CCRF-CEM much more effectively than single MAbs. Eleven IgG1 anti-Tf receptor MAbs, when combined individually with D65.30, increased the inhibition of CCRF-CEM growth from approximately 65% to greater than 90% in a 7-day growth assay. Similarly, many IgG MAbs in combination with 42/6 also inhibited CCRF-CEM growth by greater than 90%. The growth-inhibitory effects of certain combinations of MAbs were clearly synergistic, because either one or both MAbs tested separately were inactive. These pairs of MAbs also inhibited the growth of HL-60 and KG-1 leukemic cells by greater than 90% and partially inhibited the growth of K562 erythroleukemia and M21 melanoma cells, which are resistant to MAb 42/6. However, not all combinations of anti-Tf receptor MAbs were more effective; eight MAbs markedly antagonized the antiproliferative effects of D65.30, whereas 12 others had little or no effect. Preincubation of HL-60 cells with three different pairs of MAbs, D65.30 and A27.15, B3/25 and 42/6, and B3/25 and TR3A, inhibited subsequent colony formation by greater than 95%, demonstrating that their action is cytotoxic, not cytostatic. The antiproliferative activity of these pairs of MAbs correlates with their ability to block Tf-mediated 59Fe uptake and perturb Tf receptor expression. Treatment of nude mice bearing established s.c. CCRF-CEM tumors with a combination of MAbs D65.30 and A27.15 inhibited tumor growth and in some animals led to complete tumor regression. Each MAb administered separately was much less effective. We conclude that combinations of two or more anti-Tf receptor MAbs can interact synergistically to inhibit cell growth in vitro and tumor growth in vivo.

Animals↗

PubMed1990

Factor-dependent human leukemia cell lines: new models for regulation of acute non-lymphocytic leukemia cell growth and differentiation.

Human acute non-lymphocytic leukemia (ANLL) cell lines have been valuable models for studying leukemic transformation and mechanisms regulating blood cell growth and differentiation. Until recently, all human leukemia lines were grown in fetal bovine serum and were not dependent on exogenous hemopoietic growth factors. Since most primary human ANLL cells require growth factors for in vitro cell growth, the behavior of growth factor-independent cells may not be representative of most acute leukemias. Recently, factor-dependent cell lines were established from patients with acute leukemias which are absolutely dependent on growth factors for in vitro proliferation and survival. These cells were derived from different primary leukemia phenotypes, and exhibit heterogeneous growth and differentiation responses. Like the murine growth factor-dependent cell lines which preceded them, these new human lines are important models for growth factor signal transduction as well as proliferative responses and differentiation. Factor-dependent human cell lines have already provided important insights into potential mechanisms of human blood cell transformation, and identification of cellular and genetic abnormalities responsible for the leukemia phenotype.

Animals↗

PubMed1990

The role of transferrin receptors in hemopoietic cell growth.

The Tf receptor is a prototypical cell surface nutrient receptor critical for growth of both normal and malignant blood cells. Because of the apparently universal requirement of growing blood cells for Fe, control of Tf receptor expression and function will continue to be a topic of considerable interest in experimental hematology and tumor cell biology. Studies of Tf receptor gene expression have already revealed unique patterns of gene regulation, and understanding control of Tf receptor gene expression during hemopoietic cell growth and differentiation may provide insights into factors controlling expression of other proliferation-related genes. Although much further study is required, early studies suggest that measuring serum Tf receptor and Tf-Tf receptor complexes may be a major advance in clinical assessment of erythropoiesis. Whether altering Tf receptor protein function or gene expression can be exploited to treat hematologic tumors remains unclear, but further studies are in progress.

Animals↗