Induction of macrophage tumoricidal activity by granulocyte-macrophage colony-stimulating factor

The potential for monocyte-mediated immunotherapy during infection and malignancy. Part I: apoptosis induction and cytotoxic mechanisms

The mononuclear phagocyte system consists of peripheral blood monocytes and tissue macrophages that collectively play a major role in host immunity. Far from existing solely as phagocytic scavengers of cell debris and foreign matter, monocytes are highly active and responsive to inflammatory and immunological signals that activate their microbicidal and tumoricidal functions. Cytokines that are secreted as an integral component of the innate immune response such as granulocyte-macrophage colony-stimulating factor (GM-CSF) and -IFN may directly activate the functions of the monocyte system. A key mediator of the effector functions of monocytes is tumour necrosis factor (TNF) which transduces its signals upon binding to specific transmembrane receptors. TNF is highly cytotoxic to micro-organisms and susceptible malignant cells and in most cases delivers its cytotoxic signal to tumour cells by highly regulated mechanisms of programmed cell death or apoptosis. We believe that the numerous functions of the monocyte system may be harnessed for therapeutic gain both in the context of microbiological infection and malignant disease. In this review, the mechanisms by which secreted and monocyte cell-membrane-associated TNF induce apoptosis will be discussed. In addition, the cell-associated and secretory immunological mechanisms employed by monocytes in host defence will be discussed in the context of the their ability to combat infection and neoplasia.

Cytotoxic T lymphocyte response against non-immunoselected tumor antigens predicts the outcome of gene therapy with IL-12-transduced tumor cell vaccine

The colon adenocarcinoma C26, carrying two endogenous tumor-associated antigens (TAA) recognized by CTL, has been transduced with the gene coding for the human folate receptor alpha (FR alpha) as an additional antigen in order to study the efficacy of vaccination against a tumor expressing multiple antigens. A dicistronic vector was used to transduce the IL-12 genes to create C26/IL-12/FR alpha that has been used as a cellular vaccine to treat mice bearing lung metastases of C26/FR alpha. After vaccination mice were partially splenectomized and splenic lymphocytes frozen and used retrospectively to study in vitro CD8 T cell response related to the treatment outcome. Vaccination cured 50% of mice and the effect was CD8 T cell dependent. Mice either cured (responders) or not cured (nonresponders) by vaccination developed tumor-specific CTL. However, analysis of CTL specificity and pCTL frequencies revealed that responders had a predominant CTL activity against endogenous C26-related tumor antigens, whereas nonresponders had CTL that recognized preferentially the FR alpha antigen. CD8 from responder mice were characterized to release high levels of granulocyte-macrophage (GM)-CSF upon antigen stimulation. Tumors obtained from mice that died despite vaccination lost expression of the FR alpha transgene but maintained expression of endogenous C26 antigens. Immunoselection against FR alpha antigen was not observed in tumors from non-vaccinated controls and from CD8-depleted vaccinated mice. Down-regulation of FR alpha antigen expression was due, at least in part, to methylation of retroviral vector long terminal repeat promoter since FR alpha expression was partially restored, ex vivo, by treatment with 5-aza-2'-deoxy-cytidine (aza). These results indicate that CD8 T cell-mediated immunoselection and production of GM-CSF are determining factors for the efficacy of tumor vaccines.

Construction and characterization of a chimeric fusion protein consisting of an anti-idiotype antibody mimicking a breast cancer-associated antigen and the cytokine GM-CSF

Anti-idiotype antibody, 11D10 mimics biologically and antigenically a distinct and specific epitope of the high molecular weight human milk fat globule (HMFG), a cancer-associated antigen present in over 90% of breast tumor samples. To augment the immunogenicity of 11D10 without the aid of a carrier protein or adjuvant, we made a chimeric 11D10-GM-CSF fusion protein for use as a vaccine. An expression plasmid for 11D10 was made by ligation of the DNA sequences of the 11D10 light-chain variable region upstream of the human kappa constant region. The heavy-chain plasmid carrying GM-CSF was made by ligation of the heavy-chain variable region sequences upstream of the human gamma1 constant region CH1 fused to the DNA fragment encoding the mature GM-CSF peptide 3' to the CH3 exon. NS1 plasmacytoma cells were transfected with the light and heavy-chain vectors by electroporation. Fusion protein secreted in the culture medium was purified and was characterized by gel electrophoresis as well as by determination of the biological activity of the fused GM-CSF. In nonreducing SDS-polyacrylamide gels, a single band approximately 200 Kd reacted with anti-human kappa, anti-human lambda1 and anti-GM-CSF antibodies. In reducing polyacrylamide gels, a approximately 74 kd protein reacted with anti-human lambda1 and anti-GM-CSF antibodies. The fusion protein induced proliferation of GM-CSF dependent NFS-60 cells. These results suggest that the protein is a chimeric anti-idiotype antibody consisting of 11D10 variable domains, human kappa and lambda1 constant domains and that the GM-CSF moiety fused to the constant region lambda1 is biologically active.

Effect of clarithromycin and azithromycin on production of cytokines by human monocytes

We examined the in vitro effect of clarithromycin and azithromycin on cytokine production by LPS and Pansorbin stimulated human monocytes. At concentrations that are physiologically achievable, both antibiotics affected in vitro production of IL-1alpha, IL-1beta, IL-6, IL-10, GM-CSF and TNF-alpha to varying degrees. Of those individuals in whom a significant increase or decrease in cytokine production was noted, clarithromycin treatment resulted in a significant suppression of production of each cytokine in 71% and a significant increase in 29% of the individuals. Similar results were noted with azithromycin. The results with IL-6 and TNF-alpha in the clarithromycin studies were most striking. A significant decrease was noted in 60% of individuals for IL-6 and 86% for TNF-alpha. For azithromycin, the most interesting results were for IL-1alpha (decrease in 100% of individuals) and for TNF-alpha (decrease in 100% of individuals). These results show that both clarithromycin and azithromycin alter cytokine production in human monocytes and thus possess immunomodulatory activity.

Selective Expansion of Alveolar Macrophages In Vivo by Adenovirus-Mediated Transfer of the Murine Granulocyte-Macrophage Colony-Stimulating Factor cDNA

Based on the hypothesis that genetic modification of freshly isolated alveolar macrophages (AM) with the granulocyte-macrophage colony-stimulating factor (GM-CSF) cDNA would induce AM to proliferate, this study focuses on the ability of adenoviral (Ad) vectors to transfer and efficiently express the murine (m) GM-CSF cDNA in murine AM with consequent expansion in the number of AM in vitro and in vivo. To demonstrate that an Ad vector can effectively transfer and express genes in AM, murine AM recovered by bronchoalveolar lavage from the lung of Balb/c mice were infected with an Ad vector coding for green fluorescent protein (GFP) in vitro and expressed GFP in a dose-dependent fashion. Infection of AM with an Ad vector containing an expression cassette coding for mGM-CSF led to GM-CSF expression and to AM proliferation in vitro. When AM infected with AdGFP were returned to the respiratory tract of syngeneic recipient mice, GFP-expressing cells could still be recovered by bronchoalveolar lavage 2 weeks later. In vitro infection of AM with AdmGM-CSF and subsequent transplantation of the genetically modified AM to the lungs of syngeneic recipients led to GM-CSF expression in vivo. Strikingly, the AM recovered by lavage 5 weeks after transplantation demonstrated an increased rate of proliferation, and the total number of alveolar macrophages was 1.9-fold greater than controls. Importantly, the increase in the numbers of AM was selective (ie, other inflammatory cell numbers were unchanged), and there was no modification to the lung architecture. Thus, it is feasible to genetically modify AM with Ad vectors and to use this strategy to modify the behavior of AM in vivo. Based on the importance of AM in the primary defense of the respiratory epithelial surface, this strategy may be useful in enhancing pulmonary defenses in immunodeficiency states.

Selective Expansion of Alveolar Macrophages In Vivo by Adenovirus-Mediated Transfer of the Murine Granulocyte-Macrophage Colony-Stimulating Factor cDNA

Based on the hypothesis that genetic modification of freshly isolated alveolar macrophages (AM) with the granulocyte-macrophage colony-stimulating factor (GM-CSF) cDNA would induce AM to proliferate, this study focuses on the ability of adenoviral (Ad) vectors to transfer and efficiently express the murine (m) GM-CSF cDNA in murine AM with consequent expansion in the number of AM in vitro and in vivo. To demonstrate that an Ad vector can effectively transfer and express genes in AM, murine AM recovered by bronchoalveolar lavage from the lung of Balb/c mice were infected with an Ad vector coding for green fluorescent protein (GFP) in vitro and expressed GFP in a dose-dependent fashion. Infection of AM with an Ad vector containing an expression cassette coding for mGM-CSF led to GM-CSF expression and to AM proliferation in vitro. When AM infected with AdGFP were returned to the respiratory tract of syngeneic recipient mice, GFP-expressing cells could still be recovered by bronchoalveolar lavage 2 weeks later. In vitro infection of AM with AdmGM-CSF and subsequent transplantation of the genetically modified AM to the lungs of syngeneic recipients led to GM-CSF expression in vivo. Strikingly, the AM recovered by lavage 5 weeks after transplantation demonstrated an increased rate of proliferation, and the total number of alveolar macrophages was 1.9-fold greater than controls. Importantly, the increase in the numbers of AM was selective (ie, other inflammatory cell numbers were unchanged), and there was no modification to the lung architecture. Thus, it is feasible to genetically modify AM with Ad vectors and to use this strategy to modify the behavior of AM in vivo. Based on the importance of AM in the primary defense of the respiratory epithelial surface, this strategy may be useful in enhancing pulmonary defenses in immunodeficiency states.

Effect of intraperitoneally administered recombinant murine granulocyte-macrophage colony-stimulating factor (rmGM-CSF) on the cytotoxic potential of murine peritoneal cells

We studied the effect of recombinant murine granulocyte-macrophage colony-stimulating factor (rmGM-CSF) on the cytotoxic potential of murine peritoneal cells. Mice received rmGM-CSF intraperitoneally using different dosages and injection schemes. At different time points after the last injection, mice were sacrificed, peritoneal cells isolated and their tumour cytotoxicity was determined by a cytotoxicity assay using syngeneic [methyl-3H]thymidine-labelled colon carcinoma cells. Also, the cytotoxic response to a subsequent in vitro stimulation with lipopolysaccharide was determined. Upon daily injection of 6000-54,000 U rmGM-CSF over a 6-day period, the number of peritoneal cells increased over ten fold with the highest rmGM-CSF dose. Increases in cell numbers was mainly due to increases in macrophage numbers. Upon injection of three doses of 3000 U rmGM-CSF per day for 3 consecutive days, the number of macrophages remained elevated for minimally 6 days. Although the peritoneal cells from rmGM-CSF-treated mice were not activated to a tumoricidal state, they could be activated to high levels of cytotoxicity with an additional in vitro stimulation of lipopolysaccharide. Resident cells isolated from control mice could be activated only to low levels of tumour cytotoxicity with lipopolysaccharide. Tumour cytotoxicity strongly correlated with nitric oxide secretion. When inhibiting nitric oxide synthase, tumour cell lysis decreased. Thus, the expanded peritoneal cell population induced by multiple injections of rmGM-CSF has a strong tumour cytotoxic potential and might provide a favourable condition for immunotherapeutic treatment of peritoneal neoplasms.

Long-term treatment with GM-CSF in patients with chronic lymphocytic leukemia and recurrent neutropenic infections

In this prospective study we evaluated the multiple effects of long-term GM-CSF therapy on blood counts, granulocyte functions and disease progression in patients with chronic lymphocytic leukemia (CLL) with chronic neutropenia and recurrent bacterial infections. The treatment duration varied from 2 to 12 weeks. The neutrophil count was raised in all patients, by the median of 6.6-fold. The neutrophil level of 1.0 x 10(9)/l was usually reached after two weeks. The initial dose of GM-CSF was 5 microg/kg/day, and 1-7 microg/kg/day was required to maintain the neutrophil level above 1.0 x 10(9)/l. Granulocyte functions, i.e. chemiluminescence (CL), random migration, and fMLP-stimulated chemotaxis were initially depressed in all patients when compared to healthy controls. GM-CSF enhanced significantly CL even when given at small doses (less than 1 microg/kg/day), even lower than the dose required to promote granulopoiesis. We conclude that GM-CSF is effective in improving CLL associated chronic neutropenia and also enhances impaired granulocyte chemiluminescence. Thus, GM-CSF could be helpful for giving chemotherapy without neutropenic delays and for prophylaxis of infectious complications in CLL patients.

Establishment of an activated macrophage cell line, A-THP-1, and its properties

A new macrophage cell line with activated character and unique morphology was isolated by selecting adherent cells from the human monocytic cell line THP-1. The original THP-1 cells had been cultured for more than 9 years using 25 cm2 flasks, when cells with a different morphology appeared, adhering to the bottoms of the culture flasks. These were selected by discarding floating nonadherent cells at every subculture. Enrichment of adherent THP-1 cells with long processes proceeded during the cultivation. These adherent THP-1 showed remarkable phenotypic changes, not only morphologically, but also functionally. Namely, increased phagocytic activity, HLA-DR expression and MLR stimulator activity were remarkable. This adherent cell line was designated as activated-THP-1 (A-THP-1), since it demonstrated characteristics of activated macrophages continuously without exogenous stimulation. A cloned A-THP-1 cell line (A-THP-1 C1) also showed the same features and contained about 10% multinucleated giant cells probably caused by cell fusion. This A-THP-1 cell line, the first activated macrophage cell line to be established, provides a good model for understanding of activation mechanisms of macrophages and multinucleation. In this paper, morphological, immunological, and biological characters of this cell line are described.

Effect of granulocyte-macrophage colony-stimulating factor treatment on phenotype, cytokine release and cytotoxicity of circulating blood monocytes and monocyte-derived macrophages

We studied phenotype, function and differentiation of mononuclear phagocytes in 11 cancer patients treated subcutaneously with 10O microg/kg recombinant human (rhu) GM-CSF for 7 d. The rhuGM-CSF treatment induced (1) a 5.9-fold increase in the number of blood monocytes (MO), (2) a decrease of CD14bright/CD16bright cells with a diminution of the mean fluorescence intensity (MFI) of CD14, and (3) a decrease of MO cellular cytotoxicity. In patients' sera, tumour necrosis factor (TNF)-alpha, interleukin (IL)-10, IL-12, neopterin, macrophage-colony-stimulating factor (M-CSF), and IL-1 receptor antagonist (IL-1RA) increased, whereas GM-CSF and granulocyte-colony-stimulating factor (G-CSF) decreased after an initial peak. In whole blood samples the lipopolysaccharide (LPS)-stimulated release of TNF-alpha, IL-6 and IL-1RA increased initially, whereas IL-1beta, IL-10 and IL-12 decreased. During differentiation from MO to macrophages (MAC), interferon (IFN)-gamma-stimulated tumour cytotoxicity increased, but both MO and MAC were less cytotoxic upon rhuGM-CSF treatment. The differentiation-associated increase of LPS-induced TNF-alpha, IL-1RA and IL-10 secretion was reduced by the rhuGM-CSF treatment, and the expression of CD14 on MAC as well as the proportion of CD14+/CD16+, CD14+/MAX.1+ and CD14+/CD71+ cells in 7-d cultured MAC declined. We interpret these findings as (1) an increase of immature MO upon rhuGM-CSF therapy, (2) a priming effect on the LPS-induced proinflammatory cytokine repertoire of MO, and (3) an impact of rhuGM-CSF on the capacity of MO to differentiate to MAC in vitro.

Effect of trovafloxacin on production of cytokines by human monocytes

Antibiotics have previously been shown to have immunomodulatory effects. We examined the effect of the broad-spectrum fluoroquinoline antibiotic trovafloxacin on cytokine synthesis by monocytes obtained from healthy human volunteers and stimulated with either lipopolysaccharide or gram-positive cells (heat-killed Staphylococcus aureus [Pansorbin]). Trovafloxacin levels achievable in humans suppressed in vitro synthesis of each of the cytokines analyzed, viz., interleukin-1 alpha (IL-1 alpha), IL-1 beta, IL-6, IL-10, granulocyte-macrophage colony-stimulating factor, and tumor necrosis factor alpha. This effect was not due to direct effects of the drug on cellular viability; at these concentrations, trovafloxacin did not have demonstrable cytotoxicity for the monocytes, as determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. Although similar patterns of suppression of cytokine synthesis were observed in samples obtained from the same volunteers on different days, there were significant day-to-day variations. These results reveal that trovafloxacin possesses significant immunomodulatory activity in vitro and suggest that suppression of acute-phase inflammatory responses may occur in vivo, elicited through trovafloxacin's effect on cytokine synthesis by human monocytes.

Effects of granulocyte-macrophage colony-stimulating factor and tumor necrosis factor alpha on Trypanosoma cruzi trypomastigotes

We have previously shown that the addition of exogenous granulocyte-macrophage colony-stimulating factor (GM-CSF) to nonactivated mouse peritoneal macrophages (MPM) limits Trypanosoma cruzi infections in vitro (E. Olivares Fontt and B. Vray, Parasite Immunol. 17:135-141, 1995). Lower levels of infection were correlated with a higher level of production of tumor necrosis factor alpha (TNF-alpha) in the absence of nitric oxide (NO) release. These data suggested that GM-CSF and/or TNF-alpha might have a direct parasitocidal effect on T. cruzi trypomastigotes, independently of NO release. To address this question, T. cruzi trypomastigotes were treated with recombinant murine GM-CSF (rmGM-CSF), recombinant murine TNF-alpha (rmTNF-alpha), or both cytokines in a cell-free system. Treatment with rmGM-CSF but not rmTNF-alpha caused morphological changes in the parasites, and most became spherical after 7 h of incubation. Both cytokines exerted a cytolytic activity on the trypomastigotes, yet the trypanolytic activity of rmTNF-alpha was more effective than that of rmGM-CSF. Viable rmGM-CSF- and rmTNF-alpha-treated parasites were less able to infect MPM than untreated parasites, and this reduction in infectivity was greatest for rmGM-CSF. Treatments with both cytokines resulted in more lysis and almost complete inhibition of infection. The direct parasitocidal activity of rmTNF-alpha was inhibited by carbohydrates and monoclonal antibodies specific for the lectin-like domain of TNF-alpha. Collectively, these results suggest that cytokines such as GM-CSF and TNF-alpha may directly control the level of T. cruzi trypomastigotes at least in vitro and so could determine the outcome of infection in vivo.

A novel lipopolysaccharide inducible C-C chemokine receptor related gene in murine macrophages

To identify genes induced in activated macrophages, we screened a cDNA library prepared from the lipopolysaccharide (LPS)-treated cell line, RAW264, using the suppression subtractive hybridization technique. One of the clones isolated was dramatically induced by LPS in macrophages. The predicted protein sequence of this gene contains the domain unique to seven transmembrane receptors, and shows similarity with mouse C-C chemokine receptor 5 (CCR5). Therefore, we designated it LPS inducible C-C chemokine receptor related gene (L-CCR). Northern blot analysis revealed that L-CCR was specifically expressed in differentiated macrophages after LPS stimulation. These results show that L-CCR is a novel C-C chemokine receptor related gene induced by LPS in macrophages and may play an important role in inflammatory responses.

Natural and therapy-induced anti-GM-CSF and anti-G-CSF antibodies in human serum

Serum samples were obtained from patients with lymphoid and plasma cell malignancies who received after chemotherapy human recombinant GM-CSF or G-CSF. Sera from some patients revealed the presence of anti-cytokine antibodies, particularly after repetitive cytokine injections. Antibody Fab binding in a saturable manner by ELISA and Western immuno-blotting confirmed antibody specificity. Anti-cytokine antibodies were detected before the exogenous cytokine injections in some patients, but increasing antibody levels were found after one or subsequent treatments. Low levels of anti-GM-CSF and anti-G-CSF antibodies were also detected in a relatively large proportion (about 10-30%) of normal sera from different adult healthy volunteers who had never been treated before with exologous cytokines as well as from cord blood. EBV-immortalized cord blood derived B-cell cultures were also found to produce anti GM-CSF and/or anti-G-CSF antibodies with high frequency.

Regression of established mouse leukemia by GM-CSF-transduced tumor vaccine: implications for cytotoxic T lymphocyte responses and tumor burdens

This study investigated the therapeutic effects of granulocyte-macrophage colony-stimulating factor (GM-CSF) on a mouse leukemia model. By using a retroviral vector, mouse GM-CSF cDNA was transduced into a highly tumorigenic T leukemia cell line, RL male 1. Injection of GM-CSF-secreting RL male 1 cells into syngeneic BALB/c mice elicited protective immunity in the animals, which could regress preestablished tumors introduced either by a subcutaneous or in an intravenous route. However, the therapeutic effects were less prominent in the mice inoculated with a large tumor load or in mice treated later. Winn tests further demonstrated that the splenocytes from the late-treated group conferred poorer protective effects in terms of reducing the growth of parental RL male 1 cells in naive mice than the splenocytes from the early-treated group. Nonetheless, upon stimulation in vitro, the activity of tumor-specific cytotoxic T lymphocytes (CTL) was comparable in the splenocytes of both groups of mice. Histological analysis also indicated that the CD8+ T cells appeared as early as 3 days following vaccination at the vaccine sites and at the tumor sites in both groups of mice. Above observations implied that the T cells in the animals bearing large tumors appeared to be in a state of suppression or anergy. Systematic histological analyses for 2 weeks provided further insight into various infiltrates at the vaccine sites and at the tumor sites in response to the inoculation of GM-CSF-secreting tumor vaccine.

Effect of recombinant human granulocyte-macrophage colony-stimulating factor on HIV-related leukopenia: a randomized, controlled clinical study

OBJECTIVE

To assess the effect of granulocyte-macrophage colony-stimulating factor (GM-CSF) on white blood cell (WBC) count and on the rate of opportunistic infections in a large and selected population of leukopenic HIV-positive patients compared with non-treated controls.

DESIGN

Open-label, randomized, comparative clinical study.

SETTING

University hospitals and AIDS centres.

PATIENTS AND METHODS

One hundred and twenty-three leukopenic HIV-positive patients received recombinant human GM-CSF (300 microg subcutaneously daily for 1 week, and 150 microg subcutaneously two times weekly for 11 weeks thereafter); the control group comprised 121 non-treated leukopenic HIV-positive patients. A complete blood cell count with differential, platelet count, reticulocyte count, and CD4+ and CD8+ T-cell subset counts were performed in both patient groups at baseline and at weeks 1, 12 and 24.

RESULTS

The administration of GM-CSF resulted in a significant increase of WBC count in patients compared with non-treated controls. Total leukocyte count increased by 22% at week 1 and by 65% at week 12 compared with baseline levels; a 20% increase of total leukocyte count was still present at week 24. Increases of neutrophils, eosinophils and monocytes were responsible for the majority of the increase in WBC count. Opportunistic infections occurred in 61.7% of GM-CSF-treated patients and in 72% of the patients of the control group (relative risk, 0.86; 95% confidence interval, 0.72-1.03; P = 0.123). Mild flu-like side-effects were observed in most patients receiving GM-CSF, although they were not sufficiently severe to warrant withdrawal from the study.

CONCLUSIONS

GM-CSF was well tolerated and biologically active in leukopenic HIV-positive patients, with a significant, although time-limited, increase of WBC count compared with non-treated patients. The administration of this growth factor should be considered in ameliorating the myelosuppression observed with some cell-cycle-specific antiviral and anti-neoplastic agents.

A phase I/IB trial of murine monoclonal anti-GD2 antibody 14.G2a plus interleukin-2 in children with refractory neuroblastoma: a report of the Children's Cancer Group

BACKGROUND

The murine monoclonal antibody (MoAb) 14.G2a recognizes GD2, a disialoganglioside expressed in tumors of neuroectodermal origin, and facilitates antibody dependent cellular cytotoxicity (ADCC) in vitro. When given in vivo, interleukin-2 (IL-2) can increase ADCC by enhancing the activity and number of circulating lymphocytes.

METHODS

Thirty-three pediatric patients with GD2 positive malignancies, ranging in age from 2 to 17 years (median, 9.9 years), received IL-2 and 14.G2a in this Phase I/IB study of the Children's Cancer Group (CCG) and were monitored for toxicities and response to therapy. Seven of these patients also received granulocyte-macrophage-colony stimulating factor.

RESULTS

The maximum tolerated dose (MTD) of 14.G2a with IL-2 was 15 mg/m2/day. The most prevalent Grade 3-4 toxicities were generalized pain (n = 14 [42%]) and fever without documented infection (n = 17 [52%]). IL-2 was thought to be the causative agent in most cases of fever. Toxicities attributed to 14.G2a included pain, allergic or anaphylactic reactions, and rash. Human antimouse antibodies were demonstrated in 9 of 21 evaluated patients. One patient with neuroblastoma had a partial response, and one patient with osteosarcoma had a complete response. Immunocytology demonstrated that the number of neuroblastoma cells in bone marrow decreased in three patients.

CONCLUSIONS

The murine MoAb 14.G2a was well tolerated at the MTD and appeared to have some antitumor activity. Further development of this approach will involve additional engineered forms of the antibody as well as testing in the adjuvant and minimal residual disease setting.

Granulocyte-macrophage colony-stimulating factor improves immunological parameters in patients with refractory solid tumours receiving second-line chemotherapy: correlation with clinical responses

In this report, we studied the immunorestorative properties of subcutaneously administered granulocyte-macrophage colony-stimulating factor (GM-CSF) in patients with refractory solid tumours receiving second-line chemotherapy. Such patients exhibit abnormal immune responses in vivo and in vitro and, therefore, it was of interest to examine the effect of GM-CSF-induced immunomodulation on clinical response. We examined patients with primary malignant carcinomas (head and neck, n = 10; urogenital tract, n = 17; penis n = 6; colorectal, n = 8) who were treated with carboplatin (JM8), 300 ng/m2 on days 1 and 22, leucovorin (LV), 200 mg/m2 plus 5-fluoracil (5-FU), 500 mg/m2 on days 8, 15 and 29 and four cycles of daily injections with placebo or GM-CSF, 300 micrograms/day on days 3-6, 10-13, 17-20 and 24-27. Peripheral blood was collected from the patients one day after the end of each of the four-cycle injections with placebo or GM-CSF, namely on days 7, 14, 21 and 28. Peripheral blood mononuclear cells (PBMC) were tested in the autologous mixed lymphocyte reaction (AMLR) and for natural killer (NK) or lymphokine-activated killer (LAK) cell activity. Cytokine levels in serum were measured by immunoenzymatic (ELISA) assay. A total of 21 patients received a four-cycle regimen with GM-CSF (Group 1) and 20 were similarly treated with placebo (Group 2). All received standard chemotherapy as outlined above. Before GM-CSF treatment, all patients exhibited increased serum levels of interleukin-1 (IL-1 beta), tumour necrosis factor-alpha (TNF-alpha), IL-6 and prostaglandin E2 (PGE2) and decreased serum levels of IL-2. Cellular immune responses (AMLR, NK- and LAK-cytotoxicity) were also low in all patients. Five patients from Group 1 had a PR (partial response), 2 patients had CR (complete response), and 14 patients had stable disease. Seven patients from Group 2 showed progressive disease, 3 had a PR and 10 had stable disease. All immune parameters were significantly improved during treatment in Group 1 but remained unchanged or even deteriorated in Group 2. Administration of GM-CSF during treatment of cancer patients with conventional chemotherapeutic drugs results in a marked potentiation of deficient cellular immune responses in vitro and a change towards normalisation of cytokine serum levels. The results reported herein support the use of GM-CSF as immunopotentiator during chemotherapy, but more patients must be studied before definite conclusions can be drawn.

Potentiation of antitumor CTL response by GM-CSF involves a B7-dependent mechanism

We have previously demonstrated the importance of endogenous GM-CSF production for the B7-2-dependent potentiating effect of exogenous TNF for CTL generation by stimulation cultures of splenic cells from mice bearing a large MOPC-315 tumor. Here we show that addition of GM-CSF to stimulation cultures of such tumor-bearer splenic cells also leads to the generation of enhanced anti-MOPC-315 CTL activity via a B7-dependent mechanism. However, while the potentiating effect of TNF was previously shown to be IL-2-independent, the potentiating effect of GM-CSF is shown here to be completely IL-2-dependent. Still, the potentiating activity of exogenous GM-CSF for the in vitro generation of CTL activity is shown to depend completely on endogenous TNF production. Finally, TNF and GM-CSF may cooperate in enhancing the in vivo generation of CTL activity in MOPC-315 tumor bearers because low-dose melphalan (L-phenylalanine mustard) therapy, which was previously shown to lead to the rapid up-regulation of TNF production at the tumor site and the subsequent TNF-dependent in vivo acquisition of potent CTL activity, is shown here to lead to the rapid up-regulation of GM-CSF production at the tumor site.

Prothymosin alpha 1 effects, in vitro, on the antitumor activity and cytokine production of blood monocytes from colorectal tumor patients

Recent animal studies demonstrate that prothymosin alpha 1 (ProT alpha) enhances the antitumor response by stimulation of mononuclear phagocyte functions. The present study was aimed at characterizing the in vitro effects by ProT alpha on blood monocytes from human colon cancer patients. Purified peripheral blood monocytes were studied in terms of tumor cytostatic ability and cytokine production after incubation with ProT alpha or interferon (rIFN-gamma) and transforming growth factor-beta (TGF beta), used as reference substances. SW620 colon carcinoma cells were used as tumor target cells in growth inhibition experiments. The level of baseline growth inhibitory activity of unstimulated patient's monocytes was significantly lower than that of normal monocytes. The defective antitumor activity of patient monocytes was associated with a higher production of the inhibitory monokines prostaglandin E2 (PGE2) and TGF beta. The stimulation of monocytes by ProT alpha and/or rIFN-gamma elevated the average antitumor activity in all donor groups. The ProT alpha-induced increase was associated with a significantly higher monocytic secretion of IL-1 beta and TNF-alpha. Moreover, the concentrations of TGF beta and PGE2 in the culture supernatants decreased significantly, when patient's monocytes were treated with ProT alpha and/or rIFN-gamma. Additionally, ProT alpha enhanced the diminished antitumor activity of TGF beta-treated normal monocytes. These results suggest that ProT alpha selectively regulates distinct functions of blood monocytes, the effect of this cytokine varying with the parameter and donor population examined. These data provide a rational and biological endpoint for further studies with ProT alpha as an activator of mononuclear function in colon cancer.

Monocyte/macrophages as effector cells in cancer immunotherapy

Among the different strategies which have been developed for immunotherapy of cancer, adoptive immunotherapy uses leucocytes activated in vitro and reinfused into the patients. Five leucocytes subsets can be employed for this immunotherapy with activated autologous cells. Blood monocytes can be isolated in high purity and large numbers and under special culture conditions differentiated into macrophages for adoptive transfer. Once activated ex vivo, these cells display very high antibody dependent and independent specific cytotoxicity for tumour cells, are capable of phagocytosis of cancer cells and, as antigen presenting, cells are able to involve CTL in the anticancer response. As the understanding of this activation to cytotoxicity is only recent, the present paper first provides a literature review of the main points in the field. Our own results are then discussed in relation to the development of a clinical protocol for adoptive transfer of MAK (macrophage activated killer) cells, a therapeutic strategy having a pivotal role in the immunosurveillance of cancer.

Phase I/IB study of immunization with autologous tumor cells transfected with the GM-CSF gene by particle-mediated transfer in patients with melanoma or sarcoma

The objective of this Phase I study is to assess the acute and long-term toxicities of intradermal vaccination of cancer patients with lethally-irradiated tumor cells that have been transfected by particle-mediated gene transfer (PMGT) with gold particles coated with human granulocyte-macrophage colony stimulating factor (GM-CSF) DNA in a plasmid expression vector. The GM-CSF DNA-coated gold particles are delivered to tumor cells using helium pressure with a hand held gene delivery device. Preclinical studies have demonstrated that vaccination of mice with irradiated, GM-CSF-transfected melanoma cells provided protection from subsequent challenges with non-irradiated, non-transfected tumor cells. Ongoing human tumor immunotherapy studies use patients' melanoma or renal carcinoma cells transfected with a retroviral vector containing GM-CSF cDNA as a vaccine to elicit anti-tumor immune responses. PMGT transfection, unlike retroviral transfection, does not require tumor cells to proliferate in vitro to undergo gene transfer. Instead, tumor tissue can be dissociated into small tissue clumps or cell aggregates and then immediately transfected using the gene gun. PMGT physically inserts the DNA without the need for cell surface interaction with viral components or exposure of the patient to viral antigens. As described in this protocol, fresh human sarcoma and melanoma specimens can be transfected with the GM-CSF DNA-coated gold particles with subsequent production of biologically active GM-CSF protein. In this study tumor tissue will be obtained from patients with melanoma or sarcoma. Tumor tissue will be dissociated, irradiated, and transfected with GM-CSF DNA by PMGT. In this ascending dosage study, two dose levels of GM-CSF DNA will be studied in 2 groups of 6 patients each. Patients will receive two intradermal injections of the irradiated, transfected tumor in a single extremity. On days 3 and 14 post-vaccination, patients will undergo surgical excision of the vaccination sites to assess GM-CSF production and infiltration of immune effector cells. On Day 25, patients will undergo DTH testing with intradermal injection in their opposite extremity of 5 x 10(6) irradiated non-transfected autologous tumor cells cryopreserved at the time of vaccine preparation. This injection site will be assessed on day 28 post-vaccination and surgical excision of the DTH testing site will be performed on day 28 if a positive reaction is noted. The patients will be observed for local and systemic toxicity on days 2, 3, 5, 8, 14, 25, and 28 after the vaccination. Restaging of the patients' disease and long term toxicity evaluation will be performed at 3, 6, and 12 months and then yearly.

Randomized trial of filgrastim vs. sequential filgrastim and molgramostim after dose-intensified carboplatin, cyclophosphamide, and etoposide: a phase I pilot study

This phase I randomized study was designed in order to verify if the sequential administration of filgrastim, a granulocyte colony-stimulating factor (G-CSF), and molgramostim, a granulocyte-macrophage colony-stimulating factor (GM-CSF), was superior to filgrastim alone in improving tolerance of dose-intensified carboplatin (CBDCA), cyclophosphamide (CTX), and etoposide (VP-16). A group of 10 heavily pretreated patients with stage IV disease and no therapeutic option were enrolled into the study. They received two courses of the same chemotherapy with CTX and VP-16 at doses of 1,500 mg/m2 and 400 mg/m2, respectively. CBDCA doses were escalated from 450 to 600 mg/m2. After chemotherapy each patient was allocated randomly to receive either 14 days of G-CSF (arm A) or 7 days of G-CSF followed by 7 days of GM-CSF (arm B). Crossover in the second chemotherapy course was accomplished. Both G-CSF and GM-CSF were given 5 microg/kg/day, subcutaneously. Twenty chemotherapy courses are evaluable, 10 in each arm. Absolute neutrophil count < 1 x 10(3)/microl was observed for 54 days in arm A vs. 68 days in arm B (P < 0.02); platelet (PLT) count < 20 x 10(3)/microl, 57 days vs. 30 days (P < 0.01); days of hospitalization 35 vs. 16 (P < 0.38); PLT transfusion, 107 vs. 58 (P < 0.01); packed red blood cell unit transfusions, 15 vs. 5 (P < 0.13). Seven patients had responses. These data indicate that dose-intensified chemotherapy may be delivered without bone marrow or peripheral stem cell support, with acceptable toxicity, and that, while G-CSF alone shortens days of neutropenia, the combination of the two cytokines shortens the time of thrombocytopenia and decreases the number of PLT transfusions.

Construction of a recombinant human GM-CSF/MCAF fusion protein and study on itsin vitro andin vivo antitumor effects

A novel cytokine fusion protein was constructed by fusing granulocyte macrophage colony stimulating factor (GM-CSF) with monocyte chemotactic activating factor (MCAF), which acts as a factor directing effector cells (monocytes) to a target site. The recombinant human GM-CSF/MCAF fusion protein could sustain the growth of GMCSF-dependent cell line TF1 and was chemotactic for monocytes. Thein vitro antitumor effect showed that rhGM-CSF/MCAF could activate monocytes to inhibit the growth of several human tumor cell lines, including a promyelocyte leukemia cell line HL-60, a lung adenocarcinoma cell line A549, a hepatoma cell line SMMC-7721 and a melanoma cell line Bowes. Furthermore, the cytotoxicity of monocytes activated by rhGM-CSF/MCAF against HL-60 and A549 was greater than that activated by GM-CSF or MCAF alone, even greater than that activated by a combination of GM-CSF and MCAF, suggesting that the fusion protein has synergistic or enhanced effects. Thein vivo antitumor effect indicated that rhGM-CSF/MCAF had marked antitumor effect against A549 tumor in nude mice and even completely suppressed tumor formation. rhGM-CSF/MCAF was significantly more effective in inhibiting tumor growth than rhGM-CSF. Histological analysis showed that tumor site injected with rhGM-CSF/MCAF was infiltrated by a large number of monocytes while a sparse infiltration of monocytes was observed at the tumor site injected with rhGM-CSF or normal saline, suggesting that the antitumor effect of rhGM-CSF/MCAF was mediated by the recruitment of a large number of monocytes to the tumor site.

Phase I trial of etoposide, carboplatin, and GM-CSF in extensive small-cell lung cancer: a Cancer and Leukemia Group B study (CALGB 8832)

The maximum tolerated dose (MTD) of etoposide and carboplatin without growth factor support was previously defined by Cancer and Leukemia Group B (CALGB) as 200 and 125 mg/m2/day x 3, respectively, given every 28 days to previously untreated patients who have extensive, small-cell lung cancer (SCLC). Myelosuppression was dose-limiting. The purpose of this phase I trial was to determine if granulocyte macrophage colony-stimulating factor (GM-CSF) support allows the dosage of the combination of etoposide and carboplatin to be increased above the previously determined MTD. In this CALGB study of 44 evaluable patients with performance status 0-2, cohorts were treated with etoposide and carboplatin given intravenously on days 1-3 followed by GM-CSF (molgramostim) given subcutaneously on days 4-18. Four dose levels of bacteria-derived recombinant GM-CSF (5, 10, 20 microg/kg/day and 5 microg/kg every 12 h), three dose levels of etoposide (200, 250, and 300 mg/m2/day x 3), and two dose levels of carboplatin (125 and 150 mg/m2/day x 3) were evaluated. There was no chemotherapy dose escalation in individual patients. With 5 microg/kg/d GM-CSF, the first etoposide and carboplatin cycle of 300 and 150 mg/m2/day x 3, respectively, could be administered with acceptable toxicity. However, GM-CSF did not allow repeated administration of this dose-escalated regimen every 21 days, since delayed platelet and/or neutrophil recovery was dose limiting in later cycles. These results demonstrate that GM-CSF alone has limited capability to support the repeated administration of high doses of etoposide and carboplatin. CALGB currently is testing the ability of interleukin (IL)-6 given with GM-CSF to ameliorate the cumulative myelosuppression of this intense regimen.

Enhancement of Macrophage Colony-Stimulating Factor–Induced Growth and Differentiation of Human Monocytes by Interleukin-10

Interleukin-10 (IL-10) has been reported to be a negative cytokine for monocytes/macrophages. In the present study, we showed that IL-10 is rather a positive cytokine and augments the growth and differentiation of human monocytes stimulated with macrophage colony-stimulating factor (M-CSF ). Highly purified adherent human monocytes were cultured for 7 days with M-CSF in the presence or absence of IL-10. The number of recovered cells increased in the culture of monocytes with M-CSF + IL-10 compared to the culture with M-CSF alone. IL-10 alone was not enough to maintain the survival and differentiation of monocytes into macrophages. Morphological change cultured in M-CSF was also accelerated by addition of IL-10, and macrophages cultured in M-CSF + IL-10 were more elongated compared to macrophages cultured with M-CSF alone. Binding of 125I-M-CSF to monocytes incubated with M-CSF + IL-10 was about 1.7-fold higher than that to monocytes incubated with M-CSF alone. In accordance with the binding study, Northern blot analysis showed that the levels of the expression of c-fms, M-CSF receptor, mRNA in macrophages cultured in M-CSF + IL-10 were higher than that in macrophages cultured in M-CSF alone. Macrophages cultured in M-CSF + IL-10 expressed higher level of FcγRI, II, III, and showed augmented Fcγ receptor mediated phagocytosis. The former also produced higher level of H2O2 and O−2 , when stimulated with zymosan, and of IL-6 when stimulated with lipopolysaccharide compared to the latter. These results taken together suggest that IL-10 augments the growth and differentiation of human monocytes cultured in M-CSF.

Enhancement of Macrophage Colony-Stimulating Factor–Induced Growth and Differentiation of Human Monocytes by Interleukin-10

Interleukin-10 (IL-10) has been reported to be a negative cytokine for monocytes/macrophages. In the present study, we showed that IL-10 is rather a positive cytokine and augments the growth and differentiation of human monocytes stimulated with macrophage colony-stimulating factor (M-CSF ). Highly purified adherent human monocytes were cultured for 7 days with M-CSF in the presence or absence of IL-10. The number of recovered cells increased in the culture of monocytes with M-CSF + IL-10 compared to the culture with M-CSF alone. IL-10 alone was not enough to maintain the survival and differentiation of monocytes into macrophages. Morphological change cultured in M-CSF was also accelerated by addition of IL-10, and macrophages cultured in M-CSF + IL-10 were more elongated compared to macrophages cultured with M-CSF alone. Binding of 125I-M-CSF to monocytes incubated with M-CSF + IL-10 was about 1.7-fold higher than that to monocytes incubated with M-CSF alone. In accordance with the binding study, Northern blot analysis showed that the levels of the expression of c-fms, M-CSF receptor, mRNA in macrophages cultured in M-CSF + IL-10 were higher than that in macrophages cultured in M-CSF alone. Macrophages cultured in M-CSF + IL-10 expressed higher level of FcγRI, II, III, and showed augmented Fcγ receptor mediated phagocytosis. The former also produced higher level of H2O2 and O−2 , when stimulated with zymosan, and of IL-6 when stimulated with lipopolysaccharide compared to the latter. These results taken together suggest that IL-10 augments the growth and differentiation of human monocytes cultured in M-CSF.

RU 41740 (Biostim) stimulates the production of granulocyte macrophage colony-stimulating factor and interleukin-8 by human bronchial epithelial cells in vitro

1. In this study, we observed the effects of RU 41740 (Biostim) on the production of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-8 (IL-8) in human bronchial epithelial cells in vitro. 2. Cytokine production was assessed by enzyme-linked immunosorbent assay. 3. We report that epithelial cells spontaneously released both cytokines and that RU 41740 induced a significant increase in production of IL-8 and GM-CSF. 4. This is the first observation of a stimulatory effect of an immunostimulating compound used in humans on cytokine production by epithelial cells.

The interval between a septic stimulus and hypoxia/reoxygenation affects cytokine elaboration by murine peritoneal macrophages

The critically ill patient is commonly exposed to various physiological insults. The authors have previously shown that in vivo hypoxia/reoxygenation (H/R) alters the pattern of cytokines elaborated by murine peritoneal macrophages given a septic stimulus. In this study they sought to determine whether the interval between a septic stimulus and H/R affected the release of inflammatory mediators by macrophages. Adult CBA-strain mice were injected intraperitoneally with 10 micrograms of lipopolysaccharide (LPS). On day 0, 1, 2, 3, 4, or 5 after LPS injection, animals were exposed to 16 hours of hypoxia followed by 2 hours of reoxygenation. Harvested peritoneal macrophages were restimulated in vitro with 2.5 micrograms/mL LPS or left unstimulated. Culture supernatants collected at 2, 4, 6, 8, 10, and 12 hours after LPS injection were assayed for tumor necrosis factor (TNF), prostaglandin E2 (PGE2), and nitric oxide (NO) production. Macrophage-derived mediator production peaked when H/R occurred 3 days following LPS injection (P < .05). These data suggest that the interval between sepsis and subsequent H/R influences the pattern of cytokines elaborated by peritoneal macrophages given a septic stimulus.

Vaccination with syngeneic, lymphoma-derived immunoglobulin idiotype combined with granulocyte/macrophage colony-stimulating factor primes mice for a protective T-cell response

The idiotype of the Ig expressed by a B-cell malignancy (Id) can serve as a unique tumor-specific antigen and as a model for cancer vaccine development. In murine models of Id vaccination, formulation of syngeneic Id with carrier proteins or adjuvants induces an anti-idiotypic antibody response. However, inducing a potent cell-mediated response to this weak antigen instead would be highly desirable. In the 38C13 lymphoma model, we observed that low doses of free granulocyte/macrophage colony-stimulating factor (GM-CSF) 10,000 units i.p. or locally s.c. daily for 4 days significantly enhanced protective antitumor immunity induced by s.c. Id-keyhole limpet hemocyanin (KLH) immunization. This effect was critically dependent upon effector CD4+ and CD8+ T cells and was not associated with any increased anti-idiotypic antibody production. Lymphocytes from spleens and draining lymph nodes of mice primed with Id-KLH plus GM-CSF, but not with Id-KLH alone, demonstrated significant proliferation to Id in vitro without any biased production of interferon gamma or interleukin 4 protein or mRNA. As a further demonstration of potency, 50% of mice immunized with Id-KLH plus GM-CSF on the same day as challenge with a large s.c. tumor inoculum remained tumor-free at day 80, compared with 17% for Id-KLH alone, when immunization was combined with cyclophosphamide. Taken together, these results demonstrate that GM-CSF can significantly enhance the immunogenicity of a defined self-antigen and that this effect is mediated exclusively by activating the T-cell arm of the immune response.

Mapping of monoclonal antibody- and receptor-binding domains on human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) using a surface plasmon resonance-based biosensor

An automated surface plasmon resonance (SPR)-based biosensor system has been used for mapping antibody and receptor-binding regions on the recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) molecule. A rabbit antimouse IgG1-Fc antibody (RAM.Fc) was coupled to an extended carboxymethylated-hydrogel matrix attached to a gold surface in order to capture an anti-rhGM-CSF monoclonal antibody (MAb) injected over the sensing layer. rhGM-CSF was subsequently injected and allowed to bind to this antibody. Multisite binding assays were then performed, by flowing sequentially other antibodies and peptides over the surface, and the capacity of the latter to interact with the entrapped rhGM-CSF in a multimolecular complex was monitored in real time with SPR. Eleven MAb (all IgG1K), were analyzed: respectively, four antipeptide MAb raised against three distinct epitopes of the cytokine (two clones against residues 14-24, that includes part of the first alpha-helix toward the N-terminal region; one clone against peptide 30-41, an intrahelical loop; and one clone against residues 79-91, including part of the third alpha-helix) and seven antiprotein MAbs raised against the entire rhGM-CSF, whose target native epitopes are still undetermined. In addition, the binding capacity to rhGM-CSF of a synthetic peptide, corresponding to residues 238-254 of the extracellular human GM-CSF receptor alpha-chain, endowed with rhGM-CSF binding activity, was tested. The results from experiments performed with the biosensor were compared with those obtained by a sandwich enzyme-linked immunosorbent assay (ELISA), using the same reagents. The features of the biosensor technology (fully automated, measure in real time, sharpened yes/no response, less background disturbances, no need for washing step or labeling of the reagent) offered several advantages in these studies of MAb immunoreactivity and epitope mapping, giving a much better resolution and enabling more distinct epitopes to be identified over ELISA.

Granulocyte-macrophage colony-stimulating factor and the immune system

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a multifunctional cytokine currently used for the reversal of neutropenia associated with cytotoxic chemotherapy, bone marrow and haemopoietic stem cell transplantation. GM-CSF also modulates the function of differentiated white blood cells. In the context of local inflammatory responses, GM-CSF stimulates macrophages for antimicrobial and antitumor effects. GM-CSF further enhances healing and repair by its actions on fibroblasts and epidermal cells. GM-CSF is the pivotal mediator of the maturation and function of dendritic cells, the most important cell type for the induction of primary T cell immune responses. GM-CSF may enhance antibody dependent cellular cytotoxicity (ADCC) in several cell types, and the generation and cytotoxicity of natural killer (NK) cells. On this basis, GM-CSF may be useful for inducing or augmenting antibody responses to antimicrobial vaccines, to enhance killing of intracellular microorganisms, to accelerate epidermal and mucosal wound healing, and to stimulate protective immunity against tumors.

Anti-tumoral effect of GM-CSF with or without cytokines and monoclonal antibodies in solid tumors

Cytotoxicity is an important function of the immune system that results in destruction of cellular targets by humoral and cellular mechanisms. The functional capacity of granulocytes, lymphocytes and macrophages are of significance for cancer patients because of the ability of these cells to exhibit anti-tumor activity. The hallmark of immune cytotoxicity is the recognition and destruction of selected targets by humoral and cellular effects that distinguish between targets and normal cells. Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a cytokine with potential to be an anti-neoplastic cytokine. GM-CSF induces: (1) differentiation of monocytes to large macrophage like cells; (2) augmentation of MHC class II antigen expression on monocytes; (3) enhancement in vitro of macrophage and granulocyte natural cytotoxicity and ADCC; and (4) increased expression of adhesion molecules and granulocytes and monocytes. GM-CSF also cooperates with other cytokines in the expansion of specific T cells. Several experimental and clinical studies have demonstrated the anti-neoplastic effects of GM-CSF alone or in combination with cytokines or/and monoclonal antibody. Interestingly, the future might see the combination of GM-CSF and mouse monoclonal antibody MAb17-1A in the adjuvant setting in colon- and/or rectal carcinoma patients.

Granulocyte-macrophage colony-stimulating factor dependent monocyte-mediated cytotoxicity post-autologous bone marrow transplantation

We investigated the in vitro antitumor activity of monocytes derived from autologous bone marrow transplanted (ABMT) patients treated in vivo with granulocyte-macrophage colony-stimulating factor (GM-CSF). Thirty-four patients (17 female, 17 male), median age 42 (range 3-57) years, were enrolled in the study. Fourteen patients were diagnosed with non-Hodgkin's lymphoma (NHL), eight with Hodgkin's disease (HD), nine with breast cancer and three with neuroblastoma. Six patients who did not receive GM-CSF post-ABMT served as controls. We assessed cytotoxicity, antibody-dependent cellular cytotoxicity (ADCC), expression of the activation antigen CD16, and cytokine production by an enriched population of monocytes (> 90% CD+14) pre-, during and post-GM-CSF administration. Within the group of patients receiving treatment, ADCC was significantly higher during in vivo GM-CSF administration than post-therapy (P < 0.05) and in 50% of these patients, ADCC increased during in vivo GM-CSF administration over pretreatment values. In addition, in vivo GM-CSF administration caused the monocytes to secrete elevated levels of tumor necrosis factor-alpha (TNF-alpha) and GM-CSF (P < 0.05). We conclude that GM-CSF augments monocyte-mediated cytotoxicity post-ABMT, and therefore may have a role in controlling minimal residual disease post-transplant.

Granulocyte-macrophage colony-stimulating factor: involvement in control of Trypanosoma cruzi infection in mice

Several cytokines play crucial roles in Trypanosoma cruzi infection in mice, but the involvement of endogenous granulocyte-macrophage colony-stimulating factor (GM-CSF) is poorly documented. This report shows that T. cruzi infection of mice triggered an early and sharp increase in plasma GM-CSF during the ascending phase of parasitemia. The plasma GM-CSF concentration remained stable at the peak of parasitemia and subsequently increased in those mice that survived to the acute phase. GM-CSF level increased again sharply, while parasitemia was rapidly decreasing. Finally, GM-CSF was undetectable, soon after the disappearance of circulating parasites. Injection of T. cruzi-infected mice with neutralizing anti-GM-CSF monoclonal antibodies induced the early appearance of parasitemia and aggravated cumulative mortality. In contrast, recombinant mouse GM-CSF (rmGM-CSF) caused sharp decreases in both parasitemia and cumulative mortality in T. cruzi-infected mice. Peritoneal macrophages from rmGM-CSF-treated and infected or uninfected mice were less infected ex vivo than those from control mice. Taken together these data demonstrate the protective action of endogenous GM-CSF in T. cruzi infection. Neutralization of endogenous GM-CSF aggravates infection, while exogenous rmGM-CSF decreases both parasitemia and host mortality.

Identification of a lipopolysaccharide inducible transcription factor in murine macrophages

To study macrophage genes activated by lipopolysaccharide (LPS) we have constructed a cDNA library using the mouse macrophage cell line, RAW 264.7. By differential screening, a gene, designated LRG-21, was identified that showed nucleic acid sequence homology to rat liver regenerating factor-1 (LRF-1) and human activating transcription factor-3 (ATF3). Both LRG-21 and LRF-1 are transcribed within an hour following stimulation and in the absence of protein synthesis. The predicted protein sequence of LRG-21 consists of 181 amino acids with a molecular weight of 20.7 kDa. All three sequences contain basic and leucine zipper regions characteristic of the c-Fos and c-Jun family of transcription factors, but the remainder of the sequences are unrelated to this family. Recombinant LRG-21 has been shown to bind to a phorbol ester promoter element. Additional experiments have shown that LRG-21 is also induced by interferon-gamma (IFN-gamma) and by interleukin-4 (IL-4) in both RAW264.7 cells and murine peritoneal macrophages. Based on these observations, it is likely that LRG-21 plays an important role in macrophage activation.

The role of tumour necrosis factor-alpha in combination with interferon-gamma or interleukin-1 in the induction of immunosuppressive macrophages because of Mycobacterium avium complex infection

The role of some cytokines including tumour necrosis factor-alpha (TNF-alpha), interleukin-1 alpha (IL-1 alpha), interferon-gamma (IFN-gamma), transforming growth factor-beta (TGF-beta) and interleukin-6 (IL-6) in the generation of immunosuppressive macrophages (M phi s) in host spleen cells of Mycobacterium avium complex (MAC)-infected mice was studied. M phi populations with potent suppressor activity against concanavalin A (Con A)-induced mitogenesis of splenocytes (SPCs) were elicited not only in euthymic but also in athymic nude mice during MAC infection. The suppressor M phi s are, therefore, inducible not only through a T-cell-dependent mechanism but also through T-cell-independent mechanism. However, MAC-induced M phi s of athymic mice displayed about four times lower suppressor activity than those of euthymic mice, indicating that mature T cells are important for M phi activation to the highly immunosuppressive state. Anti-TNF, anti-IFN-gamma, and anti-TGF-beta antibodies (Abs) but not anti-IL-6 Ab inhibited in vivo generation of MAC-induced immunosuppressive M phi s, and the neutralizing efficacy was in the order of anti-IFN-gamma Ab > anti-TNF Ab > anti-TGF-beta Ab. The effects of TNF-alpha, IL-1 alpha, IL-6, and IFN-gamma alone or combinations of them upon the acquisition of the suppressor activity by cultured splenic M phi s were studied. When normal splenic M phi s were treated with each cytokine for 3 days, TNF-alpha, IFN-gamma, and IL-1 alpha alone caused a slight elevation of their suppressive activity. Treatment of the normal M phi s with the combination of either TNF-alpha+IL-1 alpha or TNF-alpha+IFN-gamma yielded a marked increase in the suppressor activity, followed by IL-1 alpha+IFN-gamma. These findings indicate the important roles of TNF-alpha, IFN-gamma, and IL-1 alpha in the generation of MAC-induced suppressor M phi s.

Granulocyte-macrophage colony-stimulating factor inhibits tumor growth during the postoperative period

BACKGROUND

Granulocyte-macrophage colony-stimulating factor (GM-CSF) may have important antineoplastic properties because it induces macrophage tumoricidal activity in vitro. We examined the inhibitory effect of GM-CSF on tumor growth in a murine carcinoma model and whether this inhibitory effect would persist during the postoperative period. Potential macrophage-mediated mechanisms were studied.

METHODS

The effect of GM-CSF on macrophage function in vitro was assessed by measuring superoxide anion and interleukin-6 production, percentage phagocytosis of Candida albicans, and percentage Ia expression. GM-CSF's effect on tumor volume was assessed first in a murine tumor model and second to examine whether these effects also occurred during the postoperative period in the same model after laparotomy. Macrophage function in the latter study was assessed by measuring superoxide anion, cytotoxicity, and tumor necrosis factor production.

RESULTS

GM-CSF treatment was associated with a decrease in tumor volume on day 4 after the initiation of GM-CSF treatment (0.93 +/- 0.08 cm3 for control versus 0.34 +/- 0.08 cm3 for GM-CSF; p < 0.05). This effect was also seen after laparotomy (1.07 +/- 0.2 cm3 for laparotomy+saline versus 0.16 +/- 0.04 cm3 for laparotomy+GM-CSF, p < 0.05). In vivo macrophage function showed increased superoxide anion, cytotoxicity, and tumor necrosis factor-alpha production from macrophages obtained from GM-CSF treated animals compared with saline treated controls.

CONCLUSIONS

Tumor growth is inhibited by GM-CSF treatment, and this effect also occurs after laparotomy. Thus, GM-CSF may have a therapeutic role in the treatment of the tumor bearing host after operation.

Decrease in scavenger receptor expression in human monocyte-derived macrophages treated with granulocyte macrophage colony-stimulating factor

To determine whether scavenger receptors are susceptible to regulation by granulocyte macrophage colony-stimulating factor (GM-CSF), a macrophage-specific cytokine, human monocytes were differentiated into macrophages in the absence or presence of 20 U/mL GM-CSF. Binding, uptake, and degradation of acetylated LDL (Ac-LDL) and oxidized LDL (Ox-LDL) were measured. Treatment with GM-CSF resulted in a significant twofold to threefold decrease in the number of binding sites for Ac-LDL and Ox-LDL on the surface of macrophages without affecting the affinity of the receptor for these ligands. Competition experiments revealed that two binding sites were responsible for the recognition and uptake of Ac-LDL; one specific for Ac-LDL and one that recognized both Ac-LDL and Ox-LDL. No binding site specific for Ox-LDL could be detected in either control or GM-CSF-treated macrophages. Treatment of human monocyte-derived macrophages with GM-CSF resulted in a decrease of the Ac-LDL/Ox-LDL receptor but did not affect the binding site specific for Ac-LDL. Northern blot analysis showed that mRNA levels of both types I and II scavenger receptor were reduced in macrophages differentiated in the presence of GM-CSF. Human macrophages that were differentiated in the presence of GM-CSF accumulated approximately 50% fewer cholesteryl esters. Taken together, these results indicate that GM-CSF can downregulate both types I and II scavenger receptor in human monocyte-derived macrophages, which might have implications for foam cell formation.

Enhanced human lymphokine-activated killer cell function after brief exposure to granulocyte-macrophage-colony stimulating factor

BACKGROUND

Lymphokine-activated killer (LAK) cell function can be generated in peripheral blood mononuclear cells (PBMC) after brief exposure of high dose interleukin-2 (IL-2) over the course of 1 or 2 days' culture in plain culture medium (IL-2-pulsed PBMC). The aim of the present study was to investigate the ability of granulocyte-macrophage-colony stimulating factor (GM-CSF) to augment LAK induction in low dose IL-2-pulsed PBMC derived from patients with cancer undergoing immunotherapy with IL-2.

METHODS

Peripheral blood mononuclear cells were collected from patients with cancer receiving a 5-day cycle of local (intraperitoneal or intrapleural) infusions with IL-2. The cells were incubated with IL-2 in the presence or absence of GM-CSF for 1 hour and then tested as effectors against allogeneic tumor cells and LAK-sensitive cell lines.

RESULTS

Granulocyte-macrophage-colony stimulating factor at doses between 10 and 100 ng/ml was synergized with low dose IL-2 (100 IU/ml) in the generation of LAK activity in PBMC. Lymphokine-activated killer cell-mediated cytotoxicity derived from PBMC cultures incubated with IL-2 and GM-CSF was significantly higher (up to three-fold) compared with that generated with IL-2 alone. The GM-CSF-induced enhanced LAK activity was maintained when tested at day 5. GM-CSF increased the percentages of IL-2 receptor (R) positive (+) and CD8+ cells in the IL-2-pulsed PBMC. In contrast to CD56+ cells, highly purified CD8+ cells isolated from PBMC pulsed with IL-2 and GM-CSF responded with increased LAK activity, thus representing the cell-type that mediates the augmenting effect of GM-CSF. Major histocompatibility complex (MHC) molecules or the CD3 surface antigens were not involved in the GM-CSF-mediated enhancement of LAK induction because anti-MHC class I and class II monoclonal antibodies (MoAb) or MoAb against the CD3 molecules remained without any effect in this system. The GM-CSF-mediated LAK-enhancement was IL-2-dependent because MoAb against IL-2 receptor completely inhibited the generation of LAK activity.

CONCLUSIONS

The use of GM-CSF for the enhancement of IL-2-induced LAK activity in 1 hour cultures may improve clinical results in cancer immunotherapy. In addition, implementation of this procedure could eliminate the high cost of cell culture which usually accompanies IL-2/LAK cell therapy as well as eliminate the known toxic side effects associated with this kind of therapy.

An in vivo model to compare human leukocyte infiltration in carcinoma xenografts producing different chemokines

In this study we tested whether the pattern of cytokines expressed by human carcinomas could account for a different in vivo recruitment of leukocyte subpopulations as a part of the anti-tumor immune response. Two carcinoma cell lines, SK-OV-3 ovary carcinoma and CALU-3 lung carcinoma, were analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR), immunofluorescence and ELISA for the expression and in vitro production of cytokines with chemotactic, proinflammatory and growth-stimulating activity. Although both cell lines displayed a constitutive expression of granulocyte colony-stimulating factor (G-CSF), granulocyte macrophage-CSF (GM-CSF), M-CSF, interleukin (IL-) 1 alpha and IL-8, only CALU-3 cell line expressed IL-10, RANTES (Regulated upon Activation, Normal T Expressed and Secreted) and monocyte-activating protein (MCP)-1. MCP-1 and IL-8 were detected by immunohistochemistry on sections from tumors xenografted in nude mice. To analyze whether the tumor-released cytokines modulate leukocytes in tumor infiltration, we studied the distribution of human peripheral blood leukocytes injected in the proximity of SK-OV-3 and of CALU-3 tumor xenografts. While SK-OV-3 was unable to recruit human leukocytes and appeared to be barely infiltrated by murine CD45+ cells, CALU-3 appeared to be rapidly and heavily infiltrated by human leukocytes which induced tumor necrosis within 18-24 hr.

Fresh colorectal tumor cells isolated from individual patients differ in their susceptibility to monocyte mediated cytotoxicity

Studies on monocyte/macrophage mediated cytotoxicity usually pertain to the use of cell lines that are liable to antigenic and structural changes. Therefore we compared monocyte mediated cytotoxicity against colorectal tumor cell lines (WiDR, HT29, SW620, and SW948) with fresh colorectal tumor cells from patients. Fresh tumor cells were isolated from surgical specimens by a short enzymatic treatment (Collagenase/DNAse). Monocytes were obtained from one healthy donor. Cytotoxicity was determined using the MTT-assay. Fresh colorectal tumor cells displayed a similar differential susceptibility to cytotoxic monocytes as cell lines. Cytotoxicity against fresh tumor cells ranged from 4.9% to 50.4% at E/T ratio 5 (n = 9). Activation of monocytes with Interferon-gamma (100 U/ml) induced an increase of 6.2% +/- 1.6 (n = 4, P = 0.06). In this study we demonstrate monocyte mediated cytotoxicity against colorectal tumor cells isolated from individual patients. This may be important in view of the development of adoptive immunotherapy and cell-directed immunotherapy.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) counteracts the inhibiting effect of monocytes on natural killer (NK) cells

GM-CSF is known to accelerate haematopoietic recovery following allogeneic bone marrow transplantation (BMT). In addition, it may restore and enhance both granulocyte and monocyte functions. Stimulation of monocyte functions may induce a direct or an indirect anti-leukaemic activity due to an increase of cellular cytotoxicity and production of cytokines which may result in a reduction of the relapse rate after BMT. NK cells may play a crucial role in this activity. Therefore we studied the influence of monocytes on NK activity in combination with GM-CSF. Lymphocytes and monocytes were isolated from buffy coats of healthy individuals by counterflow centrifugation elutriation (CCE). NK activity was exerted by CD3-CD56+ cell populations and could be enhanced by IL-2 incubation overnight. Incubation of CD3-CD56+ cells with GM-CSF in the presence or absence of IL-2 hardly influenced NK activity of the lymphocyte population. Low amounts of monocytes enhanced NK activity. NK activity in lymphocyte population in the presence of equivalent numbers of monocytes with or without IL-2 was strongly decreased irrespective of the effector:target ratio (ETR). This appeared not to result from sterical hindrance effects of the present number of cells. However, addition of GM-CSF abrogated the inhibition of NK activity by monocytes in the presence of IL-2. In monocyte fractions neither IL-2 nor GM-CSF yielded NK activity. Our findings indicate that GM-CSF can affect NK activity by counteracting the suppressing effects of monocytes, and hence may improve the outcome after BMT.

Cyclophosphamide in combination with sargramostim for treatment of recurrent medulloblastoma

Thirteen patients with recurrent medulloblastoma were treated with cyclophosphamide in association with Sargramostim. Cyclophosphamide was given at doses ranging between 1.0-2.5 g/m2 daily for two doses. Sargramostim was given at a fixed dose of 250 micrograms/m2 subcutaneously twice a day beginning 24 hours after the second cyclophosphamide dose and continuing through the leukocyte nadir until the ANC was more than 1,000 cells/microliters for two consecutive days. A total of 33 courses were given with toxicity consisting of grade 4 neutropenia in all courses and grade 3-4 thrombocytopenia in 10 of 13 patients. There were no deaths related to infection or bleeding. Four patients were taken off study because of prolonged myelosuppression. Three of these patients were at the 2.5 g/m2 level, and of these three, two developed lung toxicity (grades 2 and 4, respectively). One patient developed an allergic reaction following the first injection of Sargramostim and was also taken off study. Of 10 evaluable patients, there were 9 PR and 1 SD. We conclude that cyclophosphamide at a dose of 2.0 g/m2/day x 2 days q 4 weeks in association with Sargramostim demonstrates marked activity with acceptable toxicity in patients with recurrent medulloblastoma.