Recombinant gamma interferon induces hypertriglyceridemia and inhibits post-heparin lipase activity in cancer patients.

Animals suffering from malignancy or chronic infection develop characteristic metabolic abnormalities, including a well-defined hypertriglyceridemic state. These abnormalities have been attributed to release of one or more mediators from activated macrophages. We report that cancer patients receiving RIFN-gamma, a potent macrophage activator, at doses of greater than or equal to 0.25 mg/m2/d i.m. show marked increases in triglyceride but not in cholesterol levels (pretreatment triglyceride level of 180 +/- 190 mg/dl [mean +/- SD] vs. a day-14 level of 370 +/- 242 mg/dl, n = 23, p less than 0.001 by the paired t test). This hypertriglyceridemia was characterized by an increase in very low-density lipoproteins and a decrease in plasma post-heparin lipase activity, consistent with defective triglyceride clearance (mean pretreatment lipase level of 2.1 mumol/ml/h vs. a day-14 level of 1.2 mumol/ml/h, n = 6, p = 0.02 by the paired t test). rIFN-gamma did not directly inhibit lipoprotein lipase enzymatic activity in vitro. Other possible mechanisms of action, such as suppression of lipase by an rIFN-gamma-induced mediator released from activated macrophages, or a direct effect of interferon on lipase biosynthesis, require further investigation. Our observations provide evidence that factors produced by the immune system can regulate lipid metabolism in man.

Antigen solubilized from human leukemia: lymphocyte stimulation.

Soluble antigen was extracted with hypertonic (3 molar) potassium chloride from the malignant cells of seven patients with acute leukemia. The antigen and leukemia cells were used to stimulate autologous patients' and allogeneic normal donors' lymphocytes in mixed lymphocyte cultures. The lymphocytes of six patients showed significant blastogenic responses to autologous antigen. In contrast, the lymphocytes of only one of seven normal donors responded to the soluble antigens. Both patients' and normal subjects' lymphocytes responded to the intact leukemia cells. The use of these antigens should facilitate the study of specific tumor immunity in human leukemia.

A plant triterpenoid, avicin D, induces autophagy by activation of AMP-activated protein kinase.

Avicins, a family of plant triterpene electrophiles, can trigger apoptosis-associated tumor cell death, and suppress chemical-induced carcinogenesis by its anti-inflammatory, anti-mutagenic, and antioxidant properties. Here, we show that tumor cells treated with benzyloxycarbonylvalyl-alanyl-aspartic acid (O-methyl)-fluoro-methylketone, an apoptosis inhibitor, and Bax(-/-)Bak(-/-) apoptosis-resistant cells can still undergo cell death in response to avicin D treatment. We demonstrate that this non-apoptotic cell death is mediated by autophagy, which can be suppressed by chloroquine, an autophagy inhibitor, and by specific knockdown of autophagy-related gene-5 (Atg5) and Atg7. Avicin D decreases cellular ATP levels, stimulates the activation of AMP-activated protein kinase (AMPK), and inhibits mammalian target of rapamycin (mTOR) and S6 kinase activity. Suppression of AMPK by compound C and dominant-negative AMPK decreases avicin D-induced autophagic cell death. Furthermore, avicin D-induced autophagic cell death can be abrogated by knockdown of tuberous sclerosis complex 2 (TSC2), a key mediator linking AMPK to mTOR inhibition, suggesting that AMPK activation is a crucial event targeted by avicin D. These findings indicate the therapeutic potential of avicins by triggering autophagic cell death.

LIF: not just a leukemia inhibitory factor.

Increasingly it seems that many cytokines are pleiotropic, and individual molecules may have critical roles in several different organ systems. LIF exemplifies this phenomenon: it influences embryogenesis, bone and lipid metabolism, and hematopoietic and nervous system function. Many of LIF's effects are reminiscent of those of IL-1, TNF, and TGF-beta. Further, even within a single system, LIF can display totally different effects, i.e. induction of differentiation of one leukemic cell line vs. stimulation of proliferation of another. The corollary to these observations is that there appears to be many parallels in developmental systems. For instance, in the case of neuronal "lineage commitment," the events that relate to migration of neural crest cells along various pathways and their ultimate arrest in different locales demonstrate sufficient analogies to hematopoietic lineage commitment phenomena that, in a provocative review, Anderson coined the term "neuropoiesis". This type of analogy becomes even more intriguing when one realizes that some of the same molecules are regulating neuronal and hematopoietic "lineage" proliferation and differentiation. In this respect, several interleukins in addition to LIF are important in neuronal development, and nerve growth factor turns out to also be a hematopoietic regulatory molecule. Similar parallels are enacted in other organ systems as well. The mediation of identical effects by distinct cytokines bound to unique receptors could conceivably be explained by receptor transmodulation or by overlapping signaling sequences. It is nevertheless also unclear how a single cytokine attached to a single receptor can accomplish varied and opposing effects, although divergent intracellular signaling mechanisms could account for some of these phenomena. Yet another enigma relates to how cells from one system can be properly influenced by a pleiotropic molecule such as LIF without significant "cross-effects" on other potentially responsive systems. Cytokine production that is restricted to certain developmental stages, or very localized distribution and spheres of influence within a microenvironment, could be explanatory. The findings of Rathjan and colleagues, i.e. that LIF exists as both a diffusible molecule and as a molecule incorporated into the extracellular matrix, is of special interest in relation to the above questions. Indeed, the distinctions between the roles of diffusible and immobilized signaling molecules could be crucial to the multiplicity of LIF's actions. Diffusible regulatory factors allow communication between spatially separated cells. Cellular responsiveness to such factors is dictated by the presence of appropriate receptors and postreceptor machinery.(ABSTRACT TRUNCATED AT 400 WORDS)

Serial studies of immunocompetence of patients undergoing chemotherapy for acute leukemia.

Immunocompetence was followed serially for 1 yr from the onset of treatment in 55 adult patients with acute leukemia. The tests used were delayed hypersensitivity responses to a battery of five recall antigens (dermatophytin, dermatophytin 0, candida, streptokinase-streptodornase, and mumps) and in vitro lymphocyte blastogenic responses to phytohemagglutinin and streptolysin 0. There was a strong correlation between immunocompetence at the start of treatment and a good prognosis; 32/39 patients who subsequently entered remission were initially immunocompetent compared to 4/15 who failed to enter remission. In the complete remission group there was a decline in competence starting from 2 to 5 mo after the onset of treatment. In those who remained in remission for 1 yr, competence recovered at 6 mo and remained vigorous thereafter. In those who relapsed before 1 yr, the decline in competence occurred 1 mo before relapse and competence continued to decline progressively during the 1 yr follow-up period. These studies suggest that therapeutic approaches which restore immunocompetence or prevent its decline will improve both the remission rate and the remission duration of patients with acute leukemia.

Clinical study of recombinant DNA-produced leukocyte interferon (clone A) in a intermittent schedule in cancer patients.

The effects of recombinant DNA-produced leukocyte interferon (IFLrA) were studied in 37 patients with metastatic cancer who received sequentially escalating doses of 9-86 million units (MU) of IFLrA by im injection twice weekly. The IFLrA was absorbed rapidly and reached a peak serum concentration 6-8 hours after injection. Serum concentration of IFLrA increased proportionately with the dose. The most common side effects included fever, chills, asthenia, anorexia, and weight loss, and leukopenia, granulocytopenia, and lymphopenia occurred frequently. Elevation of serum glutamic-oxaloacetic transaminase was frequent above doses of 50 MU. All side effects were reversible by discontinuation of the drug. Antibodies to IFLrA were detected in 3 patients while on treatment. The presence of antibodies coincided with drastic reduction in serum IFLrA concentration and, in 1 patient, with relapse of disease. Objective tumor responses were documented in patients with lymphomas but not in other groups of patients.

Effect of BCG (Tice strain) on primary sensitization to 2,4-dinitrochlorobenzene and on established delayed hypersensitivity in human malignant melanoma.

Studies of primary sensitization and delayed hypersensitivity reactions to 2,4-dintrochlorobenzene (DNCB) and recall antigens were conducted in 71 patients with melanoma who were receiving BCG (Tice strain) immunotherapy by scarification. Similar studies were conducted in 32 control patients with melanoma who did not receive BCG. No significant differences were observed, in the various clinical stages, between patients receiving and those not receiving BCG, in terms of the frequency or intensity of primary sensitization to DNCB. Furthermore, there was no significant difference in delayed hypersensitivity to recall antigens between these groups of patients. The apparent discrepancy between the clinical benefit from BCG immunotherapy and its failure to stimulate certain parameters of cellular immunity in patients with melanoma is discussed.

The C1q binding test for soluble immune complexes: clinical correlations obtained in patients with cancer.

Sera from 134 selected patients with various types of cancer were tested for soluble antigen-antibody complexes by the C1q binding method. Sera from 85 healthy blood bank donors served as normal controls. C1q binding activity (C1q BA) values above the 95th percentile for healthy subjects were found in 83% of sera from patients with neoplastic diseases. The incidence of abnormal C1q BA values among patients with malignant melanoma was 83%, with breast cancer 74%, with colon cancer 75%, with lung cancer 88%, with leukemia and lymphoma 85%, and with miscellaneous tumors 94%. High C1q BA values were found most frequently in sera of patients who had been diagnosed relatively recently (within 5 mo) and who had evident residual disease after surgical treatment. Recurrence or progression of tumor growth occurred significantly more frequently in lung cancer patients with high C1q BA. DNA was not detected in cancer patients' sera and treatment with DNase did not decrease in C1q BA. C1q BA in sera could not be explained by the presence of antiglobulin antibodies. Sucrose density gradient ultracentrifugation studies of the serum C1q BA in 4 cancer patients showed that the major binding activity was found between 19S and 7S.

Evaluation of BCG administered by scarification for immunotherapy of metastatic hepatocarcinoma in the guinea pig.

In inbred guinea pigs, administration of Mycobacterium bovis strain BCG by scarification at a site distant from an excised skin tumor, but in the regional lymph node drainage, was evaluated for its immunotherapeutic effect on the development of lymph node metastases. Scarification was performed after surgical excision of intradermally transplanted syngeneic (line-10) hepatocarcinoma at a time when microscopic foci of tumor cells were present in regional lymph nodes. Various strains of BCG were evaluated for their immunotherapeutic potential: fresh-frozen Phipps, Pasteur, and Tice; and lyophilized Pasteur, Tice, and Connaught. Scarification commenced 3 days after surgical removal of the tumor and continued once a week for 5 weeks. Only lymph nodes from fresh-frozen Phipps- and Pasteur-scarified animals were significantly smaller than those in the control groups. Differences in lymph node weight correlated histologically with less detectable metastases. This cytostatic effect was short lived; eventually, the metastatic tumor growth was not significantly different from that of control animals. No significant differences were observed in mean survival time: All animals died as a result of metastases 3 months after tumor inoculation. These results demonstrated that limited scarification with BCG of certain strains temporarily inhibits the growth and proliferation of metastases in regional lymph nodes after removal of the primary tumor.

Effect of immunotherapy with Corynebacterium parvum and methanol extraction residue of BCG administered intravenously on host defense function in cancer patients.

The effects of active nonspecific immunotherapy were studied in 42 patients receiving daily iv Corynebacterium parvum at 2 mg/m2 in 14-day courses and in 14 patients receiving iv methanol extraction residue of BCG (MER) at 0.5 mg/m2 weekly. The host defense evaluations included measurement of the number of adherent macrophage precursors per milliliter of blood (monocyte adherence), serum lysozyme, and antibody-dependent cell-mediated cytotoxicity (ADCC) of peripheral blood mononuclear cells to chicken red blood cells (CRBC) or human red blood cells (HRBC). During a single course of C. parvum, monocyte adherence did not rise significantly, whereas ADCC of peripheral blood mononuclear cells to CRBC and HRBC rose significantly (15.7-49.9% and 34.8-53.5% lysis of target cells, respectively). However, after a mean of 4.5 months on therapy, monocyte adherence increased an average of 7.5-fold. During weekly MER therapy, monocyte adherence, serum lysozyme, and ADCC of peripheral blood mononuclear cells to CRBC rose significantly within 4-7 days after the first dose (3.8-8.7 adherent cells/ml blood x 10(4), 7.6-10.8 microgram, and 34.4-41.4% target cell lysis, respectively). The host defense parameter, which was subnormal in the cancer patients (monocyte adherence), was boosted into the normal range in all the deficient patients by iv MER. The host defense parameters, which were normal or slightly elevated in the patients before therapy (serum lysozyme and ADCC of peripheral blood mononuclear cells to CRBC and HRBC), were hyperactivated above the upper limit of the normal range in 71.4, 71.4, and 50% of the patients, respectively, by iv MER. These methods can quantitatively reflect activation of monocytes and killer cells by C. parvum and MER and may be useful for evaluation and quantitation of both active nonspecific and immunorestorative immunotherapy in general.

Analysis of natural killer cell cytotoxicity of cancer patients treated with recombinant interferon.

Peripheral blood natural killer (NK) cell cytotoxicity of 24 cancer patients was studied prior to and after single and multiple injections of various doses of human leukocyte recombinant interferon-alpha clone A (IFN-alpha rA). The NK cell cytotoxicity of all cancer patients declined consistently 4 and 8 hours after a single injection of IFN-alpha rA. Twenty-four hours after the injection of IFN-alpha rA, NK cell cytotoxicity of patients with low NK cell phenotype (NK-LR) was significantly augmented, whereas that of patients with medium (NK-MR) or high (NK-HR) NK phenotype was depressed. After multiple injections of IFN-alpha rA, depression of NK cell cytotoxicity was observed in a number of NK-MR and NK-HR patients, but in some patients with NK-LR phenotype, further potentiation was observed. No direct correlation between the NK cell augmentation and serum IFN levels was detected. In in vitro studies, IFN-alpha rA, when added to cultures of target and effector cells of normal individuals in a dose of 10(3) U/ml, was efficient in augmenting NK cell cytotoxicity. NK cell cytotoxicity of cancer patients could also be augmented by the IFN-alpha rA preparation; however, this augmentation occurred only prior to in vivo IFN-alpha rA therapy. After IFN-alpha rA in vivo therapy, their NK cells became refractory to further in vitro IFN-alpha rA treatment.

Interferon-induced changes in pharmacokinetics and tumor uptake of 111In-labeled antimelanoma antibody 96.5 in melanoma patients.

The type I interferons [both partially purified human leukocyte interferon (HuIFN-alpha) and recombinant alpha interferon] and the type II interferons have been shown to increase the expression of tumor-associated antigens in vitro. To determine whether HuIFN-alpha could increase tumor acquisition of the antimelanoma antibody 96.5 in vivo, five patients with metastatic malignant melanoma were treated with HuIFN-alpha at a dose of 3 X 10(6) units daily by im administration. Twenty-four hours after the first dose of HuIFN-alpha, 1 mg of antibody 96.5 labeled with 5 mCi of 111In was coadministered with 19 mg of unlabeled 96.5. Five patients matched for metastatic site and lesion size who had not received HuIFN-alpha were also given a dose of 5 mCi of radiolabeled 96.5 at the same total antibody dose (20 mg). In patients treated with HuIFN-alpha, there was a statistically significant increase in the plasma half-life of the 111In label (39.7 +/- 3.3 hr) compared to the untreated control group (29.8 +/- 3.2 hr). In addition, there was an increase in the apparent volume of distribution of the antibody in the HuIFN-alpha group (5.56 +/- 0.67 L) compared to controls (3.15 +/- 0.5 L) suggesting both an increased immediate extravascular distribution of radiolabeled antibody and a decrease in the subsequent rate of clearance of antibody from plasma. These two phenomena result in a 28% decrease in the area under the concentration curve in the HuIFN-alpha-treated group compared to controls. Computer analysis of whole-body scans from patients showed a threefold increase in radiolabeled antibody distributed to tumor relative to blood pool but no change in organ:blood ratios for liver, spleen, bone, or kidney compared to controls. This pilot study suggests that treatment of patients with HuIFN-alpha results in an improved distribution of radiolabeled antibody to tumor target without a concomitant increase of label in normal nontarget tissues. In addition, this change in whole-body distribution of antibody is manifested by changes in the pharmacokinetic parameters measured for monoclonal antibody.

Escalated therapy for refractory urothelial tumors: methotrexate-vinblastine-doxorubicin-cisplatin plus unglycosylated recombinant human granulocyte-macrophage colony-stimulating factor.

Thirty-two assessable patients with metastatic urothelial tumors refractory to standard chemotherapy with methotrexate, vinblastine, doxorubicin, and cisplatin (MVAC) were treated with escalated doses of MVAC plus unglycosylated recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF). Results of this phase I trial revealed that escalated MVAC (30 mg of methotrexate/m2, 4 mg of vinblastine/m2, 60 mg of doxorubicin/m2, and 100 mg of cisplatin/m2) can be tolerated by heavily pretreated patients. The side effects of rhGM-CSF are dose- and schedule-dependent. The maximum tolerated dose is 250 micrograms/m2 per day as a single dose administered subcutaneously (SC) for 10 consecutive days. This dose is well tolerated in outpatients, resulting in only modest fever and few side effects. The same dose delivered as a continuous infusion or a higher dose delivered either as a continuous infusion or SC caused significant side effects. For phase II trials, the starting dose of rhGM-CSF when combined with escalated MVAC is 120 micrograms/m2 per day SC for 10 consecutive days. forty percent of the treated patients responded, seven (23%) with complete remission and five (17%) with partial remission. This response rate is higher than anticipated from such a modest dosage escalation in chemotherapy-refractory patients.

13-cis-retinoic acid and interferon alpha-2a: effective combination therapy for advanced squamous cell carcinoma of the skin.

BACKGROUND: Retinoids (vitamin A derivatives) and interferon-alpha (IFN-alpha) are potent regulators of malignant cell differentiation and proliferation, and both have immunomodulatory and antiangiogenesis activity. A large body of preclinical and clinical data supports the use of combination therapy with 13-cis-retinoic acid (13-cRA) and IFN-alpha in patients with squamous cell carcinoma of the skin. This carcinoma is an extremely common and frequently severely disfiguring cancer, for which about 10% of patients remain uncured following standard local therapy. PURPOSE: Our purpose was to test whether a 20% or greater complete response rate could be achieved using a combination of these two agents in patients with advanced squamous cell carcinoma of the skin in whom local therapy had failed or was unfeasible or who had regional and/or distant metastases. METHODS: Thirty-two patients with heavily pretreated, advanced inoperable cutaneous squamous cell carcinoma of the skin were given a combination of oral 13-cRA (1 mg/kg per day) and subcutaneous recombinant human IFN alpha-2a (3 million units per day) for at least 2 months, unless disease progressed earlier, in a phase II trial. RESULTS: Nineteen (68%) of the 28 assessable patients responded, seven (25%) of whom had complete responses. Response rates were 93% (13 of 14) in patients with advanced local disease (six complete responses), 67% (four of six) in patients with regional disease (no complete responses), and 25% (two of eight) in patients with distant metastases (one complete response). The relationship between decreased response rate and increased extent of disease was highly statistically significant (P less than .005, chi-square test). The median response duration was greater than 5 months. No life-threatening toxic effects occurred in assessable patients treated with this combination, although dose reductions were required in 18 patients. The major limiting side effect in this elderly patient population (median age, 67 years) was cumulative fatigue. CONCLUSION: These results indicate that combined systemic therapy with 13-cRA and IFN alpha-2a is highly effective in patients with advanced squamous cell carcinoma of the skin.

Synergistic antiproliferative activity of leukocyte interferon in combination with alpha-difluoromethylornithine against human cells in culture.

alpha-Difluoromethylornithine, an enzyme-activated irreversible inhibitor of ornithine decarboxylase, was administered in combination with human leukocyte interferon to human lymphoblastoid (Daudi) cells in culture. True synergistic antiproliferative activity was observed at 72 hr after continuous exposure. This effect was observed regardless of the ratio of interferon to alpha-difluoromethylornithine concentrations. Although the mechanisms by which this effect occurs are unknown, these studies provide a rationale for combination clinical trials of alpha-difluoromethylornithine with leukocyte interferon.

Differential expression of p21ras gene products among histological subtypes of fresh primary human lung tumors.

Activation of the ras oncogene has been associated with a number of human tumors. In this study, expression of p21ras in different histological types of fresh primary bronchogenic carcinomas was examined. p21ras products were detected in all lung tissues that were analyzed. Only 1 of 23 tumors demonstrated aberrant migration of p21ras. In contrast, 10 tumors had substantially elevated levels of p21ras products with respect to the adjacent normal lung tissues and with respect to the other lung tumors. There was no correlation between increased ras protein expression and tobacco exposure of the patient or extent of disease at the time of diagnosis. However, 9 of 11 tumors with a squamous component as opposed to only 1 of 12 tumors belonging to other histological classifications demonstrated increased p21ras. These data suggest that, in bronchogenic carcinomas, mutations associated with structural abnormalities and aberrant migration of p21ras occur infrequently as compared to quantitative changes in p21ras. Furthermore, differential expression of c-ras products in primary human lung tumors correlates with pathological cell type, and may be a common event in squamous cell carcinomas, but not adenocarcinomas or small cell carcinomas of the lung.

Phase I study of recombinant tumor necrosis factor in cancer patients.

Tumor necrosis factor is a cytokine derived from activated macrophages. This agent is cytostatic and cytolytic against transformed human cell lines in vitro and has in vivo activity against a variety of murine tumors. We report a clinical study of the pharmacokinetics, toxicity, and biological activity of i.v. and i.m. administered recombinant human tumor necrosis factor (rTNF). Twenty patients with metastatic cancer were given rTNF in doses ranging from 1 to 200 micrograms/m2 by alternating i.m. and i.v. bolus injections with a minimal intervening period of 72 h. Each patient received a maximum of eight treatments given twice weekly over a 4-week period. With i.v. bolus administration, serum concentrations of rTNF were detected by enzyme-linked immunosorbent assay at doses of 25 micrograms/m2 or greater. The clearance of rTNF in the serum was described by a monoexponential equation with a half-life calculated to be 14-18 min. After i.m. administration, serum concentrations of rTNF were consistently detected by enzyme-linked immunosorbent assay at doses of 150 micrograms/m2 or greater. Peak concentrations were observed within 2 h and rTNF was occasionally detected, at the lower limit of sensitivity of the assay, at 24 h postinjection. rTNF was well tolerated clinically in this dose range, and there was evidence of antitumor effect.

Renal cell carcinoma: antitumor effects of leukocyte interferon.

Partially purified human leukocyte (alpha) interferon was administered i.m. at a dose of 3 x 10(6) units/day to 19 patients with metastatic renal cell carcinoma. Five patients (26%) showed partial responses; two patients (10.5%), objective minor responses; three patients (16%), mixed effects (evidence of biological effect with regression of some lesions but concomitant progression); two patients (10.5%), disease stabilization; and seven patients (37%), progressive disease. All tumor responses were seen in lung or mediastinal metastases. Tumor response significantly correlated with interferon-induced leukopenia and granulocytopenia and with pretreatment performance status. Antibodies to interferon were found in one patient prior to treatment. We concluded that interferon is a potential active antitumor agent in patients with renal cell carcinoma.

Analysis of the epidermal growth factor receptor gene in fresh human head and neck tumors.

Seventeen fresh uncultured tumors obtained from biopsies of patients with various forms of head and neck cancer and two squamous cell carcinoma cell lines were analyzed for RNA expression and structural alterations of the epidermal growth factor reception gene. We used cDNA probes for the external and the internal domains of the gene. Enhanced mRNA expression was found only in one squamous cell carcinoma cell line, which is known to have high levels of epidermal growth factor receptor. No amplification or structural rearrangement of the epidermal growth factor receptor gene was found.

Effect of recombinant granulocyte/macrophage colony-stimulating factor on human monocyte activity in vitro and following intravenous administration.

The purpose of these studies was to examine the antitumor properties of blood monocytes from patients undergoing a phase I trial with recombinant granulocyte/macrophage colony-stimulating factor (rGM-CSF). Peripheral blood monocytes from 7 patients receiving various doses of rGM-CSF by continuous infusion were isolated prior to therapy and at various times during the 2-wk infusion. Monocytes/cubic centimeter of blood increased in a dose-dependent fashion in patients receiving rGM-CSF. However, activation of monocyte-mediated tumorilytic properties was seen in only 1 of 7 patients. rGM-CSF administration also did not stimulate interleukin-1 or tumor necrosis factor production by blood monocytes. The failure to detect monocyte-mediated tumoricidal activation was not secondary to an inherent "defect" in the patients' monocytes because in vitro incubation with lipopolysaccharide alone or human recombinant gamma-interferon plus muramyl dipeptide resulted in monocyte-mediated cytotoxicity and in the secretion of interleukin-1 and tumor necrosis factor. rGM-CSF in vitro also did not stimulate the tumoricidal function of normal monocytes or the secretion of interleukin-1 or tumor necrosis factor. We concluded that systemic administration of rGM-CSF did not result in routine activation of monocyte-mediated cytotoxicity but did result in a dose-dependent rise in the number of circulating monocytes. Because these monocytes could be activated in vitro, we propose that, in an adjuvant therapy setting, rGM-CSF be combined with other activating agents to increase the pool of potential killer cells.