OT3-01-06: A Phase 2 Study Investigating the Safety, Efficacy and Surrogate Biomarkers of Response of 5-Azacitidine (5-AZA) and Entinostat (MS-275) in Patients with Advanced Breast Cancer

Background: Epigenetic alterations in the genome, including abnormal DNA methylation and histone hypoacetylation, initiate and promote cancerous changes via several mechanisms, including inactivation of tumor suppressor genes. Preclinical investigations in breast cancer suggest that use of epigenetic modifiers results in re-expression of aberrantly silenced genes and proteins that represent important therapeutic targets (e.g. estrogen receptor alpha, ER). Combination therapy with a DNA methyltransferase inhibitor (DNMTI) and a histone deacetylase inhibitor (HDACI) has yielded superior ER reexpression and greater restoration of tamoxifen responsiveness than with HDACI alone. We hypothesize that clinically tolerable doses of the DNMTI 5-azacitidine (5-AZA) and the HDACI entinostat may not only effect changes in DNA methylation and gene expression, but also yield objective disease responses in women with advanced breast cancer.

Trial design: This multicenter phase II study (NCT01349959) is enrolling patients with advanced human epidermal growth factor receptor 2 (HER2)-negative breast cancer with triple negative (ER/progesterone receptor [PR]/HER2−negative, Cohort A) or hormone-resistant (Cohort B) disease. Patients will receive 5-AZA 40 mg/m2 subcutaneously days 1–5 and 8–10 and entinostat 7 mg orally days 3 and 10 every 28 days. Because of the potential for re-expression of the ER with epigenetic agents, patients will be offered continuation of 5-AZA and entinostat at progression with the addition of hormonal therapy (investigator discretion). Mandatory tumor biopsies will be performed at baseline and after 8 weeks of therapy to evaluate correlative biomarkers.

Eligibility Criteria: Eligible patients must be ≥ 18 years, have measurable locally advanced/metastatic triple-negative (at least one prior chemotherapy received adjuvant/metastatic setting) or hormone-resistant (must have received two prior hormonal agents and one prior chemotherapy) disease, adequate organ function and ECOG PS ≤ 2.

Specific Aims:

1. Objective response rate (ORR) by RECIST 1.1 criteria.

2. Safety and tolerability

3. Progression-free survival, overall survival and clinical benefit rate.

4. Safety and toxicity data, feasibility and response rate where hormonal therapy is added to the combination under investigation at the time of progressive disease.

5. Pharmacokinetics, cytidine deaminase, changes from baseline of candidate gene methylation and expression in circulating deoxyribonucleic acid (DNA) and malignant tissue.

Statistical Methods:

Using a two-stage three-outcome design to assess the efficacy of the combination, a maximum of 30 patients (requiring 27 evaluable) will be accrued to each cohort unless undue toxicity is encountered for a maximum sample size of 60 patients. The study design tests the null hypothesis that the ORR is at most 5% against the alternative hypothesis that it is at least 20% with a type I error of 4% and power of 90%.

Present and Targeted Accrual: This study has just opened to patient enrollment. We anticipate a rapid accrual of 60 patients within 1 year.br](Funding from Stand Up to Cancer and CTEP).

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr OT3-01-06.

A phase I study of vorinostat in combination with bortezomib in refractory solid tumors

2531

Background: Vorinostat (suberoylanilide hydroxamic acid, SAHA) is an oral histone deacytlase (HDAC) inhibitor that has anti-tumor activity in hematologic malignancies and advanced solid tumors. Vorinostat has been postulated to act synergistically with bortezomib at the level of aggresome inhibition with creation of reactive oxygen species. We previously conducted a study of this combination with once-daily dosing of vorinostat with bortezomib (Step A). This study (Step B) was conducted to evaluate twice daily dosing of vorinostat during administration of bortezomib to determine safety and efficacy, pharmacokinetics, and activity this combination. Methods: This study used standard eligibility criteria except patients must have had no prior bortezomib. The treatment plan initially consisted of vorinostat given orally twice daily on days 1–14 with bortezomib IV on days 1, 4, 8, and 11 of a 21 day cycle. Two DLTs (elevated ALT and fatigue) were observed at level 1, and the protocol was amended to administer vorinostat twice daily on days 1–4 and 8–11. Starting dose was vorinostat 200 mg and bortezomib 1 mg/m2. RECIST was used to measure response. Results: 29 pts have been enrolled; 13 men and 16 women. Tumor types include: Prostate (1), Colorectal (3), Pancreatic (6), Sarcoma (7), Biliary (1), Thymus (1), GIST (2), Mesothelioma (1), ovarian (1), Neuroendocrine (1), Lung (1), Head and Neck (1), Breast (2), and Cervical (1). Grade 3–4 toxicities possibly related to SAHA at any dose level were as follows: thrombocytopenia (5), fatigue (3), increased ALT (1), elevated INR (1), anemia, (1), hypotension (1), diarrhea (3), anorexia (1), dizziness (1), nausea/vomiting (1), and hypoalbuminemia (1). The only dose limiting toxicities included elevated ALT (1), fatigue (1). There were two deaths but neither was felt to be related to the drug. The MTD for Step B was established at vorinostat 300 mg BID and bortezomib 1.3 mg/m2. Conclusions: The MTD for Step B was established at vorinostat 300 mg BID and bortezomib 1.3 mg/m2. Subjective evidence of clinical activity has been observed in patients with refractory solid tumors. These studies were supported by NCI, UO1, CA062491, SAIC 25XS097, and 1ULRR025011.

No significant financial relationships to disclose.

Phase I study of intravenous decitabine in combination with oral vorinostat in patients with advanced solid tumors and non-Hodgkin's lymphomas (NHL)

3528

Background: Decitabine (D), a hypomethylating agent, and vorinostat (V), a histone deacetylase inhibitor, belong to two different classes of drugs with an epigenetic effect. The ideal dose scheduling of these drugs remains controversial. This phase I study aims to determine the recommended phase II dose (RPTD) of the combination, their toxicity profile, pharmacokinetic (PK) interaction and preliminary clinical activity. Methods: Patients (pts) with advanced solid tumors or relapsed/refractory NHL are eligible. Two different schedules of D and V are being evaluated: sequential administration of D followed by V and concurrent administration of D and V. Dose escalation of D and V on the sequential schedule is described in Table. Results: To date, 27 pts have been entered into dose levels 1, -1, 1a, 1b, -1b, -2b of the sequential schedule. Demographics: median age 61 (range 31–76), F:M = 13:14, ECOG 0:1:2 = 8:16:3, tumor types: 24 solid tumor and 3 NHL. Pts received a total of 77 cycles with a median of 2 cycles (range 1–8). Adverse events (AE) of grade 3 or higher of at least possible attribution to the study treatment were neutropenia (16 pts), thrombocytopenia (4), febrile neutropenia (2), fatigue (2), and 1 pt each for constipation, dehydration, nasal bleeding, elevated alanine aminotransferase, and hyponatremia. Dose limiting toxicities (DLT) consisted mainly of myelosuppression, constitutional and gastrointestinal symptoms occurred in 7/27 (26%) of pts so far. Disease stabilization for 4 or more cycles was observed in 7 out of 22 (31.8%) evaluable pts (two with breast and one each of thymus, colon, pancreatic, appendix and non-small cell lung cancers). Conclusions: The sequential combination of D and V seems to be tolerable after some adjustments in the doses and duration of drug administration. Prolonged disease stabilization has been observed in multiple tumor types. Accrual is ongoing and RPTD will likely be dose level -1b or -2b. ( Supported by NCI Grant No. U01CA132123.)

[Table: see text]

No significant financial relationships to disclose.

Randomized, double-blind, placebo-controlled phase II study of carboplatin and paclitaxel with or without vorinostat, a histone deacetylase inhibitor (HDAC), for first-line therapy of advanced non-small cell lung cancer (NCI 7863)

8004

Background: Vorinostat, a HDAC inhibitor, enhances paclitaxel and platinum-mediated anti-cancer activity in preclinical studies by enhanced tubulin acetylation and DNA fragmentation respectively. Promising activity with carboplatin (C), paclitaxel (P), and vorinostat in patients with advanced NSCLC in the phase I study (Ramalingam et al, Clin Cancer Res, 2007) prompted this placebo-controlled, randomized phase II study. Methods: Pts. with stage IIIB (wet) or IV NSCLC, performance status (PS) 0/1, no prior therapy and adequate bone marrow, renal and hepatic function were randomized (2:1) for therapy with PC with either vorinostat or placebo. Treatment consisted of C: AUC=6 mg/ml.min; and P 200 mg/m2 both given on day 3 along with either vorinostat (400 mg PO QD) or placebo on days 1–14 of each 3 wk cycle to a maximum of 6 cycles. The estimated sample size to demonstrate a 50% improvement in response rate for vorinostat over placebo was 93 pts. (one-sided P, type I error 10%). Results: Ninety-four pts. were enrolled (vorinostat-64; placebo-32). Pts. baseline characteristics were similar between the two arms (median age 64, male 60%, PS 0 40%, brain mets 16%). Median # cycles: vorinostat-3.5; placebo - 4. The confirmed response rate was superior with vorinostat over placebo (34% vs. 12.5%, P = 0.02). At the time of analysis, the preliminary median PFS for vorinostat and placebo were 5.75 and 4.1 m respectively (ITT). Follow up for survival is ongoing. Common grade 3/4 toxicities (vorinostat vs. placebo): neutropenia (44% vs. 47%); thrombocytopenia (33% vs. 16%); fatigue (13% vs. 3%); hyponatremia (21% vs. 6%); diarrhea (5% vs. 0). Discontinuation from study after cycle 1 was higher with vorinostat (27% vs. 16%). Biomarker studies on baseline tumor tissue and peripheral blood cells are ongoing. Conclusions: Administration of vorinostat with carboplatin and paclitaxel resulted in a significantly superior response rate for pts.with advanced NSCLC. HDAC inhibition is a novel therapeutic strategy for treatment of NSCLC. Supported by ASCO Career Development Award to S.S.Ramalingam, and NCI NO1-CM-62209, NO1-CM-62201, NO1-CM-62208.

[Table: see text]

Phase II study of the histone deacetylase inhibitor belinostat in thymic malignancies

7589

Background: Thymic malignancies are rare tumors. Chemotherapy is used for advanced disease. There is no established role of second-line therapy in patients with refractory or recurrent disease. Belinostat is an HDAC inhibitor with activity in cutaneous and peripheral T cell lymphoma and is being investigated in several solid tumors. One prolonged minor response (31 m) was seen in a phase I study of this agent in a patient with thymoma. Methods: Patients with recurrent thymoma or thymic carcinoma, progressing after platinum-based chemotherapy were eligible. They were also required to have measurable disease, PS 0–2 and normal organ functions. Belinostat was given iv at 1.0 g/m2 on days 1–5 of a 21-day cycle until disease progression or intolerable side effects. Correlative markers of activity in blood and tumor were performed. Results: From December 07 to December 08, 22 patients have been accrued from 2 institutions; 12 patients were males, median age 52 (23–72), 14 thymomas and 8 thymic carcinomas, mean number of prior regimens 3.5 (1–10), 16 prior tumor resection and 3 myasthenia gravis. A median of 4 cycles have been given (1–15+). Treatment was well tolerated, with nausea being the most common side effect and well controlled with prophylactic antiemetics. 21 patients are evaluable for response: 2 had a partial response (9+, 9+ m), 13 stable disease (3–11+ m) and 6 progression. No responses were seen in 8 evaluable patients with thymic carcinomas. Acetylated lysine and tubulin were analyzed in lymphocytes and monocytes by multiparameter flow cytometry. An increase of protein acetylation (2–10 fold) over baseline was observed at 1 hour post-infusion on day 3 of the first cycle in all patients analyzed. Other correlative markers are being investigated. Conclusions: The thymoma cohort has been expanded to the second stage of the study. Belinostat has activity in patients with recurrent or refractory thymoma.

No significant financial relationships to disclose.

A phase I clinical trial of vorinostat in combination with sFULV2 in patients with refractory solid tumors

4083

Background: Thymidylate synthase (TS) over-expression is associated with 5-FU resistance. Pre-clinical studies demonstrate that vorinostat down-regulates intra-tumor TS in a dose-dependent fashion and augments 5-FU antitumor activity in xenograft models. We conducted a phase I clinical trial of an intermittent schedule of QD x 3 vorinostat in combination with a fixed dose of fluorouracil (5-FU) and leucovorin (LV) in patients (pts) with refractory solid tumors. Methods: Vorinostat was escalated in a standard 3 x 3 design in combination with a fixed dose of 5-FU and LV (simplified de Gramont regimen, sFULV2). Vorinostat was given QD x 3 on an every-2-week cycle. sFULV2 started on day 2 of vorinostat and consisted of leucovorin 400 mg/m2 i.v. over 2 hrs followed by 5-FU 400 mg/m2 bolus and 5-FU 2400 mg/m2 over 46 hrs. Results: 24 pts were enrolled: Male/Female: 11/13; ECOG 0/1: 6/18; Age: median 60 (range 42–77) yrs. 21 pts had colorectal cancer (CRC), 1 had gastric, 1 had esophageal, and 1 had anal cancer. Vorinostat dose-levels (DL) were 600 mg, 800 mg, 1000 mg, 1200 mg, 1400 mg, 1700 mg, and 2000 mg. Dose-limiting toxicities (DLT), consisting of fatigue and hand-and-foot syndrome (H&F), were seen in 2 of 3 pts at the 2000 mg DL. None of the 6 pts at the 1700 mg DL had a DLT. Cycle 1 grade 3/4 toxicities consisted of thrombocytopenia, GI bleeding, fatigue, and H&F in 2 pts at the 2000 mg DL and a non-DLT G3 diarrhea (lasted <24 hrs) in 1 pt at the 1700 mg DL. Grade 2 nausea, fatigue, and anorexia were common; especially at DL ≥ 1700 mg. Antitumor activity was noted in pts with CRC despite prior refractoriness to 5-FU and failure to oxaliplatin, irinotecan, and cetuximab in all pts. 12/21 CRC pts had a confirmed SD (11) or PR (1). CRC pts had a median PFS of 4 months, a ≥ 6 months PFS rate of 43%, and a ≥ 8 months PFS rate of 33%. Conclusions: The maximum tolerated dose (MTD) of vorinostat in combination with sFULV2 is 1700 mg PO QD x 3 every 2 weeks. This combination is associated with considerable activity in pts with 5-FU-refractory CRC and warrants further investigation. An expanded MTD cohort is accruing to investigate 5-FU-vorinostat PK interaction and intra-tumor TS down-regulation. (This work was supported by a grant from CTEP and the ACS.)

No significant financial relationships to disclose.

Bryostatin-1 and IL-2 synergize to induce IFN-gamma expression in human peripheral blood T cells: implications for cancer immunotherapy

Bryostatin-1 (Bryo-1), a protein kinase C modulator with antineoplastic activity, may exert some of its antitumor activity through activation of the immune response. Studies in tumor-bearing hosts have indicated that the T cell response, particularly IFN-gamma production, is impaired. To evaluate whether Bryo-1 plus IL-2 may affect the activation pattern of T cells, we investigated the expression of IFN-gamma mRNA and protein in human primary T cells. Northern blot analysis and ELISAs demonstrated that Bryo-1 and IL-2 synergized to induce both IFN-gamma mRNA and protein expression. This synergistic induction was seen within 3 h of treatment and with as little as 10 U/ml IL-2 and 1.0 ng/ml Bryo-1. In vitro transcription assays revealed that Bryo-1 plus IL-2 induced transcriptional activation of the IFN-gamma gene. Furthermore, mRNA stability studies indicated that this treatment also enhanced the IFN-gamma mRNA half-life. Both CD4(+) and CD8(+) T cells responded to the treatment with IFN-gamma expression. The induction of the IFN-gamma expression was decreased by a specific p38 mitogen-activated protein kinase inhibitor, but not by a protein kinase C inhibitor. Our results demonstrate for the first time that Bryo-1 in combination with IL-2 control IFN-gamma gene expression at both the transcriptional and post-transcriptional levels through a p38 mitogen-activated protein kinase-dependent process. Given the pivotal role that IFN-gamma plays in the orchestration of an effective Th1 type of response, our results suggest that Bryo-1 plus IL-2 may be a valuable combined therapy for cancer treatment.

IL-2 signaling in human monocytes involves the phosphorylation and activation of p59hck

The activating properties of IL-2 and the structure of the IL-2R on human monocytes are well characterized. However, relatively little is known about the biochemical mechanisms involved in IL-2 signal transduction in these cells. We investigated the role of protein tyrosine kinases (PTKs) in the activation of monocytes by IL-2. Incubation of monocytes with the PTK inhibitor herbimycin A (HA) resulted in the dose-dependent suppression of IL-2-induced monocyte tumoricidal activity. This inhibition was rather potent, as a concentration of HA as low as 0.5 microM caused a complete abrogation of cytolytic activity. Furthermore, HA markedly suppressed the ability of IL-2 to induce IL-1 beta, TNF-alpha, IL-6, and IL-8 mRNA expression and protein secretion by monocytes. Anti-phosphotyrosine immunoblotting demonstrated that IL-2 induced a rapid and time-dependent increase in tyrosine phosphorylation of several cellular proteins of molecular masses ranging from 35 to 180 kDa. Interestingly, IL-2 caused a significant up-regulation of the constitutive levels of hck PTK mRNA and protein relative to medium-treated cells as well as an increase in p59hck tyrosine phosphorylation. Finally, we demonstrated by in vitro kinase assay that the specific activity of p59hck PTK was also induced by IL-2 in monocytes. Thus, these data show that the activation of PTKs is required for the triggering of monocyte effector and secretory functions by IL-2 and strongly suggest that p59hck is a key participant in IL-2 signaling in human monocytes.

Enhanced B7-2 gene expression by interferon-gamma in human monocytic cells is controlled through transcriptional and posttranscriptional mechanisms

B7-2 is a costimulatory molecule expressed on professional antigen-presenting cells that provides T cells with a critical signal resulting in T-cell activation. Interferon-gamma (IFN-gamma) enhances B7-2 protein expression in monocytic cells. However, the molecular mechanisms controlling the enhanced expression of B7-2 are poorly understood. Northern blot and flow cytometry analysis revealed that human monocytes and the human monocytic cell line MonoMac6 (MM6) constitutively expressed B7-2 mRNA and protein and IFN-gamma treatment further enhanced the expression of both molecules. The ability of IFN-gamma to enhance B7-2 mRNA was evident at the dose of 31 U/mL and reached plateau levels at 500 U/mL. The effects of IFN-gamma on B7-2 mRNA expression were time dependent and occurred within 3 hours of treatment and increased through 24 hours. In vitro transcription assays and mRNA stability experiments showed that IFN-gamma increases both transcriptional activity and the stability of B7-2 mRNA. Treatment of MM6 cells with cycloheximide showed that de novo protein synthesis was not required for the IFN-gamma-enhanced expression of B7-2 mRNA. Overall, these studies show for the first time that IFN-gamma-enhanced expression of B7-2 protein in human monocytic cells is controlled at the gene level through a dual mechanism involving transcriptional and posttranscriptional mechanisms.

Functional role for the myeloid differentiation antigen CD14 in the activation of human monocytes by IL-2

Human monocytes express functional IL-2Rs and are directly activated by IL-2 to exert effector and secretory functions. In this study, we demonstrate that the myeloid differentiation Ag CD14 participates in monocyte activation by IL-2. Engagement of CD14 by specific mAbs resulted in the selective and dose-dependent suppression of IL-2-induced, but not of IFN-gamma-induced, monocyte tumoricidal activity. Furthermore, anti-CD14 mAbs effectively inhibited the secretion of IL-8 and IL-1beta in response to IL-2. Preincubation of monocytes with mAbs directed to selected epitopes on CD14 blocked the binding of IL-2 to the cell surface, providing a possible explanation for the inhibition of IL-2-triggered responses. A critical role for CD14 in IL-2-mediated monocyte activation was further demonstrated by experiments with the human U937 promonocytic cell line. These cells are negative for CD14 and unresponsive to IL-2 despite the expression of the beta and gamma subunits of the IL-2R. U937 cells acquired the capacity to respond to IL-2 following transfection with the human CD14 cDNA (U937/CD14). Stimulation of U937/CD14 cells with IL-2 up-regulated the constitutive levels of IL-8 mRNA, whereas no change in IL-8 mRNA basal expression was observed in control cells transfected with the vector alone (U937/Neo). Accordingly, increased secretion of IL-8 by U937/CD14, but not by U937/Neo cells, was detected following exposure to IL-2. Expression of IL-1beta was also augmented by IL-2 in U937/CD14 cells. These data provide the first evidence that CD14 expression is required for the response of monocytic cells to IL-2.

Functional role for the myeloid differentiation antigen CD14 in the activation of human monocytes by IL-2

Human monocytes express functional IL-2Rs and are directly activated by IL-2 to exert effector and secretory functions. In this study, we demonstrate that the myeloid differentiation Ag CD14 participates in monocyte activation by IL-2. Engagement of CD14 by specific mAbs resulted in the selective and dose-dependent suppression of IL-2-induced, but not of IFN-gamma-induced, monocyte tumoricidal activity. Furthermore, anti-CD14 mAbs effectively inhibited the secretion of IL-8 and IL-1beta in response to IL-2. Preincubation of monocytes with mAbs directed to selected epitopes on CD14 blocked the binding of IL-2 to the cell surface, providing a possible explanation for the inhibition of IL-2-triggered responses. A critical role for CD14 in IL-2-mediated monocyte activation was further demonstrated by experiments with the human U937 promonocytic cell line. These cells are negative for CD14 and unresponsive to IL-2 despite the expression of the beta and gamma subunits of the IL-2R. U937 cells acquired the capacity to respond to IL-2 following transfection with the human CD14 cDNA (U937/CD14). Stimulation of U937/CD14 cells with IL-2 up-regulated the constitutive levels of IL-8 mRNA, whereas no change in IL-8 mRNA basal expression was observed in control cells transfected with the vector alone (U937/Neo). Accordingly, increased secretion of IL-8 by U937/CD14, but not by U937/Neo cells, was detected following exposure to IL-2. Expression of IL-1beta was also augmented by IL-2 in U937/CD14 cells. These data provide the first evidence that CD14 expression is required for the response of monocytic cells to IL-2.

Bryostatin-1 and IFN-gamma synergize for the expression of the inducible nitric oxide synthase gene and for nitric oxide production in murine macrophages

Bryostatin-1 (Bryo) is a nontumor-promoting protein kinase C modulator that has been shown to have both in vitro and in vivo activity against several murine and human tumors. In this study, we investigated the effects of Bryo on nitric oxide production, measured as accumulated nitrite (NO2-) in culture supernatant, and inducible nitric oxide synthase (iNOS) gene expression in the murine macrophage cell line ANA-1. ANA-1 macrophages did not produce NO2- or iNOS mRNA constitutively, and very little or no NO2- or iNOS mRNA were detectable upon exposure to IFN-gamma. Bryo, although ineffective alone, and IFN-gamma synergized to produce high levels of NO2- and iNOS mRNA. The activity of Bryo was evident at a concentration of 0.1 ng/ml and reached its maximum at 1 ng/ml. The effects of Bryo were time dependent because expression of iNOS mRNA was detectable as early as 6 h and increased through 24 h. Analyses of the molecular mechanisms involved indicate that Bryo and IFN-gamma mainly regulate iNOS gene expression posttranscriptionally through stabilization of iNOS mRNA. Experiments designed to investigate the role of tumor necrosis factor alpha (TNF-alpha) in NO2- production by Bryo- and IFN-gamma-activated macrophages revealed that ANA-1 macrophages expressed low levels of TNF-alpha mRNA constitutively that were not augmented in the presence of IFN-gamma. However, Bryo alone augmented the TNF-alpha mRNA expression, which was only slightly increased with the addition of IFN-gamma. A polyclonal antibody to TNF-alpha was able to completely neutralize TNF-alpha secreted in either medium or Bryo plus IFN-gamma-treated cultures. Neutralizing concentrations of anti-TNF-alpha antibody suppressed the Bryo plus IFN-gamma-induced NO2- production approximately by 50%, suggesting that NO2- produced by Bryo plus IFN-gamma-treated ANA-1 macrophages may involve both TNF-alpha-dependent and TNF-alpha-independent mechanisms. Overall, these findings provide the first evidence that Bryo and IFN-gamma can synergize for the induction of NO2- production as well as iNOS gene expression and show the involvement of posttranscriptional mechanisms in the induction of iNOS mRNA.

The antineoplastic agent bryostatin-1 induces proinflammatory cytokine production in human monocytes: synergy with interleukin-2 and modulation of interleukin-2Rgamma chain expression

The antineoplastic agent bryostatin-1 (bryo-1) possesses powerful immunomodulatory properties and can function as a biological response modifier in vivo. However, there is currently little information regarding the effects of bryo-1 on cells of the monocytic lineage. In this study, we demonstrate that bryo-1 can potently induce the production of pro-inflammatory cytokines from human peripheral blood monocytes. Stimulation of monocytes with subnanomolar concentrations of bryo-1 significantly upregulated the constitutive levels of interleukin-8 (IL-8) mRNA and induced the expression of IL-1beta, tumor necrosis factor-alpha (TNF-alpha), and IL-6 mRNA in a time and dose-dependent manner. Accordingly, secretion of all four proinflammatory cytokines was induced after monocyte exposure to bryo-1. Furthermore, we showed that bryo-1 selectively synergized with IL-2 in triggering monocyte activation, and this effect seemed to be dependent, at least in part, on the ability of bryo-1 to upregulate IL-2Rgamma chain expression. Finally, we demonstrated that the responses of monocytes to bryo-1 could be blocked by the protein kinase C (PKC) inhibitors staurosporine and UCN-01, indicating a role for PKC in monocyte activation by bryo-1. These results show for the first time that bryo-1 is a powerful activator of human monocytes and suggest that stimulation of monokine secretion by bryo-1 may represent at least one of the mechanisms responsible for the in vivo antitumor activity of this drug.

IL-4 inhibits IL-2-induced tumoricidal activity and secretory functions of human monocytes. Modulation of IL-2 binding and IL-2 receptor beta gamma chain expression

Human monocytes express functional IL-2 receptors (IL-2R) and are directly activated by IL-2 to exert effector and secretory functions. In this study, we show that IL-4 selectively suppressed, in a dose-dependent manner, IL-2-induced monocyte tumoricidal activity, without affecting IFN-gamma-dependent cytotoxicity. This effect was specific because a neutralizing anti-IL-4 mAb completely restored IL-2-activated cytolysis. Furthermore, IL-4 effectively blocked the secretion of proinflammatory cytokines by IL-2-stimulated monocytes. Binding studies with biotin-conjugated IL-2 demonstrated that monocyte stimulation with IL-2 increased IL-2 binding to the cell surface, and that treatment with IL-4 inhibited this augmentation, providing a possible explanation for the decreased responsiveness of monocytes to IL-2 in the presence of IL-4. However, IL-4 suppressive effects could not be ascribed to the down-regulation of the individual components of the IL-2R complex. In fact, co-treatment of monocytes with IL-2 and IL-4 increased the expression of IL-2R gamma chain above the levels induced by IL-2 alone, whereas it did not significantly affect the expression of IL-2R beta chain. Thus, the inhibition of IL-2 binding by IL-4 may be due to the recruitment of the gamma chain into the IL-4-IL-4R system, making it unavailable for participation in the formation of IL-2 binding sites. These findings provide the first evidence of the ability of IL-4 to suppress IL-2-mediated activation of human monocytes and suggest that IL-4 may play an important role in vivo as an inhibitory signal that controls the response of monocytes to IL-2.

IL-4 inhibits IL-2-induced tumoricidal activity and secretory functions of human monocytes. Modulation of IL-2 binding and IL-2 receptor beta gamma chain expression

Human monocytes express functional IL-2 receptors (IL-2R) and are directly activated by IL-2 to exert effector and secretory functions. In this study, we show that IL-4 selectively suppressed, in a dose-dependent manner, IL-2-induced monocyte tumoricidal activity, without affecting IFN-gamma-dependent cytotoxicity. This effect was specific because a neutralizing anti-IL-4 mAb completely restored IL-2-activated cytolysis. Furthermore, IL-4 effectively blocked the secretion of proinflammatory cytokines by IL-2-stimulated monocytes. Binding studies with biotin-conjugated IL-2 demonstrated that monocyte stimulation with IL-2 increased IL-2 binding to the cell surface, and that treatment with IL-4 inhibited this augmentation, providing a possible explanation for the decreased responsiveness of monocytes to IL-2 in the presence of IL-4. However, IL-4 suppressive effects could not be ascribed to the down-regulation of the individual components of the IL-2R complex. In fact, co-treatment of monocytes with IL-2 and IL-4 increased the expression of IL-2R gamma chain above the levels induced by IL-2 alone, whereas it did not significantly affect the expression of IL-2R beta chain. Thus, the inhibition of IL-2 binding by IL-4 may be due to the recruitment of the gamma chain into the IL-4-IL-4R system, making it unavailable for participation in the formation of IL-2 binding sites. These findings provide the first evidence of the ability of IL-4 to suppress IL-2-mediated activation of human monocytes and suggest that IL-4 may play an important role in vivo as an inhibitory signal that controls the response of monocytes to IL-2.

Interleukin-2 and human monocyte activation

The recognition of the monocyte/macrophage-activating properties of IL-2 has broadened our image of the biological effects of this lymphokine from those of a T cell growth factor to those of a molecule with pleiotropic effects. The detailed analysis of the mechanisms of action of IL-2 including its biological effects on different cell types and the regulation of its receptors has increased dramatically the spectrum of the biological responses that can be modified by IL-2. The regulation of the expression of the IL-2 receptor subunits differs in terms of response to extracellular stimuli and intracellular control, suggesting that the response to IL-2 will vary depending on the nature and extent of environmental stimulation. Furthermore, the fact that the IL-2R gamma chain can be part of the receptor for IL-4, IL-7, and perhaps other cytokines indicates that IL-2 may modulate the response of monocytes simply by binding or releasing the IL-2R gamma chain and thus modulating the responsiveness to IL-4 or IL-7. Conversely, the extent of utilization of IL-2R gamma chain by various cytokines may dictate the monocytic response to IL-2. In fact, the availability of IL-2R gamma chain seems to be the limiting factor in the response of monocytes to IL-2. Modulation of cytokine receptors is an integral part of the control of the IL-2 response. The induction of CSF-1 receptor by IL-2 and the positive effect of CSF-1 on the duration of the cytotoxic response in IL-2-stimulated monocytes are an interesting example of a synergistic interaction of potential physiological relevance. The response of monocytes to IL-2 can also be modulated by inhibitory circuits, such as those involving TGF-beta 1, IFN-gamma, and IL-4. However, IFN-gamma and IL-4 can also activate monocytes and the timing and relative concentrations of the various cytokines may be critical variables in determining the ultimate monocyte phenotype. These studies have given us a glimpse of a very complex picture composed of multiple backgrounds and several players. However, the present information is not sufficient to make meaningful predictions of the resulting monocyte phenotype in an inflammatory reaction in which multiple cytokines are involved.(ABSTRACT TRUNCATED AT 400 WORDS)

LPS-inducible nuclear factor in human monocytes that binds the negative regulatory element of the HIV LTR

We studied the constitutive and lipopolysaccharide (LPS)-induced expression of nuclear protein binding to the negative regulatory element (NRE) of the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) in fresh human monocytes. We demonstrated the existence of a constitutive factor binding to the NRE 73-bp HpaII/HpaII fragment (-216 to -143) whose expression is up-regulated by LPS treatment. Competition experiments with overlapping oligonucleotides covering the HpaII/HpaII fragment and with mutated oligonucleotides mapped the binding within the TTTCATCAC region (-171 to -163). This binding pattern is unique to human monocytes.

The gamma subunit of the interleukin-2 receptor is expressed in human monocytes and modulated by interleukin-2, interferon gamma, and transforming growth factor beta 1

The interleukin-2 receptor gamma (IL-2R gamma) chain is a newly recognized component of the IL-2R of lymphoid cells that is required for their response to IL-2. We investigated the expression of IL-2R gamma protein in human monocytes by Western blot analysis using an antiserum specific for IL-2R gamma. We found that IL-2R gamma subunit is constitutively expressed in human monocytes and upregulated by the monocyte-activating factors IL-2 and interferon gamma (IFN gamma). Furthermore, we show that transforming growth factor beta 1 (TGF beta 1) downmodulates, in a dose-dependent manner, basal and IL-2-induced, but not IFN gamma-induced, IL-2R gamma chain expression, and this effect may be responsible for TGF beta 1 suppressive activity on IL-2-activated monocytes. Overall, these results show that the expression of the IL-2R gamma subunit in human monocytes is tightly regulated by the cytokine network, suggesting a critical role played by this protein on monocyte activation.

Inhibitory cytokine circuits involving transforming growth factor-beta, interferon-gamma, and interleukin-2 in human monocyte activation

We have previously reported that transforming growth factor-beta 1 (TGF-beta 1) inhibits interleukin-6 (IL-6) induction by IL-2 and IL-1 in fresh human monocytes. We investigated the effects of TGF-beta 1 on the expression of tumoricidal activity induced by IL-2 or interferon-gamma (IFN-gamma) in human monocytes. We showed that TGF-beta 1 specifically inhibited, in a dose-dependent manner, IL-2-induced but not IFN-gamma-induced monocyte tumoricidal activity. The inhibitory effects of TGF-beta 1 on IL-2-activated monocytes were not caused by down-modulation of the IL-2 receptor beta (IL-2R beta) because the treatment of monocytes with IL-2 and TGF-beta 1 increased IL-2R beta mRNA expression. However, we found that TGF-beta 1 down-modulated IL-2-induced IL-2R gamma mRNA, which may be responsible for the TGF-beta 1 inhibition of monocyte activation by IL-2. The resistance of the IFN-gamma-induced activation to the inhibitory effects of TGF-beta 1 could be caused by the ability of IFN-gamma to decrease TGF-beta 1 receptor expression, as shown by cross-linking experiments. Overall, these results showed that TGF-beta 1 is a powerful inhibitor of IL-2- but not of IFN-gamma-induced activation of monocytes to a cytotoxic stage. This differential effect may be attributed to modulation of cytokine receptor expression.

Regulation by interleukin-2 (IL-2) and interferon gamma of IL-2 receptor gamma chain gene expression in human monocytes

The interleukin-2 receptor gamma chain (IL-2R gamma) gene codes for a subunit of the IL-2R and is expressed in human lymphoid cells. The present study was undertaken to determine whether human monocytes expressed the IL-2R gamma gene constitutively or after activation by IL-2 or interferon gamma (IFN gamma). Fresh human monocytes constitutively expressed low but significant levels of IL-2R gamma mRNA, and nuclear run-on experiments showed that IL-2R gamma gene was transcriptionally active. Stimulation with IL-2 or IFN gamma induced a major increase of IL-2R gamma mRNA in a time- and a dose-dependent manner. However, neither cytokine increased the transcriptional activity of the gene. The enhancement of IL-2R gamma mRNA expression by either IL-2 or IFN gamma was concomitant with the stabilization of the mRNA, suggesting a postranscriptional level of control. Finally, the augmented expression of IL-2R gamma in IL-2- and IFN gamma-treated monocytes was associated with an increased IL-2-binding activity, compared with that of unstimulated cells. These results provide the first evidence of the expression of the IL-2R gamma gene in nonlymphoid cells and of its modulation by IL-2 and IFN gamma through posttranscriptional mechanisms.

Interferon-gamma upregulates interleukin-8 gene expression in human monocytic cells by a posttranscriptional mechanism

Interleukin-8 (IL-8) is a neutrophil chemotactic and activating cytokine that is produced in response to several stimuli. Because monocytic cells are important producers of IL-8, we investigated whether interferon-gamma (IFN-gamma), a potent inducer of activation and differentiation of mononuclear phagocytes, affected IL-8 expression in this cell lineage. We found a low constitutive level of IL-8 mRNA expression that was upregulated by IFN-gamma in a dose- and time-dependent manner and via a protein-synthesis-dependent process in the human monocytic cell line U937. IL-8 protein secretion was also stimulated by IFN-gamma. Nuclear run-on experiments showed that the IL-8 gene was transcriptionally active in control cells and that IFN-gamma did not enhance the transcriptional activity. The increase in IL-8 mRNA by IFN-gamma was concomitant with the stabilization of the mRNA and, therefore, controlled primarily at a posttranscriptional level. These results represent the first evidence that IFN-gamma upregulates IL-8 gene expression in cells of the monocytic lineage, and show the involvement of posttranscriptional mechanisms in the induction of IL-8 mRNA.

IL-2 up-regulates but IFN-gamma suppresses IL-8 expression in human monocytes

IL-2 has pleiotropic properties and is a potent activator of monocytic functions. Since monocytes are an important source of the chemoattractant cytokine IL-8, we studied the effects of IL-2 on the expression of IL-8 in human monocytes. IL-8 mRNA expression was detectable in resting human monocytes. Treatment of monocytes with IL-2 increased IL-8 mRNA expression by a protein synthesis-independent process. The augmentation of IL-8 mRNA by IL-2 was associated with an increase in IL-8 secretion. The expression of IL-8 mRNA was not a nonspecific response to any stimulus of monocyte activation. In fact, IFN-gamma, which is also a potent monocyte activator, not only failed to induce IL-8 expression but inhibited the stimulation of IL-8 by IL-2. Nuclear run-on experiments demonstrated that both the enhancement of IL-8 mRNA expression and its down-regulation by IFN-gamma occurred at the transcriptional level. These results show for the first time that in fresh human monocytes, IL-8 expression is differentially regulated by IL-2 and IFN-gamma and suggest that the interactions among IL-2, IL-8, and IFN-gamma may be important for the development and control of the inflammatory response.

IL-2 up-regulates but IFN-gamma suppresses IL-8 expression in human monocytes

IL-2 has pleiotropic properties and is a potent activator of monocytic functions. Since monocytes are an important source of the chemoattractant cytokine IL-8, we studied the effects of IL-2 on the expression of IL-8 in human monocytes. IL-8 mRNA expression was detectable in resting human monocytes. Treatment of monocytes with IL-2 increased IL-8 mRNA expression by a protein synthesis-independent process. The augmentation of IL-8 mRNA by IL-2 was associated with an increase in IL-8 secretion. The expression of IL-8 mRNA was not a nonspecific response to any stimulus of monocyte activation. In fact, IFN-gamma, which is also a potent monocyte activator, not only failed to induce IL-8 expression but inhibited the stimulation of IL-8 by IL-2. Nuclear run-on experiments demonstrated that both the enhancement of IL-8 mRNA expression and its down-regulation by IFN-gamma occurred at the transcriptional level. These results show for the first time that in fresh human monocytes, IL-8 expression is differentially regulated by IL-2 and IFN-gamma and suggest that the interactions among IL-2, IL-8, and IFN-gamma may be important for the development and control of the inflammatory response.

Regulation of IL-2 receptor subunit genes in human monocytes. Differential effects of IL-2 and IFN-gamma

We investigated the effects of IFN-gamma and IL-2 on IL-2R alpha and beta mRNA expression in human monocytes. Low basal expression of IL-2R beta mRNA was detected in fresh monocytes. Stimulation of monocytes with IL-2 induced a significant increase of IL-2R beta mRNA, but did not induce IL-2R alpha mRNA. In contrast, stimulation of monocytes with IFN-gamma-induced IL-2R alpha mRNA, but did not modify IL-2R beta mRNA. Five U/ml of IFN-gamma induced IL-2R alpha mRNA and 2.2 nM of IL-2 induced IL-2R beta mRNA, both within 3 h. Nuclear run-on experiments demonstrated that the induction of IL-2R alpha mRNA by IFN-gamma is controlled, at least in part, at the transcriptional level. In contrast, the enhancement of IL-2R beta mRNA by IL-2 is controlled at a posttranscriptional level and is associated with an increase in the half-life of IL-2R beta mRNA. The results of studies on the cytotoxic activity and on the expression of c-fms mRNA of monocytes activated by the combination of IFN-gamma and IL-2 show that pretreatment with IFN-gamma renders monocytes more sensitive to activation by IL-2. These results demonstrate that the IL-2R alpha and IL-2R beta subunits are induced by different lymphokines through distinct mechanisms and that both receptor subunits can influence the response of monocytes to IL-2.

Regulation of IL-2 receptor subunit genes in human monocytes. Differential effects of IL-2 and IFN-gamma

We investigated the effects of IFN-gamma and IL-2 on IL-2R alpha and beta mRNA expression in human monocytes. Low basal expression of IL-2R beta mRNA was detected in fresh monocytes. Stimulation of monocytes with IL-2 induced a significant increase of IL-2R beta mRNA, but did not induce IL-2R alpha mRNA. In contrast, stimulation of monocytes with IFN-gamma-induced IL-2R alpha mRNA, but did not modify IL-2R beta mRNA. Five U/ml of IFN-gamma induced IL-2R alpha mRNA and 2.2 nM of IL-2 induced IL-2R beta mRNA, both within 3 h. Nuclear run-on experiments demonstrated that the induction of IL-2R alpha mRNA by IFN-gamma is controlled, at least in part, at the transcriptional level. In contrast, the enhancement of IL-2R beta mRNA by IL-2 is controlled at a posttranscriptional level and is associated with an increase in the half-life of IL-2R beta mRNA. The results of studies on the cytotoxic activity and on the expression of c-fms mRNA of monocytes activated by the combination of IFN-gamma and IL-2 show that pretreatment with IFN-gamma renders monocytes more sensitive to activation by IL-2. These results demonstrate that the IL-2R alpha and IL-2R beta subunits are induced by different lymphokines through distinct mechanisms and that both receptor subunits can influence the response of monocytes to IL-2.

IL-2 induces IL-6 production in human monocytes

IL-2 is a potent activator of effector and secretory activities of human monocytes. Since monocytes are an important source of IL-6, we investigated whether IL-2 can induce IL-6 production and whether regulatory circuits can modulate this process. We found that stimulation of monocytes with IL-2 induced expression of IL-6 mRNA and bioactivity in a dose-dependent manner. Production of IL-6 in monocytes can be induced by other cytokines such as IL-1 beta. By using mAb alpha-IL-1 beta we showed that IL-2-induced IL-6 production is not mediated by the autocrine stimulation of IL-1 beta elicited by IL-2. IL-6 induction by monocytes is not a common response to activating signals because IFN-gamma did not induce IL-6 expression under conditions in which it elicits tumoricidal activity. In contrast, IFN-gamma could completely abrogate the induction of IL-6 expression by IL-1 beta but did not affect the levels of mRNA and the secretion of IL-2-elicited IL-6. We have previously reported that transforming growth factor-beta inhibits IL-6 production in response to IL-1 beta. Studies on the inhibitory activity of transforming growth factor-beta demonstrated that this cytokine differs from IFN-gamma because it inhibited both IL-1- and IL-2-induced IL-6 expression. These data demonstrate that, in human monocytes, both IL-1 and IL-2 stimulate IL-6 expression by independent mechanisms that can be dissociated by the susceptibility to the inhibitory effect of IFN-gamma. IL-6 production is also down-regulated by TGF-beta, whose inhibitory activity is stimulus-unrelated.

IL-2 induces IL-6 production in human monocytes

IL-2 is a potent activator of effector and secretory activities of human monocytes. Since monocytes are an important source of IL-6, we investigated whether IL-2 can induce IL-6 production and whether regulatory circuits can modulate this process. We found that stimulation of monocytes with IL-2 induced expression of IL-6 mRNA and bioactivity in a dose-dependent manner. Production of IL-6 in monocytes can be induced by other cytokines such as IL-1 beta. By using mAb alpha-IL-1 beta we showed that IL-2-induced IL-6 production is not mediated by the autocrine stimulation of IL-1 beta elicited by IL-2. IL-6 induction by monocytes is not a common response to activating signals because IFN-gamma did not induce IL-6 expression under conditions in which it elicits tumoricidal activity. In contrast, IFN-gamma could completely abrogate the induction of IL-6 expression by IL-1 beta but did not affect the levels of mRNA and the secretion of IL-2-elicited IL-6. We have previously reported that transforming growth factor-beta inhibits IL-6 production in response to IL-1 beta. Studies on the inhibitory activity of transforming growth factor-beta demonstrated that this cytokine differs from IFN-gamma because it inhibited both IL-1- and IL-2-induced IL-6 expression. These data demonstrate that, in human monocytes, both IL-1 and IL-2 stimulate IL-6 expression by independent mechanisms that can be dissociated by the susceptibility to the inhibitory effect of IFN-gamma. IL-6 production is also down-regulated by TGF-beta, whose inhibitory activity is stimulus-unrelated.

Halothane potentiates the antitumor activity of gamma-interferon and mimics calmodulin-blocking agents

This study reports effects of halothane on tumor cells in vitro. Cells from the human colon cancer cell line HT-29 were exposed to various concentrations of halothane for 8-72 h. The effect of this exposure on this colon cancer cell line, with and without coincubation with the biologic response modifier gamma-interferon (IFN-gamma), was studied. Using the tumor target cell survival (TTCS) assay, concentrations of halothane from 0.5 to 2% markedly augmented the antitumor activities of IFN-gamma against HT-29. The tumor cell cytostatic effects of IFN-gamma in the 0.75-6-unit/ml range were increased nearly 400% by concentrations of halothane as low as 1%. These results were confirmed in a separate cytolytic assay (Indium-111 release assay), which revealed that halothane concentrations in the 2-4% range markedly increased the cytolytic capacity of IFN-gamma at doses of IFN-gamma between 75 and 1,250 units/ml. The cytolytic activity of IFN-gamma was increased nearly 300% by doses of halothane as low as 1%. A nearly identical pattern of augmentation of IFN-gamma-induced antitumor activity was observed when the known calmodulin inhibitor trifluoperazine (TFP) was coincubated with IFN-gamma. At concentrations of 4-10 microM, the antitumor activity of IFN-gamma was increased nearly 400%. These observations suggest that the pattern of halothane potentiation of the antitumor activity of IFN-gamma is similar to that exhibited by known calmodulin inhibitors.

Transforming growth factor beta downregulates interleukin-1 (IL-1)-induced IL-6 production by human monocytes

We investigated the effects of transforming growth factor beta (TGF beta) on the induction by interleukin-1 beta (IL-1 beta) of IL-6 in human monocytes. We found that IL-1 beta induced IL-6 messenger RNA expression in elutriated monocytes and IL-6 secretion in the supernatant. TGF beta did not induce IL-6. In contrast, TGF beta added to the culture inhibited, in a dose-dependent manner, the induction of IL-6 by IL-1 at the level of messenger RNA and bioactivity. These results show that IL-1 beta is able to stimulate IL-6 production by monocytes, TGF beta, by inhibiting this effect, may play an important role in regulating the IL-1-mediated components of the inflammatory response.

IL-2 enhances c-fms expression in human monocytes

We investigated the effects of IL-2 and IFN-gamma on the expression of the proto-oncogene c-fms mRNA, which encodes for the macrophage CSF receptor. Low constitutive expression of c-fms mRNA was detected in fresh human monocytes. Stimulation of monocytes with IL-2 induced a significant increase in c-fms mRNA relative to medium control that was observed as early as 6 h after IL-2 stimulation. Dose-response experiments showed that 100 U/ml of IL-2 were sufficient to enhance the expression of c-fms mRNA. In contrast, IFN-gamma did not modify the levels of c-fms transcript. Immunoprecipitation experiments demonstrated that IL-2 enhanced c-fms glycoprotein levels. Experiments in which monocytes were activated with IFN-gamma or IL-2 followed by macrophage CSF-1 and then tested for tumoricidal activity demonstrated that macrophage CSF-1 sustained the cytotoxic activity induced by IL-2 but not by IFN-gamma. These data demonstrate that IL-2 enhances c-fms mRNA and c-fms glycoprotein expression suggesting that IL-2, by augmenting expression of macrophage CSF-1 receptors, can lead to prolongation of monocyte-mediated tumoricidal activity obtained in the presence of exogenous macrophage CSF-1.

IL-2 enhances c-fms expression in human monocytes

We investigated the effects of IL-2 and IFN-gamma on the expression of the proto-oncogene c-fms mRNA, which encodes for the macrophage CSF receptor. Low constitutive expression of c-fms mRNA was detected in fresh human monocytes. Stimulation of monocytes with IL-2 induced a significant increase in c-fms mRNA relative to medium control that was observed as early as 6 h after IL-2 stimulation. Dose-response experiments showed that 100 U/ml of IL-2 were sufficient to enhance the expression of c-fms mRNA. In contrast, IFN-gamma did not modify the levels of c-fms transcript. Immunoprecipitation experiments demonstrated that IL-2 enhanced c-fms glycoprotein levels. Experiments in which monocytes were activated with IFN-gamma or IL-2 followed by macrophage CSF-1 and then tested for tumoricidal activity demonstrated that macrophage CSF-1 sustained the cytotoxic activity induced by IL-2 but not by IFN-gamma. These data demonstrate that IL-2 enhances c-fms mRNA and c-fms glycoprotein expression suggesting that IL-2, by augmenting expression of macrophage CSF-1 receptors, can lead to prolongation of monocyte-mediated tumoricidal activity obtained in the presence of exogenous macrophage CSF-1.

Lipopolysaccharide, but not IFN-gamma, down-regulates c-fms mRNA proto-oncogene expression in murine macrophages

In the present study we analyzed the effects of two macrophage activators, bacterial LPS and IFN-gamma, on the expression of the c-fms proto-oncogene in the immortalized murine macrophage cell line ANA-1. ANA-1 cells constitutively expressed significant levels of c-fms mRNA. LPS stimulation induced down-regulation of the expression of c-fms mRNA. In contrast, IFN-gamma did not change c-fms expression. Combined treatment of ANA-1 with IFN-gamma plus LPS resulted in a decrease in c-fms mRNA greater than that induced by LPS alone. Nuclear runoff experiments demonstrated that the down-regulation of c-fms mRNA by LPS or LPS plus IFN-gamma was controlled at a transcriptional level. Moreover, experiments in which c-fms mRNA expression was evaluated after the block of RNA or of protein synthesis did not reveal any difference in c-fms mRNA stability in LPS-treated and in untreated cells. These results demonstrate that LPS does not affect the stability of c-fms mRNA, but it decreases the transcription of the gene.

Expression and role of p75 interleukin 2 receptor on human monocytes

We investigated the expression of IL-2R subunits in human monocytes using the TU27 mAb, which recognizes the p75 chain, and anti-Tac mAb, which recognizes the p55 moiety of the IL-2R. We found that p75 but not p55 is constitutively expressed in more than 90% of fresh human monocytes. Antibody to p75, but not to p55, inhibited the activation of monocytes to a cytotoxic stage induced by IL-2 but did not block IFN-gamma-induced cytotoxicity. Our data demonstrate that the p75 chain is expressed on human monocytes and is involved in the activation of monocytes by IL-2.

Lipopolysaccharide, but not IFN-gamma, down-regulates c-fms mRNA proto-oncogene expression in murine macrophages

In the present study we analyzed the effects of two macrophage activators, bacterial LPS and IFN-gamma, on the expression of the c-fms proto-oncogene in the immortalized murine macrophage cell line ANA-1. ANA-1 cells constitutively expressed significant levels of c-fms mRNA. LPS stimulation induced down-regulation of the expression of c-fms mRNA. In contrast, IFN-gamma did not change c-fms expression. Combined treatment of ANA-1 with IFN-gamma plus LPS resulted in a decrease in c-fms mRNA greater than that induced by LPS alone. Nuclear runoff experiments demonstrated that the down-regulation of c-fms mRNA by LPS or LPS plus IFN-gamma was controlled at a transcriptional level. Moreover, experiments in which c-fms mRNA expression was evaluated after the block of RNA or of protein synthesis did not reveal any difference in c-fms mRNA stability in LPS-treated and in untreated cells. These results demonstrate that LPS does not affect the stability of c-fms mRNA, but it decreases the transcription of the gene.