Novel role of Stat1 in the development of docetaxel resistance in prostate tumor cells

A major obstacle for clinicians in the treatment of advanced prostate cancer is the inevitable progression to chemoresistance, especially to docetaxel. It is essential to understand the molecular events that lead to docetaxel resistance in order to identify means to prevent or interfere with chemoresistance. In initial attempts to detect these events, we analysed genomic differences between non-resistant and docetaxel-resistant prostate tumor cells and, of the genes modulated by docetaxel treatment, we observed Stat1 and clusterin gene expression heightened in the resistant phenotype. In this study, we provide biochemical and biological evidence that these two gene products are related. Stat1 and clusterin protein expression was induced upon docetaxel treatment of DU145 cells and highly overexpressed in the docetaxel-resistant DU145 cells (DU145-DR). The increase in total Stat1 corresponded to an increase in phosphorylated Stat1. Interestingly, there was no detectable difference between DU145 and DU145-DR cells expression of total Stat3 and phosphorylated Stat3. Treatment of DU145-DR cells with small interfering RNA targeted for Stat1 not only resulted in the knockdown of Stat1 expression, but it also caused the inhibition of clusterin expression. Thus, Stat1 appears to play a key role in the regulation of clusterin. Remarkably, inhibition of Stat1 or clusterin expression resulted in the re-sensitization of DU145-DR cells to docetaxel. These results offer the first evidence that Stat1, and its subsequent regulation of clusterin, are essential for docetaxel resistance in prostate cancer. Targeting this pathway could be a potential therapeutic means for intervention of docetaxel resistance.

Cooperative regulation of Mcl-1 by Janus kinase/stat and phosphatidylinositol 3-kinase contribute to granulocyte-macrophage colony-stimulating factor-delayed apoptosis in human neutrophils

Polymorphonuclear neutrophils (PMN) are phagocytic cells constitutively programmed for apoptotic cell death. Exposure to GM-CSF delays apoptosis as measured by annexin-V staining and cell morphological change. We found that STAT5B, STAT1, and STAT3 DNA-binding activity was induced by GM-CSF. We also detected activation of the phosphatidylinositol 3-kinase (PI 3-kinase) pathway after GM-CSF treatment which was inhibited by treatment with the PI 3-kinase inhibitors, wortmannin and LY294002. We investigated whether STAT or PI 3-kinase activity was necessary for the pro-survival response of GM-CSF in PMN. Exposure of PMN to GM-CSF in the presence of either AG-490, antisense STAT3 oligonucleotides, or wortmannin resulted in a partial inhibition of GM-CSF-mediated pro-survival activity. GM-CSF induced a time-dependent increase in the mRNA and protein expression of the anti-apoptotic Bcl-2-family protein, Mcl-1. We examined the hypothesis that Janus kinase/STAT and PI 3-kinase regulation of Mcl-1 contributed to GM-CSF-delayed apoptosis. Using either AG-490 or wortmannin alone, we observed a dose-dependent inhibition of GM-CSF-induced Mcl-1 expression. Using suboptimal doses of AG-490 and wortmannin, we found that both drugs together had an additive effect on delayed apoptosis and Mcl-1 expression. These data suggest that cooperative regulation of Mcl-1 by the Janus kinase/STAT and PI 3-kinase pathways contribute to GM-CSF-delayed apoptosis.

Immune-type receptor genes in zebrafish share genetic and functional properties with genes encoded by the mammalian leukocyte receptor cluster

An extensive, highly diversified multigene family of novel immune-type receptor (nitr) genes has been defined in Danio rerio (zebrafish). The genes are predicted to encode type I transmembrane glycoproteins consisting of extracellular variable (V) and V-like C2 (V/C2) domains, a transmembrane region and a cytoplasmic tail. All of the genes examined encode immunoreceptor tyrosine-based inhibition motifs in the cytoplasmic tail. Radiation hybrid panel mapping and analysis of a deletion mutant line (b240) indicate that a minimum of approximately 40 nitr genes are contiguous in the genome and span approximately 0.6 Mb near the top of zebrafish linkage group 7. One flanking region of the nitr gene complex shares conserved synteny with a region of mouse chromosome 7, which shares conserved synteny with human 19q13.3-q13.4 that encodes the leukocyte receptor cluster. Antibody-induced crosslinking of Nitrs that have been introduced into a human natural killer cell line inhibits the phosphorylation of mitogen-activated protein kinase that is triggered by natural killer-sensitive tumor target cells. Nitrs likely represent intermediates in the evolution of the leukocyte receptor cluster.

Retinoblastoma protein activation of interleukin 8 expression inhibits tumor cell survival in nude mice

Loss of retinoblastoma protein (Rb) has been implicated in the formation of a variety of human malignancies. Restoration of Rb expression in the cell lines representing these tumors eliminates or significantly reduces tumorigenicity in nude mice, but the mechanism for this Rb effect is unknown. Results from this study indicated that Rb expression reduced tumor cell survival in nude mice by dramatically enhancing interleukin 8 (IL-8) secretion. IL-8 secreted by the Rb-transformed cells attracted neutrophils in vitro and tumor-infiltrating neutrophils in vivo, which is consistent with the Rb-mediated tumor regression being dependent on IL-8. The apparent, contradictory roles of IL-8 as a protumorigenic and antitumorigenic cytokine are discussed.

Pivotal role of phosphoinositide-3 kinase in regulation of cytotoxicity in natural killer cells

The mitogen-activated protein kinase-extracellular signal-regulated kinase signaling element (MAPK-ERK) plays a critical role in natural killer (NK) cell lysis of tumor cells, but its upstream effectors were previously unknown. We show that inhibition of phosphoinositide-3 kinase (PI3K) in NK cells blocks p21-activated kinase 1 (PAK1), MAPK kinase (MEK) and ERK activation by target cell ligation, interferes with perforin and granzyme B movement toward target cells and suppresses NK cytotoxicity. Dominant-negative N17Rac1 and PAK1 mimic the suppressive effects of PI3K inhibitors, whereas constitutively active V12Rac1 has the opposite effect. V12Rac1 restores the activity of downstream effectors and lytic function in LY294002- or wortmannin-treated, but not PD98059-treated, NK cells. These results document a specific PI3K-->Rac1-->PAK1-->MEK-->ERK pathway in NK cells that effects lysis.

IL-2 induces the association of IL-2Rbeta, lyn, and MAP kinase ERK-1 in human neutrophils

IL-2, first identified as a T cell growth factor, has been proven to activate many cell types including polymorphonuclear neutrophils (PMN3). However, the mechanisms involved in PMN activation, especially the signaling pathways used by the IL-2R, are currently unknown. Here we demonstrate that IL-2 has the ability to induce protein tyrosine kinases in human PMN, and we provide the first evidence that lyn kinase is activated and physically associated with MAP kinase/ERK1. Co-immunoprecipitation experiments with anti-IL-2Rbeta and Western blotting with anti-p53/56lym revealed that lyn protein was present in IL-2R precipitates and that the association of lyn with IL-2Rbeta was markedly elevated by IL-2 stimulation. Furthermore the activity of lyn kinase, evaluated by an in vitro kinase assay with enolase as a substrate, increased following IL-2 stimulation. Another important finding was that, upon IL-2 activation, MAPK/ERK1 was also phosphorylated in PMN. A direct association between lyn and ERK1 was initially demonstrated by co-immunoprecipitation/Western blotting and then definitively proven by the use of a GST-ERK1 fusion protein. We showed that ERK1 binds lyn only in IL-2 stimulated PMN, but not in unstimulated PMN. These results suggest that IL-2 can promote the association of lyn protein tyrosine kinase with IL-2Rbeta as well as the direct binding of MAPK/ERK1 to lyn. The signaling pathway utilized by human PMN in response to IL-2 may thus involve the association of lyn with IL-2Rbeta and the activation process also triggers the recruitment and activation of a specific ERK.

Direct tumor lysis by NK cells uses a Ras-independent mitogen-activated protein kinase signal pathway

Destruction of tumor cells is a key function of lymphocytes, but the molecular processes driving it are unclear. Analysis of signal molecules indicated that mitogen-activated protein kinase (MAPK)/extracellular regulated kinase 2 critically controlled lytic function in human NK cells. We now have evidence to indicate that target ligation triggers a Ras-independent MAPK pathway that is required for lysis of the ligated tumor cell. Target engagement caused NK cells to rapidly activate MAPK within 5 min, and PD098059 effectively blocked both MAPK activation and tumoricidal function in NK cells. Target engagement also rapidly activated Ras, detected as active Ras-GTP bound to GST-Raf-RBD, a GST fusion protein linked to the Raf protein fragment containing the Ras-GTP binding domain. However, Ras inactivation by pharmacological disruption with the farnesyl transferase inhibitor, FTI-277, had no adverse effect on the ability of NK cells to lyse tumor cells or to express MAPK activation upon target conjugation. Notably, MAPK inactivation with PD098059, but not Ras inactivation with FTI-277, could interfere with perforin and granzyme B polarization within NK cells toward the contacted target cell. Using vaccinia delivery of N17 Ras into NK cells, we demonstrated that IL-2 activated a Ras-dependent MAPK pathway, while target ligation used a Ras-independent MAPK pathway to trigger lysis in NK cells.

Chronic neutropenia mediated by fas ligand

Chronic neutropenia, often associated with rheumatoid arthritis, is a characteristic finding in large granular lymphocyte (LGL) leukemia. The mechanism of neutropenia is not known. Normal neutrophil survival is regulated by the Fas-Fas ligand apoptotic system. We hypothesized that neutropenia in LGL leukemia is mediated by dysregulated expression of Fas ligand. Levels of Fas ligand in serum samples from patients with LGL leukemia were measured with a Fas ligand enzyme-linked immunosorbent assay. The effects of serum from patients with LGL leukemia on apoptosis of normal neutrophils were determined by flow cytometry and morphologic assessment. High levels of circulating Fas ligand were detected in 39 of 44 serum samples from patients with LGL leukemia. In contrast, Fas ligand was undetectable in 10 samples from healthy donors. Serum from the patients triggered apoptosis of normal neutrophils that depended partly on the Fas pathway. Resolution of neutropenia was associated with disappearance or marked reduction in Fas ligand levels in 10 of 11 treated patients. These data suggest that high levels of Fas ligand are a pathogenetic mechanism in human disease. (Blood. 2000;95:3219-3222)

Requirement for Ras/Rac1-mediated p38 and c-Jun N-terminal kinase signaling in Stat3 transcriptional activity induced by the Src oncoprotein

Signal transducers and activators of transcription (STATs) are transcription factors that mediate normal biologic responses to cytokines and growth factors. However, abnormal activation of certain STAT family members, including Stat3, is increasingly associated with oncogenesis. In fibroblasts expressing the Src oncoprotein, activation of Stat3 induces specific gene expression and is required for cell transformation. Although the Src tyrosine kinase induces constitutive Stat3 phosphorylation on tyrosine, activation of Stat3-mediated gene regulation requires both tyrosine and serine phosphorylation of Stat3. We investigated the signaling pathways underlying the constitutive Stat3 activation in Src oncogenesis. Expression of Ras or Rac1 dominant negative protein blocks Stat3-mediated gene regulation induced by Src in a manner consistent with dependence on p38 and c-Jun N-terminal kinase (JNK). Both of these serine/threonine kinases and Stat3 serine phosphorylation are constitutively induced in Src-transformed fibroblasts. Furthermore, inhibition of p38 and JNK activities suppresses constitutive Stat3 serine phosphorylation and Stat3-mediated gene regulation. In vitro kinase assays with purified full-length Stat3 as the substrate show that both JNK and p38 can phosphorylate Stat3 on serine. Moreover, inhibition of p38 activity and thus of Stat3 serine phosphorylation results in suppression of transformation by v-Src but not v-Ras, consistent with a requirement for Stat3 serine phosphorylation in Src transformation. Our results demonstrate that Ras- and Rac1-mediated p38 and JNK signals are required for Stat3 transcriptional activity induced by the Src oncoprotein. These findings delineate a network of tyrosine and serine/threonine kinase signaling pathways that converge on Stat3 in the context of oncogenesis.

Retinoblastoma protein expression leads to reduced Oct-1 DNA binding activity and enhances interleukin-8 expression

Tumor cell lines with a defective retinoblastoma gene are unable to transcribe the HLA class II genes in response to IFN-gamma treatment, and reconstitution of functional Rb rescues IFN-gamma-induced class II gene expression. However, the molecular mechanism of Rb rescue of the class II genes is unknown. We have examined the effect of Rb expression on the activation of the promoter for HLA-DRA, the prototype class II gene. Oct-1, a POU domain transcription factor, was identified as a repressor of HLA-DRA promoter activity in the Rb-defective cells. Rb expression led to phosphorylation of Oct-1, thus relieving its repressive effect. Oct-1 has also been shown to repress interleukin 8 promoter activity. Consistent with reduced levels of Oct-1 DNA binding activity in the Rb-transformed cell lines, interleukin 8 expression is higher in these cell lines.

Functional association of TGF-beta receptor II with cyclin B

Utilizing the cytoplasmic tail of Transforming Growth Factor Receptor Type II (TGFbeta RII) as bait in a yeast two hybrid system, we have identified human cyclin B2 as a direct physical partner of TGFbeta RII. Analysis of deletion mutants of glutathione-S-transferase (GST)-cyclin B2 mapped its binding domain for TGFbeta RII to the C-terminal and revealed a negative regulatory region immediately upstream of the cyclin box. Using recombinant proteins, Cdc2 was demonstrated to indirectly interact with TGFbeta RII via cyclin B2. This interaction was reproduced in THP-1 monocytic cells, where TGFbeta treatment markedly enhanced the ability of cyclin B2 and, correspondingly, Cdc2 from TGFbeta-treated THP-1 cells, to bind the GST-TGFbeta RII fusion protein. More importantly, TGFbeta RII co-precipitated with cyclin B2 in TGFbeta-treated THP-1 cells. TGFbeta treatment also caused threonine phosphorylation of Cdc2 in the TGFbeta RII-cyclin B2-Cdc2 complex in THP1 cells, in parallel with down regulation of Cdc2 function as measured by histone H1 kinase activity. Cyclin B1 had the same capacity to bind TGFbeta RII and mediate indirect Cdc2 binding. These results suggest an alternative mechanism that cell cycle arrest in the G1/S phase caused by TGFbeta may, in part, be due to inactivation of cyclin B/Cdc2 kinase, which is needed for entry into the G2/M phase.

Control of lytic function by mitogen-activated protein kinase/extracellular regulatory kinase 2 (ERK2) in a human natural killer cell line: identification of perforin and granzyme B mobilization by functional ERK2

The signal pathways that control effector function in human natural killer (NK) cells are little known. In this study, we have identified the critical role of the mitogen-activated protein kinase (MAPK) pathway in NK lysis of tumor cells, and this pathway may involve the mobilization of granule components in NK cells upon interaction with sensitive tumor target cells. Evidence was provided by biological, biochemical, and gene transfection methods. NK cell binding to tumor cells for 5 min was sufficient to maximally activate MAPK/extracellular signal-regulatory kinase 2 (ERK2), demonstrated by its tyrosine phosphorylation and by its ability to function as an efficient kinase for myelin basic protein. MAPK activation was achieved in NK cells only after contact with NK-sensitive but not NK-resistant target cells. In immunocytochemical studies, cytoplasmic perforin and granzyme B were both maximally redirected towards the tumor contact zone within 5 min of NK cell contact with tumor cells. A specific MAPK pathway inhibitor, PD098059, could block not only MAPK activation but also redistribution of perforin/granzyme B in NK cells, which occur upon target ligation. PD098059 also interfered with NK lysis of tumor cells in a 5-h 51Cr-release assay, but had no ability to block NK cell proliferation. Transient transfection studies with wild-type and dominant-negative MAPK/ERK2 genes confirmed the importance of MAPK in NK cell lysis. These results document a pivotal role of MAPK in NK effector function, possibly by its control of movement of lytic granules, and clearly define MAPK involvement in a functional pathway unlinked to cell growth or differentiation.

Intact autocrine activation and cytokine production by PMNs from injured adults with elevated Candida antigen titres

Injured patients with Candida antigen titres have increased mortality due to sepsis. Polymorphonuclear leucocytes (PMNs) from injured patients with elevated Candida antigen titres demonstrate impaired function against Candida albicans growth when compared with PMNs from injury matched controls. To determine if PMN dysfunction is global, PMNs from patients with positive Candida antigen titres were evaluated for their ability to activate the anticandidal function of normal PMNs (autocrine activation) and to produce tumour necrosis factor (TNF) and interleukin 8 (IL8), known activators of PMN anticandidal function, this study demonstrates that the PMN dysfunction is not global, as PMN cytokine production and autocrine activation remain intact.

Candida antigen titre dilution and death after injury

BACKGROUND

Candida infections affect outcome after injury. Candida antigen titres were used to detect these infections early. This study was undertaken to correlate Candida antigen titre dilution with conventional injury scoring and outcome after severe injury.

METHODS

Candida antigen titres were determined by agglutination when clinically apparent source(s) of Candida were noted, when Candida was grown in culture of body fluids, or when unexplained clinical deterioration occurred. The findings were compared with the Injury Severity Score (ISS).

RESULTS

Seventy-five seriously injured adults (median ISS 25 (range 18-50)) developed raised Candida antigen titres. Multivariate analysis showed that age and Candida antigen titre correlated significantly with mortality, but not with each other. Culture evidence of Candida, or lack thereof, did not correlate with Candida antigen titre or mortality. Sixteen of 75 patients died, 14 from bacterial sepsis and none from Candida infection.

CONCLUSION

In seriously injured adults, the mortality rate is related to raised Candida antigen titres. The association between Candida antigen titre and mortality, although real, remains unexplained.

CD40-CD40L interactions provide "third-party" costimulation for T cell response against B7-1-transfected human breast tumor cells

In this study we provide evidence that a human breast carcinoma cell line, MDA-MB-231 (MDA), can be made immunogenic following B7 transfection and that full T cell activation is obtained through cooperation of T-B lymphocytes via CD40-CD40L interactions. Tumor cells transfected with either B7 gene (MDAB7), neomycin-resistant gene only (MDAneo), or untransfected (MDA) were used in an allogeneic mixed lymphocyte tumor culture (MLTC) to investigate their ability to stimulate T cell proliferation and generate cytotoxic T lymphocytes (CTL). MDAB7 induced moderate T cell proliferation while MDAneo or MDA did not. Substantial T cell proliferation and de novo generation of cytolytic T cells was obtained only in response to MDAB7 when B cells were present during the MLTC. CD8+-purified T + B cells proliferated to a greater extent than whole T cell populations + B or CD4+ + B in response to MDAB7. Addition of alpha-B7-1 or alpha-CD40 in the MLTC inhibited T cell proliferation by 65 and 40%, respectively, whereas T cell proliferation and generation of CTL was completely abrogated when MLTC was performed in the presence of both antibodies. These data suggest that the engagement of CD40L on T cells with CD40 on B cells provides a costimulatory signal which, in synergism with TCR-dependent MDAB7-T cell recognition (signal 1) and B7/CD28 interactions (signal 2), leads to full T cell activation.

Critical role of Lyn kinase in inhibition of neutrophil apoptosis by granulocyte-macrophage colony-stimulating factor

The signal pathway for control of apoptosis in human neutrophils is currently unknown. In this study, we provide the first evidence that a Src family tyrosine kinase, Lyn, plays a key role in inhibition polymorphonuclear (PMN) cell death. Several nuclear proteins associated with apoptosis, i.e., p53, cdc2, and Rb, were absent from PMN. Bcl-2, known to inhibit apoptosis, was also not expressed. Programmed cell death that rapidly occurred in PMN could be arrested by granulocyte-macrophage CSF (GM-CSF), but this activation did not induce p53, cdc2, retinoblastoma, or Bcl-2 expression. Instead, GM-CSF produced a rapid activation of Lyn and Hck, but not Fgr, tyrosine phosphorylation within 1 min. Co-immunoprecipitation studies indicated that only Lyn, but not Hck, was physically coupled to GM-CSF receptor. By histologic assessment and evaluation of DNA fragmentation, only antisense Lyn, but not antisense Hck or antisense Fgr, could reverse the cell survival advantage provided by GM-CSF. Therefore, the physical coupling of Lyn to GM-CSF receptor and its early activation are required for inhibition or delay of apoptosis in PMN.

Critical role of Lyn kinase in inhibition of neutrophil apoptosis by granulocyte-macrophage colony-stimulating factor

The signal pathway for control of apoptosis in human neutrophils is currently unknown. In this study, we provide the first evidence that a Src family tyrosine kinase, Lyn, plays a key role in inhibition polymorphonuclear (PMN) cell death. Several nuclear proteins associated with apoptosis, i.e., p53, cdc2, and Rb, were absent from PMN. Bcl-2, known to inhibit apoptosis, was also not expressed. Programmed cell death that rapidly occurred in PMN could be arrested by granulocyte-macrophage CSF (GM-CSF), but this activation did not induce p53, cdc2, retinoblastoma, or Bcl-2 expression. Instead, GM-CSF produced a rapid activation of Lyn and Hck, but not Fgr, tyrosine phosphorylation within 1 min. Co-immunoprecipitation studies indicated that only Lyn, but not Hck, was physically coupled to GM-CSF receptor. By histologic assessment and evaluation of DNA fragmentation, only antisense Lyn, but not antisense Hck or antisense Fgr, could reverse the cell survival advantage provided by GM-CSF. Therefore, the physical coupling of Lyn to GM-CSF receptor and its early activation are required for inhibition or delay of apoptosis in PMN.

Identification of an amphotericin B resistant strain of Candida albicans using a rapid 3H-glucose incorporation microassay

Using a 3H-glucose incorporation assay, antifungal sensitivity testing undertaken on an isolate of Candida albicans cultured from the blood of a bone marrow transplant patient documented resistance to amphotericin B but sensitivity to fluconazole and itraconazole. Information obtained from in vitro antifungal sensitivity testing can be used to direct in vivo antifungal therapy. Widespread application of standardized in vitro antifungal sensitivity testing is needed.

Injection of complementary DNA encoding interleukin-12 inhibits tumor establishment at a distant site in a murine renal carcinoma model

Interleukin (IL-12) protein has been shown to elicit diverse immunological responses and potent antitumor activity. We demonstrate here that intradermal injection of IL-12 cDNA induces systemic biological effects characteristic of the cytokine in vivo. Intradermal injection of IL-12 cDNA resulted in local expression of IL-12 mRNA, which correlated with a 10-fold increase in natural killer activity and a 3-4-fold increase in anti-CD3-induced IFN-gamma production in cultured splenocytes. Furthermore, when challenged with Renca tumor cells at a distant site, the day of tumor emergence was significantly delayed, and tumor growth was reduced in mice that received IL-12 cDNA, compared to mice given injections of plasmid vector alone. A number of the mice receiving IL-12 cDNA injections remained tumor free months after tumor challenge. In contrast to mice receiving recombinant IL-12 protein, no splenomegaly was detected when natural killer activity was significantly induced in mice receiving injections of IL-12 cDNA. Because purified plasmid DNA is more economical to prepare and has a longer shelf-life than recombinant proteins, and intradermal administration of cDNA encoding IL-12 did not cause splenomegaly, our findings suggest that the in vivo injection of cDNA encoding IL-12 may be a less toxic and more cost-effective alternative to IL-12 protein therapy in some clinical or experimental therapeutic applications.

Direct killing of interleukin-2-transfected tumor cells by human neutrophils

We have previously established that human polymorphonuclear cells (PMN) express IL-2R beta- and gamma-chains and that addition of IL-2 maintains the viability of PMN by preventing these cells from undergoing programmed cell death. The purpose of this study was to examine whether IL-2-releasing tumor cells are capable of stimulating PMN tumoricidal activity. We therefore investigated the ability of PMN to kill IL-2-transfected tumor cells using normal human PMN directed against the murine mammary adenocarcinoma TS/A engineered to release high amounts of murine IL-2 (3,600 U, B6) compared with TS/A parental cells and TS/A tumor cells transfected with the neomycin-resistance (NEO) gene only. The potency of PMN as IL-2-induced killer cells was indicated by the low number of cells required for killing (effector cell:target cell ratio 10:1) and the degree of tumor cell lysis (68+/-10%). Evidence for the role of IL-2 as a mediator of tumor cytotoxicity by PMN was substantiated by inhibition of tumor killing with anti-IL-2 and anti-IL-2R beta monoclonal antibodies (MAbs). Furthermore, in vivo depletion of mature granulocytes using MAb RB6-8C5 resulted in B6 adenocarcinoma growth, thereby confirming a direct role for IL-2-activated PMN in tumor cytolysis. Lastly, we suggest that one possible mechanism involved in IL-2-induced PMN cytotoxicity against the B6 clone occurs via the nitric oxide pathway, which could be inhibited upon addition of the arginine analog, N(G)-monomethyl-L-arginine.

Interleukins 2 and 12 activate natural killer cytolytic responses of peripheral blood mononuclear cells from patients with head and neck squamous cell carcinoma

OBJECTIVES

To examine the capacity of interleukin-2 (IL-2) and interleukin-12 (IL-12) to modulate the cytolytic activity of peripheral blood mononuclear cells against squamous cell carcinoma, and to determine whether peripheral blood mononuclear cells from healthy donors respond differently to IL-12 than do peripheral blood mononuclear cells from patients with head and neck squamous cell carcinoma.

DESIGN

Case-comparison study of a consecutive sample of patients with head and neck squamous cell carcinoma who were scheduled to undergo surgical excision.

PARTICIPANTS

The study included 10 patients with stage III or IV carcinoma matched with 10 volunteer blood donors.

INTERVENTION

Isolated peripheral blood mononuclear cells from patients and volunteers were treated with IL-2, 10 U/mL and 100 U/mL; IL-12, 1 U/mL or 10 U/mL; or a combination of IL-2 and IL-12.

RESULTS

The combination of IL-2 and IL-12 consistently produced the greatest activation cytolysis than either cytokine alone at all concentrations tested. This increased activity against a squamous cell carcinoma cell line was seen in lymphocytes from volunteers and patients.

CONCLUSION

Our findings suggest a new treatment regimen for the patient with head and neck cancer that uses immunomodulation with a combination of cytokines.

Interleukin 15 induction of lymphokine-activated killer cell function against autologous tumor cells in melanoma patient lymphocytes by a CD18-dependent, perforin-related mechanism

Interleukin 15 (IL-15) is a novel cytokine that shares no homology with IL-2, but it requires the use of beta and gamma chains of the IL-2 receptor complex for binding and signaling. In vitro studies have shown induction of CTL and lymphokine-activated killer (LAK) cell activity in peripheral blood mononuclear cells (PBMCs) from normal donors by IL-15 against known tumor targets. The present study attempts to define the role of IL-15 in generating LAK activity from melanoma patient lymphocytes. PBMCs of patients newly diagnosed with metastatic melanoma were incubated with different doses of recombinant human IL-15 and tested against autologous tumor cells, LAK sensitive cell lines (i.e., FMEX and Daudi), as well as the natural killer-sensitive cell line K562, in a 15-h 51Cr release assay. The effect of IL-15 was found to be both time and dose dependent, with peak activity detected after 2 or 3 days of culture with 100 ng/ml of this cytokine. LAK and not CTL activity in patient PBMCs was detected by the inability of mAbs against CD4, CD8, and MHC class I to effectively block lysis of autologous tumor and FMEX melanoma cells. In addition, interaction via the CD18 adhesion molecule was shown to be critical in IL-15-induced LAK-mediated lysis of autologous tumor cells. Finally, incubation of patient PBMCs with IL-15 for 6 h resulted in the up-regulation of perforin mRNA transcription. These findings suggest that LAK activity can be generated from melanoma patient PBMCs in the presence of IL-15 to lyse autologous tumor cells in a non-MHC-restricted manner. This new cytokine may play an important role in antitumor immunity with a possible use for cancer immunotherapy.

Interleukin-12 synergizes with interleukin-2 to generate lymphokine-activated killer activity in peripheral blood mononuclear cells cultured in ovarian cancer ascitic fluid

OBJECTIVES

The ascites-associated lymphocytes in ovarian cancer have altered immunologic function, and cell-free ascitic fluid has immunomodulating properties. We determined (1) whether interleukin (IL)-2 could induce lymphokine-activated killer (LAK) activity in normal peripheral blood mononuclear cells (PBMC) cultured in ovarian cancer ascitic fluid, and (2) whether IL-12 could synergize with IL-2 to generate LAK activity in normal PBMC cultured in ascitic fluid.

METHODS

Normal PBMC were cultured in control medium and in media consisting of 50% ascitic fluid (ascitic medium), with and without IL-2 and IL-12. Cell activation to assess LAK activity (cell lysis) was determined in a 51Cr-release assay with the tumor cell lines FMEX and SKOV3 as target cells. To determine a possible mechanism for any synergistic effect, the expression of perforin, a pore-forming protein, was determined by Northern blot analysis.

RESULTS

Interleukin-2 alone could not induce LAK activity in normal PBMC cultured in 50% ascitic fluid for up to 3 days. Interleukin-12 did mediate some or minimal LAK activity after 1, 2, or 3 days of incubation in control medium or in 50% ascitic fluid. When IL-2 and IL-12 were used in combination, PBMC cultured for 3 days in 50% ascitic fluid had remarkably high lytic activity against FMEX and SKOV3 tumor cells. In some experiments, this cytotoxicity was greater than that in PBMC cultured in control medium with IL-2 and IL-12. Lower concentrations of IL-12 (1 U/mL) with IL-2 (100 U/mL) were as effective as, and often more effective than, higher doses of IL-12 with IL-2. Very low-dose IL-12 (0.01-0.03 U/mL) in combination with IL-2 also induced a range of cytotoxicities. Only the combination of IL-2 and IL-12 up-regulated expression of perforin mRNA in ascitic medium.

CONCLUSIONS

The cytotoxicity responses of PBMC cultured in ascitic fluid in the presence of IL-2 and IL-12 are complex. Low-dose IL-2 and IL-12 can overcome the inhibitory property of ascitic fluid on LAK generation and can restore and enhance cytotoxic activity, possibly by reconstituting the expression of perforin. These findings may have therapeutic potential.

An alpha 5 beta 1-like integrin receptor mediates the binding of less pathogenic Candida species to fibronectin

The present study was undertaken to investigate whether less pathogenic Candida species (C. tropicalis, C. stellatoidea, C. krusei and C. glabrata) express a fibronectin receptor (FNr) antigenically related to alpha 5 beta 1 integrin, which mediates their binding to fibronectin (FN). By flow cytometric analysis, a monoclonal antibody (MAb) directed against human alpha 5 integrin subunit (clone SAM-1) and two different antisera to FNr positively stained C. tropicalis, C. stellatoidea and C. glabrata, with the greatest expression observed for C. tropicalis. No or only marginal immunoreactivity was found on C. krusei. C. tropicalis, C. stellatoidea, C. glabrata, but not C. krusei yeasts specifically adhered to FN; higher levels of adhesion were found for C. tropicalis and C. stellatoidea with respect to C. glabrata. Less pathogenic Candida spp. bound to the Arg-Gly-Asp (RGD) containing 120-kDa fragment of FN and adhesion to intact FN was markedly inhibited by Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP), but not by Gly-Arg-Gly-Glu-Ser-Pro (GRGESP) peptides. In addition, anti-alpha 5 SAM-1 MAb and both anti-FNr antisera strongly blocked binding of less pathogenic Candida spp. to FN. Overall, these results indicate that less pathogenic Candida spp., including C. tropicalis, C. stellatoidea and C. glabrata, express a receptor antigenically related to alpha 5 beta 1 integrin which mediates their adhesion to FN.

Augmentation of carcinoembryonic antigen release from intact, viable tumor cells by a factor in human serum

BACKGROUND

Measurement of carcinoembryonic antigen (CEA) levels in human serum is frequently used to detect tumor recurrence in patients with resected primary colorectal cancers. These levels are highly variable from patient to patient, and the mechanism that determines these levels is still poorly understood.

METHODS

Using a 6-h in vitro CEA-release assay, we determined that a factor in human and fetal bovine sera significantly augments the release of CEA from the tumor cell surface into cell culture supernatants.

RESULTS

As little as 1% serum admixed with tumor cells results in CEA release up to 200% greater than that of serum-free controls. It is not inhibited by 1,10-phenanthroline or heat inactivation (of serum) but is calcium dependent. The electrophoretic mobility and membrane linkage of CEA released by serum appear to be identical to those of CEA released by bacterial phospholipase C. Because bacterial phospholipase C is known specifically to cleave the phosphoinositol (PI) glycan moiety that anchors CEA to the tumor cell surface, a mechanism of action for serum cleaving this anchor is suggested.

CONCLUSIONS

The large range of CEA levels observed in patients with colorectal cancers may be related to differential sensitivity of the CEA membrane anchor to the CEA-releasing factor in serum.

Role of extracellular adenosine triphosphate in the cytotoxic T-lymphocyte-mediated lysis of antigen presenting cells

The lysis of antigen presenting cells (APCs) by cytotoxic T lymphocytes (CTLs) may be one mechanism whereby an immune response is downregulated by Staphylococcus superantigens. Disappearance of monocytes/macrophages from staphylococcal enterotoxin A (SEA)-activated peripheral blood mononuclear cell (PBMC) cultures, but not from control PBMC cultures was seen by flow cytometry. Recently, adenosine triphosphate (ATP) has been described as an effector molecule in CTL-mediated lysis of some murine tumor target cells. We have also shown that ATP caused the lysis of human macrophages, and that treatment of cells with interferon gamma (IFN gamma) rendered macrophages significantly more sensitive to ATP than untreated cells. To show that this purine nucleotide may play a role in modulating the immune system, we generated human CTLs that were stimulated with SEA, and used them as effector cells against SEA-pulsed autologous macrophages. CTLs were found to specifically lyse SEA-pulsed macrophages, while control, unpulsed, macrophages were unaffected. The addition of hexokinase, an enzyme that hydrolyzes ATP, significantly abrogated the killing of SEA-pulsed cells during the assay. In examining the mechanism of cytotoxicity, electron microscopy showed that macrophages incubated with both ATP and CTLs underwent necrosis, rather than apoptosis. From these results, it is suggested that ATP is released from CTLs during antigen presentation, and that IFN gamma-activated macrophages, which are inherently more sensitive to this mediator, are readily lysed and therefore removed from circulation, thus downregulating an immune response.

Interleukin-12-mediated tumoricidal activity of patient lymphocytes in an autologous in vitro ovarian cancer assay system

This study was designed to examine if interleukin-12 (IL-12) can induce cytolytic function of lymphocytes from ovarian cancer patients against either an ovarian cancer cell line or their own autologous tumor cells. Lymphocytes were obtained from the peripheral blood or ascites of ovarian cancer patients and activated with IL-12 alone or concomitantly with interleukin 2 (IL-2) for 2 to 3 days. Activation of lymphocytes and assessment of tumoricidal function by a chromium release assay were performed directly in a standard control medium (RPMI 1640 containing 2 mM glutamine, 100 micrograms/ml streptomycin, 100 units penicillin, 5% heat-inactivated human AB serum, and 5 mM 4-(2-hydroxyethyl)-1-piperazinesulfonic acid) and in 50% ascitic fluid (50% by volume filter-sterilized ascites with 50% of the above-mentioned control medium). Target cells were added directly into the medium in which the lymphocytes were activated in order to more closely mimic in vivo conditions. Lymphocytes, activated by IL-12 in 50% ascitic fluid, were able to lyse autologous tumor cells in 3 of 6 assays and were able to lyse SKOV3 cells (an ovarian cancer cell line) in 5 of 7 assays. The results were not significantly different in the control medium. When both IL-2 and IL-12 were used to activate lymphocytes in 50% ascitic fluid, significant cytotoxicity was generated in 6 of 6 autologous assays and in all 7 patient assays using SKOV3 as a target (P < 0.05). Synergy between the two cytokines was seen in all 13 patient assays in ascitic medium compared to only 5 of 13 assays in control medium. Additionally, when lymphocytes were stimulated with both IL-2 and IL-12, significantly greater cytotoxicity was seen in the ascitic fluid medium compared to the control medium in 13 of 14 assays (P < 0.05). No significant tumoricidal activity was seen by lymphocytes maintained in either medium without the addition of IL-2 or IL-12. Ascitic fluid consistently potentiates the synergy between IL-2 and IL-12 in generating cytotoxicity against ovarian cancer cells but does not increase cytotoxicity induced by IL-12 alone. IL-12 by itself activates tumoricidal activity of lymphocytes in ascitic fluid; however, the addition of IL-2 increases the degree and consistency of this effect. These data support the possibility that IL-12 may warrant further investigation as a potential therapeutic agent in the treatment of advanced ovarian cancer.

Inhibition of extracellular ATP-mediated lysis of human macrophages by calmodulin antagonists

Lysis of human culture-derived macrophages by extracellular ATP has recently been described, and treatment of macrophages with interferon-gamma rendered those cells significantly more sensitive to lysis. In addition, cell death occurred more rapidly in interferon (IFN)-treated cells than in untreated macrophages. In an attempt to identify the mechanism by which extracellular ATP affects macrophages, as well as to explore the differences between interferon-gamma-treated and untreated macrophages, selected metabolic inhibitors were included in the lytic assays. Of the compounds tested, three antagonists of calmodulin-linked pathways (trifluoperazine, KN-62, and calmidazolium) blocked the ATP-mediated lysis of both interferon-gamma-treated and colony-stimulating factor-treated macrophages in a dose-dependent manner. Early signals of the ATP ligation of the P2Z purinoceptors of human macrophages included increases in cytosolic [Ca2+] and depolarization of the plasma membrane. However, the inclusion of calmodulin antagonists in these assays did not abrogate either effect. These results suggest that the mechanism which mediates the efflux of 51Cr-labeled proteins from ATP-lysed macrophages is distinct from calcium mobilization and membrane depolarization, and may involve the generation of secondary pores/channels in the plasma membrane via a calmodulin-linked pathway.

Effect of lymphokines on 35sulfate uptake by the glomerular basement membrane

We have previously shown that lymphocytes from idiopathic minimal-lesion nephrotic patients produce a lymphokine (supernatant factor) that increases the 35sulfate uptake in the glomerular basement membrane (GBM). The purpose of this report was to further characterize the supernatant factor by studying the effects of interleukins (IL) 2-4, 6, and 8, granulocyte-macrophage colony stimulating factor, and tumor necrosis factor on the 35sulfate incorporation by rat glomeruli in vitro. A significant increase in GBM 35sulfate uptake was only seen when the glomeruli were cultured with the addition of IL-8 as compared with control cultures: 10.8 +/- (SEM) 1.7 and 7.9 +/- 1.4 cpm/micrograms GBM protein, respectively (p < 0.005). IL-8 reproduces the effect of the reported supernatant factor on the GBM 35sulfate uptake. Because IL-8 was detected in the supernatant of peripheral mononuclear cell cultures from idiopathic minimal-lesion nephrotic syndrome patients in relapse and because the increased GBM 35sulfate incorporation induced by the supernatant factor has been abolished by the addition to the culture media of anti-IL-8 neutralizing antibodies, we postulate that IL-8 is the previously described supernatant factor.

Expression of interleukin-2 receptor gamma on human monocytes: characterization of lineage specific post-translational modifications

Functional interleukin-2 receptors (IL-2R) on lymphocytes contain both IL-2R beta and gamma chains. Whereas constitutive expression of IL-2R beta has been found on monocytes, the expression of IL-2R gamma on these phagocytes has not been examined. We performed reverse-transcription-polymerase chain reaction with Southern blot analysis on RNA derived from purified human monocytes and discovered that they constitutively produce IL-2R gamma mRNA. Western immunoblotting revealed 58- and 64-kDa forms of IL-2R gamma on YT-1 and human monocytes, whereas 58-, 64-, and 69-kDa bands were detected using peripheral blood mononuclear cells and non-adherent lymphocytes. These different forms resulted from variable N-linked glycosylation since culture of the cells in tunicamycin resulted in detection of a single 39-kDa band which corresponds to the molecular weight predicted from the deduced amino acid sequence. By co-immunoprecipitation, the IL-2R beta subunit associates with only the 64-kDa IL-2R gamma protein band in monocytes.

Monocytes overcome lymphocyte dysfunction in injured adults with elevated Candida antigen titers

OBJECTIVE

Severely injured adults with elevated Candida antigen titers have increased mortality from sepsis, in part because of known neutrophil (PMN) dysfunction. Since PMN function is modulated by monocytes and lymphocytes, this study was undertaken to determine the ability of monocytes and lymphocytes isolated from injured adults with elevated Candida antigen titers to activate the anticandidal function of normal PMNs.

METHODS

Lymphocytes with or without monocytes, isolated from 18 injured adults with elevated titers, were cultured in the presence or absence of heat-killed Candida albicans for 48 hours. Culture supernatants were harvested, diluted 1:40, 1:160, and 1:640, and tested for the ability to stimulate the anticandidal function of normal PMNs using an 3H-glucose incorporation assay. Monocytes and lymphocytes isolated from nine volunteers were studied for comparison.

RESULTS

Supernatants of lymphocytes from healthy volunteers that were cultured with heat-killed C. albicans significantly augmented normal PMN anticandidal function. Supernatants of lymphocytes from injured adults with elevated titers that were cultured with heat-killed C. albicans did not significantly augment normal PMN anticandidal function. Supernatants of monocytes or lymphocytes from both groups of patients were able to upregulate PMN anticandidal function.

CONCLUSIONS

Lymphocytes from injured adults with elevated Candida antigen titers are defective in their ability to stimulate PMN anticandidal function. Monocytes from these patients can respond to Candida exposure and overcome the lymphocyte functional defect seen in injured patients with elevated titers.

Expression of interleukin-2 receptor gamma chain on human neutrophils

The interleukin-2 (IL-2) receptor gamma is an indispensable functional component of IL-2, IL-4, and IL-7 receptors, and thus, is denoted the common gamma chain, gamma c. The present study was undertaken to determine whether human polymorphonuclear neutrophils (PMNs) expressed gamma c chain. Reverse transcription-polymerase chain reaction and Northern blot analysis showed that fresh human PMN constitutively expressed a remarkable level of gamma c mRNA, which is of the size and intensity of that from the peripheral blood mononuclear cells (PBMCs). Granulocyte macrophage-colony stimulating factor, IL-2, and IL-8, which are known to activate PMN functions, failed to regulate the gamma c gene expression. Western blot analysis with a rabbit anti-gamma c polyclonal antibody identified 64-, 58-, and 50-kD gamma c bands in lysates from PMN, but only 64- and 58-kD bands from PBMCs. After the PMNs and PBMCs were treated with tunicamycin to prevent N-linked glycosylation, Western blot analysis detected a single 39-kD band, which is equal to the calculated molecular weight from the cloned cDNA. Thus, our results indicate that PMNs constitutively express high levels of gamma c and the three forms detected are caused by different glycosylation of a protein translated from a single mRNA species.

Candida albicans expresses a fibronectin receptor antigenically related to alpha 5 beta 1 integrin

Cell adhesion molecules, by regulating host-micro-organism interaction, play a major role in the pathogenesis of infectious diseases. The present study was undertaken to investigate the expression of the fibronectin (FN) receptor prototype, alpha 5 beta 1 integrin, on Candida albicans and its involvement in the adhesion to FN. By immunofluorescence and fluorescence activated cell sorter (FACS) analysis, several monoclonal antibodies (mAbs) directed against human alpha 5 or beta 1 integrin subunits, or two different antisera to FN receptor positively stained C. albicans yeast and germ tube phases, this immunoreactivity increasing upon germ tube transition. Twenty-five to thirty per cent of [3H]glucose-labelled Candida yeasts specifically adhered to FN and this adhesion was increased upon germ tube transition. C. albicans yeast and germ tube forms bound to an RGD-containing 120 kDa tryptic fragment of FN and adhesion to FN was markedly inhibited by GRGDSP, but not GRGESP peptides. Moreover, binding of both C. albicans phases to FN was strongly inhibited by anti-alpha 5 SAM-1 mAb, or both anti-fibronectin receptor (FNr) antisera. Overall these results indicate that C. albicans yeast and germ tube phases express a receptor antigenically related to alpha 5 beta 1 integrin which mediates their adhesion to FN. The alpha 5 beta 1 integrin-like receptor expression on C. albicans could be relevant for fungus-host interaction and in the dissemination process of Candida infection.

Phospholipase C-gamma 1 is present on the surface of human colorectal cancer cells

Using murine monoclonal antibodies, we have detected the novel signal transducing enzyme, phospholipase C-gamma 1, on the surface of cultured human colorectal cancer cells. We have also demonstrated the presence of this enzyme on the surface of fresh human tumor cells derived from primary and metastatic colorectal tumors. This enzyme has previously been described to be associated only with the inner face of the plasma membrane and the cell cytosol. The finding of an enzyme critical to the signal transduction pathway may have important implications for additional functions of this protein.

Candida antigen titer is a marker of neutrophil dysfunction after severe injury

Trauma patients with positive Candida antigen titers have high mortality rates. Death is the result of sepsis and multi-organ system failure. Considerations of host immunity to Candida led us to concurrently study the function of neutrophils (PMNs) from severely injured adults with positive titers (n = 20), patients with negative titers matched for age, sex, and injury (n = 20), and volunteers (n = 20). Anticandidal PMN function was determined using a 3H-glucose incorporation assay. RESULTS are expressed as mean percentage of growth inhibition +/- SEM.

RESULTS

PMN, from all groups inhibited Candida growth, although PMNs from titer-positive patients demonstrated less growth inhibition. In vitro cytokines granulocyte macrophage-colony stimulating factor [(GM-CSF), interferon-gamma (IFN-gamma), and interleukin 8 (IL-8)] improved function of PMNs from each group and corrected the impaired anticandidal function of PMNs from titer-positive patients, with GM-CSF being most effective.

CONCLUSIONS

Seriously injured patients with positive Candida antigen titers have PMNs with impaired anticandidal function, which can be restored by cytokines. These findings begin to explain why seriously injured patients with positive Candida antigen titers have increased mortality and to offer hope of therapeutic intervention.

Restoration of lytic function in a human natural killer cell line by gene transfection

NK cells can recognize and lyse target cells without restriction by the MHC. The molecular interaction responsible for NK cell recognition is poorly understood. It has been frequently suggested that the loss of beta 2 integrin in immune competent cells may lead to dysfunction due to inadequate cell-cell interaction. We examined the role of lymphocyte functional adhesion molecule-1 in the function of a human natural killer leukemia cell line, YT-1. A mutant YT-1(-) cell subclone showed an absence of killing activity against a B lymphoma cell line, compared with that against a CD11a/CD18 positive parental cell line, YT-1(+) cells. We found that this loss of cytotoxicity was correlated with lack of surface expression of CD11a/CD18 molecules due to the mutation of the CD18 gene. Using gene transfer experiments, we provide strong evidence demonstrating that CD18 transfection to this mutant NK cell line, YT-1(-), restored the surface expression of CD11a/CD18, and this restoration was accompanied by reexpression of cytotoxic function.

IL-8 production by peripheral blood mononuclear cells in nephrotic patients

We studied the interleukin 8 (IL-8) gene expression by peripheral blood mononuclear cells (PBMC) and the IL-8 serum concentration in patients with idiopathic minimal lesion nephrotic syndrome (IMLNS) and other glomerulopathies. PBMC from eight of the nine (IMLNS) patients in relapse demonstrated the presence of IL-8 mRNA. All three IMLNS patients in remission (P = 0.0026 when compared to patients in relapse) and the two patients with nephrotic syndrome with other glomerulopathies failed to elicit an IL-8 mRNA response. Eleven of the 12 IMLNS patients in relapse showed IL-8 serum concentration above the level of detection. Only one of the seven patients in remission had detectable serum levels of IL-8 (P = 0.0033 when compared to levels from IMLNS patients in relapse). IL-8 serum levels were not detectable in three patients with nephrotic syndrome and other glomerulopathies. Supernatants of PBMC cultures from IMLNS patients in relapse increased the 35sulfate uptake by rat GBM. This effect was abolished by the addition of anti-IL-8 neutralizing antibody to the culture media and reproduced by the addition to the media of IL-8 in concentrations found in the serum of IMLNS patients in relapse. Finally, the effect of IL-8 on the 35sulfate turnover of the glomerular basement membrane (GBM) sulfated compounds was evaluated in vitro. A significant decrease in the percentage of residual 35sulfate incorporated in the GBM (41 +/- 5, mean +/- SEM) was observed in cultures treated with IL-8 as compared to those that were not treated with IL-8 (58 +/- 8, P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of interleukin-2 receptor alpha (IL-2R alpha) mRNA and protein in advanced epithelial ovarian cancer

Advanced epithelial ovarian cancer has recently been identified by us to be associated with elevated serum and ascitic levels of the soluble Interleukin-2 receptor alpha (sIL-2R alpha). To determine the cellular source of sIL-2R alpha, the expression of IL-2R alpha was assessed at the mRNA and protein level in peripheral blood mononuclear cells (PBMC), in ovarian cancer ascitic cell infiltrates and in primary and metastatic epithelial ovarian cancer lesions by immunochemistry, by flow cytometric analysis and by in situ hybridization (ISH). Normal PBMC and the PBMC from ovarian cancer patients had a low or undetectable level of IL-2R alpha mRNA and of IL-2R alpha cell-surface protein expression. Flow cytometric analysis of the heterogeneous ascitic infiltrates revealed few cells positively expressing cell-surface IL-2R alpha. By immunocytochemistry, 1-2% of leukocytes in the ascitic infiltrates were IL-2R alpha+. Cytologically these IL-2R alpha+ cells were lymphocytes. Frozen sections of primary and metastatic ovarian cancer lesions showed sparse lymphocytic infiltration and very small numbers of these tumour infiltrating lymphocytes (TIL) were IL-2R alpha+. In situ hybridization demonstrated that although less than 2% of leukocytes in the ascitic infiltrate had detectable levels of IL-2R alpha mRNA, there was a wide range in the level of mRNA expression in these positive cells. The cells expressing IL-2R alpha mRNA had the cytologic characteristics of lymphocytes. Similarly, in the frozen sections of the solid tumours, there was a range in the level of IL-2R alpha mRNA expression in the few TIL that expressed IL-2R alpha. Importantly, ovarian cancer cells and mesothelial cells did not express IL-2R alpha mRNA or IL-2R alpha protein. Our observations lead us to conclude that lymphocytes are the main, if not the only, source of sIL-2R alpha in ovarian cancer patients. Although cells expressing IL-2R alpha were relatively few in number, as the source of the high levels of sIL-2R alpha, they may contribute to the immunosuppression of ascitic lymphocytes in advanced epithelial ovarian cancer.

Induction of IL-8 gene expression in human polymorphonuclear neutrophils by recombinant IL-2

Induction of IL-8 gene expression was investigated in IL-2-stimulated circulating peripheral blood polymorphonuclear neutrophils (PMN). Brief exposure of normal PMN to human rIL-2 enhanced both transcriptional and translational expression of IL-8. The IL-8 mRNA was first detectable by 3 h, followed by a continuous maintenance of high mRNA levels up to 18 h. Maximal transcription was obtained with 1000 U/ml of IL-2, which achieved the level observed with known neutrophil-activating factors such as granulocyte macrophage-CSF and Candida albicans. The protein synthesis inhibitor, cycloheximide, had no detectable effect on levels of IL-8 mRNA expression in PMN incubated in medium alone; however, cycloheximide could selectively modulate IL-8 mRNA transcription in PMN, depending on the cytokine used. Cycloheximide did not affect or alter IL-8 mRNA induction in IL-2-treated PMN but abrogated it in granulocyte macrophage-CSF-treated PMN and super-induced the level of IL-8 mRNA in C. albicans-treated PMN. Of significance was the observation that IL-2 has no direct chemotactic effect on PMN, whereas the cell-free supernatants from IL-2-stimulated PMN show potent chemotaxis for freshly isolated PMN, which can be specifically blocked by anti-IL-8 Abs. These findings suggested that the induction of IL-8 gene expression in PMN by IL-2 may be involved in the recruitment of PMN into tissues during local IL-2 therapy in human cancer and in part contribute to tumor rejection.

Induction of IL-8 gene expression in human polymorphonuclear neutrophils by recombinant IL-2

Induction of IL-8 gene expression was investigated in IL-2-stimulated circulating peripheral blood polymorphonuclear neutrophils (PMN). Brief exposure of normal PMN to human rIL-2 enhanced both transcriptional and translational expression of IL-8. The IL-8 mRNA was first detectable by 3 h, followed by a continuous maintenance of high mRNA levels up to 18 h. Maximal transcription was obtained with 1000 U/ml of IL-2, which achieved the level observed with known neutrophil-activating factors such as granulocyte macrophage-CSF and Candida albicans. The protein synthesis inhibitor, cycloheximide, had no detectable effect on levels of IL-8 mRNA expression in PMN incubated in medium alone; however, cycloheximide could selectively modulate IL-8 mRNA transcription in PMN, depending on the cytokine used. Cycloheximide did not affect or alter IL-8 mRNA induction in IL-2-treated PMN but abrogated it in granulocyte macrophage-CSF-treated PMN and super-induced the level of IL-8 mRNA in C. albicans-treated PMN. Of significance was the observation that IL-2 has no direct chemotactic effect on PMN, whereas the cell-free supernatants from IL-2-stimulated PMN show potent chemotaxis for freshly isolated PMN, which can be specifically blocked by anti-IL-8 Abs. These findings suggested that the induction of IL-8 gene expression in PMN by IL-2 may be involved in the recruitment of PMN into tissues during local IL-2 therapy in human cancer and in part contribute to tumor rejection.

Effect of the psychoactive metabolite of marijuana, delta 9-tetrahydrocannabinol (THC), on the synthesis of tumor necrosis factor by human large granular lymphocytes

The natural killer cell (NK)/3polymorphonuclear neutrophil axis has recently been identified to be important in early defense against the opportunistic fungi, Candida albicans. Repression of this system is therefore likely to contribute to susceptibility to opportunistic infections. delta 9-Tetrahydrocannabinol (THC), an active constituent of marijuana, has been reported to be immunosuppressive at concentrations that exceed attainable plasma levels. In this report, we examine the possibility that human large granular lymphocytes (LGL) can be immunosuppressed by exposure to THC at physiologically relevant concentrations and probed two functions associated with LGL, i.e., cytokine production and tumoricidal activity. We find that these low levels of THC inhibit tumor necrosis factor-alpha (TNF) induction from LGL by C. albicans and are dependent upon THC dose (0.005-5.0 micrograms/ml) and length of exposure (0.05-3.0 hr). Northern blot analysis indicates that the downregulation of TNF production from LGL by THC resides at the mRNA level. Moreover, exposure of LGL to physiological THC concentrations (0.01-2.0 micrograms/ml) diminishes their cytolytic activity against K562 tumor cells.

Lysis of neuroblastoma cell lines by human natural killer cells activated by interleukin-2 and interleukin-12

Neuroblastoma is the most common extracranial, solid tumor in children. Despite intensive chemotherapy and bone marrow transplantation, the 5-year projected survival rate is 20% to 25%. In vitro studies have shown enhanced natural killer cell (NK) lysis of tumor cells after exposure of NK cells to interleukin-2 (IL-2). In vivo studies have demonstrated similar immunologic effects but have also revealed severe toxicities associated with the use of IL-2. IL-12 is a newly described cytokine that has several properties, including the ability to act synergistically with IL-2 in generating lymphokine-activated killer cells (LAK) against known tumor targets. We investigated the role of IL-12 in the generation of peripheral blood mononuclear cell (PBMC) lysis of neuroblastoma cell lines. PBMC were activated with IL-12 alone and in combination with IL-2. Whereas IL-12 alone produced only modest enhancement of NK cell cytotoxicity, the combination of IL-2 and IL-12 was most effective in activating NK cell lysis of neuroblastoma cell lines. Further, we showed that large granular lymphocytes were the effector cells involved in target cell lysis. Finally, the CD18 molecule was shown to be critical in the lysis of neuroblastoma cells by activated PBMC.

Interleukin-2 prevention of apoptosis in human neutrophils

Evidence is presented that interleukin (IL)-2 maintains viability of human polymorphonuclear cells (PMN) in culture by preventing these cells from undergoing programmed cell death (PCD) and induces the synthesis of new RNA and protein. Our laboratory has recently discovered that human PMN constitutively express IL-2 beta receptor and more importantly, PMN are able to respond functionally to IL-2 by enhanced growth inhibitory activity against an opportunistic fungal pathogen, Candida albicans. We now report that IL-2 was able to interfere with the PCD process and reduce the number of apoptotic PMN to < 40% in 72-h culture. Freshly isolated PMN usually underwent a time-dependent aging process and > 80% of PMN cultured in medium alone for 72 h showed morphologic features of PCD as depicted by hematoxylin and eosin staining as well as by electron microscopy. During the PCD process, untreated PMN not only exhibited condensed nuclear structure and decrease in cell size, but also displayed DNA fragmentation. DNA fragmentation in PMN was prevented by IL-2. Prevention of PCD by IL-2 was associated with an increase in new RNA and protein synthesis in PMN, which may reflect cytokine induction, such as tumor necrosis factor, as we have recently shown. Thus, our data expands our current understanding of PMN in that they may be an active component of the immune system, with a longer life-span when activated than expected.

Elevated Candida antigen titers are associated with neutrophil dysfunction after injury

This study was undertaken to determine if impaired neutrophil (polymorphonuclear leukocytes [PMNL]) function is associated with an elevated Candida antigen titer after injury. PMNL from eight severely injured adults with Candida antigen titers of > or = 1:4 (titer positive) were evaluated for the ability to inhibit growth of Candida albicans in vitro by using a [3H]glucose incorporation assay. PMNL from eight severely injured adults with titers of < 1:4 (titer negative) and from eight healthy volunteers were studied for comparison. PMNL from the titer-positive patients had suppressed ability to inhibit C. albicans growth compared with PMNL from titer-negative patients and healthy volunteers. In vitro, PMNL function against C. albicans could be augmented significantly by cytokines. Granulocyte macrophage-colony-stimulating factor was most potent at augmenting function, followed by interleukin-8 and gamma interferon. Injured patients with elevated candida antigen titers have impaired PMNL function against C. albicans, and this function can be restored by cytokines.

IL-2 independent growth and cytotoxicity of herpesvirus saimiri-infected human CD8 cells and involvement of two open reading frame sequences of the virus

Herpesvirus saimiri is a primate tumor virus and induces acute T cell lymphomas and leukemias in New World monkeys and rabbits. We show in this report that infection of human peripheral white blood cells with a group C strain 484-77 results in selective expansion of CD8 lymphocytes with strong cytotoxic activity and these cells do not require interleukin-2 (IL-2) for growth. Infected cell cultures, termed herpesvirus-activated killer (HAK) cells, have been continuously maintained for several months in tissue culture and these HAK cells contain multiple copies of stable circular viral episomes. The growth and cytotoxicity of HAK cells was found independent of IL-2. Analysis of deletion mutant infected cells suggests that at least two open reading frame sequences of a bicistronic mRNA encoded by the viral genome is involved in controlling IL-2 independence. This model could facilitate studies on growth regulation of human cytotoxic T cells that are important effector cells in immune responses against infectious diseases and cancer and should help us to elucidate the mechanism of transformation by H. saimiri oncogenes.

Lymphocyte dysfunction in injured adults with elevated Candida antigen titers

BACKGROUND

Lymphocytes play an important role in the activation of polymorphonuclear neutrophil (PMN) antimicrobial functions. This study was undertaken to evaluate the ability of lymphocytes from severely injured adults with elevated Candida antigen titers to activate the anticandidal function of normal PMNs.

METHODS

Lymphocytes from 13 injured adults with elevated Candida antigen titers (titer+) were isolated and incubated with or without heat-killed C. albicans. After a 48-hour incubation, cell culture supernatants were harvested and tested for the ability to activate the anticandidal function of normal PMNs. Lymphocytes from 13 volunteers and 13 injury-matched patients with negative Candida antigen titers (titer-) were studied for comparison.

RESULTS

The patients with titer+ and titer- were well matched in terms of age, sex, Injury Severity Score, units of blood transfused, and length-breadth of antibiotic therapy. Patients with titer+ had a higher incidence of bacterial infections than did patients with titer-. Only 2 of the 13 patients with titer+ had a positive Candida culture. Lymphocytes from the volunteers and patients with titer- released large amounts of a PMN-activating factor(s) when exposed to C. albicans. Lymphocytes from the patients with titer+ were defective in their ability to release this activating factor(s) after exposure to C. albicans.

CONCLUSIONS

Although culture evidence of Candida was uncommon, injured adults with elevated Candida antigen titers have lymphocyte dysfunction and often suffer documented bacterial infections.

Lysis of human monocytic leukemia cells by extracellular adenosine triphosphate: mechanism and characterization of the adenosine triphosphate receptor

The present study shows that extracellular adenosine triphosphate (ATP) has the capacity to mediate dose-dependent lysis of the monocytic leukemia cell line THP-1. The lysis, assessed by 51Cr release, was found to be selective for ATP, because adenosine diphosphate (ADP) or other nucleotides were less effective in their ability to lyse the cells. The amount of 51Cr released was particularly enhanced by the stimulation of the cells with 1,000 U/mL of interferon gamma (IFN-gamma) for 3 days, and the sensitivity was time and dose dependent. Analysis of the mechanism of lysis indicated that the fully ionized form, ATP4-, mediated the lysis, because the addition of cation chelators or the absence of the divalent cations, Ca2+ and Mg2+, in the culture medium of a 6-hour 51Cr release assay increased the percent specific lysis. Therefore, the ATP receptors on THP-1 cells were classified as P2Z purinoceptors. Moreover, it is shown here that the Ca2+/calmodulin complex plays a role in the regulation of the lysis by extracellular ATP of THP-1 cells, because antagonists of this complex, such as trifluoperazine or KN-62, were found to inhibit the ATP-mediated cell lysis.