PBI-4050 reduces pulmonary hypertension, lung fibrosis, and right ventricular dysfunction in heart failure

AIMS

Heart failure with reduced ejection fraction (HFrEF) causes lung remodelling with myofibroblasts proliferation and fibrosis leading to a restrictive lung syndrome with pulmonary hypertension (PH) and right ventricular (RV) dysfunction. PBI-4050 is a first-in-class anti-fibrotic, anti-inflammatory, and anti-proliferative compound. The present study evaluated the therapeutic impact of PBI-4050 on PH in an HFrEF model.

METHODS AND RESULTS

HFrEF was induced after myocardial infarction (MI) in rats. Two weeks later, sham-operated and MI groups received PBI-4050 (200 mg/kg/day by gavage) or saline for 3 weeks. Animals were analysed according to infarct size as large (≥30% left ventricle) or medium MI (<30%). Large MI caused PH and RV hypertrophy (RVH) with a restrictive lung syndrome. PBI-4050 did not adversely affect left ventricular (LV) function but markedly reduced PH and RVH and improved RV dysfunction. PBI-4050 reduced lung remodelling and improved respiratory compliance with decreased lung fibrosis, alveolar wall cellular proliferation and α-smooth muscle actin expression. The increased expression of endothelin-1 (ET-1), transforming growth factor beta (TGF-β), interleukin-6 (IL-6) and of tissue inhibitor of metalloprotease-1 in the lungs from HFrEF were reduced with PBI-4050 therapy. Activation of isolated human lung fibroblasts (HLFs) to a myofibroblastic pro-fibrogenic phenotype was markedly reduced by PBI-4050. The fatty acid receptor GPR84 was increased in HFrEF lungs and in activated HLFs, and reduced by PBI-4050. GPR84 agonists activated fibrogenesis in HLFs and finally, PBI-4050 reduced ERK1/2 phosphorylation.

CONCLUSIONS

PBI-4050 reduces PH and RVH in HFrEF by decreasing lung fibrosis and remodelling. This novel agent decreases the associated restrictive lung syndrome and recovers RV function. A contributing mechanism involves reducing the activation of lung fibroblasts by IL-6, TGF-β, and ET-1 by antagonism of GPR84 and reduced ERK1/2 phosphorylation. PBI-4050 is a novel promising therapy for targeting lung remodelling in group II PH.

Fatty acid mimetic PBI-4547 restores metabolic homeostasis via GPR84 in mice with non-alcoholic fatty liver disease

Non-alcoholic Fatty Liver Disease (NAFLD) is the most common form of liver disease and is associated with metabolic dysregulation. Although G protein-coupled receptor 84 (GPR84) has been associated with inflammation, its role in metabolic regulation remains elusive. The aim of our study was to evaluate the potential of PBI-4547 for the treatment of NAFLD and to validate the role of its main target receptor, GPR84. We report that PBI-4547 is a fatty acid mimetic, acting concomitantly as a GPR84 antagonist and GPR40/GPR120 agonist. In a mouse model of diet-induced obesity, PBI-4547 treatment improved metabolic dysregulation, reduced hepatic steatosis, ballooning and NAFLD score. PBI-4547 stimulated fatty acid oxidation and induced gene expression of mitochondrial uncoupling proteins in the liver. Liver metabolomics revealed that PBI-4547 improved metabolic dysregulation induced by a high-fat diet regimen. In Gpr84^−/− mice, PBI-4547 treatment failed to improve various key NAFLD-associated parameters, as was observed in wildtype littermates. Taken together, these results highlight a detrimental role for the GPR84 receptor in the context of meta-inflammation and suggest that GPR84 antagonism via PBI-4547 may reflect a novel treatment approach for NAFLD and its related complications.

Design and Synthesis of New 1,3,5-Trisubstituted Triazines for the Treatment of Cancer and Inflammation

Low-molecular-weight synthetic molecules 1 with the general 2-(fluorophenylamino)-4,6-disubstituted 1,3,5-triazine structure and showing anti-inflammatory and anticancer activities were explored. Structure-activity relationship studies demonstrated the importance of the aminopentyl chain, the 3- or 4-fluorophenylaniline component, and the presence of at least one substituent, such as a tyramine moiety, attached directly to the triazine ring as essential for good activity. These compounds, represented by leads 4-{2-[4-(5-Aminopentylamino)-6-(3-fluorophenylamino)-1,3,5-triazin-2-ylamino]ethyl}phenol (6) and 4-{2-[4-(5-Aminopentylamino)-6-(4-fluorophenylamino)-1,3,5-triazin-2-ylamino]ethyl}phenol (10), displayed moderate and significant in vitro and in vivo dual activities, respectively, and address the molecular link between inflammation and cancer. Compound 10 demonstrated significant antitumor efficacy upon administration by the oral and intravenous routes in several animal models. This class of triazine compounds is new, safe, and nontoxic and offers a novel approach to the treatment of inflammation and cancer.

PBI-4050 Reduces Stellate Cell Activation and Liver Fibrosis through Modulation of Intracellular ATP Levels and the Liver Kinase B1/AMP-Activated Protein Kinase/Mammalian Target of Rapamycin Pathway

Hepatic fibrosis is a major cause of morbidity and mortality for which there is currently no effective therapy. We previously showed that 2-(3-pentylphenyl)acetic acid (PBI-4050) is a dual G protein-coupled receptor GPR40 agonist/GPR84 antagonist that exerts antifibrotic, anti-inflammatory, and antiproliferative action. We evaluated PBI-4050 for the treatment of liver fibrosis in vivo and elucidated its mechanism of action on human hepatic stellate cells (HSCs). The antifibrotic effect of PBI-4050 was evaluated in carbon tetrachloride (CCl₄)- and bile duct ligation-induced liver fibrosis rodent models. Treatment with PBI-4050 suppressed CCl₄-induced serum aspartate aminotransferase levels, inflammatory marker nitric oxide synthase, epithelial to mesenchymal transition transcription factor Snail, and multiple profibrotic factors. PBI-4050 also decreased GPR84 mRNA expression in CCl₄-induced injury, while restoring peroxisome proliferator-activated receptor γ (PPARγ) to the control level. Collagen deposition and α-smooth muscle actin (α-SMA) protein levels were also attenuated by PBI-4050 treatment in the bile duct ligation rat model. Transforming growth factor-β-activated primary HSCs were used to examine the effect of PBI-4050 and its mechanism of action in vitro. PBI-4050 inhibited HSC proliferation by arresting cells in the G0/G1 cycle phase. Subsequent analysis demonstrated that PBI-4050 signals through a reduction of intracellular ATP levels, activation of liver kinase B1 (LKB1) and AMP-activated protein kinase (AMPK), and blockade of mammalian target of rapamycin (mTOR), resulting in reduced protein and mRNA levels of α-SMA and connective tissue growth factor and restored PPARγ mRNA expression. Our findings suggest that PBI-4050 may exert antifibrotic activity in the liver through a novel mechanism of action involving modulation of intracellular ATP levels and the LKB1/AMPK/mTOR pathway in stellate cells, and PBI-4050 may be a promising agent for treating liver fibrosis.

Fatty acid receptor modulator PBI-4050 inhibits kidney fibrosis and improves glycemic control

Extensive kidney fibrosis occurs in several types of chronic kidney diseases. PBI-4050, a potentially novel first-in-class orally active low-molecular weight compound, has antifibrotic and antiinflammatory properties. We examined whether PBI-4050 affected the progression of diabetic nephropathy (DN) in a mouse model of accelerated type 2 diabetes and in a model of selective tubulointerstitial fibrosis. eNOS-/- db/db mice were treated with PBI-4050 from 8-20 weeks of age (early treatment) or from 16-24 weeks of age (late treatment). PBI-4050 treatment ameliorated the fasting hyperglycemia and abnormal glucose tolerance tests seen in vehicle-treated mice. In addition, PBI-4050 preserved (early treatment) or restored (late treatment) blood insulin levels and increased autophagy in islets. PBI-4050 treatment led to significant improvements in lifespan in the diabetic mice. Both early and late PBI-4050 treatment protected against progression of DN, as indicated by reduced histological glomerular injury and albuminuria, slow decline of glomerular filtration rate, and loss of podocytes. PBI-4050 inhibited kidney macrophage infiltration, oxidative stress, and TGF-β-mediated fibrotic signaling pathways, and it also protected against the development of tubulointerstitial fibrosis. To confirm a direct antiinflammatory/antifibrotic effect in the kidney, further studies with a nondiabetic model of EGFR-mediated proximal tubule activation confirmed that PBI-4050 dramatically decreased the development of the associated tubulointerstitial injury and macrophage infiltration. These studies suggest that PBI-4050 attenuates development of DN in type 2 diabetes through improvement of glycemic control and inhibition of renal TGF-β-mediated fibrotic pathways, in association with decreases in macrophage infiltration and oxidative stress.

Abstract 672: PBI-1402, a first-in-class erythropoiesis regulating agent, inhibits tumor growth and metastasis of murine mastocytoma and does not overshoot hemoglobin: Comparison with erythropoietin

BACKGROUND: PBI-1402 reduces the need for transfusion and increases hemoglobin (Hb) level and red blood cell count (RBC) in chemotherapy-induced anemia (CIA) by a mechanism of action distinct from erythropoietin (EPO).

AIM: The objective was to compare the effect of PBI-1402 and EPO on modulation of tumor growth.

METHODS: The effect of PBI-1402 (200 mg/kg, oral, once a day) or EPO (200 or 2000 U/kg, s.c. injection, twice a week) was studied in a subcutaneous P815 mastocytoma model. P815 cells express both PBI-1402 and EPO receptors. Tumor growth, metastasis, serum nitric oxide (NO) and hematocrit (Ht) were assessed.

RESULTS: P815 tumor growth is rapid and metastasizes to the liver. Inflammation is also associated with P815 tumor growth. PBI-1402 significantly reduced tumor growth (T/C=37%) and invasion as demonstrated by a 33% reduction of mice with liver metastasis. In comparison, EPO had no effect (200 U/kg, equivalent dose used in CKD treatment). However, high dose EPO (2000 U/kg, equivalent dose used in human cancer treatment) exacerbated tumor growth (T/C: 135%). Both doses of EPO induced a significant increase in the percentage of mice with liver metastasis (2X, 200 U/kg, and 3X, 2000 U/kg) compared to control. PBI-1402 treatment had no effect on NO and did not overshoot normal hematocrit. However, treatment with high dose EPO significantly increased NO and Ht levels (Table 1).

CONCLUSION: These results suggest that oral treatment with PBI-1402 may inhibit growth and metastasis of cancer cells. As an important safety feature, PBI-1402 does not induce overshoot of hemoglobin. In contrast to EPO, PBI-1402 may offer the advantage of reducing tumor growth and metastasis while preventing anemia induced by chemotherapy. In conclusion, PBI-1402 has the potential to be a safe erythropoiesis-regulating agent useful in treating anemia in cancer patients.

Abstract 3534: PBI-1402, a first-in-class erythropoiesis regulating agent, possesses differentiation properties and demonstrates synergistic anticancer activity in combination with chemotherapy

Background: PBI-1402 reduces the need for transfusion and increases hemoglobin (Hb) level and red blood cell count (RBC) in chemotherapy-induced anemia (CIA) patients by a mechanism of action which is distinct from erythropoietin (EPO). The PBI-1402 receptor is also expressed on certain cancer cells such as leukemia (K562), lung (LL-2), prostate (PC-3) and pancreas (Panc-02).

Aim: The objective of this study was to determine the role of the PBI-1402 receptor on tumor growth.

Methods: Cell proliferation and differentiation of K562 (human erythroleukemia) was studied in presence of PBI-1402 or EPO using 2,7-diaminofluorene for hemoglobin quantification. The effect of oral administration of PBI-1402 in combination with chemotherapy agents (gemcitabine or cyclophosphamide) was studied in subcutaneous syngeneic Panc02, LL-2 and xenogeneic PC-3 models.

Results: PBI-1402 inhibits proliferation of K562 cells and promotes differentiation of the remaining cells. K562 cells express both EPO and PBI-1402 receptors. EPO increases phosphorylation of ERK1/2 and Stat3 (linked to cell proliferation) while PBI-1402 decreases it in a dose dependent manner. The antitumor efficacy of oral administration of PBI-1402 was studied in combination with gemcitabine in subcutaneous LL2 and Panc02 as well as in orthotopic Panc02 cancers. In subcutaneous Panc02, gemcitabine induced a significant inhibition (p&lt;0.05) of tumor growth from day 27 to 34 with T/C from 55% to 78%. PBI-1402 induced a significant inhibition (p&lt;0.05) of tumor growth from day 23 to 44 with T/C from 26% to 58%. The combination therapy induced a significant (p&lt;0.05) inhibition of tumor growth and T/C&lt;40% from day 23 to 37 when compared to control and at day 23, 25 and 30 to 39 when compared to gemcitabine alone. In orthotopic Panc02, mice treated with gemcitabine or a combination of gemcitabine and PBI-1402 displayed prolonged survival (71 and 88 days, respectively) compared to control (48 days). In LL-2 cancer, at day 25, mice treated with PBI-1402 or gemcitabine alone had a T/C of 94% and 72%, respectively. Mice treated with a combination of gemcitabine plus PBI-1402 displayed a significant (synergistic) reduction of tumor growth (T/C: 33%). The effect of PBI-1402 alone or in combination with cyclophosphamide was also studied in a xenograft prostate PC-3 tumor. Mice treated with PBI-1402 or cyclophosphamide alone have a significant T/C&lt;40% from day 21 to 56 and day 35 to 56, respectively. Mice treated with a combination of cyclophosphamide plus PBI-1402 displayed tumor regression from day 21 to 56.

Conclusion: These results suggest that PBI-1402 has the potential to inhibit the growth of lung, prostate and pancreatic cancer by induction of cell differentiation. PBI-1402-differentiated cancer cells appear to be more susceptible to chemotherapeutic agents.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3534. doi:10.1158/1538-7445.AM2011-3534

2,4,6-trisubstituted triazines as protein a mimetics for the treatment of autoimmune diseases

A first-in-class series of low molecular weight trisubstituted triazines were synthesized and evaluated for their ability to mimic protein A binding to human IgG antibody. The structure-activity relationship (SAR) demonstrates that the 1,3-phenylenediamine component was essential for robust activity. Twenty-two compounds, represented by lead molecule 34, displayed significant activity compared to protein A. These compounds may prove useful for the treatment of autoimmune disease.

2,6,9-Trisubstituted purine derivatives as protein A mimetics for the treatment of autoimmune diseases

A series of 9-substituted and 2,9-disubstituted 6-(3-aminophenylamino) purines were synthesized and evaluated for their ability to mimic protein A binding to human IgG antibody. The structure-activity relationship (SAR) demonstrates that the 6-(3-aminoanilinyl) purine component was essential for activity. Purine 14 demonstrated significant activity, compared to protein A. These compounds may prove useful for the treatment of autoimmune diseases.

A novel RGD antagonist that targets both alphavbeta3 and alpha5beta1 induces apoptosis of angiogenic endothelial cells on type I collagen

Integrin-mediated cell adhesion is necessary for endothelial cell proliferation and apoptosis, which is a major determinant in tumor-induced angiogenesis. In this study, we compared two novel, structurally similar, Arg-Gly-Asp (RGD) peptidomimetic compounds having different integrin selectivities, for their inhibition of endothelial cell proliferation and induction of apoptosis on functionally relevant extracellular matrices (ECM) for angiogenesis. BCH-14661 was specific for integrin alphavbeta3, whereas BCH-15046 nonselectively antagonized integrins alphavbeta3, alphavbeta5, and alpha5beta1. Both compounds were potent inducers of endothelial cell apoptosis when plated on RGD-dependent ECM (vitronectin, VN), which was dependent on the ability to induce cell detachment. However, with endothelial cells plated on RGD-independent ECM (type I collagen, COL), only BCH-15046 was able to significantly prevent growth and induce apoptosis. This effect was not dependent on the induction of detachment. Experiments using the matrix metalloproteinase (MMP) inhibitor GM 6001 revealed that cleavage of COL was not required for the ability of BCH-15046 to induce apoptosis. However, the inhibition of growth factor-stimulated endothelial cell proliferation, required MMPs, and correlated with BCH-15046s' potent inhibition of endothelial cell attachment to denatured collagen. Antibody inhibition experiments showed that adhesion to denatured collagen required integrins alphavbeta3 and beta1, but not alphavbeta5. In addition, BCH-15046 exerted a significant inhibition of VEGF-stimulated angiogenesis in the chick chorioallontoic membrane in vivo. These results suggest that integrin antagonism of both alphavbeta3 and alpha5beta1 are important for MMP-independent induction of apoptosis on COL and MMP-dependent inhibition of endothelial cell-denatured collagen interactions required for proliferation.

In vitro and in vivo properties of bicyclic lactam inhibitors: a novel class of low molecular weight peptidomimetic thrombin inhibitors

We have developed potent and selective thrombin inhibitors with a novel non-peptidic structure. A bicyclic lactam was used as the scaffold on which various P1 and P3 motifs were substituted. Herein, we report the in vitro and in vivo properties of four representatives of this novel class of inhibitors. Their Ki values were less than 10 nM, they inhibited equally both free and clot-bound thrombin, and they displayed high level of specificity for thrombin over other serine proteases (trypsin, factor Xa, activated Protein C, and plasmin). They prolonged the clotting time of human plasma to twice the control value in coagulation assays (TT, APTT, and PT) at a concentration below 3 microM. Their anticoagulant activities using rat plasma were similar to, although slightly weaker, than with human plasma. Furthermore, they inhibited thrombin-induced platelet aggregation (human and rat) at concentrations close to their Ki values for thrombin. These molecules demonstrated similar dose response antithrombotic efficacy in rat arterial and venous thrombosis models when given as i.v. bolus followed by infusion. Antithrombotic efficacy of 85% and greater was observed at a dose of 5-7 microM/kg/hour in each model. Bicyclic lactam inhibitor 3, at a dose which caused a complete inhibition of visible thrombus formation in the venous and arterial models of thrombosis, showed a 1.9-2.1 and a 4.0-4.8-fold shift in APTT and TT, respectively. Unfortunately, the bicyclic lactam inhibitors exhibited low oral bioavailability in rats. Therefore, this novel class of bicyclic lactam thrombin inhibitor has the potential to be promising intravenous antithrombotic agents for the treatment of arterial as well as venous thrombosis and warrants further investigation.

Coordinate expression of group II phospholipase A2 and the acute-phase proteins haptoglobin (HP) and alpha1-anti-chymotrypsin (ACH) by HepG2 cells

The early response to inflammation is characterized by the synthesis of a variety of proteins under cytokine and glucocorticoid control. During episodes of infection or inflammation, a secretory phospholipase A2 (sPLA2) appears in the circulation along with a variety of acute-phase proteins (APP), suggesting possible common regulatory elements amongst sPLA2 and APP. Using the human hepatoma line, HepG2, regulation of sPLA2 expression was examined in relation to synthesis of HP and ACH. The patterns of induction of sPLA2, HP and ACH were distinct for each of IL- 1, tumour necrosis factor (TNF) and IL-6, oncostatin M, IL-11 and leukaemia inhibitory factor. Dexamethasone had an enhancing effect on IL-6-induced expression of HP and ACH, but inhibited sPLA2 expression by 50%. Both 8-bromo-cAMP and dibutyryl cAMP increased sPLA2 expression (48.8-fold and 64.2-fold, respectively), whereas KT5720, an inhibitor of protein kinase A, down-regulated cytokine-induced sPLA2 synthesis by 51%. These data show that a panel of cytokines induced varying patterns of up-regulation of sPLA2, ACH and HP. Although dexamethasone potentiated IL-6-induced APP expression in HepG2 cells, it suppressed sPLA2 expression in a dose-dependent manner. In several respects, sPLA2 regulation is similar to that of HP and ACH, but a notable difference is the reciprocal effect of glucocorticoids on sPLA2 expression compared with that of ACH and HP.

Secretory non-pancreatic phospholipase A2 and cyclooxygenase-2 expression by tracheobronchial smooth muscle cells

Lipid mediators of inflammation, contribute to airway hyper-reactivity in asthma. Since production of lipid mediators is largely regulated by phospholipase A2 (PLA2), and since PLA2 expression in mesenchymal cells is induced by cytokines and other signals, we examined PLA2 expression by rat tracheobronchial smooth muscle cells (TBSMC). PLA2 expression in TBSMC cultures was markedly increased by tumour-necrosis factor (TNF) alpha (130-fold) and interleukin-1beta (IL-1beta) (7.4-fold). Lipopolysaccharide (LPS;100 ng/ml) resulted in a 51-fold increase in extracellular PLA2 activity. PLA2 expression by LPS-stimulated or cytokine-stimulated cells was downregulated by dexamethasone. Whereas forskolin or dibutyrl cAMP increased PLA2 activity, inhibition of protein kinase A but not tyrosine kinase reduced PLA2 expression. Northern blot analysis showed that TNF alpha and IL-1beta increased both PLA2 and inducible cyclooxygenase (Cox-2) mRNA transcription. Addition of dexamethasone substantially blunted the increase in PLA2 and Cox-2 mRNA. In contrast, the level of Cox-1 mRNA was very low and did not change with the various treatments. Since proinflammatory lipid mediators have been implicated in the pathogenesis of asthma and PLA2 activity regulates generation of these lipid mediators, cytokine-stimulated synthesis and release of PLA2 by airway smooth cells may contribute to the potentiation of airway inflammation in asthma.

Induction of release of secretory nonpancreatic phospholipase A2 from human articular chondrocytes

OBJECTIVE

Secretory nonpancreatic phospholipase A2 (sPLA2) is a known inducer/promoter of the inflammatory process in the joints. It correlates with disease activity in adult and juvenile rheumatoid arthritis. Synovial fluids contain high concentrations of sPLA2. We discovered that human articular cartilage contains large quantities of sPLA2 and that culture chondrocytes constitutively synthesize and release sPLA2. To test the mechanism controlling the release of sPLA2, we exposed cultured human articular chondrocytes to cytokines and other agents, known to induce sPLA2 in other cells.

METHODS

Chondrocytes obtained from cartilage of normal appearance from rheumatoid and osteoarthritic joints, and from normal, neonatal joints were compared to rabbit articular chondrocytes. Radiolabeled Escherichia coli derived phospholipid assay and ELISA technique using monoclonal antibodies against recombinant human synovial type sPLA2 were employed. The cells were grown as monolayers as well as in alginate beads.

RESULTS

Human articular chondrocytes from both arthritic and neonatal joints released sPLA2 constitutively but could not be further stimulated with interleukin-1 beta (IL-1 beta), tumor necrosis factor alpha (TNF-alpha), IL-6, oncostatin M, lipopolysaccharide (LPS), or forskolin. Marked stimulation was observed when the cells were exposed to 8-bromo cyclic adenosine monophosphate (cAMP). Growing the cells as monolayers or in alginate beads did not change the results. In contrast to human cells, rabbit chondrocytes responded to IL-1 beta and IL-1/TNF, but not to TNF-alpha alone, with a very marked increase in extracellular sPLA2 activity.

CONCLUSION

Human articular chondrocytes synthesize and constitutively release sPLA2. Such continuous release is most probably responsible for the high concentration of sPLA2 in articular cartilage and may be the source of synovial fluid sPLA2. To our knowledge, human articular chondrocytes are the only sPLA2 producing cells tested to date that do not respond to cytokine stimulation with increased sPLA2 activity; yet enhancement was seen with 8-bromo cAMP. It seems therefore that, human articular chondrocytes possess signalling mechanisms for the release of sPLA2 unlike those from other mammalian cells. The significance of this observation remains to be elucidated.

Induction of TNF-alpha and proinflammatory secretory phospholipase A2 by intravenous administration of CAMPATH-1H in patients with rheumatoid arthritis

OBJECTIVE

To test the effect of infusions of CAMPATH-1H on levels of proinflammatory secretory phospholipase A2 (sPLA2) and tumor necrosis factor alpha (TNF-alpha) in patients with rheumatoid arthritis (RA).

METHODS

Two patients with RA were infused with CAMPATH-1H; extracellular nonpancreatic sPLA2 activity was tested using radiolabelled E. coli membrane phospholipid, and circulating TNF-alpha levels were tested by ultrasensitive immunoassay.

RESULTS

Circulating TNF-alpha began to rise within the first 2 h after infusion, reaching > 1000-fold values compared to preinfusion levels. Circulating sPLA2 activity began to rise a few hours after the start of infusion and reached extremely high values in 12 h, concomitant with fever and hypotension. The activity of sPLA2 decreased to pretreatment values in 3-18 days after infusion.

CONCLUSION

The mechanism leading to the increase of TNF-alpha and hyperphospholipasemia A2 has not been elucidated. It is possible that CAMPATH-1H activates cells that synthesize and release TNF-alpha and sPLA2, and/or that it induces interleukin 2 release, which in turn activates TNF-alpha, with subsequent release of sPLA2.

Inhibition of human group II phospholipase A2 by C-reactive protein in vitro

Endotoxin or cytokine-induced expression of a secretory non-pancreatic phospholipase A2 (sPLA2) has been implicated in the pathogenesis of multisystem organ dysfunction or failure in patients with septic shock. Circulating sPLA2 levels increase as much as 1000-fold during the course of septic shock. However, the mode of regulation of the activity of this lipolytic enzyme is unknown, since circulating inhibitors have not been identified. We investigated the potential inhibitory activity of the acute phase reactant, C-reactive protein (CRP), a phospholipid-binding protein whose expression increases as much as 1000-fold during severe infections. Serum CRP and sPLA2 profiles were highly concordant in patients with septic shock. In studies in vitro, human CRP inhibited hydrolysis of PC-lyso-PC (2:1) multilamellar liposomes by human recombinant sPLA2 in a dose-dependent manner, with an apparent IC50 of 50 micrograms/ml CRP and maximal inhibition at 100 micrograms/ml. Inhibition of sPLA2 activity by CRP was substrate concentration-dependent, and increasing substrate concentrations reversed the inhibitory effect of CRP using the PC-lyso-PC system. Preincubation of CRP with phosphorylcholine led to a concentration-dependent loss of CRP-induced inhibition of substrate hydrolysis. These observations are consistent with a substrate-depletion model of inhibition of sPLA2 activity by CRP.

Clinical value of immunolymphscintigraphy in patients with breast cancer

Thirty four patients suspected of suffering from breast cancer were investigated by immunolymphscintigraphy (ILS) a few days before a planned operation. Patients received 500 micrograms of the BCD-F9 monoclonal antibody or its F(ab')2 fragments containing 1 mCi of Iodin-123. Each preparation was given by a subcutaneous injection into the fingerwebs between the 2nd and 3rd fingers of both hands. Three static scintigrams were taken 4, 8 and 24 hours following injection of the radiolabelled antibodies. ILS results were always compared to histopathological findings and gave for the intact antibody a sensitivity of 83%, a specificity of 93% and an accuracy of 89%, the positive predictive value was 91% and the negative predictive value was 80%. On the other hand, when the F(ab')2 fragments were used the sensitivity of the ILS technique was 75%, the specificity was 100% while the accuracy was 86%, the positive predictive value was 100% and the negative predictive value was 75%.

Affinity purification of a high molecular weight human breast cancer-associated antigen identified by the BCD-B4 monoclonal antibody

This study reports the purification and characterization of a high molecular weight human breast cancer-associated antigen identified by a previously described (1,2) murine monoclonal antibody, BCD-B4. Immunohistochemical analysis indicated that BCD-B4 recognizes an antigen expressed in an altered form on the human breast carcinoma cell line, BT-20, compared to the non-malignant human mammary epithelial cell line, HBL-100. Chemical treatments and enzymatic digestions suggested that the recognized moiety was a protein. The antigenic determinant was resistant to neuraminidase and periodate treatments but was sensitive to trypsin and proteinase K. The antigen was purified by affinity chromatography and its molecular weight, determined by SDS-PAGE analysis under non-reducing conditions, was proven to be 250 Kd. Under reducing conditions, the molecule dissociated into two polypeptides of 125 and 45 Kd, respectively. Both subunits could be isolated from normal HBL-100 and neoplastic BT-20 cellular protein extracts by affinity chromatography. The higher molecular weight subunit showed; however, qualitative and quantitative differences between the two cell lines: it was expressed in greater quantity on BT-20 cells and its molecular weight was 15 Kd higher. Both subunits could also be identified by immunoblots of BT-20 cells.

Immunolymphscintigraphy of axillary lymph node metastases in breast cancer patients using monoclonal antibodies: first clinical findings

The results of preliminary investigations into the immunolymphscintigraphic (ILS) detection of axillary lymph node metastases in nine breast cancer patients by means of the 3C6F9 monoclonal antibody (MAs) are presented. The IgG2a monoclonal antibody detects a 37 KD antigen, consistently found on the surface of primary and metastatic breast tumors. Each patient received 1 mCi of I-123 (specific activity, 2 mCi per mg of antibody) as a subcutaneous injection between the 2nd and the 3rd finger of both hands, i.e., the healthy side serving as a control for the affected side. Clear images of lymph node metastases were visible 4 to 8 hours after injection of the antibody. Seven of the nine patients studied were positive by scanning and six showed positive lymph node involvement by histopathology (6/7; true positive = 86%). Two patients did not show any iodine uptake in the axilla and were subsequently found to be free of metastases (2/2; true negative = 100%). These data give an overall accuracy of ILS of 89% and demonstrate that 3C6F9 localizes preferentially in affected axillary lymph nodes compared to normal lymph nodes.

Role of self carriers in the immune response and tolerance. VIII. Suppression of the MOPC-104E idiotypic response by idiotype-modified self, but not by dextran-modified self

We have investigated the suppression of the anti-dextran B1355S immune response using our model of modified self. The anti-dextran response is idiotypically well defined in BALB/c mice. This system enables us to examine the contribution of various predominant idiotypes to the antibody response under conditions of suppression by antigen or by idiotype-specific suppressor cells. Our results demonstrate that the total anti-dextran response can be inhibited by pretreatment of animals with dextran-coupled syngeneic spleen cells; however, the representation of major idiotypes constituting this response are not reduced in percentage. In contrast, pretreatment of mice with MOPC-104E-coupled spleen cells leads to a specific suppression of the private IdI-104E idiotype. The total anti-dextran response remains unchanged, as well as proportions of other major idiotypes known (IdI-588 and IdX). This suppression is mediated by Thy-1.2+, Lyt-2.2+ T cells, as demonstrated by adoptive transfer assays. This system will allow the molecular dissection of the regulation of an idiotypically well-defined system for the suppression by either antigen- or idiotype-specific suppressor T cells.

Role of self carriers in the immune response and tolerance. VIII. Suppression of the MOPC-104E idiotypic response by idiotype-modified self, but not by dextran-modified self

We have investigated the suppression of the anti-dextran B1355S immune response using our model of modified self. The anti-dextran response is idiotypically well defined in BALB/c mice. This system enables us to examine the contribution of various predominant idiotypes to the antibody response under conditions of suppression by antigen or by idiotype-specific suppressor cells. Our results demonstrate that the total anti-dextran response can be inhibited by pretreatment of animals with dextran-coupled syngeneic spleen cells; however, the representation of major idiotypes constituting this response are not reduced in percentage. In contrast, pretreatment of mice with MOPC-104E-coupled spleen cells leads to a specific suppression of the private IdI-104E idiotype. The total anti-dextran response remains unchanged, as well as proportions of other major idiotypes known (IdI-588 and IdX). This suppression is mediated by Thy-1.2+, Lyt-2.2+ T cells, as demonstrated by adoptive transfer assays. This system will allow the molecular dissection of the regulation of an idiotypically well-defined system for the suppression by either antigen- or idiotype-specific suppressor T cells.