New Therapeutic Approach for Targeting Hippo Signalling Pathway

Nuclear localization signals are short amino acid sequences that target proteins for nuclear import. In this manuscript, we have generated a chimeric tri-functional peptide composed of a cell penetrating peptide (CPP), a nuclear localization sequence and an interfering peptide blocking the interaction between TEAD and YAP, two transcription factors involved in the Hippo signalling pathway, whose deregulation is related to several types of cancer. We have validated the cell penetration and nuclear localization by flow cytometry and fluorescence microscopy and shown that the new generated peptide displays an apoptotic effect in tumor cell lines thanks to the specific nuclear delivery of the cargo, which targets a protein/protein interaction in the nucleus. In addition, the peptide has an anti-tumoral effect in vivo in xenograft models of breast cancer. The chimeric peptide designed in the current study shows encouraging prospects for developing nuclear anti- neoplastic drugs.

Abstract 3904: PEP-010, a cell penetrating & interfering peptide as a new therapeutic approach in breast cancer

Introduction. The interaction between intracellular caspase-9 and PP2A proteins is critical to apoptosis. We designed PEP-010, a Cell Penetrating & Interfering Peptide, which specifically disrupts the interaction between caspase-9 and PP2A. We evaluated in vitro and in vivo its therapeutic properties to demonstrate its potential as an innovative approach to breast cancers treatment.

Material and Methods. In vitro evaluation was done by apoptosis (Annexin V) and cell viability (MTT) measurements on cancer cell lines from different origins. In vivo efficacy studies were conducted on patient-derived xenograft (PDX) mice models of triple-negative breast cancer (TNBC) and hormone-positive HER2-negative breast adenocarcinoma (BC). Pharmacokinetic and biodistribution studies were conducted on mice after administration by iv and ip route. Preliminary tolerance studies were done on mice and rats after repeated administration of PEP-010.

Results. First, we demonstrated that PEP-010 is able to penetrate into tumor cells and induces caspase-9-dependent apoptosis in several tumor cell types. Moreover, we demonstrated that PEP-010 specifically induces the death of cancer cells (CLL) without harm to healthy cells.After PEP-010 treatment, we observed a significant tumor growth inhibition in PDX mice models of TNBC, compared to the untreated control. In BC PDX mice models, we observed also a significant tumor growth inhibition with complete response after PEP-010 treatment. We also improved the stability and the pharmacokinetic parameters of PEP-010. Point mutations on a protease cleavage site clearly improved peptide stability while keeping the functional activity. Biodistribution studies demonstrated that the optimized peptide is able to reach the targeted tumor and accumulate there at higher concentration than the former peptide. Pharmacokinetic studies in mice administered with PEP-010 by iv and ip route were conducted as well as in vitro study of plasmatic clearance of PEP-010 in different species. We finally performed formulation studies to improve the solubility of PEP-010 and confirmed the efficacy of the drug product in a BC PDX mice model.Preliminary tolerance studies were done on mice and rats after repeated administration of PEP-010 without demonstrating any signs of toxicity. Moreover, no immunogenic response has be observed after repeated administration of PEP-010 in mice.

Conclusion. Using PEP-010, a CP&IP blocking caspase-9/PP2A interaction, we have demonstrated that this peptide has an interesting in vitro and in vivo therapeutic effect. PEP-010 constitutes a new innovative therapeutic approach for the treatment of human breast cancers. PEP-010 will enter GLP toxicity studies shortly in order to prepare the first in human clinical trial.

Citation Format: Sophie Lebel-Binay, Fariba Nemati, Leticia Dominguez-Berrocal, Justine Fleury, Adnan Naguez, Didier Decaudin, Angelita Rebollo. PEP-010, a cell penetrating & interfering peptide as a new therapeutic approach in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3904.

Exomics and immunogenics: Bridging mutational load and immune checkpoints efficacy

Anti-PD-1/PD-L1 antibodies are emerging as promising anticancer therapeutics. Interestingly, elevated response rates to these agents are mostly documented among patients with tumors that bear high level of somatic mutations, like melanoma or non-small cell lung carcinoma. We herein formulate the hypothesis that high levels of mutational heterogeneity in the tumor could be the key for the success of immune checkpoint-targeting therapies.

Variants With Different Mutation Patterns Persist in the Quasispecies of Enfuvirtide-Resistant HIV-1 Population During and After Treatment In Vivo

BACKGROUND

Genotypic and phenotypic resistance in 11 HIV-1-infected patients receiving enfuvirtide (ENF), as part of a salvage regimen, has been evaluated.

METHODS

Resistance mutations were detected by sequencing the gp41 ectodomain from plasma samples. During treatment, longitudinal samples from 1 patient were sequenced after limiting dilution of complementary DNA to isolate single genomes. Phenotypic resistance was evaluated with a new recombinant virus assay (PHENOSCRIPT; VIRalliance, Paris, France), allowing the determination of coreceptor use.

RESULTS

All patients experienced ENF failure. One to 4 mutations in the 36-to-45 gp41 region appeared during ENF therapy in all patients and disappeared after ENF removal. Mixtures of wild type and mutants unexpectedly persisted under ENF treatment, however, despite continued replication, leading to discordant results between genotypic and phenotypic data. Sequencing of isolated genomes from 1 patient confirmed that a wild-type first heptad repeat region (HR1) region was still present at the end of therapy. Several mutated variants coexisted at different time points, despite a tendency toward quasispecies reduction with time.

CONCLUSION

Individual variability of the mutation pattern and persistence of strains without mutation in the region mainly targeted by ENF resistance probably reflect the fact that resistance to ENF may rely on regions of gp41 or gp120 other than residues 36 to 45.

Synergistic Inhibition of Protease-Inhibitor-Resistant HIV type 1 by Saquinavir in Combination with Atazanavir or Lopinavir

Background

Double-boosted protease inhibitors (PIs) are under investigation for the treatment of patients who are unable to take nucleoside reverse transcriptase inhibitors because of cross-resistance and/or intolerance. Evidence of synergistic inhibition of wild-type HIV has been reported for saquinavir with atazanavir or lopinavir.

Methods

We investigated the activity of these two combinations against a panel of six site-directed mutant HIV-1 strains and 14 clinically derived recombinant HIV-1 strains presenting a range of PI-resistance profiles.

Results

No evidence of synergy was observed against wild-type virus for either combination. The combination of saquinavir and lopinavir showed evidence of synergy against four viruses displaying high-level resistance to lopinavir and low-level resistance to saquinavir. Similarly, evidence of synergy between saquinavir and atazanavir was only observed in two viruses which were more susceptible to saquinavir than to atazanavir.

Conclusions

We hypothesize that differences between the PIs in intracellular protein-binding behaviour or inhibition of drug transporters (P glycoprotein, MDR1 and MDR2) could result in intracellular levels of saquinavir being increased by co-administration with lopinavir or atazanavir. The effect of this increase would be masked in cases involving viruses that were susceptible to atazanavir or lopinavir. In virus resistant to lopinavir or atazanavir but susceptible to saquinavir, the majority of the antiviral effect is due to saquinavir; thus even small increases in intracellular concentration could significantly increase virus inhibition. These results confirm that in vitro synergy can be observed between PIs and suggest that the degree of synergy observed might depend on the resistance profile of the virus.

Synergistic inhibition of protease-inhibitor-resistant HIV type 1 by saquinavir in combination with atazanavir or lopinavir

BACKGROUND

Double-boosted protease inhibitors (PIs) are under investigation for the treatment of patients who are unable to take nucleoside reverse transcriptase inhibitors because of cross-resistance and/or intolerance. Evidence of synergistic inhibition of wild-type HIV has been reported for saquinavir with atazanavir or lopinavir.

METHODS

We investigated the activity of these two combinations against a panel of six site-directed mutant HIV-1 strains and 14 clinically derived recombinant HIV-1 strains presenting a range of PI-resistance profiles.

RESULTS

No evidence of synergy was observed against wild-type virus for either combination. The combination of saquinavir and lopinavir showed evidence of synergy against four viruses displaying high-level resistance to lopinavir and low-level resistance to saquinavir. Similarly, evidence of synergy between saquinavir and atazanavir was only observed in two viruses which were more susceptible to saquinavir than to atazanavir.

CONCLUSIONS

We hypothesize that differences between the PIs in intracellular protein-binding behaviour or inhibition of drug transporters (P glycoprotein, MDR1 and MDR2) could result in intracellular levels of saquinavir being increased by co-administration with lopinavir or atazanavir. The effect of this increase would be masked in cases involving viruses that were susceptible to atazanavir or lopinavir. In virus resistant to lopinavir or atazanavir but susceptible to saquinavir, the majority of the antiviral effect is due to saquinavir; thus even small increases in intracellular concentration could significantly increase virus inhibition. These results confirm that in vitro synergy can be observed between PIs and suggest that the degree of synergy observed might depend on the resistance profile of the virus.

Susceptibility to antiretroviral drugs of CRF01_AE, CRF02_AG, and subtype C viruses from untreated patients of Africa and Asia: comparative genotypic and phenotypic data

Non-B HIV-1 viruses are predominant in developing countries where access to antiretroviral drugs (ARVs) is progressively being intensified. It is important to obtain more data on the susceptibility of these viruses to available ARVs. CRF01_AE, CRF02_AG, and subtype C strains of HIV-1 obtained from untreated patients from Vietnam, Cote d'Ivoire, and India were analyzed for their in vitro susceptibility to NRTIs, NNRTIs, PIs, and an entry inhibitor (T-20) using a recombinant viral assay (PHENOSCRIPT). The corresponding viruses, which had been previously sequenced in reverse transcriptase (RT), protease (prot), plus envelope (env) C2/V3 genes and had therefore been fully characterized, were further sequenced in env HR1 + HR2 regions. CRF01_AE isolates are sensitive to NRTIs and NNRTIs with the exception of one isolate that exhibits a decreased susceptibility to NNRTIs associated with a I135T substitution in RT. CRF02_AG and subtype C viruses are sensitive to NRTIs and NNRTIs but some CRF02_AG isolates tend to be resistant to abacavir, potentially related to associated substitutions of RT at positions 123 (D123N) plus 135 (I135V). Whereas all but one CRF01_AE isolates are fully susceptible to PIs, some CRF02_AG and, more frequently, some subtype C isolates are resistant to atazanavir. The role of substitutions in prot at positions of secondary resistance mutations 20, 36, 63, and 82 is raised with a potentially crucial role of the V82I substitution. Finally, all viruses tested, regardless of the CRF or subtype, are fully susceptible to T-20.

Dynamics of enfuvirtide resistance in HIV-infected patients during and after long-term enfuvirtide salvage therapy

Enfuvirtide (ENF) is the first of a novel class of drugs that blocks HIV fusion to host cells. We analyzed the dynamics of genotypic and phenotypic resistance to ENF during and after long-term ENF therapy and its clinical implications in eight heavily treatment-experienced HIV-infected patients who underwent salvage therapy with enfuvirtide along with other antiretroviral agents. All patients showed a rapid decline in plasma HIV-RNA followed by viral rebound. Changes at codons 36, 42, 43 and/or 44 within the HR1 region of gp41 were selected in all cases, resulting in high-level phenotypic resistance to ENF, ranging from 15- to 445-fold. Both genotypic and phenotypic resistance to ENF rapidly disappeared after discontinuation of the drug, suggesting that ENF-resistant viruses may have an impaired replicative capacity.

Epstein-Barr virus nuclear antigen 2 induces interleukin-18 receptor expression in B cells

Epstein-Barr virus (EBV) latently infects and immortalizes B lymphocytes and causes lymphoproliferative malignancies. We show here that the EBV nuclear antigen EBNA2 induces expression of the 2 chains of the interleukin-18 receptor (IL-18R) in Burkitt lymphoma (BL) cell lines and in nontransformed B cells. Activation of IL-18R expression by EBNA2 is independent of its interaction with the transcriptional repressor RBPJ kappa. It occurs in the absence of any other viral protein but requires de novo synthesis of cellular proteins. IL-18R induction is a highly specific function of EBNA2, because neither other EBV latent proteins nor the cellular proteins c-myc or Notch can exert this effect. Using cDNA microarray expression profiling, we find that the IL-18 receptor expressed in EBV-infected BL cells has signaling capacity, because IL-18 significantly modified gene expression. We report that EBNA2 expression is associated with IL-18R expression in vivo in EBV-positive B-lymphomas from AIDS patients.

IL-18 is produced by prostate cancer cells and secreted in response to interferons

Murine models have shown that IL-18 has antiangiogenic and antitumor effects, but little is known about IL-18 production in human tumors. We investigated IL-18 expression in clinically localized prostate cancers by immunohistochemistry and showed that 75% of the prostate cancers studied (27/36 cases) presented with tumor cells producing IL-18. Prostate tumor cell lines PC-3, DU 145 and LNCaP synthesized the immature form of IL-18 (p24). IFN-gamma produced in prostate cancers induced caspase-1 mRNA and IL-18 secretion of tumor cell lines, which was inhibited by the cell-permeable Tyr-Val-Ala-Asp-aldehyde caspase-1 inhibitor (YVAD-CHO). Interestingly, IFN-alpha also induced IL-18 secretion of the poorly differentiated cell line PC-3. PC-3 and DU 145, but not the well-differentiated cell line LNCaP, expressed IL-18R alpha (IL-1Rrp) protein and transcripts for IL-18R beta (AcPL). Exogenous IL-18 increased mitochondrial activity of both cell lines evaluated by the tetrazolium (MTT) assay but did not influence their proliferation. This indicated that prostate tumor cells could secrete IL-18 in response to IFN-gamma in the tumor microenvironment and that IL-18 could act as a autocrine/paracrine factor for the tumor. In the cohort of patients studied, IL-18 expression in prostate cancers (with up to 10% of tumor cells stained) was associated with a favorable outcome and equally predictive as pathologic stage on multivariate analysis (log rank test, p = 0.02). Tumor IL-18 production is a novel physiopathologic feature of prostate cancer and appears to be a favorable event in the course of the disease. Modulation of IL-18 production by interferons could have a beneficial clinical effect, which deserves further investigation.

Local immunostimulation induced by intravesical administration of autologous interferon-gamma-activated macrophages in patients with superficial bladder cancer

We conducted a phase I/II clinical trial of the safety and efficacy of intravesical administration of autologous IFN-gamma-activated macrophages (MAK) in patients with superficial bladder cancer. Monocyte-derived MAK cells were prepared in vitro and patients received six instillations of 1.4 x 10(8) to 2.5 x 10(8) cells, once a week, for five consecutive weeks. Treatment was well tolerated, with seven grade 1 and five Grade 2 protocol-related adverse effects. Nine out of 17 included patients had no recurrences during the year following the first instillation of MAK. The aim of the present study was to search for immune parameters related to local immunostimulation induced by MAK. Monitoring of the patients showed that urinary IL-8, GM-CSF and, to a lesser extent, IL-18 were increased following MAK instillations, with inter-individual differences. The urinary IL-8 level was about 10-fold higher than that observed for other cytokines, and its biological activity was reflected by a concomitant increase of urinary elastase, indicating neutrophil activation and degranulation. We also showed that nine out of 12 patients investigated presented an increase of urinary neopterin, a marker of IFN-gamma-activated macrophages, 7 days after MAK instillation, while serum neopterin levels were almost stable. These results are in line with persistence of activated macrophages in the bladder wall after infusions. Moreover, there was evidence of macrophages in urine smears 2 months after the sixth MAK instillation, and the score of macrophages correlated with the quantity of neutrophils in the urine. Overall, this study provides evidence of a local immunostimulation induced by this novel and safe immunotherapeutic approach of MAK instillations in patients with superficial bladder cancer.

Analysis of interleukin-18, interleukin-1 converting enzyme (ICE) and interleukin-18-related cytokines in Crohn's disease lesions

A local increase of interleukin-18 (IL-18) expression has been recently demonstrated in Crohn's disease (CD), suggesting a role for mature IL-18 (cleaved by ICE protease) in the induction of proinflammatory cytokines and Th1 polarization observed in CD lesions. The aim of this study was to investigate IL-18 modulation and its potential immune consequences in CD lesions. We showed increased IL-18 production in chronic CD lesions and identified epithelial cells and macrophages as IL-18-producing cells. A twofold increase in ICE alpha, beta, and/or gamma mRNA that encodes for the complete mature peptide was required for ICE activity, and a marked increase in IL-18R-positive immune cells was observed in chronic lesions compared to uninvolved areas or normal control samples. Chronic lesions also displayed intense transcription of IL-18-induced cytokines, IFN-gamma, IL-1beta, TNF-alpha, and IL-8. By contrast, when neither IL-18 nor ICE mRNAs were enhanced (early asymptomatic CD lesions), IL-18-induced cytokines were not up-regulated. These results are in accordance with a putative role of mature IL-18 in the pathogenesis of CD.

Proinflammatory and antitumor properties of interleukin-18 in the gastrointestinal tract

Interleukin-18 (IL-18) plays a central role in the immune response by acting on Th1 cell differentiation, cell-mediated cytotoxicity and inflammation. The role of IL-18 in cancers and inflammatory diseases is discussed in the light of our investigations on IL-18 synthesis in normal colonic mucosa, colonic cancer and Crohn's disease (CD).

Interleukin-18: biological properties and clinical implications

IL-18, originally identified as interferon-gamma inducing factor (IGIF), is related to the IL-1 family in terms of its structure, processing, receptor, signal transduction pathway and pro-inflammatory properties. IL-18 is also functionally related to IL-12, as it induces the production of Th1 cytokines and participates in cell-mediated immune cytotoxicity. This review summarizes the recent advances in the understanding of IL-18 structure, processing, receptor expression and immunoregulatory functions, and focuses on the role of IL-18 modulation in tumours, infections, and autoimmune and inflammatory diseases.

Signaling through the tetraspanin CD82 triggers its association with the cytoskeleton leading to sustained morphological changes and T cell activation

In this report, we provide new evidence of a crosstalk between T cell activation and adhesion processes through a functional cytokeleton. We show that CD82 signaling induces long-lasting adhesion, spreading and development of membrane extensions, involving actin polymerization. Addition of various co-stimuli (phorbol 12-myristate 13-acetate or monoclonal antibodies to CD3 or CD2) increases the CD82-induced morphological alterations and, reciprocally, CD82 engagement synergizes with these stimuli to induce T cell activation as indicated by both primary tyrosine phosphorylation and IL-2 production. Different kinases are involved in both processes. CD82 co-signaling involves src kinases including p56 Ick. On the other hand, the CD82-induced alterations of cell morphology are negatively regulated by cAMP-dependent kinases independently of activation of src kinases. Simultaneously with cytoskeletal rearrangements, we observed an inducible association of CD82 with the cytoskeletal matrix. In addition, the potentiating and stabilizing effects induced by CD82 cross-linking on tyrosine phosphorylation were abolished by cytoskeleton-disrupting agents. These results suggest that the actin polymerization triggered by CD82, through its ability to associate with the cytoskeletal matrix, is the primary step involved in the CD82 induced co-stimulatory activity. Our data provide further evidence for a direct role of the actin cytoskeleton as a major component for sustained signal transduction in T cells and suggest that tetraspanins could be "membrane organizers" connecting both surface and intracellular molecules.

Consequences of ddI-induced reduction of acute SIVmac251 virus load on cytokine profiles in cynomolgus macaques

This study evaluates the consequences of antiretroviral treatment of the acute simian immunodeficiency virus (SIV) primary infection on virus load and cytokine responses. Four cynomolgus macaques were inoculated intravenously with a pathogenic primary isolate (SIVmac251). Animals were pretreated with 10.8 mg/kg/day of dideoxyinosine (ddI) from 4 days before inoculation, and treatment was continued for 28 days. Proinflammatory (IL6, IL1 beta and TNF alpha) and antiinflammatory (IL10) cytokine and lymphokine (IL2, IL4 and IFN gamma) polymerase chain reaction (PCR) ratios were monitored in unmanipulated peripheral blood mononuclear cells (PBMCs) during acute infection by using a semiquantitative reverse transcription (RT)-PCR method. PBMC-associated virus loads were dramatically reduced compared to those of placebo-treated macaques. Nevertheless, a transient rise in IL6, IL1 beta, TNF alpha and IL10 mRNA expression was observed in PBMCs. IL2, IL4 and IFN gamma mRNAs were either undetectable or weakly detectable throughout the study, with no major changes. Despite a dramatic reduction in the acute viral loads in ddI-treated monkeys, early cytokine mRNA profiles were comparable to those of untreated SIVmac251-infected monkeys. Contrary to what was previously evidenced during primary infection with an attenuated SIV clone, no increase in IL2 and IL4 mRNA was detected in PBMCs of the ddI-treated monkeys, although these monkeys exhibited virus loads similar to those evidenced in macaques infected by attenuated SIV. These data indicate that differential lymphokine expression patterns found in pathogenic and Nef-truncated SIV-infected monkeys may not be strictly dependent on virus load levels.

Functional analysis of four tetraspans, CD9, CD53, CD81, and CD82, suggests a common role in costimulation, cell adhesion, and migration: only CD9 upregulates HB-EGF activity

Molecules of the tetraspan superfamily are engaged in multimolecular complexes containing other proteins such as beta 1 integrins and MHC antigens. Although their functions are not clear, they have been suggested to play a role in cell adhesion and migration, signal transduction, and costimulation. We have in this paper directly compared the functional properties of four tetraspans, CD9, CD53, CD81, and CD82. mAbs to any of these molecules were able to deliver a costimulatory signal for CD3-mediated activation of the T cell line Jurkat. CD82 mAbs were the most efficient in triggering this effect. Moreover, engagement of CD9, CD81, and CD82 induced the homotypic aggregation of the megakaryocytic cell line HEL, and inhibited the migration of this cell line. Similar results were obtained with the preB cell line NALM-6 using the CD9 and CD81 mAbs. The CD81 mAb 5A6 produced the strongest effects. Therefore, the tetraspans are recognized by mAbs which produce similar effects on the same cell lines. This is consistent with the tetraspans being included in large molecular complexes and possibly forming a tetraspan network (the tetraspan web). We also demonstrate that the tetraspans are likely to keep specific functional properties inside this network. Indeed, we have demonstrated that the human CD9 is able, like the monkey molecule, to upregulate the activity of the transmembrane precursor of heparin-binding EGF as a receptor for the diphtheria toxin when cotransfected in murine LM cells. Neither CD81, nor CD82 had such activity. By using chimeric CD9/CD81 molecules we demonstrate that this activity requires the second half of CD9, which contains the large extracellular loop, the fourth transmembrane region, and the last short cytoplasmic domain.

The tetraspanin protein CD82 associates with both free HLA class I heavy chain and heterodimeric beta 2-microglobulin complexes

CD82 is a tetraspan transmembrane protein on NK/LAK-susceptible targets. A single highly glycosylated protein of heterogeneous molecular mass (50-90 kDa) was immunoprecipitated by anti-CD82 from Nonidet P-40 lysates of various B cell lines, Raji, Daudi, 721, and 721.134. Using the milder detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS), additional proteins were coprecipitated with CD82 from surface iodinated B cell lines, including a major band at 45 kDa, identified as the HLA class I heavy chain by sequential immunoprecipitations and sequential immunoprecipitation-Western blot analysis. Cocapping experiments confirmed the molecular association of CD82 and HLA class I at the cell surface of these B cell lines. CD82 could be coprecipitated with both mature and beta 2-microglobulin (beta 2m)-free heavy chains of MHC-I from CHAPS extracts. No association between MHC-I and CD82 was found in the beta 2m-deficient Daudi cell line or after co-in vitro translation of CD82, MHC heavy chain, and beta 2m mRNA. The most likely source of free class I heavy chains at the cell surface is by dissociation of beta 2m-associated class I molecules. These results suggest that association of CD82-MHC-I takes place at the cell surface and could interfere with the capacity of the MHC-I complex to protect targets from NK-mediated cytotoxicity.

The tetraspanin protein CD82 associates with both free HLA class I heavy chain and heterodimeric beta 2-microglobulin complexes

CD82 is a tetraspan transmembrane protein on NK/LAK-susceptible targets. A single highly glycosylated protein of heterogeneous molecular mass (50-90 kDa) was immunoprecipitated by anti-CD82 from Nonidet P-40 lysates of various B cell lines, Raji, Daudi, 721, and 721.134. Using the milder detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS), additional proteins were coprecipitated with CD82 from surface iodinated B cell lines, including a major band at 45 kDa, identified as the HLA class I heavy chain by sequential immunoprecipitations and sequential immunoprecipitation-Western blot analysis. Cocapping experiments confirmed the molecular association of CD82 and HLA class I at the cell surface of these B cell lines. CD82 could be coprecipitated with both mature and beta 2-microglobulin (beta 2m)-free heavy chains of MHC-I from CHAPS extracts. No association between MHC-I and CD82 was found in the beta 2m-deficient Daudi cell line or after co-in vitro translation of CD82, MHC heavy chain, and beta 2m mRNA. The most likely source of free class I heavy chains at the cell surface is by dissociation of beta 2m-associated class I molecules. These results suggest that association of CD82-MHC-I takes place at the cell surface and could interfere with the capacity of the MHC-I complex to protect targets from NK-mediated cytotoxicity.

Experimental gene therapy of cancer using tumor cells engineered to secrete interleukin-13

Cytokines locally delivered to the site of a tumor boost both specific and nonspecific host anti-tumor defenses. Interleukin (IL)-13 is a recently described cytokine produced by mouse type 2 helper T lymphocytes. The aim of this study was to evaluate the inhibition of tumor growth induced by IL-13 delivered locally within or around transplanted tumor cells in mice. We observed that local administration of IL-13 at the site of transplanted tumor cells in vivo had potent inhibitory effects on growth of both immunogenic (P815 mastocytoma, H-2d) or nonimmunogenic (3LL lung carcinoma, H-2b) tumor cells. Mice injected with transfected P815 cells secreting large amounts of IL-13 rejected the P815 tumor and developed systemic specific anti-tumor immunity leading to long-lasting specific anti-tumor protection. Less efficient anti-tumoral effects were obtained with the nonimmunogenic 3LL tumor model when local administration of IL-13 was achieved by co-inoculating xenogeneic chinese hamster ovary (CHO) IL-13 cells. Several local injections of CHO IL-13 cells were needed to obtain rejection of 3LL tumors and no induction of long-lasting anti-3LL memory was obtained. Several studies were performed to elucidate the IL-13 anti-tumoral effects. Experiments with nude mice indicated that Il-13 can also stimulate nonspecific anti-tumor defenses. The histological examination of P815 IL-13 cells undergoing rejection showed monocytic cells and neutrophils infiltrating the tumor. Studies indicated that IL-13 administered in vitro did not directly stimulate the cytotoxicity of peritoneal macrophages and natural killer cells. However, experiments with Boyden chemotaxis chambers indicated that IL-13 was chemotactic for macrophages. Finally, preliminary experiments in vitro suggest that IL-13 improved antigenic presentation of P815 membranes. Thus, anti-tumor effects of IL-13 in vivo most probably result from pleiotropic effects including recruitment of nonspecific cells and improved stimulation of immune-specific anti-tumor effectors.

CD82, member of the tetra-span-transmembrane protein family, is a costimulatory protein for T cell activation

It is now well documented that full activation of T cells requires a two-signal triggering that can be mimicked, in the absence of accessory cells, by co-immobilization of mAbs directed to stimulatory/accessory molecules (CD2, CD3, CD28, adhesion molecules, etc.). In this report, we describe that engagement of CD82 can delivery such a costimulatory signal for full activation of the human T cell line Jurkat, leading to strong IL-2 production and cell differentiation. The CD82 Ag, which belongs to the new tetra-span-transmembrane family (CD9, CD37, CD53, CD63, and CD81 (TAPA-1)), has been identified originally in our laboratory for its enhanced expression on three LAK-susceptible cell lines, and has been characterized as an activation/differentiation marker of mononuclear cells. Jurkat cells, stimulated in vitro by co-immobilization of anti-CD82 and anti-CD3 mAbs, produced high levels of IL-2, became strongly adherent to plastic dishes, and developed dendritic processes. These morphologic changes, associated with a total arrest of cell proliferation, were not the result of cell death but rather of cell differentiation, as shown by an increase in their metabolic activity. Costimulation through both CD82 and CD3 induced up-regulation of both IL-2 and IFN-gamma mRNA synthesis (but not of IL-4) and an increased expression of HLA class I molecules at the cell surface, which was inhibited by anti-IFN-gamma Ab.

CD82, member of the tetra-span-transmembrane protein family, is a costimulatory protein for T cell activation

It is now well documented that full activation of T cells requires a two-signal triggering that can be mimicked, in the absence of accessory cells, by co-immobilization of mAbs directed to stimulatory/accessory molecules (CD2, CD3, CD28, adhesion molecules, etc.). In this report, we describe that engagement of CD82 can delivery such a costimulatory signal for full activation of the human T cell line Jurkat, leading to strong IL-2 production and cell differentiation. The CD82 Ag, which belongs to the new tetra-span-transmembrane family (CD9, CD37, CD53, CD63, and CD81 (TAPA-1)), has been identified originally in our laboratory for its enhanced expression on three LAK-susceptible cell lines, and has been characterized as an activation/differentiation marker of mononuclear cells. Jurkat cells, stimulated in vitro by co-immobilization of anti-CD82 and anti-CD3 mAbs, produced high levels of IL-2, became strongly adherent to plastic dishes, and developed dendritic processes. These morphologic changes, associated with a total arrest of cell proliferation, were not the result of cell death but rather of cell differentiation, as shown by an increase in their metabolic activity. Costimulation through both CD82 and CD3 induced up-regulation of both IL-2 and IFN-gamma mRNA synthesis (but not of IL-4) and an increased expression of HLA class I molecules at the cell surface, which was inhibited by anti-IFN-gamma Ab.

CD82, tetra-span-transmembrane protein, is a regulated transducing molecule on U937 monocytic cell line

The mononuclear cell surface protein IA4, recently classified as CD82, was originally identified in our laboratory by the IA4 monoclonal antibody (mAb), because of its high expression on three lymphoblastoid, LAK-susceptible, variant cell lines. We have characterized CD82 as a new activation/differentiation marker of mononuclear cells. This protein belongs to the new family of TST proteins (tetra spans transmembrane), which includes CD9, CD37, CD53, CD63, and CD81 (TAPA-1). Here we demonstrate that cross-linking of IA4 mAbs induces an increase of intracellular free calcium in U937 cells and tyrosine phosphorylation of various proteins. Our data indicate that the intracellular calcium increase is initiated by a phospholipase C (PLC)-induced PtdIns(1,4,5)P3 second messenger followed by a more stable change, linked to extracellular calcium entry. This transducing signal was dependent on dual engagement of both CD82 and Fc receptors. Surface cross-linking of CD82 together with Fc receptors (FcRs) induces a specific long-lasting increase of intracellular calcium, whereas FcR cross-linking alone induces only a transient calcium mobilization. These results suggest that, upon cross-linking of CD82, a multimolecular complex including CD82 and FcR could be induced that is able to trigger signal transduction. We have previously shown that CD82 membrane expression is up-regulated during differentiation of human monocytes. Using U937 cells, we demonstrate here that several cytokines [interleukin-1 beta (IL-1 beta), IL-4, IL-6, IL-13, interferon-gamma, tumor necrosis factor alpha] could significantly up-regulate the surface expression of CD82 antigen, by contrast with FcR surface expression, which was up-regulated only after IFN-gamma treatments. Based on our finding of a strict dependence of CD82 activation on FcR stimulation, we suggest a putative role of CD82 in enhancing FcR-mediated activation of cells from the monocyte/macrophage lineage.

Further characterization of CD82/IA4 antigen (type III surface protein): an activation/differentiation marker of mononuclear cells

The mononuclear cell surface protein IA4 was originally identified in our lab using a mAb selected because of its strong reactivity with three lymphoblastoid variant cell lines which are HLA class I deficient, are LAK susceptible, and form a high number of conjugates with LAK effectors. We previously cloned the cDNA of the IA4 protein, coding for a 267-amino-acid type III integral membrane protein, with four transmembrane domains and three possible N-glycosylation sites. The IA4 protein belongs to the tetra span transmembrane (TST) new family of surface molecules, which also includes CD9, CD37, CD53, CD63, and TAPA-1. IA4 antigen was recently recognized as belonging to a new cluster of differentiation CD82 (International CD Workshop, Boston 1993). The IA4 antigen expression pattern at the surface of immune cells from normal donors was studied. On T lymphocytes, IA4 was barely detectable on resting cells and increased 3.5- to 7-fold following PHA or PHA+PMA stimulation. This IA4 increased expression is correlated with the morphologic change in blast cells and with the expression of activation markers such as CD2 and MHC class II antigens, therefore suggesting that IA4 is an activation marker on T lymphocytes. The expression of IA4 was low on circulating resting monocytes collected by elutriation. However, these monocytes, cultured in medium alone or with GM-CSF, acquired the morphology of macrophage and simultaneously overexpressed MHC Class II, CD14, and IA4 antigens, suggesting that IA4 is a differentiation marker for macrophages, whatever the culture conditions, either adherent (plastic culture dishes) or nonadherent (Teflon culture bags). IA4 stable transfectants of the murine mastocytoma cell line P815 were obtained and used to generate a new mAb. Competitive epitope binding studies have shown that IA4 antigen presents a dominant epitope recognized by most of the mAb prepared either in our lab or elsewhere. This dominant epitope is not shared by any of the other antigens of the TST family. Using this new mAb we were able to biochemically characterize the IA4 antigen as a 28-kDa protein, highly N-glycosylated with different patterns on various cells.

A member of the tetra spans transmembrane protein superfamily is recognized by a monoclonal antibody raised against an HLA class I-deficient, lymphokine-activated killer-susceptible, B lymphocyte line. Cloning and preliminary functional studies

The IA4 mAb was identified among a series of antibodies raised in BALB/c mice after immunization against a HLA class I-deficient, lymphokine-activated killer (LAK)-susceptible EBV-B lymphocyte line. The IA4 antibody was selected because of its high expression, in the range of 10(5) to 25 x 10(5) sites/cell, on several B lymphocyte lines (EBV-transformed or Burkitt) and monocytic lines such as HL60 and U937, and because its expression was correlated with both target susceptibility to LAK lysis and reduced expression of HLA class I surface Ag on two pairs of EBV-B-transformed cell lines (721/721.134 and MM/10F2). Despite the strategy followed to raise the mAb and the correlation mentioned above, no direct role of the IA4 molecules in LAK susceptibility has been established, since the IA4 molecule is poorly expressed on the sensitive targets Daudi and K562; moreover, the IA4 antibody did not affect reproducibly the in vitro killing of positive target cells by LAK effectors. The IA4 antibody was poorly immunoprecipitating and the surface molecule recognized was identified by gene cloning following an expression strategy using a U937 cDNA library transfected in COS cells, and a screening strategy based on membrane expression of IA4 molecule. The IA4 cDNA is virtually identical to "R2," a mRNA species previously identified in activated human T cells by subtractive hybridization. The IA4 cDNA contains an open reading frame coding for a protein 267 amino acids long with four potential transmembrane domains and one large external hydrophilic domain of about 110 amino acids, possibly glycosylated. The encoded protein belongs to a family of surface molecules, the tetra spans transmembrane protein superfamily, all displaying the four transmembrane domains, expressed on various cell types including lymphocytes (CD9, CD37, CD53, TAPA-1), melanoma cells (ME491), and intestinal cells (CO-029). These molecules have been reported to be involved in cell activation and cell death. Surprisingly, the Schistosoma mansoni Ag Sm23 displays significant homologies with this family. The IA4 molecule is a widely distributed surface marker expressed on circulating lymphocytes and monocytes, newborn thymocytes, and the cell lines mentioned above. The IA4 molecule expression is up-regulated upon cell activation. Weakly expressed on resting peripheral T and B lymphocytes and large granular lymphocytes (NK), its expression roughly doubles after activation by PHA, staphylococcus aureus Cowan I, and IL-2, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

A member of the tetra spans transmembrane protein superfamily is recognized by a monoclonal antibody raised against an HLA class I-deficient, lymphokine-activated killer-susceptible, B lymphocyte line. Cloning and preliminary functional studies

The IA4 mAb was identified among a series of antibodies raised in BALB/c mice after immunization against a HLA class I-deficient, lymphokine-activated killer (LAK)-susceptible EBV-B lymphocyte line. The IA4 antibody was selected because of its high expression, in the range of 10(5) to 25 x 10(5) sites/cell, on several B lymphocyte lines (EBV-transformed or Burkitt) and monocytic lines such as HL60 and U937, and because its expression was correlated with both target susceptibility to LAK lysis and reduced expression of HLA class I surface Ag on two pairs of EBV-B-transformed cell lines (721/721.134 and MM/10F2). Despite the strategy followed to raise the mAb and the correlation mentioned above, no direct role of the IA4 molecules in LAK susceptibility has been established, since the IA4 molecule is poorly expressed on the sensitive targets Daudi and K562; moreover, the IA4 antibody did not affect reproducibly the in vitro killing of positive target cells by LAK effectors. The IA4 antibody was poorly immunoprecipitating and the surface molecule recognized was identified by gene cloning following an expression strategy using a U937 cDNA library transfected in COS cells, and a screening strategy based on membrane expression of IA4 molecule. The IA4 cDNA is virtually identical to "R2," a mRNA species previously identified in activated human T cells by subtractive hybridization. The IA4 cDNA contains an open reading frame coding for a protein 267 amino acids long with four potential transmembrane domains and one large external hydrophilic domain of about 110 amino acids, possibly glycosylated. The encoded protein belongs to a family of surface molecules, the tetra spans transmembrane protein superfamily, all displaying the four transmembrane domains, expressed on various cell types including lymphocytes (CD9, CD37, CD53, TAPA-1), melanoma cells (ME491), and intestinal cells (CO-029). These molecules have been reported to be involved in cell activation and cell death. Surprisingly, the Schistosoma mansoni Ag Sm23 displays significant homologies with this family. The IA4 molecule is a widely distributed surface marker expressed on circulating lymphocytes and monocytes, newborn thymocytes, and the cell lines mentioned above. The IA4 molecule expression is up-regulated upon cell activation. Weakly expressed on resting peripheral T and B lymphocytes and large granular lymphocytes (NK), its expression roughly doubles after activation by PHA, staphylococcus aureus Cowan I, and IL-2, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)