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The cyclopentenone-type prostaglandin 15-deoxy-delta 12,14-prostaglandin J2 inhibits CD95 ligand gene expression in T lymphocytes: interference with promoter activation via peroxisome proliferator-activated receptor-gamma-independent mechanisms.

15-Deoxy-delta(12,14)-PGJ(2) (15d-PGJ(2)) is a cyclopentenone-type PG endowed with anti-inflammatory properties and produced by different cells, including those of the immune system. 15d-PGJ(2) is a natural ligand of the peroxisome proliferator-activated receptor (PPAR)-gamma nuclear receptor, but relevant PPARgamma-independent actions mediated by this prostanoid have been described. Fas (APO-1/CD95) and its ligand (Fas-L) are cell surface proteins whose interaction activates apoptosis of Fas-expressing targets. In T cells, the Fas-Fas-L system regulates activation-induced cell death and has been implicated in diseases in which lymphocyte homeostasis is compromised. Moreover, several studies have described the pathogenic functions of Fas and Fas-L in vivo, particularly in the induction-progression of organ-specific autoimmune diseases. In this study we describe the effect of 15d-PGJ(2) on the activation of the fas-L gene in T lymphocytes. We show that 15d-PGJ(2) inhibits fas-L mRNA expression, activation-induced cell death, and fas-L promoter activity by mechanisms independent of PPARgamma and mediated by its chemically reactive cyclopentenone moiety. Our data indicate that 15d-PGJ(2) may repress fas-L activation by interfering with the expression and/or transcriptional activity of different transcription factors (early growth response types 3 and 1, NF-kappaB, AP-1, c-Myc, Nur77) whose altered balancing and transactivation may contribute for overall repression of this gene. In addition, the activation/expression of the heat shock response genes HSF-1 and HSP70 is not directly involved in the repression, and the electrophilic molecule cyclopentenone (2-cyclopenten-1-one) may reproduce the effects mediated by 15d-PGJ(2). These results suggest that modulation of Fas-L by 15d-PGJ(2) in T cells may represent an additional tool to consider for treatment of specific autoimmune and inflammatory disorders.

Animals↗

Dominant-negative interference of the transforming growth factor beta type II receptor in mammary gland epithelium results in alveolar hyperplasia and differentiation in virgin mice.

Transforming growth factor (TGF)-beta1 and TGF-beta3 are normally expressed at high levels in the mammary gland during quiescence and at all stages of development, except lactation. Exogenously added TGF-beta1, -beta2, and -beta3 have been shown to regulate growth and differentiation of mammary epithelial cells in vitro and in vivo. TGF-betas signal through a heteromeric complex of type I and type II serine/threonine kinases. The type II receptor is necessary for ligand binding and growth suppression by TGF-betas. Deletions of the cytoplasmic domains of several kinase receptors known to function in multimeric complexes have been shown to act as dominant-negative mutations. To evaluate the role of endogenous TGF-betas in the growth and differentiation of the mammary gland in vivo, we have targeted expression of a truncated, kinase-defective TGF-beta type II receptor to mammary epithelial cells in transgenic mice using the mouse mammary tumor virus promoter/enhancer. Transgene expression was localized to the epithelial cells of terminal ducts and alveolar buds. At approximately 20 weeks of age, virgin female transgenic mice demonstrated varying degrees of mammary epithelial hyperplasia. Mammary glands from transgenic, virgin animals exhibited alveolar development and expression of the milk protein, beta-casein. The data suggest that impaired responsiveness in the epithelium to endogenous TGF-betas results in inappropriate alveolar development and differentiation in the mammary gland. We conclude that endogenous TGF-betas signal to the epithelium to maintain quiescence in the mammary glands of virgin animals.

Animals↗

Specific binding of recombinant foamy virus envelope protein to host cells correlates with susceptibility to infection.

The interaction of simian foamy viruses (FVs) with their putative cellular receptor(s) was studied with two types of recombinant envelope protein (Env). Transient expression of full-length Env in BHK-21 cells induced syncytia formation. However, selected stable transfectants fused with naive cells but not with each other. A soluble fusion protein of the Env surface domain with the Fc fragment of a human IgG1 heavy chain (EnvSU-Ig) was produced in the baculovirus expression system, purified to homogeneity, and used for binding and competition analyses. EnvSU-Ig but not unrelated Ig fusion proteins bound to cells specifically. Neutralizing serum blocked binding of EnvSU-Ig and, vice versa, serum-mediated neutralization was abrogated by the chimeric protein. Concomitant reduction of EnvSU-Ig binding and FV susceptibility was seen in Env-expressing target cells. Although EnvSU-Ig did not inhibit FV infection, very likely due to its displacement by multivalent virus-cell interactions, this divalent ligand should help to characterize functionally and to identify the ubiquitous FV receptor.

Animals↗

Digital image processing for rapid analysis of differentially expressed transcripts on high-density cDNA arrays.

Usage of filter arrays is becoming increasingly attractive for many research laboratories involved in determination of gene-expression profiles. However, analysis of numerous spots, representing genes or partial gene sequences (ESTs), is still tedious work involving the ordered analysis of vast amounts of numerical tabular data. We present a rapid and efficient method for the visual identification of differentially expressed targets on high-density cDNA filter arrays using standard laboratory equipment and standard software, which is available for free. The method we introduce provides an inexpensive alternative, and no changes in the experimental set up are required. Our results were verified by densitometric analyses performed with an established system.

Autoradiography↗

Beta-cell lines derived from transgenic mice expressing a hybrid insulin gene-oncogene.

Three pancreatic beta-cell lines have been established from insulinomas derived from transgenic mice carrying a hybrid insulin-promoted simian virus 40 tumor antigen gene. The beta tumor cell (beta TC) lines maintain the features of differentiated beta cells for about 50 passages in culture. The cells produce both proinsulin I and II and efficiently process each into mature insulin, in a manner comparable to normal beta cells in isolated islets. Electron microscopy reveals typical beta-cell type secretory granules, in which insulin is stored. Insulin secretion is inducible up to 30-fold by glucose, although with a lower threshold for maximal stimulation than that for normal beta cells. beta TC lines can be repeatedly derived from primary beta-cell tumors that heritably arise in the transgenic mice. Thus, targeted expression of an oncogene with a cell-specific regulatory element can be used both to immortalize a rare cell type and to provide a selection for the maintenance of its differentiated phenotype.

Adenoma, Islet Cell↗

Binding of the intracellular Fas ligand (FasL) domain to the adaptor protein PSTPIP results in a cytoplasmic localization of FasL.

The tumor necrosis factor family member Fas ligand (FasL) induces apoptosis in Fas receptor-expressing target cells and is an important cytotoxic effector molecule used by CTL- and NK-cells. In these hematopoietic cells, newly synthesized FasL is stored in specialized secretory lysosomes and only delivered to the cell surface upon activation and target cell recognition. FasL contains an 80-amino acid-long cytoplasmic tail, which includes a proline-rich domain as a bona fide Src homology 3 domain-binding site. This proline-rich domain has been implicated in FasL sorting to secretory lysosomes, and it may also be important for reverse signaling via FasL, which has been described to influence T-cell activation. Here we report the identification of the Src homology 3 domain-containing adaptor protein PSTPIP as a FasL-interacting partner, which binds to the proline-rich domain. PSTPIP co-expression leads to an increased intracellular localization of Fas ligand, thereby regulating extracellular availability and cytotoxic activity of the molecule. In addition, we demonstrate recruitment of the tyrosine phosphatase PTP-PEST by PSTPIP into FasL.PSTPIP.PTP-PEST complexes which may contribute to FasL reverse signaling.

Adaptor Proteins, Signal Transducing↗

Transgenic mouse models for studying the functions of insulin-like growth factor-binding proteins.

The insulin-like growth factor-binding proteins (IGFBPs) comprise a family of six related peptides that interact with high affinity with IGFs. IGFBPs compete with IGF receptors for IGF binding, and as a consequence of this competition they can affect cell growth. In addition, IGF-independent regulatory mechanisms of IGFBPs have been described. Despite their common property to interact with IGFs every IGFBP is expressed in a tightly regulated time- and tissue-specific manner suggesting that each protein may have its own distinct functions. Several transgenic mouse models overexpressing IGFBP-1, -2, -3, or -4 were developed in the past few years. Brain abnormalities were a common feature of IGFBP-1 transgenic models. Individual strains showed alterations in glucose homeostasis, reproductive performance, and a reduction of somatic growth as the most prominent phenotypes. The latter was also the main effect observed in IGFBP-2 transgenic mice. The overexpression of IGFBP-3 under the control of an ubiquitous promoter resulted in selective organomegaly, whereas mammary gland-targeted expression of this protein caused an altered involution after pregnancy in this organ. Tissue-specific overexpression of IGFBP-4 resulted in hypoplasia and reduced weight of smooth muscle-rich tissues such as bladder, aorta, and stomach. This review summarizes the current knowledge about the actions of IGFBPs in vivo based on the presently established transgenic mice.

Animals↗

Extrathymic deletion of CD8+ alloreactive T cells in a transgenic T cell receptor model of neonatal tolerance.

BACKGROUND: Immunological tolerance to foreign antigen is most easily achieved during the neonatal period. Although deletion of T cells has been demonstrated in neonatal tolerance models in which donor and recipient express different MHC class II molecules, the requirement for deletion in MHC class I-disparate models is less clear. To address this issue, we used as recipient the T cell receptor (TCR) transgenic mouse (TgM) strain 2C in which the majority of CD8+ T cells express a single alpha/beta TCR alloreactive to H-2Ld, thus facilitating direct monitoring of the class I alloreactive population. METHODS: Newborn (less than 24 hr of age) 2C TgM received injections i.v.with syngeneic C57BL/6J (H-2b) (B6) or semiallogeneic (B6xDBA)F1 (H-2bd; H-2Ld+) splenocytes. Adults were subsequently analyzed in terms of tolerance, deletion of 2C+ T cells, and chimerism. RESULTS: The results showed that semiallogeneic-, but not syngeneic-, injected neonates were unresponsive as adults to H-2Ld-expressing target cells in vitro and the majority of these mice accepted H-2Ld+ skin grafts. Delaying the injection to 72 hr after birth or reducing the number of cells injected essentially abolished in vivo unresponsiveness in 2C recipients. Thus, the 2C TCR Tg model demonstrates the characteristics typical of neonatal tolerance. Injection of 2C neonates within 24 hr of birth with semiallogeneic versus syngeneic cells led to more than a 12-fold reduction of CD8+ 2C+ T cells in adult spleen and LNCs. In contrast, deletion of CD8+ 2C+ cells in adult thymus was not consistently observed. Based on MHC class II expression to distinguish donor (I-E+) and recipient (I-E-) cells, semiallogeneic-injected mice were chimeric in spleens and lymph nodes (LNs). CONCLUSIONS: These results demonstrate that neonatal MHC class I tolerance in the adult is associated with low level hematopoietic chimerism and extrathymic deletion of alloreactive CD8+ T cells.

Animals↗

Functional equivalence of Hox gene products in the specification of the tritocerebrum during embryonic brain development of Drosophila.

Hox genes encode evolutionarily conserved transcription factors involved in the specification of segmental identity during embryonic development. This specification of identity is thought to be directed by differential Hox gene action, based on differential spatiotemporal expression patterns, protein sequence differences, interactions with co-factors and regulation of specific downstream genes. During embryonic development of the Drosophila brain, the Hox gene labial is required for the regionalized specification of the tritocerebral neuromere; in the absence of labial, the cells in this brain region do not acquire a neuronal identity and major axonal pathfinding deficits result. We have used genetic rescue experiments to investigate the functional equivalence of the Drosophila Hox gene products in the specification of the tritocerebral neuromere. Using the Gal4-UAS system, we first demonstrate that the labial mutant brain phenotype can be rescued by targeted expression of the Labial protein under the control of CNS-specific labial regulatory elements. We then show that under the control of these CNS-specific regulatory elements, all other Drosophila Hox gene products, except Abdominal-B, are able to efficiently replace Labial in the specification of the tritocerebral neuromere. We also observe a correlation between the rescue efficiency of the Hox proteins and the chromosomal arrangement of their encoding loci. Our results indicate that, despite considerably diverged sequences, most Hox proteins are functionally equivalent in their ability to replace Labial in the specification of neuronal identity. This suggests that in embryonic brain development, differences in Hox gene action rely mainly on cis-acting regulatory elements and not on Hox protein specificity.

Animals↗

Improvement in nuclear entry and transgene expression of baculoviruses by disintegration of microtubules in human hepatocytes.

Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV), a potent virus for mammalian cell gene delivery, possesses an ability to transduce mammalian cells without viral replication. We examined the role of the cellular cytoskeleton in the cytoplasmic trafficking of viral particles toward the nucleus in human hepatic cells. Microscopic studies showed that capsids were found in the nucleus after either viral inoculation or cytoplasmic microinjection of nucleocapsids. The presence of microtubule (MT) depolymerizing agents caused the amount of nuclear capsids to increase. Overexpression of p50/dynamitin, an inhibitor of dynein-dependent endocytic trafficking from peripheral endosomes along MTs toward late endosomes, did not significantly affect the amount of nuclear accumulation of nucleocapsids in the inoculated cells, suggesting that viral nucleocapsids are released into the cytosol during the early stages of the endocytic pathway. Moreover, studies with recombinant viruses containing the nuclear-targeted expression beta-galactosidase gene (beta-gal) showed a markedly increased level in the cellular expression of beta-galactosidase in the presence of MT-disintegrating drugs. The maximal increase in expression at 10 h postinoculation was observed in the presence of 80 muM nocodazole or 10 muM vinblastine. Together, these data suggest that the intact MTs constitute a barrier to baculovirus transport toward the nucleus.

Active Transport, Cell Nucleus↗

Inhibition of tumor growth by plant-derived mAb.

The tumor-associated antigen EpCAM (GA733-2) is a highly expressed target on adenocarcinoma cells, as defined by murine mAb CO17-1A. We recently developed a transgenic plant system for the safe and inexpensive production of large quantities of mAb CO17-1A as a future source of clinical-grade protein. Although the glycosylation pattern of plant-derived mAb (mAb(P)) CO17-1A differs considerably from that of the mammalian-derived mAb (mAb(M)), we show here that the biological activity of both mAbs is quite similar. mAb(P) heavy and light chains assembled to bind the recombinant antigen GA733-2E and specifically bound to human SW948 colorectal carcinoma cells expressing the antigen GA733-2 to the same extent as mAb(M). mAb(P) was as effective as mAb(M) CO17-1A in inhibiting tumor growth of xenotransplanted SW948 cells in nude mice. These results suggest the promise of transgenic plants as a useful alternative way to produce full-size mAb for cancer immunotherapy.

Animals↗

Construction of multi-purpose vectors, pCNS and pCNS-D2, are suitable for collection and functional study of large-scale cDNAs.

To efficiently perform collection and functional studies of large-scale cDNAs, we constructed multi-functional cDNA vectors for efficient full-length cDNA cloning, direct sequencing, easy screening, and the expression of cDNA in vitro and in vivo without subcloning the cDNA into other vectors. The constructed vectors, pCNS and pCNS-D2, contain a multi-cloning site for uni-directional full-length cDNA cloning, T7 and Sp6 RNA polymerase promoters for in vitro transcription and translation, and hCMV immediate early promoter and BGH poly(A) to allow expression in mammalian cells. Using these vectors, we constructed full-length enriched cDNA libraries containing 60-75% of the full-length cDNAs using two different oligo-capping methods. The subtracted cDNA libraries could also be constructed by removing of EF1-alpha cDNA, a highly expressed cDNA. In addition, we confirmed the translation of EF1-alpha cDNA in vitro and the expression of luciferase cDNA in mammalian cells. The expression efficiency of luciferase cDNA in different cell lines, such as HeLa, Hep3B, SNU638, and SNU668, showed that pCNS vectors can highly express target genes in different cell types. These results indicated that our multi-purpose vectors, pCNS and pCNS-D2, are useful tools for the construction of full-length cDNA libraries and high-throughput based functional study of cDNAs.

Animals↗

The equine luteinizing hormone beta-subunit promoter contains two functional steroidogenic factor-1 response elements.

The requirements for basal expression of the LH beta-subunit promoter in pituitary gonadotropes are largely unknown. We have used the equine (e) LHbeta subunit promoter as a model to unravel the combinatorial code required for gonadotrope expression. Through the use of 5'-deletion mutagenesis, a region between -185 and -100 of the eLHbeta promoter was shown to play a critical role in maintaining basal promoter activity in alphaT3-1 and LbetaT2 cells. This region encompasses the steroidogenic factor-1 (SF-1) binding site that has been reported to have a functional role in expression of the LHbeta promoter in other species. We have also identified an additional SF-1 site at -55 to -48. Binding of SF-1 to both sites was confirmed by electrophoretic mobility shift assays. Mutations within these sites, either individually or in combination, did not attenuate basal activity of the eLHbeta promoter in alphaT3-1 cells, but did diminish promoter activity in LbetaT2 cells. Interestingly, cotransfection with an expression vector encoding SF-1 induced eLHbeta promoter activity, and this induction was abrogated by mutations within the SF-1 sites in alphaT3-1 cells. Block replacement mutagenesis was performed on the -185/-100 region of the eLHbeta promoter to identify DNA response elements responsible for maintaining basal promoter activity. From this analysis, two regions emerged as being important: a distal 31-bp segment (-181 to -150) and an element located immediately 3' to the distal SF-1 site (-119 to -106). It is hypothesized that these two regions as well as the SF-1 sites represent regulatory elements that contribute to a combinatorial code involved in targeting expression of the eLHbeta promoter to gonadotropes.

Animals↗

Gain-of-function screen identifies a role of the Src64 oncogene in Drosophila mushroom body development.

Mushroom bodies (MB) are substructures in the Drosophila brain that are essential for memory. At present, MB anatomy is rather well described when compared to other brain areas, and elucidation of the genetic control of the development and projection patterns of MB neurons will be important to the understanding of their functions. We have performed a gain-of-function screen in order to identify genes that are involved in MB development. We drove expression of genes in MB neurons by crossing 2407 GAL4-driven UY element lines to lines containing an MB GAL4 source and UAS-GFP elements, and looked for defects in the MB structure. We have molecularly identified the genomic regions adjacent to the 26 positive UY insertions and found 18 potential genes that exhibit adult MB gain-of-function phenotypes. The proteins encoded by these candidate genes include, as well as genes with yet unknown function, transcription factors (e.g., tramtrack), nanos RNA-binding protein, microtubule-severing protein, vesicle trafficking proteins, axon guidance receptor, and the Src64 cytoplasmic protein tyrosine kinase. These genes are involved in key features of neuron cell biology. In three cases, tramtrack, nanos, and Src64, we show that the open reading frame located directly downstream of the UY P element is indeed the expressed target gene. Loss-of-function mutations of both ttk and Src64 lead to MB phenotypes proving that these genes are involved in the genetic control of MB development. Moreover, Src64 is shown here to act in a cell-autonomous fashion and is likely to interact with the previously-identified linotte/derailed receptor tyrosine kinase in MB development.

Animals↗

Drosophila damaged DNA-binding protein 1 is an essential factor for development.

The damaged DNA-binding protein (DDB) complex, thought to recognize (6-4) photoproducts and other lesions in DNA, has been implicated to have a role in global genomic nucleotide excision repair (NER) and E2F-1-mediated transcription. The complex consists of a heterodimer of p127 (DDB1) and p48 (DDB2), the latter also being known as XPE. We reported previously that in Drosophila expression of the DDB1 (D-DDB1) gene is controlled by the DRE/DREF system, and external injury to DNA is not essential for D-DDB1 function. In the present study of the function of D-DDB1 in a multicellular system, we prepared transgenic flies, which were knocked down for the D-DDB1 gene due to RNA interference (RNAi), and performed immunocytochemistry to ascertain the distribution of D-DDB1 in the eye imaginal disc. It was found to be abundant in the anterior of the morphogenetic furrow (MF). Whole-body overexpression of dsRNA of D-DDB1 in Drosophila using a GAL4-UAS targeted expression system induced melanotic tumors and caused complete lethality. When limited to the eye imaginal disc, a severe rough eye phenotype resulted. Correspondingly, all of the D-DDB1 gene knocked-out flies also died. D-DDB1 therefore appears to be an essential development-associated factor in a multicellular organism.

Animals↗

Cultured blood dendritic cells retain HIV-1 antigen-presenting capacity for memory CTL during progressive HIV-1 infection.

Dendritic cells (DC) are potent APC that may be involved in the pathogenesis of HIV-1 infection. We studied the APC function of DC from HIV-1-infected subjects that were derived from monocyte-depleted PBMC by culture in human IL-4 and human granulocyte-macrophage CSF. The cultured cells from the HIV-1-infected subjects had similar morphology and phenotype of mature DC (CD80 = 41 +/- 8%, CD86 = 77 +/- 5%, CD40 = 87 +/- 6%, CD1a = 1 +/- 1%) to DC cultured from seronegative subjects. The yield of these DC was lower than from HIV-1-seronegative subjects (4 +/- 0% vs 11 +/- 2%, p < 0.01), and the lower DC yields correlated with lower numbers of blood CD4+ T cells (r = 0.60, p < 0.01) and higher plasma viral load (r = -0.49, p < 0.01). DC from HIV-1-infected subjects were infected with recombinant vaccinia virus vectors expressing Gag, Pol, and Env and were able to stimulate equal or higher levels of MHC class I-restricted, anti-HIV-1 memory CTL (CTLm) than were similarly treated, autologous B lymphocyte cell lines. DC pulsed with peptides representing HIV-1 CTL epitopes stimulated higher levels of anti-HIV-1 CTLm responses than did DC infected with the vaccinia virus-HIV-1 constructs. Allogeneic, MHC class I-matched DC also stimulated anti-HIV-1 CTLm activity in cells from HIV-1-infected subjects. DC from early and late stages of HIV-1 infection had a similar ability to activate CTLm specific for targets expressing either HIV-1 genes via vaccinia virus vectors or HIV-1 immunodominant synthetic peptides. However, DC from either early or late stages of HIV-1 infection could not overcome the defect in anti-HIV-1 CTLm response in advanced infection.

Acquired Immunodeficiency Syndrome↗

Increased expression but not targeting of ENaC in adrenalectomized rats with PAN-induced nephrotic syndrome.

Sodium retention is a hallmark of nephrotic syndrome (NS). Puromycin aminonucleoside (PAN)-induced NS is associated with high aldosterone levels and increased ENaC expression and apical targeting. However, the mechanisms associated with increased apical targeting of ENaC in NS remain undefined, and it is unclear whether this is secondary to high aldosterone levels and whether aldosterone and/or apical ENaC targeting are important for the development of sodium retention. This study aimed at uncovering 1) whether aldosterone is essential for sodium retention in PAN-induced NS, 2) whether ENaC expression or apical targeting is secondary to high aldosterone levels, and 3) the role of aldosterone in the dysregulation of sodium transporters in NS. Puromycin treatment of adrenalectomized (ADX) rats supplemented with dexamethasone induced sodium retention despite the absence of aldosterone. Immunocytochemical analyses revealed an absence of enhanced apical targeting of ENaC subunits in PAN-treated ADX (ADX-PAN) rats, with distribution of labeling similar to adrenalectomized dexamethasone-treated control rats (ADX). Moreover, ENaC subunit abundance was increased in ADX-PAN rats. The abundance of aquaporin-2 was unchanged, whereas apical targeting was enhanced. Key sodium transporters were downregulated as previously observed in nonadrenalectomized puromycin-treated rats (Kim SW, Wang W, Nielsen J, Praetorius J, Kwon TH, Knepper MA, Frøkiaer J, and Nielsen S. Am J Physiol Renal Physiol 286: F922-F935, 2004), whereas the global expression of the alpha1-subunit of the Na-K-ATPase was unchanged. In conclusion, PAN treatment in the absence of aldosterone induced sodium retention, increased ENaC expression, but did not change the subcellular distribution of ENaC. This indicates that the previously observed enhanced apical targeting of ENaC in PAN-induced NS (Kim SW, Wang W, Nielsen J, Praetorius J, Kwon TH, Knepper MA, Frøkiaer J, and Nielsen S. Am J Physiol Renal Physiol 286: F922-F935, 2004) is caused by aldosterone and that development of sodium retention can occur in the absence of aldosterone in NS.

11-beta-Hydroxysteroid Dehydrogenase Type 2↗

Lymphokine-activated killer cells targeted by monoclonal antibodies to the disialogangliosides GD2 and GD3 specifically lyse human tumor cells of neuroectodermal origin.

Monoclonal antibodies 14.18 (IgG3) and 11C64 (IgG3) directed against disialogangliosides GD2 and GD3, respectively, when used in conjunction with human peripheral blood mononuclear cells (PBMCs) stimulated with human recombinant interleukin (rIL-2) lyse both human melanoma and neuroblastoma cells by antibody-dependent cellular cytotoxicity. Such monoclonal antibody-"armed" effector cells are specifically directed to targets expressing the given disialoganglioside without detectable cross-reactivity. In addition, antibody-dependent cellular cytotoxicity as well as the natural killing ability of human PBMCs is augmented by a brief coincubation with rIL-2. PBMCs augmented by rIL-2 and armed with monoclonal antibodies significantly suppressed tumor growth in the xenotransplant nude mouse model. Our results suggest that once a threshold level of activation of PBMCs is achieved, additional rIL-2 (over three orders of magnitude of concentration) does not significantly enhance cytolytic augmentation. Furthermore, anti-GD3 monoclonal antibody 11C64 together with rIL-2-stimulated PBMCs from melanoma patients with widely differing tumor burdens effectively lyse melanoma tumor targets in antibody-dependent cellular cytotoxicity. Our results also suggest that GD2 and GD3 represent distinct and relevant immunotherapeutic target structures on melanoma whereas GD2 does the same for neuroblastoma tumors. Our data suggest that targeting of activated human effector cells may provide a new and effective cancer immunotherapy protocol.

Animals↗