Inhibition of plasmacytoma development in BALB/c mice by indomethacin

Preclinical validation of interleukin 6 as a therapeutic target in multiple myeloma

Studies on the biologic and molecular genetic underpinnings of multiple myeloma (MM) have identified the pleiotropic, pro-inflammatory cytokine, interleukin-6 (IL-6), as a factor crucial to the growth, proliferation and survival of myeloma cells. IL-6 is also a potent stimulator of osteoclastogenesis and a sculptor of the tumor microenvironment in the bone marrow of patients with myeloma. This knowledge has engendered considerable interest in targeting IL-6 for therapeutic purposes, using a variety of antibody- and small-molecule-based therapies. However, despite the early recognition of the importance of IL-6 for myeloma and the steady progress in our knowledge of IL-6 in normal and malignant development of plasma cells, additional efforts will be required to translate the promise of IL-6 as a target for new myeloma therapies into significant clinical benefits for patients with myeloma. This review summarizes published research on the role of IL-6 in myeloma development and describes ongoing efforts by the University of Iowa Myeloma Multidisciplinary Oncology Group to develop new approaches to the design and testing of IL-6-targeted therapies and preventions of MM.

Lupus Nephritis: Animal Modeling of a Complex Disease Syndrome Pathology

Nephritis as a result of autoimmunity is a common morbidity associated with Systemic Lupus Erythematosus (SLE). There is substantial clinical and industry interest in medicinal intervention in the SLE nephritic process; however, clinical trials to specifically treat lupus nephritis have not resulted in complete and sustained remission in all patients. Multiple mouse models have been used to investigate the pathologic interactions between autoimmune reactivity and SLE pathology. While several models bear a remarkable similarity to SLE-driven nephritis, there are limitations for each that can make the task of choosing the appropriate model for a particular aspect of SLE pathology challenging. This is not surprising given the variable and diverse nature of human disease. In many respects, features among murine strains mimic some (but never all) of the autoimmune and pathologic features of lupus patients. Although the diversity often limits universal conclusions relevant to pathogenesis, they provide insights into the complex process that result in phenotypic manifestations of nephritis. Thus nephritis represents a microcosm of systemic disease, with variable lesions and clinical features. In this review, we discuss some of the most commonly used models of lupus nephritis (LN) and immune-mediated glomerular damage examining their relative strengths and weaknesses, which may provide insight in the human condition.

Epstein-Barr virus and its role in the pathogenesis of Burkitt's lymphoma: an unresolved issue

For several reasons Burkitt's lymphoma (BL) has become a paradigm in cancer research: for its particular geographical distribution, the presence of Epstein-Barr virus (EBV) in the cases in high incidence areas, and for the activation of the proto-oncogene c-myc by chromosomal translocation in one of the immunoglobulin gene loci. As c-MYC activates both, proliferation and apoptosis, at least two events have to cooperate in lymphomagenesis: activation of c-MYC and a shift in the balance from apoptosis towards survival. Antigenic and/or polyclonal stimulation of the B cell receptor, genetic instability imposed by activation induced deaminase (AID), as well as the viral gene products EBNA1 and several small non-coding non-polyadenylated RNAs are the main factors suspected to play an important role in the pathogenesis of BL. Despite intensive research, the role of the virus has remained largely elusive in the past decades, but the discovery of two viral microRNA clusters that are expressed in EBV associated tumors including BL has raised new hopes and expectations that EBV is going to reveal its mystery. This review focuses on the interplay between cellular and viral factors and puts special emphasis on mouse models and experimental cell culture systems that address these points.

Cyclooxygenase-2 expression in non-Hodgkin's lymphomas

Cyclooxygenase 2 (Cox-2) is a key enzyme in prostaglandin synthesis and it has an important role in the pathogenesis of various malignancies. Cox-2 has been studied in solid tumors; however, studies about the role of Cox-2 in non-Hodgkin's lymphomas (NHL) are limited. The aim of this study is to determine the importance of Cox-2 expression in lymphomas. To this end, Cox-2 expression was determined in 177 cases with NHL. In histological terms, 60 cases (33%) had low grade and 117 (67%) had aggressive lymphoma. Ninety-nine cases were found to be positive for Cox-2 (56%); Cox-2 score was between 50 and 100, 101 and 200 and over 200 in 38, 46 and 15 cases, respectively. There was an important association between aggressive histology and Cox-2 expression: Cox-2 was negative in about half of the cases with indolent morphology, while two thirds of the Cox-2 positive cases had aggressive histology (p = 0.036). There was no significant association between Cox-2 expression and clinical-laboratory parameters. Although the overall survival times were longer in cases with lower or no Cox-2 expression as compared with higher Cox-2 expression, the difference was not significant. In conclusion Cox-2 expression is seen about 60% of the cases with NHL and is associated with aggressive morphology.

A mutant collagen XIII alters intestinal expression of immune response genes and predisposes transgenic mice to develop B-cell lymphomas

Epithelial cells of mucosal surfaces are critical for maintaining immune homeostasis by aiding in the discrimination of pathogenic and commensal microorganisms and modulating the activities of antigen-presenting cells and lymphocytes. Functional breakdowns resulting in chronic infection and inflammation are associated with the development of hematologic and solid neoplasms for which detailed pathogenetic mechanisms are poorly understood. Mice heterozygous for a transgene Col13a1(del) expressing a mutant collagen XIII developed clonal mature B-cell lineage lymphomas originating in mesenteric lymph nodes (MLN). The tumors were associated with T cells and macrophages. The incidence of disease was reduced 2-fold in transgenic mice raised under specific pathogen-free conditions, suggesting a role for infectious agents. The lymphomas did not express the mutant collagen XIII, indicating that its influence on tumorigenesis was B-cell extrinsic and likely to be associated with collagen XIII-positive tissues drained by the MLN. Studies of the small intestines of transgenic mice showed that the subepithelial basement membranes (BM) were highly abnormal and that they exhibited heightened expression of genes involved in immune responses. These results define collagen XIII-dependent maintenance of the intestinal BM as a previously unappreciated component of immune responses and a critical determinant of cancer susceptibility.

The role of interleukin 6 in plasmacytomagenesis

Interleukin 6 (IL-6) is a polyfunctional cytokine which regulates the immune response, the acute-phase reaction and haemopoiesis. IL-6 plays a critical role in differentiation of B cells into plasma cells, and is a potent growth factor for plasmacytomas and myelomas. A relationship between IL-6 and polyclonal plasma cell abnormalities has been demonstrated. Abnormal production of IL-6 was first suggested to be related to hypergammaglobulinaemia with autoantibody production in patients with cardiac myxoma. A role of IL-6 in the generation of plasmacytoma has also been indicated. In support of these clinical and experimental observations, we demonstrated that transgenic C57BL/6 mice carrying the human IL-6 gene showed a massive polyclonal plasmacytosis with production of autoantibodies. However, the tumour was not transplantable to syngeneic animals. Susceptibility to pristane-induced plasmacytomagenesis is genetically determined--pristane can induce plasmacytomas in BALB/c but not in C57BL/6 mice. IL-6 transgenic C57BL/6 mice were backcrossed to BALB/c mice to elucidate the genetic influence on plasmacytomagenesis. Transplantable monoclonal plasmacytoma with a t(12;15) chromosomal translocation was generated in some of the backcrossed mice, indicating that IL-6 plays a key role in the multistep oncogenesis of plasma cell neoplasia.

Efficacy of an osmotic pump delivered, GM-CSF-based tumor vaccine in the treatment of upper aerodigestive squamous cell carcinoma in rats

PURPOSE

Upper aerodigestive tract (UADT) cancer has not experienced significant overall survival improvement for over 20 years, and no successful treatments for systemic disease exist. Most patients with UADT cancer experience immune suppression, therefore immune restorative therapies may offer promise for these patients. We presently tested the efficacy of granulocyte macrophage-colony stimulating factor (GM-CSF) delivered via 28-day continuous infusion pump, in combination with irradiated tumor cells, in a flank model of UADT cancer.

METHODS

Five groups of rats were inoculated with syngeneic mucosally derived squamous carcinoma cells (FAT-7). Osmotic minipumps were implanted in the contralateral flank to deliver GM-CSF at 0 (PBS), 0.1, 1, 10, or 100 ng/day (n = 6 per group) for 28 days; 10(6) irradiated FAT-7 cells (ITC) were injected at the site of the GM-CSF infusion on days 0, 3, 7, 14, and 21 immune infiltrates in tumors were analyzed.

RESULTS

Rats that received 10 or 100 ng/day GM-CSF/ITC had a significantly slower tumor growth rate compared to those who received 0, 0.1, or 1 ng/day (ANOVA, P < 0.01). There were increased CD 4+, CD 8+, and CD 68+ cells in tumors of GM-CSF/ITC treated animals over controls.

CONCLUSION

GM-CSF (10 or 100 ng/day) delivered locally via osmotic pump with ITC slows the growth rate of mucosally derived squamous cell carcinoma in rats while improving immune cell infiltrates. The efficacy of locally delivered GM-CSF immunotherapy in this model may be a first step toward this immunotherapy strategy for humans.

Prostaglandin E2 promotes degranulation-independent release of MCP-1 from mast cells

Mast cells (MCs) are common components of inflammatory infiltrates and a source of proangiogenic factors. Inflammation is often accompanied by vascular changes. However, little is known about modulation of MC-derived proangiogenic factors during inflammation. In this study, we evaluated the effects of the proinflammatory mediator prostaglandin E2 (PGE2) on MC expression and release of proangiogenic factors. We report that PGE2 dose-dependently induces primary MCs to release the proangiogenic chemokine monocyte chemoattractant protein-1 (MCP-1). This release of MCP-1 is complete by 2 h after PGE2 exposure, reaches levels of MCP-1 at least 15-fold higher than background, and is not accompanied by degranulation or increased MCP-1 gene expression. By immunoelectron microscopy, MCP-1 is detected within MCs at a cytoplasmic location distinct from the secretory granules. Dexamethasone and cyclosporine A inhibit PGE2-induced MCP-1 secretion by approximately 60%. Agonists of PGE2 receptor subtypes revealed that the EP1 and EP3 receptors can independently mediate MCP-1 release from MCs. These observations identify PGE2-induced MCP-1 release from MCs as a pathway underlying inflammation-associated angiogenesis and extend current understanding of the activities of PGE2.

The role of IL-6 and STAT3 in inflammation and cancer

The defense of the host from foreign pathogens is the commonly accepted function of the vertebrate immune system. A complex system consisting of many differing cells and structures communicating by both soluble and cell bound ligands, serves to protect the host from infection, and plays a role in preventing the development of certain types of tumours. Numerous signalling pathways are involved in the coordination of the immune system, serving both to activate and attenuate its responses to attack. The ability of the immune system, specifically those cells involved in acute inflammatory responses, to mediate the directed (and sometimes indirect) killing of cells and pathogens, make it a potential threat to host survival. Furthermore, the production and release of various survival factors such as the pleiotropic cytokine IL-6, a major mediator of inflammation and activator of signal transducer and activator of transcription 3, serves to block apoptosis in cells during the inflammatory process, keeping them alive in very toxic environments. Unfortunately, these same pathways serve also to maintain cells progressing towards neoplastic growth, protecting them from cellular apoptotic deletion and chemotherapeutic drugs. Here, we discuss the relationships between cancer and inflammation, and some of the molecular mechanisms involved in mediating the unintended consequences of host defense and tumour survival.

Mast cell-derived angiopoietin-1 plays a critical role in the growth of plasma cell tumors

Multiple myeloma in humans is frequently associated with mast cell infiltration and neovascularization, which correlate directly with disease severity, but the mechanisms underlying this relationship remain unclear. Here, we report that primary murine mast cells express angiopoietin-1 (Ang-1) and low levels of VEGF-A but not Ang-2 and that 2 established murine plasmacytoma cell lines express high levels of VEGF-A but little or no Ang-1 or Ang-2. An in vivo angiogenesis assay using extracellular matrix components shows that mast cells and plasmacytoma cells, together, promote marked neovascularization composed of dilated vessels, which is prevented by neutralization of VEGF-A and Ang-1 but is only partially reduced by neutralization of either VEGF-A or Ang-1. Mast cells within extracellular matrix components express Ang-1, and recombinant Ang-1 together with plasmacytoma cells promotes extracellular matrix neovascularization similar to that induced by mast cells. A transplantation assay shows that primary mast cells accelerate tumor growth by established plasmacytoma cell lines and that neutralization of Ang-1 alone or with VEGF-A reduces significantly the growth of plasmacytomas containing mast cells. These results demonstrate that mast cell-derived Ang-1 promotes the growth of plasmacytomas by stimulating neovascularization and provide further evidence supporting a causal relationship between inflammation and tumor growth.

Increased cyclooxygenase-2 (COX-2): a potential role in the pathogenesis of lymphoma

B cell lymphomas are a diverse group of clinicopathologic diseases with an increasing incidence. As with other malignancies, the accumulation of genetic abnormalities are required for malignant transformation of human lymphocytes. Cyclooxygenase-2 (COX-2) is a key biosynthetic enzyme in prostaglandin synthesis and has been implicated in the pathogenesis of numerous malignancies including colon, breast, and lung cancer. There is little data on the potential role of COX-2 in lymphoma pathogenesis. In this study, several B lymphoma cell lines and primary B cells obtained from normal volunteer controls were examined for COX-2 protein expression. Immunoblot analysis demonstrated between an approximately 2.2-4.3-fold increase in COX-2 protein expression relative to primary B cells in all lymphoma cell lines examined. Increased COX-2 phosphorylation was found in the BJAB, BL41, and Raji cells whereas the levels in Daudi, Namalwa, and Ramos did not differ from that of primary B cells. Treatment with 25-100 microM celecoxib (CEL) resulted in decreased proliferation as measured by [3H]thymidine in all cell lines examined, and the effect was dose-dependent, and not significantly enhanced by chlorambucil (CHL). The effect of COX-2 inhibition on apoptosis in lymphoma cells was examined and revealed apoptotic induction of greater than 85% in all cell lines examined at 50 microM celecoxib. The pro-apoptotic effect was dose-dependent, and was not significantly enhanced by chlorambucil. Examination of apoptosis-related proteins by immunoblot analysis revealed levels of BCL-2, BCL-X(L), and Bax to be unaffected by celecoxib. In contrast, levels of Akt, MCL-1, and phosphorylated SAP-kinase were all decreased after incubation with 50 microM celecoxib. These findings suggest that increased COX-2 expression and activity, contributes to the pathogenesis of B cell lymphomas and point to a possible role for COX-2 inhibition in their treatment.

Neoplastic development in plasma cells

An increasing number of model systems of plasma cell tumor (PCT) formation have been and are being developed. Discussed here are six models in mice and multiple myeloma (MM) in humans. Each model illustrates a unique set of biological factors. There are two general types of model systems: those that depend upon naturally arising mutagenic changes (pristane-induced PCTs, 5TMM, and MM) and those that are associated with oncogenes (Emu-v-abl), growth factors [interleukin-6 (IL-6)], and anti-apoptotic factors (Bcl-xL/Bcl-2). PCTs develop in several special tissue microenvironments that provide essential cytokines (IL-6) and cell-cell interactions. In mice, the activation and deregulation of c-myc by chromosomal translocations is a major feature in many of the models. This mechanism is much less a factor in MM and the 5T model in mice. Genetically determined susceptibility is involved in many of the mouse models, but only a few genes have been implicated thus far.

Lymphoma- and leukemia-associated chromosomal translocations in healthy individuals

Chromosomal translocations (CTs) are hallmark mutations of hematopoietic malignancy that result in the deregulated expression of oncogenes or the generation of novel fusion genes. The polymerase chain reaction (PCR) can be used to detect illegitimate recombinations of genomic DNA sequences as a more sensitive assay than cytogenetics for determining the presence of CTs. Both direct DNA-PCR and reverse transcriptase-PCR were used to examine healthy individuals for lymphoma- and leukemia-associated CTs. Two oncogene-activating CTs [t(14;18)(q32;q21) and t(8;14)(q24;q32)] and one fusion-gene CT [t(2;5)(p23;q35)] from lymphomas and five fusion-gene CTs from leukemia [t(9;22)(q34;q11), t(4;11)(q21;q23), t(15;17)(q22;q11), t(12;21)(p13;q22), t(8;21)(q22;q22)] were detected in such studies. The biological implication is that CTs associated with malignant tumors may also be found in cells that are not neoplastic. CTs are characteristic attributes of neoplastic clones but are by themselves insufficient to cause malignant transformation. A better understanding of the special biology of non-neoplastic CT-bearing cells will provide insight into their putative role as tumor precursors. Prospective epidemiological studies are needed to determine whether such cells in healthy individuals may, in some instances, become clonogenic founders of lymphoma or leukemia.

Burkitt lymphoma in the mouse

Chromosomal translocations juxtaposing the MYC protooncogene with regulatory sequences of immunoglobulin (Ig) H chain or kappa (Ig kappa) or lambda (Ig lambda) L chain genes and effecting deregulated expression of MYC are the hallmarks of human Burkitt lymphoma (BL). Here we report that lymphomas with striking similarities to BL develop in mice bearing a mutated human MYC gene controlled by a reconstructed Ig lambda locus encompassing all the elements required for establishment of locus control in vitro. Diffusely infiltrating lymphomas with a typical starry sky appearance occurred in multiple founders and an established line, indicating independence from positional effects. Monoclonal IgM(+)CD5(-)CD23(-) tumors developed from an initially polyclonal population of B cells. These results demonstrate that the phenotype of B lineage lymphomas induced by MYC dysregulation is highly dependent on cooperativity among the regulatory elements that govern expression of the protooncogene and provide a new system for studying the pathogenesis of BL.

Immunization as a model for systemic lupus erythematosus

BACKGROUND

Immunization of laboratory animals is a new model system for systemic lupus erythematosus (SLE) and the autoimmunity of SLE.

OBJECTIVE

Review the published reports describing immunization as a model of SLE and describe the state of this research as well as future objectives as related to human illness.

METHODS

Medline search for relevant articles as well as review of cited bibliographies.

RESULTS

Either rabbits or mice can be immunized with proteins or oligopeptides that are lupus autoantigens with a resulting immune response not just to the immunogen but instead to a host of other self components that are also SLE-associated autoantigens. Several studies have noted clinical illness in these animals that resembles human SLE. In addition, injection of pristane (a component of mineral oil) also results in SLE-like autoimmunity, even though lupus autoantigens are not present. Pristane injected animals may also develop an SLE-like illness. There are reports of human SLE having its onset after immunization, but there have been no prospective studies.

CONCLUSIONS

Studies are needed to determine whether human SLE tends to begin soon after immunization. Meanwhile, continued study of animal models developed after immunization is needed in order to determine the relevance of this model to human disease.

RELEVANCE

SLE and/or SLE-like autoimmunity can be triggered after immunization of animals. This may be a model for an environmental trigger of human SLE.

Inhibition of pristane-induced peritoneal plasmacytoma formation

While the mechanism of how Indo inhibits PCTGEN is not established, Several hypothetical explanations provide new potential experimental approaches. Indo may block production of cytokines such as Il-6 in accessory cells that are critical for B-cell growth, viability and maturation, or it may directly target B cells via PPAR-gamma receptors. The latter mode of action is described in other cell types but not yet defined in B cells.

BALB/c.CBA/N mice carrying the defective Btk(xid) gene are resistant to pristane-induced plasmacytomagenesis

The X-chromosome from the CBA/N mouse which carries the defective Bruton's tyrosine kinase (Btk) allele (Xxid) has been introgressively backcrossed onto the plasmacytoma (PCT) induction-susceptible BALB/cAN. Inbred BALB/c.CBA/N-xid/xid (C.CBA/N) mice raised and maintained in our conventional colony were given three 0.5 ml injections of pristane and were highly refractory to PCT induction. Only one PCT was found among 59 mice followed for > or =300 days. Twenty mice were examined at day 200 for foci of plasma cells in the oil granuloma. Ten mice had small foci of plasma cells, most of which were plasmacytotic, embedded in the inflammatory oil granuloma. In one there were multiple foci, but most of the mice had only one or two foci. F1 hybrid XxidY males derived from CBA/N females crossed to BALB/cAnPt were also resistant to PCT induction, while heterozygous and homozygous XY males were susceptible. C.CBA/N mice can develop extensive mucosal plasma cells as well as plasma cell accumulations in oil granuloma tissue, but the precursors of these plasma cells do not give rise to PCT in genetically susceptible hosts. The failure of C.CBA/N mice to develop PCT is probably due to the elimination of B cell clones that can be perpetuated by repeated exposure to thymus-independent type 2 antigens.

Murine plasmacytomas, carrier of the t(12;15) chromosomal translocation, develop from immature/mature B cells not from differentiated plasma cells

Dysregulation of the c-myc gene by chromosomal translocation in >95% of murine plasmacytomas (MPCs) is an obligatory requirement for the transformation of B lymphocytes into MPCs. However, it is still unknown whether sIg+ B cells or differentiated plasma cells are the legitimate precursor cells from which MPCs develop. To address this question, C.B-17 scid/scid (SCID) mice were reconstituted with splenic surface Ig-positive (sIg+) B lineage cells originating from BALB/cRb6.15 (B/cRb6.15) or human IL-6 transgene-congenic BALB/cRb8.12 mice (B/cRb8.12 IL-6-Tg). Six of 80 SCID mice reconstituted with B/cRb6.15 sIg+ B cells developed MPCs after pristane (2,6,10,14-tetramethylpentadecane) treatment followed by Abelson murine leukemia virus (A-MuLV) infection (incidence 7.5%) and four of 40 after pristane treatment alone (incidence 10%). Similarly, in 20 SCID mice reconstituted with B/cRb8.12 IL-6-Tg splenic sIg+ B cells the MPC incidence was 10%. Karyotype analysis revealed that all the translocations were of typical t(12;15) type and all tumors carried the Rb6.15 or Rb8.12 marker chromosome, indicating their donor cell origin. In contrast, none of the 48 SCID mice reconstituted with plasma cells obtained from the lymph nodes of B/cRb8.12 IL-6-Tg mice developed MPCs when treated either with pristane plus A-MuLV (20 mice) or with pristane alone (28 mice), although the transferred plasma cells were still functional in the recipient SCID mice 6 months after transfer. The findings indicate that the malignant transformation triggered by Ig/myc juxtaposition occurs more in immature (sIgM+) and/or mature (sIgM+/sIgD+, sIgG+ and sIgA+) B cells than in differentiated G0 or cycling plasma cells. We inferred that immature and/or mature B cells and not differentiated plasma cells are most likely the principal source of precursor cells from which the typical t(12;15) MPCs develop.

Interleukin-1 in multiple myeloma: producer cells and their role in the control of IL-6 production

We studied the role of interleukin (IL)-1beta in patients with multiple myeloma. By in situ hybridization and immunochemistry, myeloid and megakaryocytic cells expressed high levels of the IL-1beta gene and produced IL-1beta. Myeloma cells less potently expressed the IL-1beta gene and IL-1beta protein. IL-1beta gene expression was not constitutive since it was detected in the bone marrow myeloma cells of two patients, unlike circulating tumoural cells. In addition, nine myeloma cell lines failed to express the IL-1beta gene and this expression could not be induced by 12 different cytokines. We demonstrated that IL-1 was mainly responsible for IL-6 production in the tumoural environment through a PGE2 loop. In fact, an IL-1 receptor antagonist (IL-1RA) blocked PGE2 synthesis and IL-6 production by 80%; this blockage could be reversed by adding synthetic PGE2. Similar findings were found with indomethacin, an inhibitor of cyclooxygenase that blocks PGE2 synthesis. Taken together, these data emphasize the possibility of blocking IL-1 by using IL-1RA or other antagonists in order to block IL-6 production, which is a major tumoural survival and proliferation factor.

Genetics of quantitative and qualitative aspects of lung tumorigenesis in the mouse: multiple interacting Susceptibility to lung cancer (Sluc) genes with large effects

Inbred strains of mice exhibit large differences in their susceptibility to various complex quantitative genetic traits, among which is the susceptibility to lung cancer. These differences are caused by the combined effects of multiple quantitative trait loci (QTLs). Due to their multiplicity, it is relatively difficult and laborious to study the effects of individual QTLs. To dissect complex genetic traits the authors make use of recombinant congenic strains (RCS), a system of mouse inbred strains in which the genetic complexity is reduced. The susceptibility to lung cancer is studied by using the series of O20-congenic-B10.O20 (OcB) RC strains. They are derived from the parental background strain O20 and the parental donor strain B10.O20, two mouse inbred strains that differ from each other in both quantitative and qualitative aspects of lung tumorigenesis. This study describes the segregation of lung tumor number, size, and histology among the OcB RC strains, and indicates that these traits are influenced by multiple interacting QTLs with considerable individual effects. The results suggest that some of the susceptibility loci to lung cancer affect the susceptibility to other types of cancer as well, possibly by functioning systematically.

Influence of microbial stimulation on hypergammaglobulinemia and autoantibody production in pristane-induced lupus

Pristane induces a lupus-like syndrome characterized by autoantibody production and glomerulonephritis in nonautoimmune strains of mice. Although it has been suggested that this syndrome results from nonspecific immune activation, there is little evidence so far that B cells are activated nonspecifically by pristane or that this promotes autoimmunity. In this study, we examined whether polyclonal hypergammaglobulinemia occurs in pristane-induced lupus, and its relationship to the production of anti-DNA, nRNP/Sm, and Su autoantibodies. In conventionally housed mice, there was a marked increase in total IgM and IgG3 2 weeks after i.p. pristane injection, followed by increased IgG1, IgG2a, and IgG2b levels. IgM levels were higher in pristane-treated specific pathogen-free (SPF) mice than in conventionally housed mice, whereas IgG and IgA levels were reduced. Pristane induced anti-nRNP/Sm and Su autoantibodies in SPF mice, but their onset was delayed and levels were lower than those in conventionally housed mice. There was no consistent relationship between total IgG1, 2a, and 2b hypergammaglobulinemia and production of anti-nRNP/Sm and Su autoantibodies. Moreover, the total Ig levels were similar in the anti-nRNP/Sm-positive and -negative groups. In contrast, production of IgM anti-ssDNA antibodies paralleled IgM hypergammaglobulinemia in some, but not all, mice. These studies indicate that pristane-induced lupus is associated with marked hypergammaglobulinemia, the magnitude of which is influenced by the microbial environment. However, anti-nRNP/Sm and Su autoantibody production is at least partly independent of polyclonal B cell activation. The data strongly suggest that pristane-induced lupus is not exclusively the consequence of nonspecific immune stimulation. They also point to the importance of microbial stimulation in the development of hypergammaglobulinemia in this inducible lupus model.

Indomethacin Is a Potent Inhibitor of Pristane and Plastic Disc Induced Plasmacytomagenesis in a Hypersusceptible BALB/c Congenic Strain

Continuous indomethacin (INDO) administration in the drinking water (10 to 20 μg/mL) profoundly inhibited plasmacytoma (PCT) development initiated by three 0.2- or 0.5-mL intraperitoneal (i.p.) injections of pristane in hypersusceptible BALB/c.DBA/2-Idh1-Pep3 congenic mice. The most effective inhibitions were obtained with continuous INDO treatment. When treatment was delayed until 50 to 60 days after the first pristane injection, there was approximately a 50% reduction in PCT incidence. The primary action of pristane is the induction of a chronic inflammation in the peritoneal connective tissues and the formation of a microenvironment where PCTs develop. INDO, a powerful inhibitor of prostaglandin synthases (cyclooxygenases 1 and 2), did not inhibit the formation of mesenteric oil granuloma nor the appearance of cells in this chronic inflammatory tissue carrying c-myc illegitimately joined to an Ig heavy chain switch region, ie, the t(12; 15) chromosomal translocation. INDO inhibited PCT induction by the i.p. implantation of 21 × 2 mm polycarbonate discs. These solid objects predominantly induce the formation of a patchy fibroplastic tissue on contacting peritoneal surfaces. These and previous data indicate that indomethacin inhibits an intermediate stage in PCT development after the arrival of cells bearing the T(12; 15) translocation in the oil granuloma and before these cells acquire transplantability to a pristane-conditioned host. The biological mechanism that explains how INDO inhibits PCT development is not yet established but appears to result from decreased production of prostaglandins in chronic inflammatory tissues (oil granuloma, fibroplasia), suggesting that prostaglandins play an active role in oil and solid plastic induced PCT formation.

Indomethacin Is a Potent Inhibitor of Pristane and Plastic Disc Induced Plasmacytomagenesis in a Hypersusceptible BALB/c Congenic Strain

Continuous indomethacin (INDO) administration in the drinking water (10 to 20 μg/mL) profoundly inhibited plasmacytoma (PCT) development initiated by three 0.2- or 0.5-mL intraperitoneal (i.p.) injections of pristane in hypersusceptible BALB/c.DBA/2-Idh1-Pep3 congenic mice. The most effective inhibitions were obtained with continuous INDO treatment. When treatment was delayed until 50 to 60 days after the first pristane injection, there was approximately a 50% reduction in PCT incidence. The primary action of pristane is the induction of a chronic inflammation in the peritoneal connective tissues and the formation of a microenvironment where PCTs develop. INDO, a powerful inhibitor of prostaglandin synthases (cyclooxygenases 1 and 2), did not inhibit the formation of mesenteric oil granuloma nor the appearance of cells in this chronic inflammatory tissue carrying c-myc illegitimately joined to an Ig heavy chain switch region, ie, the t(12; 15) chromosomal translocation. INDO inhibited PCT induction by the i.p. implantation of 21 × 2 mm polycarbonate discs. These solid objects predominantly induce the formation of a patchy fibroplastic tissue on contacting peritoneal surfaces. These and previous data indicate that indomethacin inhibits an intermediate stage in PCT development after the arrival of cells bearing the T(12; 15) translocation in the oil granuloma and before these cells acquire transplantability to a pristane-conditioned host. The biological mechanism that explains how INDO inhibits PCT development is not yet established but appears to result from decreased production of prostaglandins in chronic inflammatory tissues (oil granuloma, fibroplasia), suggesting that prostaglandins play an active role in oil and solid plastic induced PCT formation.

Experimental plasmacytomagenesis in mice

This article discusses some of the mechanistic aspects of plasma cell tumor development. Plasmacytomagenesis, much like other forms of neoplastic development, is a highly complex process that develops in the B cell differentiation lineage. As more is learned about the molecular genetics of multiple myeloma and PCTs in mice, a unifying concept will emerge that possibly can explain the phenotypic differences in the two neoplastic cell processes as variants of a common process.

Spontaneous development of plasmacytomas in a selected subline of BALB/cJ mice

Sixty per cent of BALB/cAnPt mice injected intraperitoneally (i.p.) with tetramethylpentadecane (pristane) develop plasmacytomas (PCs), whereas less than 10% of BALB/cJ develop such tumours. Most other mouse strains are completely resistant. Resistance is dominant over susceptibility in F1 hybrids between BALB/cAnPt and the resistant non-BALB/c strains, suggesting that susceptibility may be due to some genetic defect. (BALB/cAnPtxBALB/cJ)F1 hybrids have a PC incidence of 36-42%. Previously, BALB/cJ has been shown to harbour at least one resistance gene (Potter et al., Genomics 1988, Vol. 2, pp. 257-262). On the assumption that BALB/cJ may contain a segregating resistance gene, we cross BALB/cJ females with pristane-pretreated BALB/cJ males that were found to be carrying PC cells intraperitoneally 5-7 months after pristane treatment. After two selective crosses, 62% of the BALB/cJ subline BALB/cM2/22 developed PC after pristane and 52% after pristane followed by Abelson virus, while unselected controls had an incidence of 11% and 0%, respectively. Moreover, six spontaneous plasmacytomas developed in untreated females of the selected colony. Five of these carried T(12; 15) (F2; D2/3) translocations. The sixth had a T(1; 10) (G; C1) translocation and an interstitial duplication of segment (C1/E3) on one chromosome 5. It may be concluded that pristane treatment is not a prerequisite for the induction of the PC associated Ig/myc translocations.

Recombinant interleukin-1 promotes leishmaniasis in susceptible mice

Interleukin-1 exacerbates leishmanial lesions in Leishmania major-infected BALB/c mice. Indomethacin can modulate the effect of IL-1, so at least part of the IL-1 effect on disease progression is due to the induction of prostaglandin synthesis.

Elevated interleukin 6 is induced by prostaglandin E2 in a murine model of inflammation: possible role of cyclooxygenase-2

Injection of mineral oils such as pristane into the peritoneal cavities of BALB/c mice results in a chronic peritonitis associated with high tissue levels of interleukin 6 (IL-6). Here we show that increased prostaglandin E2 (PGE2) synthesis causes induction of IL-6 and that expression of an inducible cyclooxygenase, Cox-2, may mediate this process. Levels of both PGE2 and IL-6 are elevated in inflammatory exudates from pristane-treated mice compared with lavage samples from untreated mice. The Cox-2 gene is induced in the peritoneal macrophage fraction isolated from the mice. A cause and effect relationship between increased macrophage PGE2 and IL-6 production is shown in vitro. When peritoneal macrophages are activated with an inflammatory stimulus (polymerized albumin), the Cox-2 gene is induced and secretion of PGE2 and IL-6 increases, with elevated PGE2 appearing before IL-6. Cotreatment with 1 microM indomethacin inhibits PGE2 production by the cells and reduces the induction of IL-6 mRNA but has no effect on Cox-2 mRNA, consistent with the fact that the drug inhibits catalytic activity of the cyclooxygenase but does not affect expression of the gene. Addition of exogenous PGE2 to macrophages induces IL-6 protein and mRNA synthesis, indicating that the eicosanoid stimulates IL-6 production at the level of gene expression. PGE2-stimulated IL-6 production is unaffected by addition of indomethacin. Taken together with the earlier finding that indomethacin diminishes the elevation of IL-6 in pristane-treated mice, the results show that PGE2 can induce IL-6 production in vivo and implicate expression of the Cox-2 gene in the regulation of this cytokine.

Induction of plasmacytomas in genetically susceptible mice with silicone gels

Silicone gels injected intraperitoneally into strains of mice related to BALB/c develop plasmacytomas in approximately the same numbers and with similar phenotypes as previously obtained with pristane. Silicone gels produce few side effects and are well tolerated for long periods. Silicone gels contain several components that are potentially biologically active: residual vinyl groups and platinum. Microscopic and histological evidence suggests the silicone gel is degraded over a long period of time. Preliminary studies with long chain liquid dimethylpolysiloxanes with viscosities of 1000 cSt and 12,500 cSt have not produced plasmacytomas as yet. The plasmacytomagenic action of the gel appears to be due to the release of liquids from the gel matrix.

Activated murine neutrophils induce unscheduled DNA synthesis in B lymphocytes

Activated neutrophils induce DNA damage in neighboring cells by secreting reactive oxygen compounds into the extracellular milieu. Repair of this damage is required to prevent mutagenesis and neoplastic transformation. Conditions were established to detect the activation of excision-repair pathways (unscheduled DNA synthesis) by measuring stimulated thymidine uptake in target B lymphocytes exposed to activated neutrophils. Murine neutrophils were cocultured in serum-free medium with splenic B cells or with murine plasmacytoma cells for 2 h. Unscheduled DNA synthesis in the B cells was detected at neutrophil:target cell ratios of 1:1 to 4:1 when the neutrophils were activated with phorbol myristate acetate. Reagent H2O2 alone (> or = 6 microM) also induced UDS whereas HOCl (up to 4 mM) did not. No repair synthesis was observed within the neutrophils themselves. Control experiments indicated that the induction of UDS by neutrophils and H2O2 was not due to formation of a stable genotoxic compound from HU. On the contrary, scavenging of free H2O2 by HU probably lowered the levels of UDS that could be detected by these agents. Induction of unscheduled DNA synthesis by neutrophils and H2O2 occurred under conditions of less cytostasis than was found with other DNA-damaging agents such as 4-nitroquinoline 1-oxide or gamma-irradiation. This may reflect a heightened responsiveness of the cells to repair of damage from physiological oxidants. The results demonstrate that DNA damage induced by reactive oxygen intermediates can be repaired by nucleotide excision-repair pathways.

Regulation of early precursor B cell proliferation in mouse bone marrow: stimulation by exogenous agents mediated by macrophages in the spleen

An increase in pre-B cell proliferation and B lymphocyte production in mouse bone marrow has previously been shown to follow the administration of various foreign agents in vivo. The responses of early precursor B cells before the expression of mu chains (pro-B cells) have now been examined, using double immunofluorescence labeling for terminal deoxynucleotidyl transferase (TdT) and B220 glycoprotein as detected by monoclonal antibody 14.8. A single injection of sheep red blood cells (SRBC) was followed by an increase in the number of cells in three defined populations of early precursor B cells lacking mu chains (TdT+ 14.8- cells, TdT+ 14.8+ cells, and 14.8+ mu- cells) as well as cytoplasmic mu-bearing pre-B cells and surface mu-bearing B lymphocytes. An accompanying increase in proliferative activity was indicated by the numbers of 14.8+ mu- cells and pre-B cells which accumulated in metaphase after inducing mitotic arrest with vincristine. These effects were all abrogated either by treating mice with silica to depress macrophage function or by splenectomy. In mice given multiple injections of SRBC for 4 weeks the elevated levels of early precursor B cell production and B cell genesis were sustained. The work demonstrates that the in vivo production of early precursor B cells, putatively including those at the stage of Ig heavy chain gene rearrangement, can be stimulated by exposure to external agents acting indirectly by a silica-sensitive, spleen-dependent mechanism. The findings suggest that the level of pro-B cell proliferation and primary B cell genesis normally taking place in mouse bone marrow may reflect the level of exposure to potential stimulants in the external environment mediated by activation of splenic macrophages. The possibility that abnormally high levels of macrophage activation could predispose to dysregulations of the B cell lineage is raised.

Interleukin 6 (IL-6) and its receptor: their role in plasma cell neoplasias

Interleukin 6 (IL-6) is a multifunctional cytokine regulating immune response acute phase reaction and hematopoiesis. IL-6 plays a critical role in B cell differentiation to plasma cells and is a potent growth factor for plasmacytoma and myeloma. Abnormal production of IL-6 has been suggested to be involved in polyclonal plasma cell abnormalities and plasma cell neoplasias. The deregulated expression of the IL-6 gene in transgenic mice resulted in the generation of malignant plasmacytoma. Based on these findings, it could be considered that continuous IL-6 gene expression plays an essential role in a multistep oncogenesis of plasma cell neoplasias. The role of IL-6 and its receptor in the generation of plasma cell neoplasias and the mechanisms of the IL-6 gene expression and IL-6 receptor-mediated signal transduction are described.

A new method for delivering alkanes to mammalian cells: preparation and preliminary characterization of an inclusion complex between beta-cyclodextrin and pristane (2,6,10,14-tetramethylpentadecane)

Pristane (2,6,10,14-tetramethylpentadecane) is an isoalkane which induces plasma cell tumorigenesis in genetically susceptible strains of mice. Attempts to study the biological activity of pristane on cells in vitro have been hindered by the extreme hydrophobicity and hence complete immiscibility of the compound in aqueous cell culture media. In comparing different solubilization protocols such as using organic solvents, liposomes, and molecular encapsulation into beta-cyclodextrin (beta-CyD), it was found that beta-CyD/pristane inclusion complexes were optimal for delivery of the hydrocarbon to cells. After solubilization in beta-CyD, pristane was cytotoxic (51Cr release assay) to murine B lymphocyte lines in culture (P388, NSF-1, and SJL-4) and inhibited the lipopolysaccharide-induced stimulation of splenic B lymphocyte proliferation and blast formation (Coulter counter analysis) when added in the micromolar concentration range. Moreover, sub-toxic concentrations of beta-CyD/pristane inclusion complexes were found to have a small but reproducible mitogenic effect [( 3H]thymidine incorporation) on SJL-4 and 308 (murine initiated keratinocyte) cells in culture but not on P388 cells. The results indicate that molecular encapsulation of pristane into beta-CyD provides a new and effective method for delivering low concentrations of alkanes to mammalian cells in vitro.

Proliferation of B cell precursors in bone marrow of pristane-conditioned and malaria-infected mice: implications for B cell oncogenesis

Two widely different agents implicated in the etiology of neoplasias of the B cell lineage, pristane and malaria, have both been found to produce a prolonged increase in the level of proliferative activity and cell production by early B lymphocyte precursor cells in mouse bone marrow. This apparently leads to an elevated level of cell loss, suggesting the production of many aberrant early cells. The mechanism and significance of this effect remain to be determined. However, the present findings focus attention on the early stages of B cell genesis in the bone marrow as possible target cells for the initiation of genetic events leading to neoplasia. Together with previous work, the results suggest that pathologically elevated levels of macrophage activation may play a role in predisposing to various B cell neoplasias.

Interleukin 6 and plasma cell neoplasias

Interleukin 6, an essential factor for B cells to differentiate to immunoglobulin-producing cells has been demonstrated to be involved in abnormal polyclonal plasmacytosis in cardiac myxoma. Castleman's disease, rheumatoid arthritis and AIDS. Furthermore, IL-6 was found to be a potent growth factor for both plasmacytoma and myeloma. The involvement of IL-6 in plasma cell abnormalities was further demonstrated by the generation of a lethal plasma cell growth in IL-6 transgenic mice. Continuous IL-6 gene expression could be considered to play an essential role in both polyclonal plasmacytosis and the generation of plasma cell neoplasias.

Rapid induction of IgM-secreting murine plasmacytomas by pristane and an immunoglobulin heavy-chain promoter/enhancer-driven c-myc/v-Ha-ras retrovirus

A retroviral vector, RIM, containing murine c-myc under the control of immunoglobulin heavy-chain gene promoter and enhancer elements and v-Ha-ras driven by a Moloney murine leukemia virus long terminal repeat induced IgM-secreting plasmacytomas in 28% of adult and 83% of 3-week-old pristane-conditioned mice with mean latency periods of 60-70 days. In contrast, the same vector only harboring c-myc or v-Ha-ras was virtually ineffective. RIM-induced plasmacytomas expressed retroviral myc and ras genes while their endogenous c-myc alleles were unrearranged and transcriptionally inactive. These plasmacytomas were clonal as each possessed a unique immunoglobulin heavy-chain joining region rearrangement and a single recombinant provirus. Moloney murine leukemia helper virus did not play an obligatory role in tumorigenesis since insertions of Moloney murine leukemia proviruses were found in only 6 of 24 plasmacytomas induced in adult mice. Taken together, these findings support the view that the v-Ha-ras oncogene can cooperate with an activated myc gene in pristane plasmacytomagenesis.

Moloney murine leukemia virus-induced myeloid tumors in adult BALB/c mice: requirement of c-myb activation but lack of v-abl involvement

BALB/c mice treated with pristane and Abelson virus have been used as an animal model system for the rapid induction of plasmacytomas. Myelomonocytic tumors with helper Moloney murine leukemia virus clonally inserted into the c-myb locus were observed in about 10% of pristane-primed BALB/c mice infected with Abelson virus. However, v-abl was absent in almost all of those tumors. Since Moloney virus is thought to induce mostly T-cell lymphomas, we have carried out studies to investigate this alteration of disease specificity and to determine whether v-abl played an obligatory role in the development of these tumors. We found that, whereas lymphomas developed late (greater than 3 months) in both pristane-primed and unprinted control mice, the myelomonocytic tumors arose at a high frequency, within 3 months, but only in pristane-treated mice. Clonal Moloney virus insertion was again found in each of the seven myelomonocytic tumors examined. Northern blot analyses and S1 mapping studies revealed the presence of virally promoted chimeric mRNAs that lack the three 5'-most myb coding exons. Hence it appears that the requirement for the v-abl gene product in tumor induction is not obligatory. Our results also indicate that tumor-specific alteration at the 5' end of the myb gene plays an important role in the development of these tumors.

Differential stimulation of mononuclear phagocyte IL 1 production and oxidative burst by tumor-promoting and non-tumor-promoting agents

Adherent bone marrow, spleen and peritoneal mouse macrophages, as well as human peripheral blood monocytes were exposed in vitro to the phorbol ester derivatives 12-O-tetradecanoyl-phorbol-13-acetate (TPA), phorbol 13-monoacetate (PA), phorbol 12-myristate (PM), phorbol 12,13-diacetate (PDA), phorbol 12,13 dibutyrate (PDBu), TPA-20 aldehyde (TPA-AL), phorbol 12-retinoate 13-acetate (PRA), 4-alpha TPA (alpha-TPA) and to mezerein (MEZ) and aplysiatoxin (APL). The triggered macrophages/monocytes were tested for the production of an IL 1-like activity by the thymocyte proliferation assay and for H2O2 generation in a quantitative method which is based on the H2O2-mediated and horseradish peroxidase-dependent oxidation of phenol red. The results showed that strong first stage and second stage tumor promoters such as TPA, PDBu, PRA, MEZ and APL are also strong stimulators of IL 1 and H2O2 generation, whereas weak tumor promoters exhibited a low, if any, effect at all. The afore-described findings lend support to the idea that chronic inflammatory phagocytes might play a role in the tumor promoting process by furnishing both carcinogenic and growth factors at the site of tumor origin.