The role of cytokines in the pathogenesis and management of AIDS-related lymphomas

Inflammation induced loss of skeletal muscle

Inflammation is an important contributor to the pathology of diseases implicated in skeletal muscle dysfunction. A number of diseases and disorders including inflammatory myopathies and Chronic Obstructive Pulmonary Disorder (COPD) are characterized by chronic inflammation or elevation of the inflammatory mediators. While these disease states exhibit different pathologies, all have in common the loss of skeletal muscle mass and a deregulated skeletal muscle physiology. Pro-inflammatory cytokines are key contributors to chronic inflammation found in many of these diseases. This section of the review focuses on some of the known inflammatory disorders like COPD, Rheumatoid Arthritis (RA) and inflammatory myopathies that display skeletal muscle atrophy and also provides the reader an overview of the mediators of inflammation, their signaling pathways, and mechanisms of action. This article is part of a Special Issue entitled "Muscle Bone Interactions".

Microenvironment abnormalities and lymphomagenesis: Immunological aspects

Innate and adaptive immune cells within the microenvironment identify and eliminate cells displaying signs of malignant potential. Immunosurveillance effector Natural Killer (NK) cells and Cytotoxic T Lymphocytes (CTL) identify malignant cells through germline receptors such as NKG2D and in the case of CTLs, presentation of antigen through the T cell receptor. Manipulation of immunosurveillance through altered tumor-identifying ligand expression or secretion, resistance to cytotoxicity, or compromised cytotoxic cell activity through immune tolerance mechanisms all contribute to failure of these systems to prevent cancer development. This review examines the diverse mechanisms by which alterations in the immune microenvironment can promote lymphomagenesis.

Interleukin-6 signaling pathway in targeted therapy for cancer

Interleukin-6 (IL-6) is a multifunctional cytokine which plays an important role in a wide range of biologic activities in different types of cell including tumor cells. IL-6 is involved in the host immune defense mechanism as well as the modulation of growth and differentiation in various malignancies. These effects are mediated by several signaling pathways, in particular the signal transducer and transcription activator 3 (Stat3). There exists abundant evidence demonstrating that deregulated overexpression of IL-6 was associated with tumor progression through inhibition of cancer cell apoptosis, stimulation of angiogenesis, and drug resistance. Clinical studies have revealed that increased serum IL-6 concentrations in patients are associated with advanced tumor stages of various cancers (e.g., multiple myeloma, non-small cell lung carcinoma, colorectal cancer, renal cell carcinoma, prostate cancer, breast cancer and ovarian cancer) and short survival in patients. Therefore, blocking IL-6 signaling is a potential therapeutic strategy for cancer (i.e., anti-IL-6 therapy) characterized by pathological IL-6 overproduction. Preliminary clinical evidence has shown that antibody targeted IL-6 therapy was well tolerated in cancer patients. In this review, we detail the progress of the current understanding of IL-6 signaling pathway in cancer as well as an antibody targeted IL-6 therapy for human cancer.

IL-6 and IL-10 in post-transplant lymphoproliferative disorders development and maintenance: a longitudinal study of cytokine plasma levels and T-cell subsets in 38 patients undergoing treatment

IL-6 and IL-10 have previously been implicated in the pathogenesis of post-transplant lymphoproliferative disorders (PTLD) and, like peripheral lymphocyte populations, are markers of immune status that are amenable to study in vivo. Thus, we analyzed cytokine plasma levels as well as lymphocyte subsets in a longitudinal analysis of 38 adult transplant recipients undergoing treatment for PTLD. Pretherapeutically, we found significantly elevated IL-6 (13.8 pg/ml) and IL-10 plasma levels (54.7 pg/ml) - in the case of IL-10, even higher in treatment nonresponders than in responders (116 vs. 14 pg/ml). Over time, however, IL-10 levels did not correlate with the course of disease, whereas those of IL-6 did, falling in responders and rising in nonresponders. These findings were independent of histological EBV-status, treatment type, and total peripheral T-cell counts, which were significantly reduced in patients with PTLD. Our observations support the idea that although IL-10 is important for creating a permissive environment for post-transplant lymphoma development, IL-6 is associated with PTLD proliferation. The analysis of lymphocyte subsets further identified HLA-DR+ CD8+ lymphocyte numbers as significantly different in non-PTLD controls (33%), treatment responders (44%) and nonresponders (70%). Although the specificity of these cells is unclear, their increase might correlate with the impaired tumor-specific cytotoxic-T-lymphocyte (CTL)-response in PTLD.

Significance of Epstein-Barr virus (EBV) load and Interleukin-10 in post-transplant lymphoproliferative disorders

The complex relationship between EBV, IL-10 and lymphomagenesis has been widely investigated and several studies have highlighted the diagnostic value of EBV DNA copies and serum IL-10, that may be considered as tumor markers. Notwithstanding the great number of data published in the last few years on the behavior of EBV DNA copies in the peripheral blood of transplanted patients, a threshold value significant for impending or overt post-transplant lymphoproliferative disorder (PTLD) has not yet been defined. Too many factors, both technical and clinicopathological, may affect the results of clinical studies, making their comparison difficult. On the contrary, although the role of IL-10 in PTLDs has been well documented, a sufficient number of studies exploring sensitivity and specificity of serum IL-10 measurement is lacking. The aim of this review is to summarise data on EBV load quantification and serum IL-10 detection in transplanted patients, providing clinicians with wide and useful information in order to improve bedside management of transplanted patients with regard to PTLDs occurrence and treatment.

Growth regulation of simian and human AIDS-related non-Hodgkin's lymphoma cell lines by TGF-beta1 and IL-6

Background

AIDS-related non-Hodgkin's lymphoma (AIDS-NHL) is the second most frequent cancer associated with AIDS, and is a frequent cause of death in HIV-infected individuals. Experimental analysis of AIDS-NHL has been facilitated by the availability of an excellent animal model, i.e., simian Acquired Immunodeficiency Syndrome (SAIDS) in the rhesus macaque consequent to infection with simian immunodeficiency virus. A recent study of SAIDS-NHL demonstrated a lymphoma-derived cell line to be sensitive to the growth inhibitory effects of the ubiquitous cytokine, transforming growth factor-beta (TGF-beta). The authors concluded that TGF-beta acts as a negative growth regulator of the lymphoma-derived cell line and, potentially, as an inhibitory factor in the regulatory network of AIDS-related lymphomagenesis. The present study was conducted to assess whether other SAIDS-NHL and AIDS-NHL cell lines are similarly sensitive to the growth inhibitory effects of TGF-beta, and to test the hypothesis that interleukin-6 (IL-6) may represent a counteracting positive influence in their growth regulation.

Methods

Growth stimulation or inhibition in response to cytokine treatment was quantified using trypan blue exclusion or colorimetric MTT assay. Intracellular flow cytometry was used to analyze the activation of signaling pathways and to examine the expression of anti-apoptotic proteins and distinguishing hallmarks of AIDS-NHL subclass. Apoptosis was quantified by flow cytometric analysis of cell populations with sub-G1 DNA content and by measuring activated caspase-3.

Results

Results confirmed the sensitivity of LCL8664, an immunoblastic SAIDS-NHL cell line, to TGF-beta1-mediated growth inhibition, and further demonstrated the partial rescue by simultaneous treatment with IL-6. IL-6 was shown to activate STAT3, even in the presence of TGF-beta1, and thereby to activate proliferative and anti-apoptotic pathways. By comparison, human AIDS-NHL cell lines differed in their responsiveness to TGF-beta1 and IL-6. Analysis of a recently derived AIDS-NHL cell line, UMCL01-101, indicated that it represents immunoblastic AIDS-DLCBL. Like LCL-8664, UMCL01-101 was sensitive to TGF-beta1-mediated inhibition, rescued partially by IL-6, and demonstrated rapid STAT3 activation following IL-6 treatment even in the presence of TGF-beta1.

Conclusion

These studies indicate that the sensitivity of immunoblastic AIDS- or SAIDS-DLBCL to TGF-beta1-mediated growth inhibition may be overcome through the stimulation of proliferative and anti-apoptotic signals by IL-6, particularly through the rapid activation of STAT3.

Interleukin-10 - 1082 GG polymorphism influences the occurrence and the clinical characteristics of hepatitis C virus infection

BACKGROUND/AIMS

In this study, we determined the genotypic and allelic frequencies of the Interleukin (IL)-10(-1082G/A) IL-10(-592A/C), and IL-10(-819C/T) polymorphisms, and their association with the risk to develop B cell Non Hodgkin Lymphoma (NHL) in hepatitis virus C (HCV) carriers.

RESULTS

Genetic polymorphisms in the IL-10 gene promoter were studied in 250 consecutive patients with B-cell NHL with no clinical and/or laboratory findings of cryoglobulinemia, 142 NHL/HCV- and 108 NHL/HCV+ with chronic hepatitis (CH), 120 consecutive subjects with HCV-related CH, and 110 age, sex-matched healthy blood donors. The frequency of the IL-10(-1082GG) genotype vs remaining genotypes (IL-10(-1082GA/AA)) was higher in NHL/HCV+ patients than HCV-related CH patients (P=0.0002, OR=2.89, CI: 1.62-5.15) and in NHL/HCV+ than NHL/HCV- patients (P=0.0001, OR=2.99, CI: 1.72-5.19). Moreover, the IL-10(-1082GG) genotype was more prevalent in indolent NHL/HCV+ cases than aggressive NHL/HCV+ (P=0.0004, OR=4.97, CI: 2.10-11.79). Finally, we confirmed that IL-10(-1082GG) genotype is associated with higher IL-10 production compared to AA homozygous (P=0.037).

CONCLUSIONS

The high IL-10 production, due to IL-10(-1082GG) genotype, influences the clinical expression of the HCV infection by increasing susceptibility to develop NHL and might contribute to the indolent form of the disease.

The cancer stem cell: evidence for its origin as an injured autoreactive T cell

This review explores similarities between lymphocytes and cancer cells, and proposes a new model for the genesis of human cancer. We suggest that the development of cancer requires infection(s) during which antigenic determinants from pathogens mimicking self-antigens are co-presented to the immune system, leading to breaking T cell tolerance. Some level of autoimmunity is normal and necessary for effective pathogen eradication. However, autoreactive T cells must be eliminated by apoptosis when the immune response is terminated. Apoptosis can be deficient in the event of a weakened immune system, the causes of which are multifactorial. Some autoreactive T cells suffer genomic damage in this process, but manage to survive. The resulting cancer stem cell still retains some functions of an inflammatory T cell, so it seeks out sites of inflammation inside the body. Due to its defective constitutive production of inflammatory cytokines and other growth factors, a stroma is built at the site of inflammation similar to the temporary stroma built during wound healing. The cancer cells grow inside this stroma, forming a tumor that provides their vascular supply and protects them from cellular immune response.

As cancer stem cells have plasticity comparable to normal stem cells, interactions with surrounding normal tissues cause them to give rise to all the various types of cancers, resembling differentiated tissue types. Metastases form at an advanced stage of the disease, with the proliferation of sites of inflammation inside the body following a similar mechanism. Immunosuppressive cancer therapies inadvertently re-invigorate pathogenic microorganisms and parasitic infections common to cancer, leading to a vicious circle of infection, autoimmunity and malignancy that ultimately dooms cancer patients. Based on this new understanding, we recommend a systemic approach to the development of cancer therapies that supports rather than antagonizes the immune system.

NF-kappaB is essential for the progression of KSHV- and EBV-infected lymphomas in vivo

Activated NF-kappaB is a critical mechanism by which lymphoma cells infected by Epstein-Barr virus (EBV/HHV-4) and Kaposi sarcoma herpesvirus (KSHV/HHV-8) are protected from apoptotic stress. Selective pharmacologic inhibition of constitutive NF-kappaB activity induces apoptosis in KSHV- and EBV-infected lymphoma cells. In both tumor types, pharmacologic inhibition of NF-kappaB in vitro induced identical mitochondrially mediated apoptosis cascades. Assessment of gene regulation by microarray analysis revealed that the inhibition of NF-kappaB in tumor cells results in the down-regulation of a distinct group of prosurvival genes, including cIAP-1, cIAP-2, cFLIP, and IL-6. Using EBV- and KSHV-associated lymphomas in a murine system, we demonstrated that Bay 11-7082, a selective pharmacologic inhibitor of NF-kappaB, prevents or delays tumor growth and prolongs disease-free survival. Inhibition of NF-kappaB activity and tumor growth responses were further documented using a traceable reporter KSHV-positive cell line and in vivo imaging. These findings indicate that specific NF-kappaB-regulated survival factors work cooperatively to protect KSHV- and EBV-infected lymphoma cells from apoptosis such that they promote the establishment and progression of KSHV- and EBV-associated lymphomas in mice. They also support the use of selective NF-kappaB inhibitors in the treatment of herpesvirus-associated lymphomas.

Stromelysin-2 (Matrix Metalloproteinase 10) Is Inducible in Lymphoma Cells and Accelerates the Growth of Lymphoid Tumors In Vivo

Matrix metalloproteinase (MMP) 10 (stromelysin-2) is known to degrade various components of the extracellular matrix; however, the signals that regulate its expression and its role in lymphoma growth remain unknown. In the present work, we report the up-regulated expression of MMP10 in T lymphoma cells following contact with endothelial cells. The induction of MMP10 was found to be dependent on the specific interaction between LFA-1 and ICAM-1, which play a central role in regulating the expression of genes involved in the rate-limiting steps of lymphoma development. MMP10, but not MMP3 (stromelysin-1), was also up-regulated in human B lymphoma cells following exposure to IL-4, IL-6, and IL-13, but not to IL-1. To gain further insight into the role of MMP10 in lymphoma development, we generated lymphoma cell lines constitutively expressing high levels of MMP10 and studied these cells for their ability to form thymic lymphoma in vivo. Mice injected with lymphoma cells constitutively expressing MMP10 developed thymic lymphoma more rapidly than those injected with control lymphoma cells. These results provide the first in vivo evidence that overexpression of MMP10 promotes tumor development, and indicate that MMP10 induction is an important pathway activated not only upon ICAM-1/LFA-1-mediated intercellular contact, but also following activation of tumor cells with inflammatory cytokines.

Posttransplant lymphoproliferative disorders presenting at sites of previous surgical intervention

Early diagnosis of posttransplant lymphoproliferative disorder (PTLD) requires a high level of clinical suspicion. PTLD occurs mainly in the lymphoid tissue, allograft organ, bowel, and central nervous system. The diagnosis may not be considered initially when disease is localized to other sites. Retrospective review of the PTLD series at the University of Pittsburgh Medical Center showed that 4 of 418 patients (1%) presented with signs and symptoms localized to sites of previous surgical intervention (choledochojejunostomy site, ileosigmoid anastomotic site, site of saphenous vein stripping, and intrabiliary site of percutaneous transhepatic catheter). All patients showed symptomatic, Epstein-Barr virus-positive B-cell PTLD of varying histology. Three of four patients ultimately died with tumor, and the fourth died of unrelated causes. PTLD should be included in the differential diagnosis when clinical signs and symptoms localize to anastomotic sites, surgical incision sites, or sites of longstanding catheter placement in immunosuppressed organ transplant recipients.

Transcriptional regulation of the interleukin-6 gene of human herpesvirus 8 (Kaposi's sarcoma-associated herpesvirus)

Human herpesvirus 8 (HHV-8; Kaposi's sarcoma-associated herpesvirus is linked to Kaposi's sarcoma (KS), primary effusion lymphoma (PEL), and multicentric Castleman's disease (MCD), all of which are viewed as cytokine-driven malignancies. In particular, interleukin-6 (IL-6) has been found to promote the growth and proliferation of cells from KS and PEL. HHV-8 encodes a homologue of IL-6 (viral IL-6 [vIL-6]), which functions similarly to the cellular IL-6. Therefore, vIL-6 has been proposed to play an important role in tumor progression. Several groups have reported that vIL-6 is expressed from the HHV-8 genome at higher levels in PEL and MCD lesions than in KS lesions. However, it is not clear how vIL-6 expression is regulated. We characterized the transcription at the vIL-6 gene locus by Northern blot analysis and, in contrast to previous reports, we observed two distinct transcripts from induced PEL cell lines. This observation was confirmed by primer extension, as well as 5' and 3' rapid amplification of cDNA ends. Two transcription initiation sites and putative TATA boxes were mapped. A luciferase reporter system was used to show that each of the two putative TATA boxes contributed to vIL-6 promoter activity. Since virally encoded transcriptional activator Rta potently activates the viral lytic gene expression cascade, we examined the role of Rta in controlling vIL-6 gene expression and found that Rta activated the vIL-6 promoter. The Rta-responsive element was further mapped through a series of deletion constructs. Electrophoretic mobility shift assays demonstrated that Rta binds directly to the vIL-6 Rta-responsive element, and the core Rta-responsive element was mapped to a 26-bp region spanning from nucleotide 18315 to 18290 on the viral genome. We propose that the existence of two vIL-6 promoters offers opportunities for differential regulation of vIL-6 gene expression in different tissue types and may account for the variable vIL-6 levels observed in KS, PEL, and MCD.

Epstein-Barr virus and HIV-AIDS-associated diseases

Among the secondary problems of patients with the human immune deficiency virus (HIV) infection are lymphadenopathy, atypical lymphoproliferations, and malignant transformations of lymphoid, muscle, and epithelial cells caused by infection with Epstein-Barr virus (EBV). The lymphoproliferative diseases associated with EBV infection include lymphocytic interstitial pneumonitis, lymphomas of primary and extra-nodal sites, such as the central nervous system (CNS), and mucosa-associated lymphoid tissue (MALT). EBV infection causes these diseases through a combination of mechanisms including use of virus-encoded transforming genes, stimulation of diverse cytokines, and interaction with receptors for the tumor necrosis factor (TNF) family of cytokines.