Inhibition of AIDS-associated Kaposi's sarcoma cell growth by DAB389-interleukin 6

Expression profiling of nuclear receptors in the NCI60 cancer cell panel reveals receptor-drug and receptor-gene interactions

We profiled the expression of the 48 human nuclear receptors (NRs) by quantitative RT-PCR in 51 human cancer cell lines of the NCI60 collection derived from nine different tissues. NR mRNA expression accurately classified melanoma, colon, and renal cancers, whereas lung, breast, prostate, central nervous system, and leukemia cell lines exhibited heterogeneous receptor expression. Importantly, receptor mRNA levels faithfully predicted the growth-inhibitory qualities of receptor ligands in nonendocrine tumors. Correlation analysis using NR expression profiles and drug response information across the cell line panel uncovered a number of new potential receptor-drug interactions, suggesting that in these cases, individual receptor levels may predict response to chemotherapeutic interventions. Similarly, by cross-comparing receptor levels within our expression dataset and relating these profiles to existing microarray gene expression data, we defined interactions among receptors and between receptors and other genes that can now be mechanistically queried. This work supports the strategy of using NR expression profiling to classify various types of cancer, define NR-drug interactions and receptor-gene networks, predict cancer-drug sensitivity, and identify druggable targets that may be pharmacologically manipulated for potential therapeutic intervention.

Lack of antitumor activity and intolerance of interleukin-4 in patients with advanced HIV disease and Kaposi's sarcoma

Kaposi's sarcoma (KS), the most common malignancy associated with HIV infection, is caused by the Kaposi sarcoma herpesvirus (KSHV). Exacerbations of KSHV are associated with increased human interleukin-6 (HuIL-6), and elevated IL-6 could be related to the development of KS. IL-4, a cytokine with pleiotropic effects, suppresses IL-6 in vivo and modestly inhibits AIDS-KS-derived cells in vitro. Suppression of IL-6 by exogenous IL-4 could result in antitumor activity. We report the results of a clinical trial to test this hypothesis. A phase I/II dose escalation safety, tolerance, and efficacy trial was conducted in patients with biopsy-proven AIDS-related KS, at two university medical centers. Patients were scheduled to receive IL-4 (0.5, 1.5, 3.0, or 4.0 microg/kg/day) administered subcutaneously (s.c.) in sequential cohorts. Patients were continued on study as long as the drug was tolerated or the disease progressed. Patients were followed for antitumor activity, effects on viral replication, immune status, and clinical and laboratory toxicity. Seventeen patients were enrolled at two sites over a 21-month period. There were 15 males and 2 females, and 1 patient was Hispanic. All patients had a Karnofsky score >70. Patients enrolled only into the two lower dose cohorts (0.5 and 1.5 microg/kg/day). Both groups had similar baseline characteristics. The median time on treatment was only 7.4 and 8.4 weeks for the 0.5 and 1.5 microg/kg/day dose levels, respectively. There was significant neutropenia, with 6 patients having grade 3 or greater toxicity requiring granulocyte colony-stimulating factor (G-CSF). Three patients on a dose of 1.5 microg/kg/day stopped treatment due to protocol-defined toxicity. There were no appreciable effects on CD4/CD8 counts. HIV viral RNA did not significantly change over time. However, in several people, it appeared to decline with treatment and rebound with discontinuation of treatment. Corresponding changes were noted in the HIV immunocomplex dissociated (ICD) p24 antigen. One patient had a partial response, 11 patients had stable disease, and 5 patients had disease progression during the short period of treatment. The maximum tolerated dose for IL-4 in patients with advanced AIDS-related KS is 1.5 microg/kg/day. At this dose level, IL-4 is poorly tolerated and is not an effective KS treatment. Treatment of the majority of patients is discontinued because of drug-related toxicity or because of disease progression. Future studies of IL-4 should be confined to studies of cytokine manipulation of the underlying HIV infection, as there appears to be little antitumor activity.

Contradictory Concepts in the Etiology and Regression of Kaposi's Sarcoma. The Ferenc Györkey Memorial Lecture

The Introduction is an overview of 3 decades of works performed by Professor Ferenc Györkey (in many cases in collaboration with the author) and aimed at the elucidation of viral participation in the etiology of arteriosclerosis, SLE, hairy cell leukemia, HD, AIDS and KS. Controversial issues surrounding the etiology, treatment and regression of KS are discussed in terms of paracrine and autocrine loops of growth factors; protooncogene-oncogene activations, immunosuppression and retro- and/or herpesviral etiology. In regressing KS lesions the roles played by Fas, Bcl-2, Bax, TNFß; apoptotic-antiapoptotic events; and antiangiogenesis agents especially that of Hu-r-IFNa are elaborated on.

Interleukin-13 fusion cytotoxin as a potent targeted agent for AIDS-Kaposi's sarcoma xenograft

Clinically advanced and rapidly progressive AIDS-associated Kaposi sarcoma (AIDS-KS) tumors require an aggressive tumor-directed therapy. We have observed that AIDS-KS cells express high levels of receptors for immune regulatory cytokine, interleukin-13 (IL-13). Two tumorigenic AIDS-KS cell lines, KS Y-1 and KS-imm, expressed 4560 and 9480 IL-13 binding sites per cell with an affinity (kd) of ∼0.9 and 3.7 nmol/L, respectively. IL-13 cytotoxin IL13-PE38QQR, consisting of human IL-13 and a derivative of Pseudomonas exotoxin, is specifically cytotoxic to KS tumor cells. Systemic and loco regional administration of IL13-PE38QQR in immunodeficient mice with established human KS tumors produced remarkable antitumor activity. Three intratumoral (IT) injections of IL-13 toxin (250 μg/kg per dose) on alternate days (qod) or 5 daily (qd) IT injections with lower doses (50 or 100 μg/kg per dose) resulted in a complete regression of established subcutaneous tumors in most animals. Daily IT treatment with 250 μg/kg of IL-13 toxin in another KS-derived cell line also produced complete responses. Twice daily intraperitoneal injections of IL13-PE38QQR (25 or 50 μg/kg per dose) for 10 days (total injections = 20) also completely eradicated KS Y-1 tumors. Intravenous administration of IL13-PE38QQR also suppressed tumor growth; however, complete responses were not observed. All animals tolerated the therapeutic doses of IL-13 toxin without any visible signs of toxicity. The efficacy of receptor-directed IL13-PE38QQR therapy in mice warrants further exploration of this drug for AIDS-KS treatment.

Interleukin-13 fusion cytotoxin as a potent targeted agent for AIDS-Kaposi's sarcoma xenograft

Clinically advanced and rapidly progressive AIDS-associated Kaposi sarcoma (AIDS-KS) tumors require an aggressive tumor-directed therapy. We have observed that AIDS-KS cells express high levels of receptors for immune regulatory cytokine, interleukin-13 (IL-13). Two tumorigenic AIDS-KS cell lines, KS Y-1 and KS-imm, expressed 4560 and 9480 IL-13 binding sites per cell with an affinity (kd) of ∼0.9 and 3.7 nmol/L, respectively. IL-13 cytotoxin IL13-PE38QQR, consisting of human IL-13 and a derivative of Pseudomonas exotoxin, is specifically cytotoxic to KS tumor cells. Systemic and loco regional administration of IL13-PE38QQR in immunodeficient mice with established human KS tumors produced remarkable antitumor activity. Three intratumoral (IT) injections of IL-13 toxin (250 μg/kg per dose) on alternate days (qod) or 5 daily (qd) IT injections with lower doses (50 or 100 μg/kg per dose) resulted in a complete regression of established subcutaneous tumors in most animals. Daily IT treatment with 250 μg/kg of IL-13 toxin in another KS-derived cell line also produced complete responses. Twice daily intraperitoneal injections of IL13-PE38QQR (25 or 50 μg/kg per dose) for 10 days (total injections = 20) also completely eradicated KS Y-1 tumors. Intravenous administration of IL13-PE38QQR also suppressed tumor growth; however, complete responses were not observed. All animals tolerated the therapeutic doses of IL-13 toxin without any visible signs of toxicity. The efficacy of receptor-directed IL13-PE38QQR therapy in mice warrants further exploration of this drug for AIDS-KS treatment.

c-Src mediates mitogenic signals and associates with cytoskeletal proteins upon vascular endothelial growth factor stimulation in Kaposi's sarcoma cells

Vascular endothelial growth factor (VEGF) appears to be a critical cytokine modulating the growth and spread of Kaposi's sarcoma (KS). Furthermore, infection with the KS herpes virus results in up-regulation of VEGF and triggering of VEGF receptor activation. The molecular mechanisms regulating such cytokine-driven proliferation of KS cells are not well characterized. We investigated the role of Src-related tyrosine kinases in VEGF-mediated signaling in model KS 38 tumor cells. VEGF stimulation specifically activated c-Src kinase activity but not that of other related Src kinases such as Lyn, Fyn, or Hck in KS cells. Pyrazolopyrimidine, a selective inhibitor of Src family tyrosine kinases, significantly blocked the VEGF-induced growth of KS cells. Further studies using mutants of c-Src kinase revealed that Src mediates mitogen-activated protein kinase activation induced by VEGF. We also observed that VEGF stimulation resulted in increased tyrosine phosphorylation of the focal adhesion components paxillin and p130cas. Furthermore, VEGF induction enhanced the complex formation between Src kinase and paxillin. Src kinase appears to play an important functional role in VEGF-induced signaling in KS cells and may act to link pathways from the VEGF receptor to mitogen-activated protein kinase and cytoskeletal components, thereby effecting tumor proliferation and migration.

Interleukin-4 receptor-directed cytotoxin therapy of AIDS-associated Kaposi's sarcoma tumors in xenograft model

The elusive and enigmatic origin of AIDS-associated Kaposi's sarcoma (AIDS-KS) makes it a complex tumor and therefore difficult to treat. Here we demonstrate that AIDS-KS cells express surface interleukin-4 (IL-4) receptors, and that IL-4 toxin (IL-4(38-37)-PE38KDEL) is specifically cytotoxic to these cells. Intratumoral, intraperitoneal and intravenous administration of IL-4 toxin in nude mice with established subcutaneous AIDS-KS tumors caused considerable anti-tumor activity in a dose-dependent manner, with highest dose producing durable complete responses. Metabolic changes, including cachexia and lymphopenia, induced by KS tumors were prevented by IL-4 toxin treatment. This report establishes IL-4(38-37)-PE38KDEL as an experimental therapeutic agent for the treatment of AIDS-KS.

The role of HHV-8 in Kaposi's sarcoma

The epidemiology of Kaposi's sarcoma (KS) amongst North American and Northern European patients with AIDS suggests that an infectious agent other than HIV is involved in its pathogenesis. Several lines of evidence indicate that human herpesvirus 8 (HHV-8), also termed Kaposi's sarcoma associated herpesvirus, is the sought after agent. DNA of HHV-8 is invariably found in all forms of KS where the virus is present in the KS spindle cell. In contrast, HHV-8 DNA is not regularly detected in most other malignancies. Antibodies against HHV-8 are more frequently found in groups at risk of KS, and HHV-8 seroconversion precedes KS development. Several HHV-8 genes have been identified that exhibit transforming potential in cell culture systems. In addition, the virus encodes and induces several cytokines and angiogenic factors. This is of particular interest as models of KS pathogenesis developed before the discovery of HHV-8 emphasized the importance of inflammatory cytokines. Although the expression pattern of viral genes in KS is not certain yet, it appears likely that the pathogenetic role of HHV-8 in KS may be rather complex and differs from other virus-induced malignancies. 1999 Academic Press.

Human immunodeficiency virus tat modulates the Flk-1/KDR receptor, mitogen-activated protein kinases, and components of focal adhesion in Kaposi's sarcoma cells

Kaposi's sarcoma (KS) spindle cell growth and spread have been reported to be modulated by various cytokines as well as the human immunodeficiency virus (HIV) gene product Tat. Recently, HIV-1 Tat has been shown to act like a cytokine and bind to the Flk-1/KDR receptor for the vascular endothelial growth factor A (VEGF-A), which is expressed by KS cells. We have characterized signal transduction pathways stimulated by HIV-1 Tat upon its binding to surface receptors on KS cells. We observed that stimulation in KS 38 spindle cells resulted in tyrosine phosphorylation and activation of the Flk-1/KDR receptor. We also report that HIV-1 Tat treatment enhanced the phosphorylation and association of proteins found in focal adhesions, such as the related adhesion focal tyrosine kinase RAFTK, paxillin, and p130(cas). Further characterization revealed the activation of mitogen-activated protein kinase, c-Jun amino-terminal kinase (JNK), and Src kinase. HIV-1 Tat contains a basic domain which can interact with growth factor tyrosine kinase receptors and a classical RGD sequence which may bind to and activate the surface integrin receptors for fibronectin and vitronectin. We observed that stimulation of KS cells with basic as well as RGD sequence-containing Tat peptides resulted in enhanced phosphorylation of RAFTK and activation of MAP kinase. These studies reveal that Tat stimulation activates a number of signal transduction pathways that are associated with cell growth and migration.

Interleukin 6 and AIDS-associated Kaposi's sarcoma: a nested case control study within the Multicenter AIDS Cohort Study

Since the beginning of the AIDS epidemic, there has been considerable research on the etiology of Kaposi's sarcoma (KS) among HIV-infected individuals. A number of studies have confirmed that HIV or HIV-encoded products can interact with human cells to induce the production of cytokines, including interleukin 6 (IL-6). In vitro observations have indicated that AIDS-KS cells can produce significant levels of IL-6 and also respond to this cytokine. Preliminary data suggested that IL-6 may be elevated among HIV-infected individuals that subsequently develop AIDS-KS. The objective of this study was to determine if elevated levels of IL-6 are associated with an increased incidence of AIDS-KS compared to other AIDS-defining illnesses such as opportunistic infections (OIs). Serum IL-6 levels were determined by ELISA in frozen sera collected from participants in the Multicenter AIDS Cohort Study (MACS) at 6 months prior to AIDS diagnosis, in 73 cases (AIDS-KS), and 152 controls (OI). Elevated IL-6 levels were more prevalent among men with AIDS-OI than those with AIDS-KS: crude odds ratio (OR), 0.4 (95% CI, 0.2-0.9). Models of multivariate logistic regression were used to study potential confounders. Sexual behavior variables did not seem to confound the association between IL-6 and AIDS-KS. The higher prevalence of IL-6 among controls could be explained by the association of higher levels of IL-6 with lower levels of CD4 T cell number. IL-6 may be a marker of severe immune dysfunction among HIV-infected individuals.

Cytokine signaling through the novel tyrosine kinase RAFTK in Kaposi's sarcoma cells

A number of cytokines, including basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), oncostatin M (OSM), IL-6, and tumor necrosis factor alpha (TNF-alpha), have been postulated to have a role in the pathogenesis of Kaposi's sarcoma (KS). The proliferative effects of bFGF and OSM may be via their reported activation of the c-Jun NH2-terminal kinase (JNK) signaling pathway in KS cells. We now report that KS cells express a recently identified focal adhesion kinase termed RAFTK which appears in other cell systems to coordinate surface signals between cytokine and integrin receptors and the cytoskeleton as well as act downstream to modulate JNK activation. We also report that the tyrosine kinase receptor FLT-4, present on normal lymphatic endothelium, is robustly expressed in KS cells. Treatment of KS cells with VEGF-related protein (VRP), the ligand for the FLT-4 receptor, as well as with the cytokines bFGF, OSM, IL-6, VEGF, or TNF-alpha resulted in phosphorylation and activation of RAFTK. Following its activation, there was an enhanced association of RAFTK with the cytoskeletal protein paxillin. This association was mediated by the hydrophobic COOH-terminal domain of the kinase. Furthermore, JNK activity was increased in KS cells after VEGF or VRP stimulation. We postulate that in these tumor cells RAFTK may be activated by a diverse group of stimulatory cytokines and facilitate signal transduction to the cytoskeleton and downstream to the growth promoting JNK pathway.

Vascular endothelial growth factor/vascular permeability factor is an autocrine growth factor for AIDS-Kaposi sarcoma

Kaposi sarcoma (KS) is the most common tumor associated with HIV-1 infection and develops in nearly 30% of cases. The principal features of this tumor are abnormal vascularization and the proliferation of endothelial cells and spindle (tumor) cells. KS-derived spindle cells induce vascular lesions and display enhanced vascular permeability when inoculated subcutaneously in the nude mouse. This finding suggests that angiogenesis and capillary permeability play a central role in the development and progression of KS. In this study, we show that AIDS-KS cell lines express higher levels of vascular endothelial growth factor/vascular permeability factor (VEGF/VGF) than either human umbilical vein endothelial cells or human aortic smooth muscle cells. AIDS-KS cells and primary tumor tissues also expressed high levels of Flt-1 and KDR, the receptors for VEGF, while the normal skin of the same patients did not show any expression. We further demonstrate that VEGF antisense oligonucleotides AS-1 and AS-3 specifically block VEGF mRNA and protein production and inhibit KS cell growth in a dose-dependent manner. Furthermore, growth of KS cells in nude mice was specifically inhibited by VEGF antisense oligonucleotides. These results show that VEGF is an autocrine growth factor for AIDS-KS cells. To our knowledge, this is the first report that shows that VEGF acts as a growth stimulator in a human tumor. Inhibitors of VEGF or its cognate receptors may thus be candidates for therapeutic intervention.

Advances in Kaposi's sarcoma

KS remains a challenge to clinicians and investigators more than a century after its initial description. Debate continues as to the cell of origin, as well as whether or not it is a true cancer. KS appears to be an opportunistic neoplasm, which in its earliest phase retains some features of a benign hyperproliferative process, but in its late stages behaves like an aggressive malignancy. Pathogenesis seems to involve a predisposed individual (genetically susceptible or immunologically compromised) who comes into contact with an infectious agent, most likely a virus. Cytokines appear to play a major role in the growth of the tumor. The exact role of the KSHV in this process will likely be the subject of much investigation in the future.

Human herpesvirus 8 encodes a homolog of interleukin-6

Kaposi's sarcoma is a multifocal lesion that is reported to be greatly influenced by cytokines such as interleukin-6 (IL-6) and oncostatin M. DNA sequences of a novel human gammaherpesvirus, termed human herpesvirus 8 (HHV-8) or Kaposi sarcoma-associated herpesvirus, have been identified in all epidemiological forms of Kaposi's sarcoma with high frequency. The presence of HHV-8 DNA is also clearly associated with certain B-cell lymphomas (body cavity-based lymphomas) and multicentric Castleman's disease. Sequence analysis of a 17-kb fragment revealed that adjacent to a block of conserved herpesvirus genes (major DNA-binding protein, glycoprotein B, and DNA polymerase), the genome of HHV-8 encodes structural homolog of IL-6. This cytokine is involved not only in the pathogenesis of Kaposi's sarcoma but also in certain B-cell lymphomas and multicentric Castleman's disease. The viral counterpart of IL-6 (vIL-6) has conserved important features such as cysteine residues involved in disulfide bridging or an amino-terminal signal peptide. Most notably, the region known to be involved in receptor binding is highly conserved in vIL-6. This conservation of essential features and the remarkable overlap between diseases associated with HHV-8 and diseases associated with IL-6 disregulation clearly suggest that vIL-6 is involved in HHV-8 pathogenesis.

Immunotoxins: an update

The use of immunotoxins (ITs) in the therapy of cancer, graft-vs-host disease (GvHD), autoimmune diseases, and AIDS has been ongoing for the past two decades. ITs contain a targeting moiety for delivery and a toxic moiety for cytotoxicity. Theoretically, one molecule of a toxin, routed to the appropriate cellular compartment, will be lethal to a cell. Newly developed MoAbs, toxins, and molecular biological technologies have enabled researchers to construct ITs that can effectively kill many different cell types. In fact, phase I/II clinical trials have given promising results. Although nonspecific toxicity and immunogenicity still limit the use of IT therapy, these agents hold enormous promise in an optimal setting to treat minimal disease.

Tumorigenesis and metastasis of neoplastic Kaposi's sarcoma cell line in immunodeficient mice blocked by a human pregnancy hormone

Kaposi's sarcoma (KS) occurs more often in men than in women and HIV-1-associated KS has a high occurrence in homosexual men (over 30%). Most cultures of KS tumours yield cells with properties of hyperplastic (not malignant) endothelial cells under the control of several cytokines. The role of HIV-1 may be in promoting high levels of some cytokines and providing stimulation to angiogenesis by the HIV-1 Tat protein, which synergizes with basic fibroblast growth factor in promoting these effects. Here we describe an immortalized AIDS-KS cell line (KS Y-1) and show that these cells produce malignant metastatic tumours in nude mice and are killed in vitro and in vivo (apparently by apoptosis) by a pregnancy hormone, the beta-chain of human chorionic gonadotropin. Similarly, chorionic gonadotropin kills KS SLK, cells from another neoplastic cell line (established from a non-HIV-associated KS), as well as the hyperplastic KS cells from clinical specimens grown in short-term culture, but does not kill normal endothelial cells. These results provide evidence that KS can evolve into a malignancy and have implications for the hormonal treatment of this tumour.