Biomedical subjects

R K Puri

Publications and source records attributed to R K Puri.

At least 19 recordsLinked to original sources

PubMed1998

Complete regression of established human glioblastoma tumor xenograft by interleukin-4 toxin therapy.

No curative therapy is available for malignant gliomas. We have discovered that human glioblastoma cells express high affinity interleukin-4 receptor (IL-4R), which is an attractive target for receptor-directed IL-4 toxin therapy. The IL-4 toxin, IL-4(38-37)-PE38KDEL, is a fusion protein containing translocation and enzymatic domains of Pseudomonas exotoxin and a circularly permuted human IL-4. The IL-4 toxin binds specifically to the IL-4R and is highly cytotoxic to glioblastoma cells, as determined by clonogenic and protein synthesis inhibition assays. Intratumoral administration of the IL-4 toxin given on alternate days for 3-4 doses into U251 glioblastoma flank tumors in nude mice, showed a complete remission of small (approximately 13 mm3) and large (approximately 60 mm3) tumors in all animals, without any evidence of toxicity. A significant antitumor activity was also observed when the IL-4 toxin was administered via i.p. and i.v. routes. These results demonstrate that the IL-4 toxin may be a new therapeutic drug for the treatment of human glioblastoma. Therefore, we have begun a Phase I clinical trial with IL-4(38-37)-PE38KDEL for treatment of human glioblastoma.

ADP Ribose Transferases↗

PubMed1998

Novel way to increase targeting specificity to a human glioblastoma-associated receptor for interleukin 13.

Human brain cancers (gliomas) overexpress large numbers of a receptor for interleukin 13 (IL13), making this receptor an attractive target for anti-glioma therapies. We have recently proposed that the glioma-associated IL13 receptor is different from the one expressed on some hemopoietic and somatic cells. In an attempt to identify an even more glioma-specific target, we have used an antagonist of a related cytokine, IL4, which neutralizes the physiological effects of both IL13 and IL4 on normal cells. Here we demonstrate that the IL4 antagonist also counteracts the action of cytotoxins targeted to the IL13 receptor on normal human cells. Importantly, the IL4 antagonist does not inhibit IL13-based cytotoxins on glioma cells at all. Thus, the IL13 receptor on glioma cells can be categorized as tumor-specific in the presence of an IL4 antagonist. We conclude that IL13 receptor-directed cytotoxins can be delivered to glioma cells without being cytotoxic to normal cells.

ADP Ribose Transferases↗

PubMed1998

Interleukin-13 receptor alpha' but not alpha chain: a functional component of interleukin-4 receptors.

In hematopoietic cells, interleukin-2 receptor (IL-2R) gamma chain (termed gammac) is shown to be a component of the IL-4R system, whereas in nonhematopoietic cells, gammac is absent and it is not a component of the IL-4R system. Here, we show that the IL-13R alpha' chain (termed IL-13Ralpha') but not the IL-13R alpha chain (termed IL-13Ralpha) can substitute for gammac and, thus, IL-13Ralpha' forms a novel component of the IL-4R system. This conclusion was drawn on the basis of chemical cross-linking, immunoprecipitation, the ability of IL-13Ralpha' but not IL-13Ralpha to augment IL-4 binding affinity, and the requirement of IL-13Ralpha' for IL-4-induced STAT6 activation in Chinese hamster ovary (CHO) cells transfected with various receptor subunits. Cotransfection of IL-4 receptor p140 (termed IL-4Rbeta) with gammac or IL-13Ralpha' increased IL-4 binding affinity and allowed for STAT6 activation in response to IL-4. However, cotransfection of all three chains did not further increase IL-4 binding or alter the extent of STAT6 activation suggesting that all three chains together do not seem to participate in IL-4 function. Instead, IL-4Rbeta heterodimerizes with gammac or IL-13Ralpha' and mediates STAT6 activation. Cotransfection of IL-4Rbeta with IL-13Ralpha neither increased IL-4 binding affinity nor allowed for STAT6 activation in response to IL-4 indicating that IL-13Ralpha does not convert binding affinity nor transmit signals for IL-4. Because IL-4 phosphorylates JAK1 and JAK2 tyrosine kinases in nonhematopoietic cells, we investigated whether JAK1 and JAK2 are required for IL-4-induced STAT6 activation in various transfectants. Cotransfection experiments with different chains of IL-4R and kinase-deficient JAK1 and JAK2 mutants in CHO cells showed that JAK1 and JAK2 are required for optimal activation of STAT6 in the alpha' beta transfectant but only partially in the beta gammac transfectant. Taken together, our results show that IL-13Ralpha' is a novel functional component of the IL-4R system and that JAK1 and JAK2 mediate IL-4-induced optimal activation of STAT6 in nonhematopoietic cells.

Animals↗

PubMed1998

Novel anti-brain tumor cytotoxins specific for cancer cells.

The vast majority of brain cancers (gliomas) express a receptor (R) for interleukin 13 (IL13). In order to achieve specific targeting of the IL13R in gliomas, we have mutagenized human (h) IL13. The mutation was made to alter IL13 interaction with the shared functional IL13/4 normal tissue receptor, but not with the glioma-associated receptor. We have thus produced hIL13.E13K (glutamic acid at position 13 changed to lysine) and fused it to derivatives of Pseudomonas exotoxin A. The hIL13.E13K-based cytotoxins are less active on normal cells and thus less toxic, and are better antitumor agents compared with the cytotoxins containing nonmutagenized hIL13.

Antineoplastic Agents↗

PubMed1998

Two different IL-13 receptor chains are expressed in normal human skin fibroblasts, and IL-4 and IL-13 mediate signal transduction through a common pathway.

IL-13 and IL-4, pleiotropic immune regulatory cytokines, have been shown to mediate similar prominent effects in human fibroblast cell lines. However, molecular mechanisms for their redundant effects are not known. Here, we have investigated the structure of IL-13 receptors (IL-13R) and molecular mechanisms of signal transduction through IL-13 and IL-4 receptors in non-transformed normal skin fibroblast cell lines. We demonstrate that high-affinity IL-13R is expressed in normal skin fibroblast cell lines. Upon [125I]1L-13 cross-linking, a approximately 60-70 kDa band was observed in sk559 and sk574 fibroblast cell lines. By RT-PCR analysis, mRNA for IL-13R alpha, IL-13R alpha' and IL-4Rbeta chains were expressed; however, the IL-2Rgamma chain, shown to participate and modulate IL-4 and IL-13 binding, was not expressed in any of the cell lines examined. The Janus kinase (JAK)2 and Tyk2 were phosphorylated in response to IL-4 or IL-13 in sk559 and sk574 cell lines. JAK1 was also phosphorylated in one of two cell lines while JAK3 was present but not phosphorylated in any of the cell lines studied. A signal transduction and activator of transcription (STAT)6 was also activated in response to both IL. An insulin receptor substrate (IRS)-1 was constitutively phosphorylated and its phosphorylation level was augmented in response to both IL. These results suggest that the mechanism of signal transduction through IL-13 and IL-4 receptors in human fibroblast cell lines is similar, and this may, at least in part, be responsible for the redundant effects of these two cytokines. In addition, JAK2 tyrosine kinase instead of JAK3 appears to play a major role in IL-4- and IL-13-induced signal transduction in human fibroblasts.

Affinity Labels↗

PubMed1998

Structure of and signal transduction through interleukin-4 and interleukin-13 receptors (review).

We have recently demonstrated that two different forms of IL-4R exist; classical or alternative. The classical IL-4R is predominantly expressed in hematopoietic cells and consist of IL-4R and IL-2Rgammac (gammac) chains. On the other hand, alternative form of IL-4R is predominantly expressed in non-hematopoietic cells and consists of IL-4R and IL-13Ralpha' chains. Moreover, the alternative form of IL-4R is also utilized as a functional component IL-13R complex. It has been shown that the phosphorylation and activation of JAK3 tyrosine kinase is crucial for IL-4 activation of STAT6 in hematopoietic cells. However, we have recently demonstrated that non-hematopoietic cells lack JAK3 expression. We also demonstrated that in these cells, STAT6 activation is mediated through JAK1 and JAK2 tyrosine kinases instead. Furthermore, our results show that IL-4 and IL-13 signals are transmitted through the alternative form of IL-4R in these cells. Thus, major differences exist between hematopoietic and non-hematopoietic cells with regard to structure and signal transduction through IL-4R and IL-13R systems.

Animals↗

PubMed1997

Structure of IL-13 receptor: analysis of subunit composition in cancer and immune cells.

The structure of IL-13 receptor (IL-13R) is currently under investigation. Recently, two different human IL-13R chains, termed here IL-13R alpha and -alpha' have been cloned. We have examined various cancer and normal cell lines for the presence of mRNA for IL-13R alpha and alpha, as well as IL-4R p140 (termed beta chain) and IL-2R gamma c chains. In renal cell carcinoma, glioblastoma and ovarian carcinoma (IGROV-1) cell lines, both IL-13R alpha and alpha chains were expressed (type I IL-13R). In epidermoid, colon, ovarian adenocarcinoma (PA-1) and normal mouse fibroblast (COS7) cell lines, only IL-13R alpha' was expressed (type II IL-13R). In hematopoietic TF-1 and EBV-immortalized normal B cell lines only IL-13R alpha' but not alpha chain was expressed along with gamma c (type III or type IV IL-13R). IL-13R alpha' chain was faintly detected in human T cells. All cells expressed the IL-4Rp140 beta chain. These data provide a direct support for our model of IL-13R which consists of three different forms composed of different subunits.

Animals↗

PubMed1997

Human immunodeficiency virus-1-tat protein induces the cell surface expression of endothelial leukocyte adhesion molecule-1, vascular cell adhesion molecule-1, and intercellular adhesion molecule-1 in human endothelial cells.

Human vascular endothelial cells (EC) have been implicated in the dissemination of human immunodeficiency virus type-1 (HIV-1). HIV-1-tat, a viral gene product essential for HIV replication, has been shown to interact with different cell types, altering their growth and inducing gene expression. In the present report, we have examined the effect of HIV-tat on the expression of various adhesion molecules in human umbilical vein EC. Our results show that treatment of EC with HIV-tat induces the cell surface expression of intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and endothelial leukocyte adhesion molecule-1 in a time- and dose-dependent manner. Cycloheximide abolished the HIV-tat-dependent induction of all the adhesion molecules, indicating that protein synthesis was required for induction. The effect of HIV-tat on expression of adhesion molecules was potentiated by tumor necrosis factor (TNF), a well-known inducer of adhesion molecules. Like TNF, HIV-tat also enhanced the adhesion of human promyelomonocytic HL-60 cells to EC, and this effect was abolished by treatment with antibodies either against HIV-tat or adhesion molecules. Our results thus indicate that the HIV-tat protein can activate human vascular EC to induce the expression of various adhesion molecules that may play a role in the extravasation of HIV-infected cells.

Cycloheximide↗

PubMed1997

Modulation of interleukin (IL)-13 binding and signaling by the gammac chain of the IL-2 receptor.

Interleukin (IL)-13 and IL-4 are cytokine products of TH2 cells which exert similar effects in a variety of cell types. We recently described IL-13R expression on human renal cell and colon carcinoma cells and demonstrated that gammac is not a component of IL-13R or IL-4R systems in these cells. In lymphoid cells such as B cells and monocytes, which respond to IL-13, gammac is a component of IL-4R but does not appear to be a component of IL-13R. Furthermore, while significant IL-13 binding is observed on carcinoma cells, IL-13 barely binds these lymphoid cells and the binding characteristics are different. To better understand the role of gammac in IL-13 binding and signaling, we have transfected a renal cell carcinoma cell line with gammac and examined IL-13 and IL-4 binding and signaling. IL-13 binding as well as IL-13 and IL-4 signaling through the JAK-STAT signaling pathway were severely inhibited. This inhibition was paralleled by a loss of expression of one of the IL-13R chains and intercellular cell adhesion molecule-1. Thus, although gammac has been shown to enhance IL-4 binding and function in some cell types, its influence on IL-13R function in tumor cells appear to be largely negative.

Enzyme Activation↗

PubMed1997

Human ovarian-carcinoma cell lines express IL-4 and IL-13 receptors: comparison between IL-4- and IL-13-induced signal transduction.

We have reported that human ovarian-carcinoma cell lines express high-affinity IL-4 receptor. Since IL-4R has been hypothesized to share a chain with IL-13R, we investigated whether ovarian cancer cells express IL-13 receptor. In the present study, we report that the ovarian-carcinoma cell lines IGROV-1 and PA-1 express varying numbers of high-affinity IL-13 receptors. Furthermore, IL-13 inhibited the binding of IL-4 on both ovarian-carcinoma cell lines, while IL-4 did not inhibit IL-13 binding on IGROV-1 cell line. IL-13 and IL-4 induced the phosphorylation of JAK1, JAK2 and Tyk2 Janus kinases in PA-1 cells. In contrast, JAK3 tyrosine kinase was expressed in PA-1 cells, but IL-4 or IL-13 did not augment its phosphorylation. In IGROV-1 cells, Tyk2 was constitutively phosphorylated and this phosphorylation was augmented by IL-4 or IL-13. JAK1 and JAK2 but not JAK3 were expressed but only JAK2 was faintly phosphorylated in response to either IL-13 or IL-4 respectively. IRS (insulin-receptor substrate)-1 and IRS-2 were also phosphorylated constitutively in both ovarian cancer cell lines examined, but only the phosphorylation of IRS-1 was augmented in response to IL-4 or IL-13. STAT6 was phosphorylated and activated in response to IL-4 and IL-13 in all cell lines examined. Our results demonstrate that ovarian cancer cell lines may express 2 types of IL-13R and the IL-13- or IL-4-induced signaling patterns may be slightly different in each type of receptor.

Adenocarcinoma↗

PubMed1997

The IL-13 receptor structure differs on various cell types and may share more than one component with IL-4 receptor.

We have reported on the expression and characteristics of IL-13R and have demonstrated that IL-13 competes for IL-4 binding while IL-4 did not compete for the IL-13 binding on some cell types. Based on these observations, and the size of IL-13 and IL-4 cross-linked proteins, we concluded that the receptor for IL-13 is complex and shares a subunit with the receptor for IL-4. To explore the complexity of the IL-13R, a wide variety of cell types was examined for IL-13 and IL-4 binding. We report in this work that IL-4 does not always bind well to cells that bind IL-13, but the reverse is also true. We also found that IL-4 can compete more effectively for IL-13 binding than IL-13 itself. Cross-linking studies support these observations and demonstrate that 125I-labeled IL-13 bound exclusively to a single 65- to 70-kDa protein in MA-RCC and U251 cells, while in TF-1 cells it cross-linked to two membrane proteins of 65 to 70 kDa and 140 kDa. Furthermore, by using a chimeric protein composed of IL-13 and Pseudomonas exotoxin A, we observed that IL-4 neutralized the cytotoxicity of the IL-13 toxin on COS-7 cells by blocking a common form of the two cytokine receptors. We propose that the 65- to 70-kDa form of the IL-13R is the predominant common component shared between IL-13 and IL-4R. However, the primary IL-4 binding (p140) protein also participates in the formation of the IL-13R complex in some cell types. In addition, the gamma(c) or another interactive subunit may influence IL-13 binding to its receptor complex. Thus, we propose that there are at least four forms of IL-13R.

ADP Ribose Transferases↗

PubMed1997

Comparison of IL-13- and IL-4-induced signaling in EBV-immortalized human B cells.

Interleukin 4 (IL-4) and Interleukin 13 (IL-13) have been shown to have numerous similar effects on human B cells; however, the mechanism of signal transduction is not known. We have examined IL-4- and IL-13-induced signal transduction in Epstein-Barr virus (EBV)-immortalized B cells. We demonstrate that Janus kinase 3 (JAK3) and Tyk2 but not JAK1 and JAK2 tyrosine kinases were constitutively phosphorylated in three EBV B cell lines. The phosphorylation level of Tyk2 was augmented at a low level in response to IL-13 and IL-4 in two of three cell lines; however, IL-13 did not induce or augment phosphorylation of the other JAK kinases. On the other hand, IL-4 further augmented phosphorylation of JAK3 and induced the phosphorylation of JAK1 kinases. IL-4 receptor p140 protein was also constitutively phosphorylated in two of three EBV B cell lines examined and both IL-4 and IL-13 further augmented its phosphorylation. Insulin receptor substrate (IRS)-1 or IRS-2 proteins were not constitutively phosphorylated nor did IL-13 and IL-4 induce phosphorylation of these proteins. In contrast to JAKs, IL-4-specific signal transducer and activator of transcription (STAT6) was not constitutively phosphorylated or activated in these cell lines, but both IL-4 and IL-13 induced their phosphorylation and activation. These findings suggest that in EBV-immortalized B cells JAK3 and Tyk2 proteins were constitutively phosphorylated but STAT6 protein was not constitutively phosphorylated. In addition, despite major similarities in biological effects between IL-4 and IL-13, phosphorylation patterns of JAK kinases in response to IL-13 in EBV-immortalized B cells appear to be different from those of IL-4.

Animals↗

PubMed1997

Interleukin-13 receptors on human prostate carcinoma cell lines represent a novel target for a chimeric protein composed of IL-13 and a mutated form of Pseudomonas exotoxin.

We have discovered a new cell surface protein in the form of interleukin-13 receptor on several solid tumor cells, including human renal cell carcinoma cells (Obiri et al., 1995; Debinski et al., 1995). This study reports that human prostate cancer cell lines also express high affinity IL-13 receptors (Kd = 159 pM). These receptors are functional because IL-13 surprisingly increased proliferation of all three prostate cancer cell lines studied as determined by thymidine uptake and clonogenic assays. IL-13 receptors on prostate cancer cell lines were targeted using a chimeric protein composed of IL-13 and a mutated form of Pseudomonas exotoxin (PE38QQR). This molecule, termed IL13-PE38QQR, has been found cytotoxic to all three prostate cancer cell lines as determined by the inhibition of protein synthesis. The IC50 ranged between 1 nmol/l, to 15 nmol/l. These data were confirmed by clonogenic assays in which IL13-PE38QQR almost completely inhibited colony formation at 10 nmol/l. IL13-PE38QQR was not cytotoxic to cells that express little or no IL-13R. Heat inactivated IL13-PE38QQR was not cytotoxic to prostate cancer cells indicating specificity. IL13-PE38QQR was also cytotoxic to colonies when they were allowed to form first for several days before the addition of toxins. Our data suggest that additional studies should be performed to target IL-13 receptor bearing prostate cancer.

ADP Ribose Transferases↗

PubMed1997

Interleukin-4 receptor expression on AIDS-associated Kaposi's sarcoma cells and their targeting by a chimeric protein comprised of circularly permuted interleukin-4 and Pseudomonas exotoxin.

BACKGROUND: AIDS-associated Kaposi's sarcoma (AIDS-KS) represents one of the most common malignancies associated with human immunodeficiency virus infection. To target effective therapeutic agents to AIDS-KS, we have identified a new target in the form of interleukin-4 receptors (IL-4R). MATERIALS AND METHODS: The expression of IL-4R on AIDS-KS cells and their subunit structure was determined by radioligand receptor binding, cross-linking and Northern and RT-PCR analyses. The in vitro effect of IL-4 and recombinant fusion protein made up of circularly permuted IL-4 and a mutated form of Pseudomonas exotoxin, IL-4(38-37)-PE38KDEL, was examined by clonogenic and protein synthesis inhibition assays. RESULTS: Five AIDS-KS cell lines expressed high-affinity IL-4R with a Kd of 23.5-219 pM. IL-4 appeared to cross-link to one major protein corresponding to 140 kDa and a broad band corresponding to 60-70 kDa. Both cross-linked proteins were immunoprecipitated with an antibody to human IL-4R beta chain. AIDS-KS cells exhibited IL-4R beta-specific mRNA. IL-4 caused a modest inhibition (31-34%) of colony formation in two AIDS-KS cell lines tested. IL-4(38-37)-PE38KDEL was found to be highly effective in inhibiting the protein synthesis in all five AIDS-KS examined. The IC50 ranged from 32 to 1225 pM. The cytotoxic action of IL-4 toxin was blocked by an excess of IL-4, exhibiting the specificity of IL-4(38-37)-PE38KDEL. The cytotoxicity of IL-4 toxin observed by a clonogenic assay corroborated well with the IC50 obtained by protein synthesis inhibition assay. Normal human endothelial cells expressed a negligible number of IL-4R (< 50 sites/cell) and were less sensitive or not sensitive to IL-4(38-37)-PE38KDEL. CONCLUSION: The presence of a new plasma membrane protein in the form of IL-4R on AIDS-KS cells may be targeted by IL-4(38-37)-PE38KDEL for its potential implication in the treatment of AIDS-KS.

AIDS-Related Opportunistic Infections↗

PubMed1997

Interleukin-4 receptor expression in vivo on human AIDS-related Kaposi's sarcoma.

We have investigated the expression of interleukin-4 receptors (IL-4R) in acquired immunodeficiency syndrome (AIDS)-related Kaposi's Sarcoma (KS) in situ by immunohistochemistry. Frozen and fixed sections from five patch stage and two nodular stage KS lesions were stained with anti-IL-4R monoclonal antibody with similar results. Skin biopsies from the clinically apparent lesions and adjacent clinically uninvolved skin were also examined. We observed that individual KS cells lining the irregular vascular spaces were stained with anti-IL-4R antibody, although the degree of staining was variable. The epithelioid and oval cells appear to stain more than the spindle cells in plaque stages or nodular lesions. The sections from nonclinically involved skin also contained a few cells with features of KS, singly or in clusters that also stained for IL-4R. Skin sections from four normal donors did not stain with IL-4R antibody except for hair follicles, sweat glands, and faint staining of blood vessels. KS sections were also stained with antibodies to basic fibroblast growth factor (FGF), S100, fibronectin, and von Willebrand factor. KS lesions from clinically involved and uninvolved skin sections were positive for all four antibodies. Thus, the differences between KS lesion and clinically uninvolved skin adjacent to a KS lesion may be more quantitative than qualitative. The IL-4 receptors on KS cells were functional as IL-4 modulated intercellular adhesion molecule 1 (ICAM-1) on these cells. Taken together, our results suggest that AIDS-KS cells express elevated levels of IL-4R compared to normal endothelial and skin cells and, thus, the receptors for IL-4 on KS may serve as an attractive target for anticancer therapy.

Acquired Immunodeficiency Syndrome↗

PubMed1997

Inhibition of murine renal carcinoma pulmonary metastases by systemic administration of interferon gamma: mechanism of action and potential for combination with interleukin 4.

We have previously demonstrated that IFN-gamma causes cell growth inhibition and up-regulation of MHC antigens in human renal cell carcinoma cell lines. In this study, we have investigated the therapeutic potential of IFN-gamma for the treatment of 5-day established pulmonary metastases induced by i.v. injection of Renca cells, a murine renal adenocarcinoma. We found that systemic injections of IFN-gamma significantly reduced the number of lung metastases in a dose-dependent manner and increased mouse survival. Histological evaluation of IFN-gamma-treated lungs showed residual small tumor nodules containing extensive necrosis and mononuclear infiltrates. Immunohistochemistry studies on lung sections showed macrophage infiltration into tumor nodules, and in vivo depletion of macrophages partially inhibited IFN-gamma antitumor effect, suggesting a role for the macrophages in tumor destruction. Lymphocyte depletion of either natural killer (NK) cells or CD4+ or CD8+ T-cell subsets or both T-cell subsets did not affect the IFN-gamma effect, whereas depletion of both NK and T cells decreased the antitumor activity of IFN-gamma. These data indicate that neither T cells nor NK cells are essential for this activity but that either lymphocyte population can contribute to the IFN-gamma effect. An optimal dose of IFN-gamma inhibited by 60% the growth of Renca cells treated for 3 days in vitro, but this effect was transient and less pronounced in a long-term colony assay, suggesting that IFN-gamma direct growth inhibition may play a role but may not be sufficient to mediate its antitumor effect in vivo. In vitro, IFN-gamma caused up-regulation of class I MHC antigens and induction of class II antigen expression in Renca cells, an effect that may enhance Renca immunogenicity but may be relevant only when a T-cell response is elicited. A sequential administration of IFN-gamma followed by interleukin 4 was therapeutically better than IFN-gamma alone for the treatment of advanced pulmonary metastases, probably due to different antitumor mechanisms induced by these two cytokines.

Animals↗

PubMed1997

Receptor for interleukin 13 on AIDS-associated Kaposi's sarcoma cells serves as a new target for a potent Pseudomonas exotoxin-based chimeric toxin protein.

AIDS-associated Kaposi's sarcoma (AIDS-KS), the most common malignant complication of human immunodeficiency virus infection, is characterized by neoplastic proliferation of mesenchymal cells. AIDS-KS cells release and respond to an array of cytokines through specific plasma membrane receptors. Specific targeting of potent cytotoxic agents to cell surface receptors/antigens on Kaposi's sarcoma cells may provide effective therapy for this malignancy. We have identified a new target in the form of an interleukin 13 (IL-13) receptor that is overexpressed in the five AIDS-KS cell lines examined. Radiolabeled IL-13 cross-linked to a single protein of about Mr 70,000 in AIDS-KS cells. We utilized a chimeric cytotoxic protein composed of IL-13 and a truncated Pseudomonas exotoxin (IL13-PE38QQR), which was found to be specifically and highly cytotoxic to AIDS-KS cells, as determined by protein synthesis inhibition and clonogenic assays. IL13-PE38QQR demonstrated significant antitumor activity in a human epidermoid carcinoma xenograft model. Normal human umbilical vein-derived endothelial, lymphoid, and bone marrow precursor cells expressed low levels of IL-13 receptors, and IL-13 toxin was not cytotoxic to them. Thus, IL-13 receptor on AIDS-KS cells may represent a novel plasma membrane protein(s) that could be utilized to target therapeutic agents.

ADP Ribose Transferases↗

PubMed1996

Preclinical development of a recombinant toxin containing circularly permuted interleukin 4 and truncated Pseudomonas exotoxin for therapy of malignant astrocytoma.

Effective treatment is lacking for malignant glioblastoma/astrocytoma. We have identified interleukin-4 receptors (IL-4R) on human malignant astrocytoma. We demonstrate that 16 of 21 surgical samples of high-grade astrocytoma and glioblastoma but not normal brain tissues expressed IL-4R as assessed by reverse transcriptase PCR. We further demonstrate that human malignant astrocytoma cell lines express high-affinity IL-4R. Using a chimeric protein composed of circularly permuted IL-4 and a truncated form of Pseudomonas exotoxin A, we observed that this toxin IL4(38-37)-PE38KDEL) is highly cytotoxic to IL-4R-bearing glioblastoma cells. Compared with a previously reported IL4-PE chimeric protein (IL-PE4E), IL4(38-37)-PE38KDEL bound with higher affinity and was 3-30-fold more cytotoxic to glioblastoma cell lines. Upon intrathecal administration in monkeys, high cerebrospinal fluid IL4(38-37)-PE38KDEL levels were achieved using 2- and 6-microg/kg doses without any central nervous system or other abnormalities. IL4(38-37)-PE38KDEL levels were not detectable in the serum of any monkey studied. When IL4(38-37)-PE38KDEL was injected into the right frontal cortex of rats, localized necrosis was observed at 1000-ng/ml doses but not at < or = 100-ng/ml doses. We conclude that by localized administration, nontoxic levels of IL4(38-37)-PE38KDEL can be achieved, which may have significant cytotoxic activity against malignant astrocytoma.

ADP Ribose Transferases↗