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.

In vivo overexpression of IL-13 receptor alpha2 chain inhibits tumorigenicity of human breast and pancreatic tumors in immunodeficient mice.

Interleukin 13 receptor alpha2 (IL-13R(alpha)2) chain is highly expressed on some tumor cell lines and primary cell cultures. This receptor chain plays an important role in ligand binding and internalization. To determine the functional significance of overexpression of this chain, we stably transfected IL-13R(alpha)2 chain in human breast (MDA-MB-231) and pancreatic (PANC-1) cancer cell lines that naturally do not express this chain. There was no difference in growth between vector only transfected and IL-13R(alpha)2 chain transfected cells in vitro. However, surprisingly, in immunodeficient mice, tumorigenicity was profoundly inhibited in IL-13R(alpha)2 chain overexpressing tumors. Because breast tumors that grew later showed loss of IL-13R(alpha)2 gene expression, lack of tumorigenicity correlated positively with IL-13R(alpha)2 chain expression. Inflammatory cells including neutrophils and macrophages were identified in IL-13R(alpha)2 overexpressing regressing tumors and neutrophils were found to produce IL-13. IL-13 showed a modest antitumor activity to IL-13R(alpha)2 chain overexpressing tumors in vitro and in vivo. Furthermore, IL-13R(alpha)2 chain overexpressing tumors constitutively produced IL-8 that has been shown to have antitumor effect. These results establish a novel function of a cytokine receptor chain and further suggest that the presence of this chain on tumor cells by itself may play a key role in tumorigenicity.

Reversal of multidrug resistance in human colon cancer cells expressing the human MDR1 gene by liposomes in combination with monoclonal antibody or verapamil.

BACKGROUND: Colorectal cancer is a major cause of cancer-related mortality in the world and the second leading cause of neoplastic death in the United States. A major obstacle in the chemotherapy of this neoplasm is the emergence of multidrug resistance that is frequently associated with the expression of P-glycoprotein (p170) encoded by MDR1 (also known as PGY1) genes. Previously, we demonstrated that liposome-encapsulated doxorubicin is more cytotoxic than free doxorubicin in human promyelocytic leukemia and human breast cancer cells with the multidrug-resistant phenotype. PURPOSE: Our purpose was to investigate modulation of multidrug resistance by liposome-encapsulated vincristine (VCR) in a drug-resistant human colon cancer cell line HT-29mdr1 and the potentiation of this modulation in combination with monoclonal antibody MRK-16 or verapamil. METHODS: HT-29 parental cells and HT-29mdr1 cells were exposed to free VCR or liposome-encapsulated VCR alone or in combination with MRK-16 or verapamil. Cytotoxicity of cells after various treatments was determined by neutral red staining, and cellular content of VCR was measured by using radiolabeled VCR; p170 expression of cells was assessed by azidopine. RESULTS: HT-29mdr1 cells express a high amount of p170, thus conferring sixfold to sevenfold resistance to VCR compared with the parent cell line. Liposome-encapsulated VCR lowers drug resistance in HT-29mdr1 cells fourfold; IC50 values (concentration that causes 50% reduction in cell number) were 12.5 +/- 2.5 ng/mL compared with 42.5 +/- 5.0 ng/mL with free VCR. IC50 values for free VCR with empty liposomes were 25 +/- 1.25 ng/mL. The combination of MRK-16 and free VCR produced a twofold increase in cytotoxicity over free VCR in p170-expressing cells; the combination of MRK-16 and liposome-encapsulated VCR produced a 10-fold potentiation of cytotoxicity. toxicity. Nonspecific monoclonal antibody NR-LU-10 had no effect on cytotoxicity of HT-29mdr1 cells with free VCR or liposome-encapsulated VCR. The combination of 1.5 microM verapamil potentiated the cytotoxicity of free VCR ninefold to 10-fold, IC50 values reduced to 5.0 +/- 1.5 ng/mL, and in combination with liposome-encapsulated VCR, IC50 values reduced to 2.5 +/- 1.0 ng/mL, demonstrating a 15- to 17-fold potentiation of cytotoxicity. There were no significant differences in drug accumulation in HT-29mdr1 cells when treated with liposome-encapsulated VCR or free VCR. Liposomes inhibited the photoaffinity labeling of azidopine to p170 HT-29mdr1 cells. CONCLUSIONS: Liposome encapsulation of VCR effectively modulates multidrug resistance in human colon cancer cells and may become an important modality in treatment for colon cancers.

Liposome-mediated modulation of multidrug resistance in human HL-60 leukemia cells.

BACKGROUND: Multidrug resistance (MDR) is a major obstacle in cancer treatment. Resistance of cultured tumor cells to major classes of cytotoxic drugs is frequently due to expression of a plasma membrane P-glycoprotein encoded by MDR genes. We have demonstrated that liposome-encapsulated doxorubicin is more toxic than the free drug and that it modulates MDR in Chinese hamster LZ cells and human colon cancer cells. PURPOSE: To investigate further the association between expression of P-glycoprotein and modulation of MDR by liposome-encapsulated doxorubicin, we studied vincristine-resistant HL-60/VCR leukemia cells, which express P-glycoprotein, and doxorubicin-resistant HL-60/ADR leukemia cells, which do not. METHODS: Cells were exposed to various concentrations of free doxorubicin and liposome-encapsulated doxorubicin. The cellular content of doxorubicin was determined by fluorescence analysis, and cytotoxicity was determined by cell growth inhibition. Photoaffinity-labeling studies of P-glycoprotein binding were performed on HL-60/VCR and HL-60/ADR cells and KB-GSV2 cells transfected with the MDR1 gene (also known as PGY1). RESULTS: The concentrations that caused 50% inhibition of growth (IC50) for free doxorubicin in HL-60, HL-60/ADR, and HL-60/VCR cells were 30 nM, 9 microM, and 0.9 microM, respectively. The values for liposome-encapsulated doxorubicin in parental HL-60 cells and HL-60/ADR cells were 20 nM and 9 microM, respectively, indicating little or no sensitization. In contrast, HL-60/VCR cells were fivefold more sensitive to liposome-encapsulated doxorubicin than to free doxorubicin, and IC50 was reduced to 0.17 microM. In HL-60 cells exposed to liposome-encapsulated doxorubicin, intracellular doxorubicin accumulation was less than that seen with free drug. In contrast, in HL-60/VCR cells, accumulation was twofold to threefold higher than that with free doxorubicin. Liposome-encapsulated doxorubicin completely inhibited the photoaffinity labeling of P-glycoprotein by azidopine in membrane vesicles of HL-60/VCR cells, with a potency comparable to that of azidopine, suggesting that circumvention of MDR by liposomes is related to their specific interaction with P-glycoprotein. The studies with KB-GSV2 cells indicated that blank liposomes can directly inhibit photoaffinity labeling of P-glycoprotein. CONCLUSIONS: These results demonstrate the effectiveness of liposome-encapsulated doxorubicin in overcoming resistance in the multidrug-resistant phenotype of HL-60/VCR cells by direct interaction with P-glycoprotein. Furthermore, they indicate that liposome-encapsulated doxorubicin may be an effective treatment for human cancers.

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.

Interleukin 13 inhibits growth of human renal cell carcinoma cells independently of the p140 interleukin 4 receptor chain.

Interleukin-13 (IL-13) is a cytokine produced primarily by activated T lymphocytes. It exerts a variety of effects on different cell types, including monocytes, B lymphocytes, mast cells, and keratinocytes. The effects of IL-13 on target cells are often similar to the effects of IL-4, which is another cytokine product of activated T lymphocytes. We recently described the expression of intermediate- to high-affinity receptors for IL-13 (IL-13R) on renal cell carcinoma (RCC) cells. In the present study, we examined the effect of IL-13 on the growth of RCC cells as measured by [3H]thymidine uptake and a clonogenic assay. In addition, we used an IL-4R-specific antibody to examine the specificity of IL-4R and IL-13R binding and function. We observed that IL-13 inhibited RCC cell proliferation by up to 50% and colony formation by up to 32% when compared with cells cultured in medium alone. A combination of IL-4 and IL-13 did not have an additive or synergistic effect on the growth of RCC cells. These cells expressed mRNA for IL-13 and secreted immunoreactive IL-13 protein in culture. The growth-inhibitory effects of IL-13 were specific, because they were not affected by antibodies to IL-4 or to the 140-kilodalton subunit of IL-4R. Furthermore, polyclonal antibodies to IL-4R failed to inhibit the binding of 125I-IL-13 to RCC cells. These results indicate that IL-13 has significant antiproliferative effects on human RCC cells, and the inhibition of IL-13 effects by anti-IL-4R antibody previously reported in lymphoid cells does not occur in RCC cells.

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.

Gene therapy for cancer: regulatory considerations for approval.

The rapidly changing field of gene therapy promises a number of innovative treatments for cancer patients. Advances in genetic modification of cancer and immune cells and the use of oncolytic viruses and bacteria have led to numerous clinical trials for cancer therapy, with several progressing to late-stage product development. At the time of this writing, no gene therapy product has been approved by the United States Food and Drug Administration (FDA). Some of the key scientific and regulatory issues include understanding of gene transfer vector biology, safety of vectors in vitro and in animal models, optimum gene transfer, long-term persistence or integration in the host, shedding of a virus and ability to maintain transgene expression in vivo for a desired period of time. Because of the biological complexity of these products, the FDA encourages a flexible, data-driven approach for preclinical safety testing programs. The clinical trial design should be based on the unique features of gene therapy products, and should ensure the safety of enrolled subjects. This article focuses on regulatory considerations for gene therapy product development and also discusses guidance documents that have been published by the FDA.

Gene transfer of interleukin 13 receptor alpha2 chain dramatically enhances the antitumor effect of IL-13 receptor-targeted cytotoxin in human prostate cancer xenografts.

IL-13Ralpha2 chain, the primary interleukin-13 (IL-13) binding protein, plays an important role in IL-13 binding and internalization. Based on these findings, in our previous study we transiently transfected four cancer cell lines that do not express IL-13Ralpha2 chain and demonstrated that these cells acquired increased sensitivity to IL-13 receptor-targeted recombinant cytotoxin, IL13-PE38QQR, which is composed of IL-13 and a mutated form of a Pseudomonas exotoxin. Although some prostate cancer cell lines express functional IL-13R, they are not highly sensitive to IL-13 cytotoxin. Here we investigated whether human prostate cancer and normal prostate epithelial cell lines express IL-13Ralpha2 chain and whether they can be sensitized to the cytotoxic effect of IL-13 cytotoxin after transient or stable gene transfer of IL-13Ralpha2 chain. Gene transfer of IL-13Ralpha2 chain improved binding activity of IL-13 and sensitivity to IL-13 cytotoxin in vitro. In vivo experiments demonstrated that gene transfer of IL-13Ralpha2 chain dramatically enhanced the antitumor activity of IL-13 cytotoxin in human prostate cancer xenograft models. These results suggest that IL-13R-targeted cytotoxin therapy of prostate cancer may be dramatically enhanced by gene transfer of IL-13Ralpha2 chain and this strategy, the combination of gene therapy and cytotoxin therapy, may be utilized in the treatment of localized prostate cancer.

Transcriptional up-regulation of interleukin 4 receptors by human immunodeficiency virus type 1 tat gene.

The human immunodeficiency virus type 1 (HIV-1) regulatory gene, tat, encodes an early transactivator protein (Tat) necessary for virus replication. We have reported that the HIV-1 tat gene can up-regulate interleukin 4 receptors (IL-4R) however, the mechanism of this up-regulation is not understood. We now show that in Raji cells, 125I-labeled IL-4 cross-linked to three proteins of 140, 70, and 63 kDa, which were immunoprecipitated with an antibody to the human IL-4R. Although this level of all three IL-4 binding proteins increased in tat-transfected cells, the binding characteristics of IL-4R on control or mock transfected control and tat-transfected cells remained similar. The exogenous recombinant Tat protein or supernatant of tat transfected Raji cells also up-regulated the expression of the IL-4R on two renal cell carcinoma cell lines in a concentration-dependent manner. The actinomycin D chase experiments revealed that the half-lives of the IL-4R protein (t1/2 3.5 hr) and mRNA transcripts (t1/2 2.5 hr) were similar in both control and tat-transfected cells. In contrast, nuclear run-on experiments revealed that the rate of the IL-4R mRNA transcription increased 3- to 5-fold in Raji-tat compared to Raji cells. These data indicate that the HIV-1 tat gene up-regulates IL-4R expression by increasing the transcription rate rather than posttranscriptional stabilization of either the mRNA or the protein. HIV-tat inducible exogenous tumor necrosis factor (TNF-alpha) did not up-regulate IL-4R and IL-4R inducible activation of signal transducers and activators of transcription (STAT-6) was not observed by Tat even though IL-4R were up-regulated. These results allow us to speculate that HIV-1 tat may interact directly with the IL-4R gene and up-regulate IL-4R transcription.

Potentiation of cytotoxicity of Kaposi's sarcoma related to immunodeficiency syndrome (AIDS) by liposome-encapsulated doxorubicin.

Kaposi's sarcoma is an independent criterion for the diagnosis of AIDS and develops in nearly 15% of all cases. Current chemotherapy regimens are associated with substantial toxicity, particularly bone marrow suppression, which limit their long-term use. In an attempt to reduce treatment-related toxicity and enhance uptake of the drug in tumor cells, free and liposome-encapsulated doxorubicin was tested in vitro. The liposomes were prepared with cardiolipin, phosphatidylcholine, and cholesterol. Kaposi's sarcoma (KS)-derived spindle cells were exposed to free doxorubicin (DOX) and liposome-encapsulated doxorubicin (LED) for various time intervals and analyzed for cellular cytotoxicity, thymidine incorporation, and cellular drug uptake. Cytotoxicity studies of KS cells with free DOX and LED showed an IC50 of 288 and 7.5 ng/ml, respectively, hence demonstrating a 38-fold higher cytotoxicity by LED. Thymidine incorporation studies in KS cells demonstrated over one log higher toxicity to LED compared to free DOX. Cellular drug uptake studies showed that free DOX concentration peaked in 1 hr in KS cells whereas LED continued to accumulate up to 4 hr. At 4 hr, anthracycline uptake through LED was fivefold higher than the uptake of free drug. Similarly LED uptake in the cells evaluated by direct fluorescent microscopy was much more intense and more frequent than the uptake of free drug. Thus AIDS-KS cells appear to be exquisitely sensitive to LED, which may provide a higher therapeutic to toxicity index in clinical use.

Preclinical studies with IL-13PE38QQR for therapy of malignant glioma.

To develop novel therapeutic agents for the treatment of brain tumors, we have been investigating the expression of unique tumor-associated receptors or antigens on the tumor cell surface. About six years ago, we discovered that human solid tumor cell lines, including human malignant glioma, express high- to intermediate-affinity receptors (R) for a Th2 cell-derived cytokine, interleukin-13 (IL-13). Analysis of the subunit composition of IL-13R in primary explants of malignant glioma cells has demonstrated that IL-13R is composed of three different chains (IL-13R alpha 1, IL-13R alpha 2 and IL-4R alpha, also known as IL-13R alpha', alpha and IL-4R beta, respectively) and that IL-13R alpha 2 chain is overexpressed on these cells. Normal brain tissues express IL-13R alpha 1 and IL-4R alpha chains, but show only marginal expression of IL-13R alpha 2 chain. Thus IL-13R alpha 2 chain appears to be overexpressed on glioma cells and may serve as a novel tumor biomarker or a target for receptor-directed therapeutic agents for brain tumors. To target IL-13 receptors, we have produced a recombinant fusion protein composed of IL-13 and a mutated form of Pseudomonas exotoxin (PE). This cytotoxin, termed IL-13PE38QQR or IL-13 cytotoxin, is highly and specifically cytotoxic to a spectrum of human glioma cell lines. In preclinical models of human glioblastoma tumors growing subcutaneously in immunodeficient mice, IL-13 cytotoxin has been found to have remarkable antitumor activity. The data that emerged from these studies reveal that localized or systemic administration of IL-13 cytotoxin can produce nontoxic drug levels and that IL-13 cytotoxin is potently effective against established glioblastoma tumors. On the basis of these and other preclinical studies, we have begun a phase I clinical trial using IL-13PE38QQR for therapy of recurrent malignant glioma.

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.

Head and neck cancers, but not benign lesions, express interleukin-4 receptors in situ.

We have previously reported on the expression of interleukin-4 receptor (IL-4R) on many solid cancer cell lines. In the present study, we have examined the expression of IL-4R on head and neck cancers in situ by immunohistochemistry. Seven primary squamous cell carcinomas of the head and neck region were stained by a monoclonal antibody to human IL-4Rp140 protein (M-57). We report that all squamous cell carcinoma samples were positively stained although at variable intensity with anti-IL-4R antibody. Tumors stained with IgG control did not show any staining. On the other hand, six benign lesions from the same anatomical area showed faint or no staining at all. Three uterine endometrium samples were also negative for the IL-4R expression. In contrast to published contrary results, we did not observe any effect of IL-4 on the proliferation of four squamous cell carcinoma of head and neck (SCCHN) cell lines examined. These results demonstrate that human squamous carcinoma of the head and neck express IL-4R, which could be targeted for diagnosis and therapy by anti-IL-4 receptor antibody fused to toxins or radionuclides or alternatively by IL-4 toxins.

Derivatization of keto fatty acids, X: Synthesis of thiazanones.

The synthesis of alkyl chain-substituted thiazanones from oxo fatty esters and a long chain aldehyde is reported. Four oxo compounds-methyl 10-oxoundecanoate, methyl 9-oxooctadecanoate, methyl 9,10-dioxooctadecanoate and octadecanal-were allowed to react with ß-mercaptopropionic acid in the presence of ammonium carbonate in benzene to give the corresponding 4-m-thiazanones in high yields. The structures of these compounds were confirmed by combustion and spectral data.