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

99mTc-labeled peptide targeting interleukin 13 receptor α 2 for tumor imaging in a cervical cancer mouse model

OBJECTIVE

Pep-1 (CGEMGWVRC) can potently bind to interleukin 13 receptor α 2 (IL-13Rα2), a tumor-restricted receptor found to be expressed in various malignancies. In this study, we intended to prepare a ^99mTc-labeled probe and evaluate its in vivo tumor accumulation properties in a cervical cancer xenograft model.

METHODS

The Pep-1 was designed and radiolabeled with ^99mTc by conjugation with mercaptoacetyl-triglycine (MAG₃). The labeling yield, radiochemical purity and stability were characterized in vitro. Cell uptake assays and fluorescence imaging were conducted for qualitative and quantitative evaluation of the specificity and affinity of Pep-1. Flow cytometry and tissue immunofluorescence were used to confirm the IL-13Rα2 expression in cervical cancer. Biodistribution and in vivo imaging were performed periodically to evaluate the imaging value of ^99mTc-MAG₃-Pep-1 in cervical cancer xenograft model.

RESULTS

^99mTc-MAG₃-Pep-1 was successfully prepared with a high labeling yield and radiochemical purity (> 95%). Specific cell uptake was demonstrated by scramble control and unlabeled MAG₃-Pep-1 blockade. Flow cytometry and tissue immunofluorescence also confirmed the mild IL-13Rα2 expression of HeLa. In the gamma imaging study and biodistribution, the tumors were imaged clearly at 2-6 h after injection of ^99mTc-MAG₃-Pep-1 and the accumulation of ^99mTc-MAG₃-Pep-1 in tumor was significantly higher than that in the blocking and scramble controls, demonstrating ligand-receptor binding specificity.

CONCLUSIONS

This work demonstrated that ^99mTc-MAG₃-Pep-1 can bind to cervical cancer with high affinity and specificity. MAG₃-Pep-1 may be a prospective precursor for IL-13Rα2-expressing cancer therapy.

Elevated IL-13 in effusions of patients with HIV and primary effusion lymphoma as compared with other Kaposi sarcoma herpesvirus-associated disorders

OBJECTIVE

To assess the cytokine and viral profiles of effusions and peripheral blood among patients diagnosed with HIV and Kaposi sarcoma herpesvirus [KSHV, also known as human herpesvirus 8 (HHV-8)]-associated conditions.

DESIGN

Retrospective comparative study evaluating clinicopathologic findings in patients with HIV and KSHV-associated conditions presenting with an effusion between 2010 and 2018.

METHODS

Paired peripheral blood and effusion samples collected at the time of pathological diagnosis of KSHV-associated conditions [Kaposi sarcoma, KSHV-associated multicentric Castleman disease (KSHV-MCD), primary effusion lymphoma (PEL), or KSHV-associated inflammatory cytokine syndrome (KICS)] were evaluated for disease-specific and compartment-specific (effusion vs. blood) characteristics. We assessed 12 cytokines, KSHV viral DNA (KSHV-VL), and Epstein--Barr virus (EBV) viral DNA (EBV-VL).

RESULTS

Nine patients had PEL, five patients had KSHV-MCD, and eight patients met criteria for KICS; all but one patient had concurrent Kaposi sarcoma in addition to these conditions. PEL effusions had substantially higher levels of IL-13 (median 16.9 pg/ml; interquartile range 9.7--26.9 pg/ml) compared with KSHV-MCD (median <0.114 pg/ml; P = 0.0037) or KICS (median <0.114 pg/ml; P = 0.0003) effusions. IL-13 was also higher in PEL effusions as compared with serum (median <0.12 ng/ml; P = 0.007). KSHV-VL levels were significantly higher in PEL effusions as compared with KICS effusions (median 31 × 10 vs. 569 copies/million-cell equivalent; P = 0.0005) or KSHV-MCD effusions (median 231,884 copies/million-cell equivalent; P = 0.02).

CONCLUSION

PEL effusions had a distinct profile as compared to other KSHV-associated diseases with regard to elevated IL-13 and KSHV-VL. These findings may provide insights into PEL pathogenesis and aid in diagnosis.

Improved anti-glioblastoma efficacy by IL-13Rα2 mediated copolymer nanoparticles loaded with paclitaxel

Glioma presents one of the most malignant brain tumors, and the therapeutic effect is often limited due to the existence of brain tumor barrier. Based on interleukin-13 receptor α2 (IL-13Rα2) over-expression on glioma cell, it was demonstrated to be a potential receptor for glioma targeting. In this study, Pep-1-conjugated PEGylated nanoparticles loaded with paclitaxel (Pep-NP-PTX) were developed as a targeting drug delivery system for glioma treatment. The Pep-NP-PTX presented satisfactory size of 95.78 nm with narrow size distribution. Compared with NP-PTX, Pep-NP-PTX exhibited significantly enhanced cellular uptake in C6 cells (p < 0.001). The in vitro anti-proliferation evaluation showed that the IC50 were 146 ng/ml and 349 ng/ml of Pep-NP-PTX and NP-PTX, respectively. The in vivo fluorescent image results indicated that Pep-NP had higher specificity and efficiency in intracranial tumor accumulation. Following intravenous administration, Pep-NP-PTX could enhance the distribution of PTX in vivo glioma section, 1.98, 1.91 and 1.53-fold over that of NP-PTX group after 0.5, 1 and 4 h, respectively. Pep-NP-PTX could improve the anti-glioma efficacy with a median survival time of 32 days, which was significantly longer than that of PTX-NP (23 days) and Taxol(®) (22 days). In conclusion, Pep-NP-PTX is a potential targeting drug delivery system for glioma treatment.

Characterization and immunotherapeutic implications for a novel antibody targeting interleukin (IL)-13 receptor α2

The high affinity interleukin-13 receptor α2 (IL13Rα2) is selectively expressed at a high frequency by glioblastoma multiforme (GBM) as well as several other tumor types. One approach for targeting this tumor-specific receptor utilizes the cognate ligand, IL-13, conjugated to cytotoxic molecules. However, this approach lacks specificity because the lower affinity receptor for IL-13, IL13Rα1, is widely expressed by normal tissues. Here, we aimed to develop and characterize a novel monoclonal antibody (mAb) specific to IL13Rα2 for the therapeutic purpose of targeting IL13Rα2-expressing tumors. Hybridoma cell lines were generated and compared for binding affinities to recombinant human IL13Rα2 (rhIL13Rα2). Clone 47 demonstrated binding to the native conformation of IL13Rα2 and was therefore chosen for further studies. Clone 47 bound specifically and with high affinity (K(D) = 1.39 × 10(-9) M) to rhIL13Rα2 but not to rhIL13Rα1 or murine IL13Rα2. Furthermore, clone 47 specifically recognized wild-type IL13Rα2 expressed on the surface of CHO and HEK cells as well as several glioma cell lines. Competitive binding assays revealed that clone 47 also significantly inhibited the interaction between human soluble IL-13 and IL13Rα2 receptor. Moreover, we found that N-linked glycosylation of IL13Rα2 contributes in part to the interaction of the antibody to IL13Rα2. In vivo, the IL13Rα2 mAb improved the survival of nude mice intracranially implanted with a human U251 glioma xenograft. Collectively, these data warrant further investigation of this novel IL13Rα2 mAb with an emphasis on translational implications for therapeutic use.

Challenges in immunotherapy presented by the glioblastoma multiforme microenvironment

Glioblastoma multiforme (GBM) is the most common and aggressive primary brain tumor in adults. Despite intensive treatment, the prognosis for patients with GBM remains grim with a median survival of only 14.6 months. Immunotherapy has emerged as a promising approach for treating many cancers and affords the advantages of cellular-level specificity and the potential to generate durable immune surveillance. The complexity of the tumor microenvironment poses a significant challenge to the development of immunotherapy for GBM, as multiple signaling pathways, cytokines, and cell types are intricately coordinated to generate an immunosuppressive milieu. The development of new immunotherapy approaches frequently uncovers new mechanisms of tumor-mediated immunosuppression. In this review, we discuss many of the current approaches to immunotherapy and focus on the challenges presented by the tumor microenvironment.

Intracellular trafficking considerations in the development of natural ligand-drug molecular conjugates for cancer

Overexpressed receptors, characteristic of many cancers, have been targeted by various researchers to achieve a more specific treatment for cancer. A common approach is to use the natural ligand for the overexpressed receptor as a cancer-targeting agent which can deliver a chemically or genetically conjugated toxic molecule. However, it has been found that the therapeutic efficacy of such ligand-drug molecular conjugates can be limited, since they naturally follow the intracellular trafficking pathways of the endogenous ligands. Therefore, a thorough understanding of the intracellular trafficking properties of these ligands can lead to novel design criteria for engineering ligands to be more effective drug carriers. This review presents a few commonly used ligand/receptor systems where intracellular trafficking considerations can potentially improve the therapeutic efficacy of the ligand-drug molecular conjugates.

Expression of IL-13Ralpha2 in liver cancer cells and its effect on targeted therapy of liver cancer

PURPOSE

Liver cancer is the third leading cause of cancer-related deaths globally. The number of liver cancers diagnosed in the world is increasing at an alarming rate. It is of great significance to find the new targets of the tumor cells and specific medicine. This research investigated the expression of interleukin-13 receptor alpha2 (IL-13Ralpha2) in different liver cancer cell lines and liver cancer tissues, and assessed the cytotoxin DT389-hIL13-13E13K (IL-13 and diphtheria toxin fusion protein) targeted killing effect on liver cancer cells. Based on study above, we further analyzed the function of IL-13Ralpha2 on the targeted liver cancer therapy. The results will provide a novel strategy and an alternative way for liver cancer therapy.

METHODS

The expression of IL-13Ralpha2 in different liver cancer cell lines and tissues were analyzed by RT-PCR and immunohistochemistry. Cytotoxicity assay of DT389-hIL13-13E13K was performed in eight different concentrations in liver cancer cell lines in vitro. At the same time, siRNA-mediated knockdown was introduced to assess the role of IL-13Ralpha2 in liver cancer therapy.

RESULTS

Two out of four tested liver cancer cell lines and 27 out of 33 (81.82%) liver tissues expressed the IL-13Ralpha2. The fusion protein DT(389)-hIL13-13E13K showed a moderate cytotoxicity to the cancer cell line BEL-7402 in vitro, which 50% inhibition (IC(50)) concentration occurred at 1.4 x 10(-5 )M. Besides, the sensitivity to fusion protein DT(389)-hIL13-13E13K was decreased in siRNA-transfected liver cells compared with control ones. These results suggest that IL-13Ralpha2 chain is a specific target for IL-13-directed fusion protein.

CONCLUSIONS

We reported the expression of IL-13Ralpha2 in liver cancer cell lines and tissues as well as investigated the cytotoxin (DT389-hIL13-13E13K) targeted killing efficiency of liver cancer cells and potential role of IL-13Ralpha2 in the cancer treatment.

IL-13 cytotoxin has potent antitumor activity and synergizes with paclitaxel in a mouse model of oral squamous cell carcinoma

Interleukin-13 receptor-targeted cytotoxin (IL13-PE38) is highly cytotoxic to certain types of human cancers expressing abundant levels of IL-13Ralpha2 chain. Although IL13-PE38 is being tested in a Phase III clinical trial in brain tumors, the activity of IL13-PE38 alone or when combined with taxane, a chemotherapeutic drug for oral squamous cell carcinoma (OSCC), has not been investigated. Here, we show that approximately 40% of OSCCs (n = 50) in a tissue array are strongly positive for IL-13Ralpha2, whereas normal oral mucosa (n = 10) expresses very low or undetectable levels evaluated by immunohistochemistry. IL13-PE38 was highly cytotoxic to OSCC cell lines, but not cytotoxic to normal oral fibroblasts. IL13-PE38 mediated a synergistic antitumor effect with paclitaxel in OSC-19 in vitro and in vivo in the orthotopic OSCC tongue tumor model. Real-time tumor growth was monitored by optical imaging using a Xenogen-IVIS imaging system. Treated animals showed significant (p < 0.05) improvement in survival, which correlated with in vivo imaging of tumor response without evidence of visible toxicity. Gene transfer of IL-13Ralpha2 in oral cancer cells increased sensitivity of OSCC cell line to IL13-PE38 in vitro. Retrovirus-mediated gene-transfer of IL-13Ralpha2 in HSC-3 into tongue tumors in vivo dramatically enhanced the antitumor activity of IL13-PE38, providing complete elimination of established tumors and prolonging survival of these animals. These results indicate that IL13-PE38 in combination with paclitaxel acting via different mechanisms may be a potential treatment option for IL-13Ralpha2 expressing OSCC or for the treatment of non-IL-13Ralpha2 expressing OSCC combined with gene transfer of IL-13Ralpha2.

Novel role of IL-13 in fibrosis induced by nonalcoholic steatohepatitis and its amelioration by IL-13R-directed cytotoxin in a rat model

Nonalcoholic steatohepatitis (NASH), the most common cause of chronic liver fibrosis, progresses to cirrhosis in up to 20% of patients. We report that hepatic stellate cells (HSC) in sinusoidal lesions of liver of patients with NASH express high levels of high-affinity IL-13R (IL-13Ralpha2), which is colocalized with smooth muscle actin, whereas fatty liver and normal liver specimens do not express IL-13Ralpha2. HSCs engineered to overexpress IL-13Ralpha2 respond to IL-13 and induce TGFB1 promoter activity and TGF-beta1 production. We also developed NASH in rats by feeding a choline-deficient l-amino acid diet. These rats developed liver fibrosis as assessed by H&E staining, Masson's trichrome and Sirius red staining, and hydroxyproline assays. Treatment of these rats with IL-13R-directed cytotoxin caused a substantial decline in fibrosis and liver enzymes without organ toxicity. These studies demonstrate that functional IL-13Ralpha2 are overexpressed in activated HSCs involved in NASH and that IL-13 cytotoxin ameliorates pathological features of NASH in rat liver, indicating a novel role of this cytotoxin in potential therapy.

Human adrenomedullin up-regulates interleukin-13 receptor alpha2 chain in prostate cancer in vitro and in vivo: a novel approach to sensitize prostate cancer to anticancer therapy

Interleukin-13 (IL-13) receptor alpha2 (IL-13Ralpha2), a high-affinity IL-13 binding subunit and a tumor antigen, is amplified in a variety of human tumor cell lines and tumors in vivo. By cDNA microarray, we have shown that gene transfer of human and rat adrenomedullin (AM) up-regulates IL-13Ralpha2 in a human prostate tumor cell line. Here, we show that IL-13Ralpha2 mRNA and protein are also up-regulated in PC-3 prostate tumor cells by recombinant AM (rAM) and human synthetic AM peptide in a dose-dependent manner in vitro and in vivo in mouse prostate tumor model. The 8- to 10-fold up-regulation of IL-13Ralpha2 by rAM or AM peptide in prostate tumor cells in vitro and in vivo increased their sensitivity to IL-13PE cytotoxin consisting of IL-13 and a truncated form of Pseudomonas exotoxin. Immunodeficient mice with established prostate tumors transfected with AM or treated with AM peptide showed reduction in tumor size by intratumoral administration of IL-13PE in a dose-dependent manner. At the highest dose (three 100 mug/kg/d every alternate day), >70% reduction of tumor size was observed compared with controls (P Collapse

Key Words Collapse

MESH Headings

• ADP Ribose Transferases/therapeutic use
• Adrenomedullin/analysis
• Adrenomedullin/genetics
• Adrenomedullin/physiology
• Animals
• Bacterial Toxins/therapeutic use
• Cell Line, Tumor
• Exotoxins/therapeutic use
• Gene Expression Regulation, Neoplastic
• Humans
• Immunotoxins/therapeutic use
• Interleukin-13/metabolism
• Interleukin-13/therapeutic use
• Interleukin-13 Receptor alpha2 Subunit/genetics
• Male
• Mice
• Prostatic Neoplasms/drug therapy
• Prostatic Neoplasms/metabolism
• Prostatic Neoplasms/pathology
• RNA, Messenger/analysis
• Up-Regulation
• Virulence Factors/therapeutic use
• Pseudomonas aeruginosa Exotoxin A

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Grants

• Z01 BC005740 Intramural NIH HHS

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Affiliation(s)

Bharat H Joshi Tumor Vaccines and Biotechnology Branch, Division of Cellular and Gene Therapies, Center for Biologics Evaluation and Research, Food and Drug Administration, National Cancer Institute, NIH, Bethesda, Maryland 20892, USA
Pamela Leland
Alfonso Calvo
Jeffrey E Green
Raj K Puri

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Targeting IL-13Ralpha2-positive cancer with a novel recombinant immunotoxin composed of a single-chain antibody and mutated Pseudomonas exotoxin

We have shown previously that high-affinity receptors for interleukin-13 (IL-13Ralpha2) are overexpressed on a variety of solid cancer cells, diseased fibroblasts, and other cells, and a chimeric fusion protein composed of human IL-13 and mutated Pseudomonas exotoxin (IL-13-PE38) is highly and specifically cytotoxic to these cells in vitro and in vivo. To improve the specificity for the target, we isolated specific antibodies against IL-13Ralpha2 from human single-chain Fv (scFv) antibody phage library and developed immunotoxin by selecting two high-affinity clones of scFv and fused to PE. The fusion chimeric gene was expressed in Escherichia coli, and highly purified IL-13R-specific immunotoxin, termed anti-IL-13Ralpha2(scFv)-PE38, was tested for its cytotoxicity. This molecule was highly cytotoxic to U251 glioma and PM-RCC renal cell carcinoma cell lines in vitro. The cytotoxic activity was neutralized by purified extracellular domain of IL-13Ralpha2 but not by IL-13, indicating that cytotoxic activity is specific. Anti-IL-13Ralpha2(scFv)-PE38 showed significant antitumor activity in immunodeficient mice with s.c. glioma tumors. Both i.p. and i.t. routes of administration showed antitumor activity in a dose-dependent manner. The maximum tolerated dose of anti-IL-13Ralpha2(scFv)-PE38 was 200 microg/kg i.p. twice daily for 5 days. These results indicate that anti-IL-13Ralpha2(scFv)-PE38 is a highly selective therapeutic agent for cancer therapy and should be further tested in animal models of human cancer.

Cintredekin besudotox in treatment of malignant glioma

BACKGROUND

Interleukin-13 (IL-13) receptors are overexpressed in glioblastoma multiforme (GBM). The presence of IL-13 binding sites in GBM and their absence in normal brain tissue validates IL-13 receptor as an important target in human GBM.

OBJECTIVE

This review discusses the bench-to-bedside experience with a recombinant cytotoxin composed of human IL-13 and a truncated form of Pseudomonas exotoxin A (PE38QQR), delivered via convection-enhanced delivery (CED), in GBM treatment.

METHODS

The authors review publications regarding the laboratory research and clinical development of IL-13-directed therapies and summarize the future of IL-13-targeted cytotoxin.

CONCLUSION

The IL-13 receptor remains an important potential target in GBM, and preliminary experience with the IL-13-PE38QQR cytotoxin (also called cintredekin besudotox) has helped to pave the way for study of CED as an important means of drug delivery to malignant gliomas. Ongoing analysis of recently completed clinical trials will determine the future of this agent and its potential therapeutic targets.

Identification of interleukin-13 receptor alpha2 chain overexpression in situ in high-grade diffusely infiltrative pediatric brainstem glioma

Human malignant glioma cell lines and adult brain tumors overexpress high levels of interleukin-13 receptor alpha2 chain (IL-13Ralpha2). Because the IL-13Ralpha2 chain is an important target for cancer therapy and prognosis for patients with brainstem glioma (BSG) remains dismal, we investigated the expression of this receptor in specimens of diffusely infiltrative pediatric BSG relative to normal brain tissue. Twenty-eight BSG specimens and 15 normal brain specimens were investigated for IL-13Ralpha2 protein expression by immunohistochemical analysis (IHC) using two different antibodies in two different laboratories. Highly sensitive Q-dot-based IHC and in situ hybridization (ISH) assays were also developed to identify IL-13Ralpha2 protein and RNA in these specimens. The results were evaluated independently in two laboratories in a blinded fashion. By Q-dot IHC or a standard IHC assay, 17 of 28 (61%) tumor specimens showed modest to strong staining for IL-13Ralpha2, while 15 normal brain tissue samples showed weak expression for IL-13Ralpha2 protein. Significant interrater agreement between the two laboratories was seen in the assessment of IL-13Ralpha2 intensity. High-level IL-13Ralpha2 RNA expression was detected in tumor samples by Q-dot ISH, but only weak RNA expression was observed in normal brain. Significant agreement between ISH and IHC assays was observed (simple kappa [kappa] estimate=0.358, weighted kappa=0.89, p=0.001). IL-13Ralpha2 protein and mRNA are expressed to significantly higher levels in BSG than in normal brain tissue. Both IHC and ISH represent robust methods to detect expression of the IL-13Ralpha2 receptor in BSG that could represent an important new drug target for treatment of this disease.

Role of interleukin-13 in cancer, pulmonary fibrosis, and other T(H)2-type diseases

Interleukin (IL)-13 plays a major role in various inflammatory diseases including cancer, asthma, and allergy. It mediates a variety of different effects on various cell types including B cells, monocytes, natural killer cells, endothelial cells, and fibroblasts. IL-13 binds to two primary receptor chains IL-13Ralpha1 and IL-13Ralpha2. The IL-13Ralpha2 but not IL-13Ralpha1 chain binds IL-13 with high affinity and is overexpressed in a variety of human cancer cells derived from glioma, squamous cell carcinoma of head and neck, and AIDS-associated Kaposi's sarcoma. We have also demonstrated that IL-13Ralpha2 expression is greatly increased in lung cells when mice were challenged intranasally with bleomycin or Aspergillus fumigatus. In addition, IL-13Ralpha2 increased in surgical lung biopsies from patients with usual interstitial pneumonia, nonspecific interstitial pneumonia, and respiratory bronchiolitic interstitial pneumonia of unknown origin. Based on various studies, it is concluded that IL-13Ralpha2-expressing cells are involved in various pulmonary pathological conditions. In contrast, normal tissues such as brain, lung, endothelial cells, and head and neck tissues express IL-13Ralpha1 chain, but show only marginal expression of IL-13Ralpha2 chain. Thus, IL-13Ralpha2 chain may serve as a novel biomarker for diseased cells such as cancer or fibrosis and a target for receptor-directed therapeutic agents. To target IL-13R, a recombinant fusion protein composed of IL-13 and a derivative of Pseudomonas exotoxin (PE) has been produced. This cytotoxin termed as IL-13PE38QQR or IL-13PE38, or IL-13PE is highly and specifically cytotoxic to a variety of human tumor cell lines. In preclinical models of human glioblastoma, head and neck and AIDS-associated Kaposi's cancer, IL-13PE has been found to have significant antitumor activity at a tolerated dose. Several phase I clinical trials have been completed in patients with recurrent malignant glioma. Recently a phase III clinical trial (PRECISE) in patients with recurrent malignant glioma has been completed recruiting a total of 294 patients. IL-13PE cytotoxin has also shown a significant therapeutic effect in preclinical bleomycin or A. fumigatus or Schistosoma mansoni-induced pulmonary pathology including granulomatous fibrosis in mouse models. A clinical study in these diseases has yet to be initiated.

Interleukin-13 receptor alpha2 chain: a potential biomarker and molecular target for ovarian cancer therapy

BACKGROUND

Epithelial ovarian cancer demonstrates high mortality due to diagnosis at an advanced stage. In the search for a biomarker for early diagnosis and a target for therapy, the issue of whether interleukin-13 receptor (IL-13R), shown to be expressed on a variety of human cancers, is expressed in ovarian tumor samples was explored. In addition, whether this receptor serves as a biomarker and can be targeted by IL-13 cytotoxin was examined.

METHODS

IL-13R expression in 15 normal and 68 ovarian tumor tissue samples was determined by immunohistochemistry. Correlation between clinicopathologic features and IL-13R expression was analyzed. The efficacy of IL-13R-directed cytotoxin was determined in mice with subcutaneous, orthotopic, and peritoneal metastatic ovarian cancer.

RESULTS

Immunohistochemical analyses revealed that 83% of ovarian cancer specimens express IL-13Ralpha2, a high-affinity IL-13R subunit chain, whereas normal ovary samples expressed none or very low levels. The majority of clear cell ovarian carcinomas with the worst prognosis showed strong staining for IL-13Ralpha2. IL-13 cytotoxin was highly cytotoxic to the IGROV-1 ovarian cancer cell line in vitro, and it mediated significant antitumor activity against a xenografted tumor model. The antitumor effects were confirmed by treating orthotopically implanted or peritoneal metastatic ovarian tumors, which showed significant extension of survival in immunodeficient mice. IL-13 cytotoxin also prevented cachexia in treated mice. The soluble form of IL-13Ralpha2 was detected in the serum of mice with peritoneal metastasis, and the level decreased to baseline in the treated group.

CONCLUSIONS

IL-13Ralpha2 is a promising target for ovarian cancer therapy, and the soluble form of IL-13R may be a possible surrogate marker for disease monitoring.

N-linked glycosylation of IL-13R alpha2 is essential for optimal IL-13 inhibitory activity

A high-affinity receptor for interleukin (IL)-13 (interleukin-13R alpha 2) is over-expressed in disease-related fibroblasts and neoplastic cells and is involved in cancer, allergic, and inflammatory diseases. The extracellular domain of IL-13R alpha2 (ECD alpha2) could be cleaved, which serves as a decoy receptor. We have expressed and purified ECD alpha2 in both Escherichia coli (E. coli) and mammalian systems as a soluble fragment and studied its biological activities. Although both products of ECD alpha2 showed IL-13 inhibitory activities, mammalian cell-derived ECD alpha2 appeared to be superior compared with purified protein from E. coli. When expressed in E. coli, ECD alpha2 appeared to be a monomer of 42 but a 60 kDa protein when purified from mammalian cells due to heavy glycosylation. The purified glycosylated ECD alpha2 efficiently inhibited IL-13-induced STAT6 phosphorylation in immune and Hodgkin's lymphoma cell lines, IL-13 binding, and cytotoxicity of IL-13 cytotoxin in various cancer cell lines. The improved potency of mammalian cell-derived ECD alpha2 was shown over ECD alpha2/Fc fusion protein. The N-linked glycosylation of ECD alpha2 was found to be essential for optimal IL-13 inhibitory activity as deglycosylation by PNGase F showed lower activity. ECD alpha2 did not inhibit IL-4-induced STAT6 phosphorylation, indicating that inhibitory effects of ECD alpha2 are receptor specific. These results indicate that glycosylated ECD alpha2 can serve as a potent inhibitor of IL-13 in a variety of conditions in which IL-13 is a key mediator, e.g., pulmonary, allergic, fibrotic, and neoplastic diseases.

Convection-enhanced delivery of interleukin-13 receptor-directed cytotoxin for malignant glioma therapy

The treatment of patients with malignant brain tumors, in particular glioblastoma multiforme (GBM) is very challenging because of their diffuse infiltrative nature and the cytological heterogeneity. The median survival of patients with newly diagnosed GBM is only 12-15 months, and only 8-12% of them survive for two years. Novel approaches for brain tumor therapy are needed. Recently, targeted therapies have emerged as promising modality for cancer targeting. We have discovered that high affinity plasma membrane receptor for interleukin-13 (IL-13), an immune regulatory cytokine, is over-expressed in 60-80% of malignant brain tumors. To target these IL-13R, we generated a chimeric fusion protein, composed of human IL-13 and mutated Pseudomonas exotoxin (PE), termed IL-13 cytotoxin (IL13-PE), and tested its cytotoxicity to IL-13R-expressing GBM cells. IL-13 cytotoxin was highly potent and selective in killing IL-13R-expressing GBM cells. In contrast, normal cells including brain, immune, and endothelial cells were generally not affected by this cytotoxin due to no or low expression of IL-13R. In vivo pre-clinical studies for safety and toxicity were also performed in mice, rats, and monkeys, and IL-13 cytotoxin was found to be well tolerated by both systemic and intracerebral administrations. IL-13 cytotoxin was found to mediate remarkable efficacy in animal models of human brain tumors. Encouraged by these pre-clinical studies, four Phase 1/2 clinical trials in adult patients with recurrent malignant glioma have been completed. These clinical trials involved convection-enhanced delivery (CED) of IL-13 cytotoxin either intratumoral or intraparenchymal after resection of tumor. CED is a novel loco-regional drug delivery method for intracranial tumors that relies on a continuous pressure gradient to distribute drug into interstitial space. This route of IL-13 cytotoxin administration appears to be very well tolerated and have a good risk-benefit profile. Most recently, a randomized controlled Phase 3 clinical trial (PRECISE) with intraparenchymal IL-13 cytotoxin administration was completed and subjects are being monitored for safety and survival.

Evidence that IL-13R alpha2 chain in human glioma cells is responsible for the antitumor activity mediated by receptor-directed cytotoxin therapy

The interleukin-13 receptor alpha2 (IL-13R alpha2) chain is a primary IL-13 binding and internalization component of the IL-13R system. Previous studies have shown that human brain tumors, including glioblastoma multiforme (GBM), overexpress IL-13R alpha2 chain, while normal brain cells do not express this protein or express very low levels of it. To target IL-13R on brain tumor cells, the authors have developed an IL-13R-directed cytotoxin termed IL13-PE38QQR to induce specific cancer cell killing. To investigate the role of IL-13R alpha2 chain in GBM, cells were treated with antisense oligonucleotide or siRNA to IL-13R alpha2 chain, and cellular IL-13 binding and sensitivity to IL-13 cytotoxin were assessed. IL-13R alpha2 gene interference in GBM cells showed decreased ligand binding, and consequently IL-13 cytotoxin exhibited less cytotoxicity to these cells. The authors next evaluated the antitumor activity of IL-13 cytotoxin in native IL-13R-expressing tumors and after gene transfer of IL-13R alpha2 by injecting plasmid in U87MG tumors subcutaneously implanted in nude mice. These mice were then treated with IL-13 cytotoxin. Mean tumor size in mice receiving intraperitoneal or intratumoral IL-13 cytotoxin was significantly smaller in control tumors; however, tumor sizes were much smaller in IL-13R alpha2-transfected tumors. Furthermore, convection-enhanced delivery of IL-13R alpha2 cDNA in intracranially established U87MG glioma followed by IL-13 cytotoxin administration by the same route mediated tumor regression and prolonged survival of animals by 164% compared with control. These results indicate that IL-13R alpha2 chain in GBM cells is essential for IL-13 cytotoxin-induced cytotoxicity and that IL-13R alpha2 chain plays a critical biologic role in IL-13 cytotoxin-mediated therapy for GBM.

Adenoviral vector-mediated gene transfer of IL-13Ralpha2 chain followed by IL-13 cytotoxin treatment offers potent targeted therapy for cytotoxin-resistant cancers

Previous studies demonstrated that IL-13Ralpha2 chain-overexpressing cancer cells were highly sensitive to IL-13 cytotoxin (IL13-PE38QQR) and could be targeted by cytotoxin treatment. However, the majority of human tumors do not express high levels of IL-13Ralpha2 chain. To expand the IL-13 cytotoxin-mediated cancer targeting therapy, we combined cytotoxin treatment with gene transfer of IL-13Ralpha2 chain. We constructed a recombinant adenoviral vector carrying the human IL-13Ralpha2 gene (Ad-IL-13Ralpha2), which expresses high levels of IL-13Ralpha2 chain on infected cells. Human cancer cell lines A549 and HOS, which originally show no IL-13Ralpha2 expression and little sensitivity to IL-13 cytotoxin, were effectively converted to become sensitive to this cytotoxin after Ad-IL-13Ralpha2 infection. The CC(50) of IL-13 cytotoxin for Ad-IL-13Ralpha2-infected A549 cells was <10 ng/ml, whereas the CC(50) for uninfected or control vector-infected cells was >500 ng/ml. We also examined the antitumor activity of IL-13 cytotoxin in an established xenograft model of cytotoxin-resistant human lung tumor. Only a single i.t. injection of Ad-IL-13Ralpha2 markedly enhanced the sensitivity of established tumors to IL-13 cytotoxin treatment; furthermore, this antitumor effect was significantly sustained for more than 1 month after the last treatment with IL-13 cytotoxin. Taken together, these results suggest the combination of adenoviral vector-mediated IL-13Ralpha2 gene transfer and IL-13 cytotoxin administration can be an effective targeting approach for several types of IL-13 cytotoxin-resistant cancers which show no or little expression of IL-13Ralpha2 chain.

Nitric oxide accelerates interleukin-13 cytotoxin-mediated regression in head and neck cancer animal model

Receptors for interleukin-13 (IL-13R) are overexpressed on several types of solid cancers including gliobastoma, renal cell carcinoma, AIDS Kaposi's sarcoma, and head and neck cancer. Recombinant fusion proteins IL-13 cytotoxin (IL13-PE38QQR or IL13-PE38) have been developed to directly target IL-13R-expressing cancer cells. Although it has been found that IL-13 cytotoxin has a direct potent antitumor activity in vivo in nude mice models of human cancers, the involvement of indirect antitumor effecter molecules such as nitric oxide (NO) is unknown. To address this issue, we assessed the effect of NO inhibiter N(omega)-monomethyl-l-arginine on IL-13 cytotoxin-mediated cytotoxicity and NO2/NO3 production in HN12 head and neck cancer cells. In addition, antitumor effects and NO levels in HN12 and KCCT873 head and neck tumors xenografted s.c. in nude mice when treated with IL-13 cytotoxin were evaluated by tumor measurement, Western blot, and immunohistochemistry analyses. Pretreatment of animals with N(omega)-monomethyl-l-arginine significantly decreased the NO levels and IL-13 cytotoxin-mediated antitumor effects. In addition, depletion of macrophages, known to produce NO, also decreased antitumor activity of IL-13 cytotoxin. Based on these studies, we concluded that NO accelerates antitumor effect of IL-13 cytotoxin on head and neck tumor cells. Because IL-13 cytotoxin is currently being tested in the clinic for the treatment of patients with recurrent glioblastoma maltiforme, our current findings suggest maintaining macrophage and NO-producing cellular function for optimal therapeutic effect of this targeted agent.

Analysis of target genes induced by IL-13 cytotoxin in human glioblastoma cells

IL-13 cytotoxin comprised of IL-13 and a mutated form of Pseudomonas exotoxin (fusion protein termed IL-13-PE38QQR) has been shown to inhibit protein synthesis leading to necrotic and apoptotic cell death in glioblastoma cells that express high levels of interleukin-13 receptors (IL-13R). To identify target genes of cell death and other cellular genes with IL-13 receptors in glioblastoma cells, we utilized the cDNA microarrays to analyze global gene expression profiles after IL-13 cytotoxin and IL-13 treatment. IL-13 cytotoxin mediated cytotoxicity to U251 cells in a dose-dependent manner. Hierarchical cluster analysis of differentially expressed genes in U251 glioma cells at different time points after IL-13 cytotoxin treatment showed three major groups, each representing a specific expression pattern. Randomly selected differentially expressed genes from each group were confirmed by RT-PCR analysis. Most down-regulated genes belong to cell adhesion, motility, angiogenesis, DNA repair, and metabolic pathways. While up-regulated genes belong to cell cycle arrest, apoptosis, signaling and various metabolic pathways. Unexpectedly, at early time points, both IL-13 and IL-13 cytotoxin induced several genes belonging to different pathways most notably IL-8, DIO2, END1, and ALDH1A3 indicating that these genes are early response genes and their products may be associated with IL-13R. In addition, IL-13 cytotoxin induced IL-13Ralpha2 mRNA expression during the treatment in glioma cells. Our results indicate that novel cellular genes are involved with IL-13 receptors and that IL-13 cytotoxin induced cell death involves various target genes in human glioblastoma cells. On going studies will determine the role of associated genes and their products in the IL-13R functions in glioma cells.

Optimization of expression and purification of two biologically active chimeric fusion proteins that consist of human interleukin-13 and Pseudomonas exotoxin in Escherichia coli

We have previously reported that a variety of solid human tumor cell lines express a large number of receptors for interleukin-13 (IL-13). These receptors could be targeted with a chimeric fusion protein consisting of human IL-13 and a truncated form of Pseudomonas exotoxin (PE). We describe here optimization of critical steps involved in high yield expression of two recombinant chimeric fusion proteins for obtaining highly purified and biologically active cytotoxins in Escherichia coli. The chimeric constructs of human IL-13 and two 38 kDa truncated PEs: (i) PE38 and (ii) PE38QQR, (three lysine residues in PE38 at 590, 606, and 613 substituted with two glutamine and one arginine) were used for protein expression in pET prokaryotic expression vector system with kanamycin as a selection antibiotic. Our results suggest that fresh transformation of E. coli and induction by isopropyl-beta-D-thiogalactopyranoside (IPTG) for 6 h resulted in maximum protein expression. To further improve the yield, we used a genetically modified E. coli strain, BL21(DE3)pLysS, which carries a plasmid for lysozyme with a weak promoter that inhibits T7 RNA polymerase and minimizes protein production in the absence of IPTG. Use of this strain eliminated the need for lysozyme digestion of the induced bacteria to release inclusion bodies, which resulted in expression of purer protein as compared to the conventional BL21(DE3) strain. Additional protocol optimizations included 16 h solubilization of inclusion bodies, constitution of refolding buffer, and timing of dialysis. These proteins were finally purified by Q-Sepharose, mono-Q, and gel filtration chromatography. Between 14-22 and 21-28 mg highly purified and biologically active protein was obtained from 1L of BL21 (DE3) and BL21 (DE3) pLysS bacteria culture, respectively. As IL-13R targeting for brain tumor therapy offers an exciting treatment option, optimization of production of IL-13PE will enhance production of clinical grade material for Phase III clinical trials.

Analysis of antitumor activity of an interleukin-13 (IL-13) receptor-targeted cytotoxin composed of IL-13 antagonist and Pseudomonas exotoxin

We have shown previously that a chimeric fusion protein composed of human interleukin-13 (IL-13) and Pseudomonas exotoxin (PE), termed IL-13 cytotoxin (IL13-PE38), is specifically cytotoxic to various cancer cell lines and primary cell cultures derived from a variety of solid cancers. In addition, we have shown that IL-13 mutant IL-13E13K, in which glutamic acid (E) residue at position 13 of IL-13 molecule was substituted by a lysine (K), is a powerful antagonist of IL-13 and binds to IL-13 receptor with a higher affinity compared with wild-type IL-13. In this study, we have generated an IL-13 cytotoxin IL13E13K-PE38, in which IL-13 antagonist is fused to PE to determine whether this molecule has improved cytotoxicity to tumor cells compared with wild type (wt)IL13-PE38. Highly purified IL13E13K-PE38 was tested in various tumor cell lines including seven glioblastoma multiforme cell lines to compare its binding to the cells, in vitro cytotoxicity, in vivo antitumor activity, and safety in mouse model with wtIL13-PE38. IL13E13K-PE38 bound to U251MG and IL-13Ralpha2 chain-transfected tumor cell lines with 3 to 10 times higher affinity compared with wtIL13-PE38. However, IL13E13K-PE38 did not show higher cytotoxicity compared with wtIL13-PE38 in glioblastoma multiforme or any other cell lines tested. The antitumor activity of IL13E13K-PE38, when administered intraperitoneally to nude mice bearing U251 tumors, was also similar to wtIL13-PE38. Some improvement in antitumor activity was observed when lower doses of IL13E13K-PE38 were injected intratumorally in subcutaneous tumors. These results indicate that in general, IL13E13K-PE38 mediates similar cytotoxicity and antitumor activity to wtIL13-PE38 despite its improved binding affinity to IL-13 receptors.

Differential expression of interleukins IL-13 and IL-15 in normal ovarian tissue and ovarian carcinomas

OBJECTIVE

To determine the temporal and spatial expression of interleukins (IL)-13 and IL-15 in ovarian carcinoma compared to normal ovarian tissue.

METHODS

Quantitative RT-PCR, ELISA and immunohistochemistry.

RESULTS

Q-RT-PCR, ELISA and immunohistochemical analysis indicates that IL-13 and IL-15 mRNA and protein are expressed in normal ovary at various phases of the menstrual cycle with immunoreactive proteins detected in granulosa/theca and luteal cells and to a lesser extent in stromal cells and surface epithelial cells. Compared to normal ovary, ovarian carcinoma expresses elevated levels of IL-13 and IL-15 mRNA, with higher IL-13 expression in primary vs. metastatic tumors. IL-13 and IL-15 protein expression was also higher in the tumor tissues compared to ascites. In normal ovary, ovarian tumors and ascites, the ratio of IL-13/IL-15 favored IL-13. Immunoreactive IL-13 and IL-15 proteins were localized primarily in the tumor cells and infiltrated inflammatory cells with increased intensity with disease stage.

CONCLUSION

Normal ovary and ovarian tumors express IL-13 and IL-15 and pattern of their expression in carcinomas suggests that these cytokines may function in various ovarian cellular activities including inflammatory/immune responses that are integrated cellular events taking place in normal ovary and ovarian tumors.

Specifically targeted killing of interleukin-13 (IL-13) receptor-expressing breast cancer by IL-13 fusion cytotoxin in animal model of human disease

Interleukin-13 receptor (IL-13R) α2 chain binds IL-13 with high affinity and can internalize after binding to ligand. We have exploited this property of IL-13Rα2 chain by receptor-targeted breast cancer therapy. Previous studies have demonstrated that in vivo intratumoral (i.t.) gene transfer of this chain followed by IL-13 cytotoxin [comprised of IL-13 and Pseudomonas exotoxin (IL13-PE38QQR)] therapy causes regression of established human tumors in xenografted models. Breast carcinoma cells do not express IL-13Rα2 chain and are resistant to the antitumor effect of IL-13 cytotoxin. To determine whether IL-13Rα2 chain can render sensitivity of breast cancer to IL-13 cytotoxin, we injected IL-13Rα2 plasmid in s.c. established tumors by i.t. route, followed by systemic or i.t. IL-13 cytotoxin administration. This combination approach showed profound antitumor activity against human breast tumors in xenografted immunodeficient mice. Interestingly, there was dominant infiltration of inflammatory cells in regressing tumors, which were identified to be macrophages producing nitric oxide (NO) and natural killer cells. The partial role of inducible nitric oxide synthase (iNOS)-positive macrophages was confirmed by in vivo macrophage depletion experiments. Serum chemistry, hematology, and organ histology from treated mice did not show any remarkable toxicity resulting from the combination therapy. Taken together, local gene transfer of IL-13Rα2 followed by receptor-targeted IL-13 cytotoxin therapy may be applied safely and effectively to the treatment of localized breast cancer.

IL-13 effector functions

IL-13 was first recognized for its effects on B cells and monocytes, where it upregulated class II expression, promoted IgE class switching and inhibited inflammatory cytokine production. It was also thought to be functionally redundant with IL-4. However, studies conducted with knockout mice, neutralizing antibodies, and novel antagonists demonstrate that IL-13 possesses several unique effector functions that distinguish it from IL-4. Resistance to most gastrointestinal nematodes is mediated by type-2 cytokine responses, in which IL-13 plays a dominant role. By regulating cell-mediated immunity, IL-13 modulates resistance to intracellular organisms including Leishmania major, Leishmania mexicana, and Listeria monocytogenes. In the lung, IL-13 is the central mediator of allergic asthma, where it regulates eosinophilic inflammation, mucus secretion, and airway hyperresponsiveness. Manipulation of IL-13 effector function may also prove useful in the treatment of some cancers like B-cell chronic lymphocytic leukemia and Hodgkin's disease, where IL-13 modulates apoptosis or tumor cell growth. IL-13 can also inhibit tumor immunosurveillance. As such, inhibitors of IL-13 might be effective as cancer immunotherapeutics by boosting type-1-associated anti-tumor defenses. Finally, IL-13 was revealed as a potent mediator of tissue fibrosis in both schistosomiasis and asthma, which indicates that it is a key regulator of the extracellular matrix. The mechanisms that regulate IL-13 production and/or function have also been investigated, and IL-4, IL-12, IL-18, IFN-gamma, IL-10, TGF-beta, TNF-alpha, and the IL-4/IL-13 receptor complex play important roles. This review highlights the effector functions of IL-13 and describes multiple pathways for modulating its activity in vivo.

Potent antitumor activity of IL-13 cytotoxin in human pancreatic tumors engineered to express IL-13 receptor alpha2 chain in vivo

Interleukin-13 receptor (IL-13R) alpha2 chain plays a key role in ligand binding and internalization. We have recently demonstrated that this cytokine receptor chain has unique characteristics in tumor biology: it inhibits tumorigenicity of breast and pancreatic cancer in animal models. In this study, we have exploited IL-13Ralpha2 chain and established a novel approach for pancreatic cancer therapy. For this, a plasmid encoding the IL-13Ralpha2 chain gene was mixed with liposomes and injected into subcutaneously or orthotopically xenografted human pancreatic tumors in immunodeficient mice, followed by systemic or local therapy by a recombinant IL-13 cytotoxin. Only tumors forced to express IL-13Ralpha2 chain acquired extreme susceptibility to the antitumor effect of IL-13 cytotoxin. There was a dominant infiltration of cells including macrophages and natural killer cells in the regressing tumors. Since macrophages were found to produce nitric oxide, IL-13Ralpha2-targeted cancer therapy involved not only a direct tumor cell killing by IL-13 cytotoxin but also activation of innate immune response at the tumor site. Therefore, this approach may be a new powerful tool for pancreatic cancer or other localized cancer therapy.

Impact of interleukin-13 responsiveness on the synthetic and proliferative properties of Th1- and Th2-type pulmonary granuloma fibroblasts

Interleukin-13 (IL-13) has emerged as a major cytokine mediator of fibroblast activation and pulmonary fibrosis. Normal (from noninflamed lung), Th1-type (induced by the pulmonary embolization of purified peptide derivative-coated beads in mice sensitized to purified peptide derivative), and Th2-type (induced by the pulmonary embolization of Schistosoma mansoni egg antigen-coated beads in mice sensitized with S. mansoni eggs) primary fibroblast cell lines all exhibited constitutive gene expression of two receptor chains that bind and signal IL-13-mediated cellular events: IL-4Ralpha and IL-13Ralpha1. However, all three fibroblast cell lines exhibited divergent synthetic and proliferative responses to the exogenous addition of either recombinant IL-13 or a chimeric protein comprised of IL-13 and a truncated version of Pseudomonas exotoxin (IL13-PE), which targets and kills IL-13 receptor overexpressing cells. The exogenous addition of IL-13 to Th1-type and Th2-type fibroblast cultures significantly increased the cellular expression of IL-13Ralpha2, which may function as an IL-13 decoy receptor. After a 24-hour exposure to IL-13, the total collagen generation and cellular proliferation by Th2-type fibroblasts were significantly higher than that observed in similar numbers of normal and Th1-type fibroblasts. In addition IL13-PE, which binds with highest affinity to IL-13Ralpha2, exhibited down-regulatory effects on proliferation and matrix generation expression by Th1- and Th2-type, but not normal, fibroblasts. Thus, these data demonstrate that fibroblasts derived from murine pulmonary granulomas exhibit divergent expression of functional IL-13 receptor and this expression dictates the responsiveness and susceptibility to recombinant IL-13 and IL-13 immunotoxin, respectively.

IL-13 receptor-targeted cytotoxin cancer therapy leads to complete eradication of tumors with the aid of phagocytic cells in nude mice model of human cancer

Tumor-directed therapeutic approaches require unique or overexpressed specific Ag or receptor as a target to achieve selective tumor killing. However, heterogeneous expression of these targets on tumor cells limits the efficacy of this form of therapy. In this study, we forced abundant expression of IL-13Ralpha2 chain by plasmid-mediated gene transfer in head and neck, as well as prostate tumors to provide a potential target. This was followed by successfully treating xenograft tumor-bearing nude mice with IL-13R-directed cytotoxin (IL13-PE38QQR). Although we did not observe an indirect cytotoxic bystander effect conveyed to nontransduced tumor cells in vitro, our approach in vivo led to a complete regression of established tumors transfected with IL-13Ralpha2 chain in most animals. We found that the tumor eradication was achieved in part by infiltration of macrophages and NK cells, assessed by immunohistochemistry. Moreover, head and neck tumors xenografted in macrophage-depleted nude mice were less sensitive to the antitumor effect of IL-13 cytotoxin. Because we did not observe vector-related toxicity in any vital organs, our novel combination strategy of gene transfer of IL-13Ralpha2 chain and receptor-directed cytotoxin therapy may be a useful approach for the treatment of localized cancer.

Interleukin-13 fusion cytotoxin arrests Schistosoma mansoni egg-induced pulmonary granuloma formation in mice

Schistosoma mansoni egg-induced lung pathology requires the actions of interleukin (IL)-4 and IL-13. Because receptors for IL-4 and IL-13 share chains, we examined the effect of a fusion protein comprised of IL-13 and Pseudomonas exotoxin (IL13-PE) on the development of pulmonary granulomas in mice. At day 8 after an intravenous injection of live S. mansoni eggs, whole lung samples from IL13-PE-treated mice exhibited significantly lower IL-4 and IL-13 gene expression, smaller granulomas, decreased collagen levels, and increased IL-13 receptor alpha2 gene expression compared to controls. The therapeutic effects of IL13-PE were also observed at day 16 despite the termination of IL13-PE treatment at day 8. These studies demonstrate that targeting IL-4- and IL-13- responsive cells with IL13-PE effectively arrests S. mansoni egg granuloma formation.

Cytokine receptor as a sensitizer for targeted cancer therapy

Introducing a cytokine receptor as a sensitizer into cancer cells offers a unique opportunity for receptor-targeted cancer therapy. It has been shown that transfection of the tumor necrosis factor (TNF) receptor gene in cancer cells or exposing cancer cells to certain reagents which increase expression of TNF receptors results in enhancement of the cytotoxic effect of TNF. In addition, the literature suggests that Fas/CD95-mediated apoptotic tumor cell killing is augmented by gene transfer of Fas into cancer cells or treatment of cells with agents like cisplatin and interferon (IFN)-gamma. In contrast to these approaches, we have discovered a new approach to cancer therapy; wherein introduction of a cytokine receptor chain into cancer cells sensitizes them to receptor-directed cytotoxins. We have demonstrated that when interleukin (IL)-13 receptor (IL-13R) alpha2 chain, one of the two known IL-13 binding proteins, is introduced into cancer cells that do not express this chain the cells acquire extreme sensitivity to a chimeric fusion cytotoxin composed of IL-13 and a mutated form of Pseudomonas exotoxin (IL13-PE). Cells that do not express this chain or express low levels show limited sensitivity to IL13-PE. Acquisition of sensitivity to IL13-PE was observed both in vitro and in vivo when IL-13R alpha2-transfected human tumor cells were implanted in immunodeficient animals followed by systemic or regional IL13-PE therapy. Our third generation experiments suggest that this approach is feasible for clinical situations as intratumor administration of plasmid carrying the IL-13R alpha2 chain gene sensitized these tumors to systemic or regional IL13-PE therapy. This unique approach comprising gene transfer of cytokine receptor chain and receptor-targeted cytotoxin administration represents a novel strategy for cancer therapy.

Stat6-deficient mice develop airway hyperresponsiveness and peribronchial fibrosis during chronic fungal asthma

Signal transducer and activator of transcription 6 (Stat6) is critical for Th2-mediated responses during allergic airway disease. To investigate the role of Stat6 in fungus-induced airway hyperresponsiveness and remodeling, Stat6-deficient (Stat6-/-) and Stat6-wildtype (Stat6+/+) mice were sensitized to Aspergillus fumigatus and airway disease was subsequently assessed in both groups at days 21, 30, 38, and 44 after an intratracheal challenge with live A. fumigatus conidia. At all times after conidia, histological analysis revealed an absence of goblet cell hyperplasia and markedly diminished peribronchial inflammation in Stat6-/- mice in contrast to Stat6+/+ mice. Airway hyperresponsiveness and peribronchial fibrosis in Stat6-/- mice were significantly reduced at day 21 after conidia compared with Stat6+/+ mice, but both groups exhibited significant, similar increases in these parameters at all subsequent times after conidia. In separate experiments, IL-13-responsive cells in Stat6-/- mice were targeted via the daily intranasal administration of 200 ng of IL-13-PE38QQR (IL13-PE), comprised of human IL-13 and a derivative of Pseudomonas exotoxin, from days 38 to 44 after the conidia challenge. IL13-PE treatment abolished airway hyperresponsiveness, but not peribronchial fibrosis in Stat6-/- mice. Taken together, these data demonstrate that the chronic development of airway hyperresponsiveness during fungal asthma is IL-13-dependent but Stat6-independent.

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.

IL-13 fusion cytotoxin ameliorates chronic fungal-induced allergic airway disease in mice

IL-13 has emerged as a major contributor to allergic and asthmatic responses, and as such it represents an attractive target in these diseases. In this study, IL-13-responsive cells in the lung were targeted via the intranasal administration of IL-13-PE38QQR (IL-13-PE), comprised of human IL-13 and a derivative of Pseudomonas exotoxin, to Aspergillus fumigatus-sensitized mice challenged with A. fumigatus spores, or conidia. Mice received 50, 100, or 200 ng of IL-13-PE or diluent alone (i.e., control group) on alternate days from day 14 to day 28 after the conidia challenge. The control group of mice exhibited significant airway hyperreactivity, goblet cell hyperplasia, and peribronchial fibrosis at day 28 after conidia. Although the two lower doses of IL-13-PE had limited therapeutic effects in mice with fungal-induced allergic airway disease, the highest dose of IL-13-PE tested significantly reduced all features of airway disease compared with the control group. Whole lung mRNA expression of IL-4Ralpha and IL-13Ralpha1 was markedly reduced, whereas bronchoalveolar lavage and whole lung levels of IFN-gamma were significantly elevated in mice treated with 200 ng of IL-13-PE compared with the control group. This study demonstrates that a therapy designed to target IL-13-responsive cells in the lung ameliorates established fungal-induced allergic airway disease in mice.

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.

Conjugation of anti-My9 antibody to stealth monensin liposomes and the effect of conjugated liposomes on the cytotoxicity of immunotoxin

The carboxylic ionophore, monensin, was successfully entrapped in stealth liposomes by employing the pH-gradient method (interior pH of liposomes 9.5; exterior pH 5.0-5.9). A maximum of 14% of monensin could be entrapped in stealth liposomes by this method. The stealth liposomes could be successfully freeze-dried having mean particle size varying between 197 and 223 nm. The stealth liposomes were conjugated to anti-My9 monoclonal antibody (targeted against CD 33 antigen) by a disulfide linkage with almost full retention of immunoreactivity. The method of conjugation of liposomes with the antibody did not alter the particle size of liposomes and resulted in only 10% leakage of monensin. In-vitro cytotoxicity studies showed that antibody-conjugated monensin liposomes (3.5x10(-8) M monensin) potentiated the cytotoxicity of anti-My9 immunotoxin by a factor of 2070, in comparison to 360-fold potentiation observed with unconjugated monensin liposomes against human HL-60 promyelocytic leukemia cells. These results indicate that it is possible to enhance the in-vitro cytotoxicity of immunotoxin by several folds using antibody-conjugated monensin liposomes.

Suppression of an IL-13 autocrine growth loop in a human Hodgkin/Reed-Sternberg tumor cell line by a novel IL-13 antagonist

IL-13 has been proposed to be an autocrine growth factor for Hodgkin/Reed-Sternberg tumor cells (H/RS cells). Since we have recently identified and produced a novel IL-13 antagonist (IL-13E13K) that can suppress the biological activity of IL-13, here we examined whether IL-13E13K can inhibit growth of Hodgkin lymphoma (HL)-derived cell lines. IL-13E13K not only inhibited the growth of an unstimulated H/RS cell line (L1236) but also cells that were stimulated by exogenous IL-13 in a dose-dependent manner. Several HL-derived cell lines expressed IL-13 message and protein and message for various chains of IL-13R. H/RS cell lines expressed mRNA for the IL-13R alpha 1, IL-4R alpha, and IL-2R gamma chains. However, none of these cell lines expressed the IL-13R alpha 2 chain. An H/RS cell line (L1236) internalized the ligand-receptor complex after binding to a fusion protein composed of IL-13 and a mutated form of Pseudomonas exotoxin A (IL-13-PE38QQR, or IL-13 cytotoxin), as IL-13 cytotoxin was specifically cytotoxic to H/RS cells in vitro. These results indicate that IL-13E13K and IL-13 cytotoxin can effectively suppress growth of a L1236 H/RS cell line. Therefore, additional studies should be performed to determine the expression of IL-13 and IL-13R in primary clinical samples of Hodgkin's lymphoma and both agents should be further tested in vitro and in vivo as possible therapeutic agents for HL.

Characterization of a powerful high affinity antagonist that inhibits biological activities of human interleukin-13

Interleukin-13 (IL-13), a predominantly Th2-derived cytokine, appears to play a central pathological role in asthma, atopic dermatitis, allergic rhinitis, some parasitic infections, and cancer. We hypothesized that an IL-13 antagonist may have profound therapeutic utility in these conditions. We, therefore, mutagenized human IL-13 in which Glu at position 13 was substituted by a Lys residue. This highly purified recombinant IL-13 variant, IL-13E13K, bound with 4-fold higher affinity to the IL-13 receptor than wild-type IL-13 but retained no detectable proliferative activity on the TF-1 hematopoietic cell line. IL-13E13K competitively inhibited IL-13- and IL-4-dependent TF-1 proliferation. It also inhibited IL-13-induced STAT-6 (signal transduction and activator of transducer-6) activation in immune cells and cancer cells and reversed IL-13-induced inhibition of CD14 expression on human primary monocytes. These results demonstrate that high affinity binding and signal generation can be uncoupled efficiently in a ligand receptor interaction. These results also suggest that IL-13E13K may be a useful antagonist for the treatment of allergic, inflammatory, and parasitic diseases or even malignancies in which IL-13 plays a central role.

Interleukin-13 receptor as a unique target for anti-glioblastoma therapy

Surgery, radiotherapy and chemotherapy have minimally altered survival of glioblastoma patients. We explored a specific approach for glioblastoma therapy in which cellular interleukin-13 (IL-13) receptors were targeted by an IL-13 cytotoxin. A wide array of human glioblastoma cell lines expressing the receptor for IL-13 were effectively killed by an IL-13 cytotoxin, a chimeric protein composed of human IL-13 and a mutated form of Pseudomonas exotoxin (termed IL13-PE38QQR or IL-13 toxin). Daily (qd) intratumoral injections of IL-13 toxin (50 and 100 microg/kg/day) for 5 consecutive days into subcutaneous human U251 glioblastoma tumors (approx. 30 mm(2)) in nude mice resulted in complete regression of tumors in 4/5 and 5/5 mice, respectively. Tumor regression persisted for at least 221 days postimplantation. Three alternate day injections (qod) of IL-13 toxin (250 microg/kg/day) into other subcutaneous U87 glioblastoma tumors also produced durable complete responses (CR) in all 5 mice. Twice daily (bid) intraperitoneal injections of IL-13 toxin at 25 or 50 microg/kg/dose for 5 days (total doses = 10) regressed U251 tumors by 45% and 58% with 1/5 and 2/5 CRs, respectively, on day 54. Intraperitoneal administration of IL-13 toxin with an identical schedule at a dose of 50 microg/kg injected into mice bearing U87 xenografts reduced tumor burden by one-half on day 36. Similar doses (25 or 50 microg/kg) with a daily schedule (qd x 5) by the intravenous route also suppressed growth of U251 subcutaneous tumors by 75% and 81% with 1/6 CR in either group by day 34. All mice tolerated therapy well without any visible signs of toxicity. On the basis of these studies, we have initiated a Phase I clinical trial using IL13-PE38QQR in patients with recurrent glioblastoma. Published 2001 Wiley-Liss, Inc.

Sensitization of cancer cells to interleukin 13-pseudomonas exotoxin-induced cell death by gene transfer of interleukin 13 receptor alpha chain

We have demonstrated that primary interleukin 13 (IL-13) binding protein IL-13 receptor (IL-13R) alpha chain plays an important role in IL-13 binding and internalization in the IL-13R system. Although IL-13R alpha chain is expressed on many cancer cell lines, some cancer types do not express or express low levels of this receptor chain. Consequently, these cells show no or low sensitivity to the cytotoxic effect of a recombinant chimeric protein composed of IL-13 and a mutated form of a Pseudomonas exotoxin, IL13-PE38QQR. Here we demonstrate that pancreatic cancer, renal cell carcinoma, head and neck cancer, and glioblastoma cell lines that were genetically altered to express high levels of IL-13R alpha chain increase their binding affinity for IL-13, and increase their sensitivity to IL13-PE38QQR by at least 6-fold to 1000-fold compared with mock-transfected control cells. This observation was made by protein synthesis inhibition assay and confirmed by clonogenic assay. Our studies provide a proof of principle for a novel strategy for cancer therapy that combines gene transfer and targeted cytotoxin therapy.