Pamela Leland

Interleukin-13 Receptors on Human Prostate Carcinoma Cell Lines Represent a Novel Target for a Chimeric Protein Composed of IL-13 and a Mutated Form of Pseudomonas Exotoxin

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

Mutation and functional analysis of IL-13 receptors in human malignant glioma cells

We have previously demonstrated that human brain tumor cells, in particular glioblastoma multiforme (GBM), express abundant receptors for interleukin-13 on the cell surface. These receptors are composed of IL-13 receptor (IL-13R)alpha1, IL-13Ralpha2, and IL-4Ralpha chains. The significance of overexpression of IL-13R on tumor cells is not known. Because expression of IL-13R on glioma cells is an unexpected phenomenon, we examined whether these receptors are polymorphic. Therefore, we analyzed cDNA for IL-13Ralpha1 and IL-13Ralpha2 chain genes by PCR-based single-strand conformation polymorphism and direct sequencing techniques for a possible polymorphism in 19 GBM, one normal human astrocyte, and two fibroblast cell lines. All analyzed samples except normal astrocytes overexpressed IL-13Ralpha2; however, none of these cell lines showed a mutation in cDNA for IL-13Ralpha2 chain. In contrast, all GBM samples, normal astrocytes, and fibroblasts expressed mRNA for IL-13Ralpha1 with apparent single nucleotide polymorphism in the transmembrane domain. To study the function of IL-13R on brain tumor cells, we investigated the regulation of adhesion molecules by IL-13 as assessed by flow cytometric analysis. A172 cell line expressed a low level of vascular cell adhesion molecule-1 (VCAM-1), while U251 and LA1-5g cell lines expressed intercellular adhesion molecule-1 (ICAM-1). On the other hand E-selectin was not expressed in any cell lines. Interestingly, IL-13 increased the expression level of VCAM-1 in A172 cell line in a dose- and time-dependent manner. However, IL-13 did not modulate any other adhesion molecules. These results suggest that IL-13R on GBM cells are not rearranged but appear to be functional.

IL-13Rα2-bearing, type II NKT cells reactive to sulfatide self-antigen populate the mucosa of ulcerative colitis

Objective Previous studies have shown that ulcerative colitis (UC) is associated with the presence of lamina propria non-invariant (Type II) NKT cells producing IL-13 and mediating epithelial cell cytotoxicity. Here we sought to define the antigen(s) stimulating the NKT cells and to quantitate these cells in the UC lamina propria. Design Detection of Type II NKT cells in UC lamina propria mononuclear cells (LPMC) with lyso-sulfatide loaded tetramer and quantum dot-based flow cytometry and staining. Culture of UC LPMCs with lyso-sulfatide glycolipid to determine sulfatide induction of epithelial cell cytotoxicity, IL-13 production and IL-13Rα2 expression. Blinded quantum dot-based phenotypic analysis to assess UC LPMC expression of IL-13Rα2, CD161 and IL-13. Results Approximately 36% of UC LPMC were lyso-sulfatide tetramer positive, whereas few, if any, control LPMCs were positive. When tested, the positive cells were also CD3 and IL-13Rα2 positive. Culture of UC LPMC with lyso-sulfatide glycolipid showed that sulfatide stimulates UC LPMC production of IL-13 and induces UC CD161 LPMC-mediated cytotoxicity of activated epithelial cells; additionally, lyso-sulfatide induces enhanced expression of IL-13Rα2. Finally, blinded phenotypic analysis of UC LP MC using multicolour quantum dot-staining technology showed that approximately 60% of the LPMC bear both IL-13Rα2 and CD161 and most of these cells also produce IL-13. Conclusions These studies show that UC lamina propria is replete with Type II NKT cells responsive to lyso-sulfatide glycolipid and bearing IL-13Rα2. Since lyso-sulfatide is a self-antigen, these data suggest that an autoimmune response is involved in UC pathogenesis.

Targeting of IL-4 and IL-13 receptors for cancer therapy.

The Th2 cytokines, interleukin (IL)-4 and -13, are structurally and functionally related. They regulate immune responses and the immune microenvironment, not only under normal physiological conditions, but also in cancer. Both cytokines bind to their high-affinity receptors and form various configurations of receptor subtypes. We and others have reported that IL-4 and IL-13 bind to IL-4Rα and IL-13Rα1 chains, forming functional receptors in cancer cells. IL-13 also binds with high affinity to a private chain IL-13Rα2. After forming ligand-receptor complexes, both cytokines initiate signal transduction and mediate biological effects, such as tumor proliferation, cell survival, cell adhesion and metastasis. In certain cancers, the presence of these cytokine receptors may serve as biomarkers of cancer aggressiveness. In a series of studies, we reported that overexpression of IL-4 and IL-13 receptors on cancer cells provides targets for therapeutic agents for cancer therapy. In addition, both of these cytokines and their receptors have been shown to play important roles in modulating the immune system for tumor growth. IL-4, IL-13 and their receptors seem to play a role in cancer stem cells and provide unique targets to eradicate these cells. In this review article, we summarize some of the important attributes of IL-4 and IL-13 receptors in cancer biology and discuss pre-clinical and clinical studies pertaining to recombinant immunotoxins designed to target these receptors.

Identification of interleukin-13 receptor α2 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.

Gene expression profiling identifies IL‐13 receptor α2 chain as a therapeutic target in prostate tumor cells overexpressing adrenomedullin

Human adrenomedullin (AM) is a 52 amino acid peptide, which shares homology with the calcitonin gene‐related peptide. Overexpression of AM in the prostate carcinoma cell line PC‐3 results in growth inhibition with a 20% (for human AM) and 35% (for rat AM) increase in doubling time compared to parental or mock‐transfected cells. We demonstrate by gene expression profiling that AM overexpression results in the dysregulation of approximately 100 genes. Examples of such genes include many involved in the formation of the cytoskeleton, cell adhesion and the extracellular matrix, as well as regulators of the cell cycle and apoptosis, cytokines and transcription factors. Several genes related to cell growth arrest, such as GADD45, IGF‐BP6 and RUNX‐3, are upregulated by AM. Interestingly, interleukin‐13 receptor α2 (IL‐13Rα2) transcripts were significantly increased in clones overexpressing AM, which was confirmed by semiquantitative RT‐PCR analysis. In addition, PC‐3 cells treated with AM showed an overexpression of IL‐13Rα2, which was abolished when cells were preincubated with an anti‐AM blocking antibody. When PC‐3 cells overexpressing AM and the IL‐13Rα2 were treated with the highly specific IL13‐PE38 cytotoxin, which binds to this receptor, a concentration‐dependent inhibition of protein synthesis was observed. The IC50 (concentration of cytotoxin inhibiting protein synthesis by 50%) ranged from 1 to 4 ng/ml. This cytotoxicity was specific as it was neutralized by the excess of IL‐13 and confirmed by clonogenic assays. This study describes a novel AM‐induced mechanism of tumor sensitization through the upregulation of functional IL‐13Rα2 chain, an ideal target for the highly specific recombinant chimeric cytotoxin IL13‐PE38.

Interleukin‐4 receptor alpha overexpression in human bladder cancer correlates with the pathological grade and stage of the disease

Previously, we have demonstrated that interleukin‐4 receptor α (IL‐4Rα) is overexpressed on a variety of human cancers and can serve as target for IL‐4 immunotoxin comprised of IL‐4 and a mutated Pseudomonas exotoxin. However, its expression and association with grade and clinical stage of bladder cancer has not been studied. IL‐4Rα expression was examined in human bladder cancer cell lines, mouse xenografts, and biopsy specimens at mRNA and protein levels by real‐time RT‐PCR and IHC/ISH techniques. We also examined the effect of IL‐4 on proliferation and invasion of bladder carcinoma cell lines. For tissue microarray (TMA) results, we analyzed the precision data using exact binomial proportion with exact two‐sided P‐values. We used Cochran–Armitage Statistics with exact two‐sided P‐values to examine the trend analysis of IL‐4Rα over grade or stage of the bladder cancer specimens. The influence of age and gender covariates was also analyzed using multiple logistic regression models. IL‐4Rα is overexpressed in five bladder cancer cell lines, while normal bladder and human umbilical vein cell lines (HUVEC) expressed at low levels. Two other chains of IL‐4 receptor complex, IL‐2RγC and IL‐13Rα1, were absent or weakly expressed. IL‐4 modestly inhibited the cell proliferation, but enhanced cell invasion of bladder cancer cell lines in a concentration‐dependent manner. Bladder cancer xenografts in immunodeficient mice also maintained IL‐4Rα overexpression in vivo. Analysis of tumor biopsy specimens in TMAs revealed significantly higher IL‐4Rα immunostaining (≥2+) in Grade 2 (85%) and Grade 3 (97%) compared to Grade 1 tumors (0%) (P ≤ 0.0001). Similarly, 9% stage I tumors were positive for IL‐4Rα (≥2+) compared to 84% stage II (P ≤ 0.0001) and 100% stages III–IV tumors (P ≤ 0.0001). IL‐13Rα1 was also expressed in tumor tissues but at low levels and it did not show any correlation with the grade and stage of disease. However, the IL‐2RγC was not expressed. Ten normal bladder specimens demonstrated ≤1+ staining for IL‐4Rα and IL‐13Rα1 and no staining for IL‐2RγC. These results demonstrate that IL‐4Rα is overexpressed in human bladder cancer, which correlates with advanced grade and stage of the disease. Thus, IL‐4Rα may be a bladder tumor‐associated protein and a prognostic biomarker.

Human Adrenomedullin Up-regulates Interleukin-13 Receptor α2 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 <or= 0.01). These results indicate that two completely unrelated hormones (AM and IL-13) are closely related to each other and that we have identified a novel role of AM in sensitizing certain types of prostate tumors to IL-13R-directed therapeutic agent.

Analysis of Biodistribution of Intracranially Infused Radiolabeled Interleukin-13 Receptor–Targeted Immunotoxin IL-13PE by SPECT/CT in an Orthotopic Mouse Model of Human Glioma

Interleukin-13 Pseudomonas exotoxin (IL-13PE), a targeted agent for interleukin-13 receptor α2 (IL-13Rα2)–expressing tumors, has been administered intracranially by convection-enhanced delivery (CED) for glioma therapy in several clinical trials including a randomized phase 3 clinical trial. However, its intracranial distribution was not optimally evaluated. We investigated the intracranial distribution of radiolabeled IL-13PE after CED in a murine model of glioblastoma multiforme. Methods: IL-13PE was radiolabeled with Na125I and evaluated for its activity in vitro in receptor-positive U251 or -negative T98G human glioma cell lines. Gliomas were grown in nude mice after intracranial implantation with U251 cells, and 125I-IL-13PE was stereotactically administered by bolus or CED for 3 d, followed by micro-SPECT/CT imaging. SPECT images were evaluated quantitatively and compared with histology and autoradiography results. Results: The radioiodination technique resulted in a specific and biologically active 125I-IL-13PE, which bound and was cytotoxic to IL-13Rα2–positive but not to IL-13Rα2–negative tumor cells. Both the binding and the cytotoxic activities were blocked by a 100-fold excess of IL-13, which indicated the specificity of binding and cytotoxicity. SPECT/CT imaging revealed retention of 125I-IL-13PE administered by CED in U251 tumors and showed significantly higher volumes of distribution and maintained detectable drug levels for a longer period of time than the bolus route. These results were confirmed by autoradiography. Conclusion: IL-13PE can be radioiodinated without the loss of specificity, binding, or cytotoxic activity. Intracranial CED administration produces a higher volume of distribution for a longer period of time than the bolus route. Thus, CED of IL-13PE is superior to bolus injection in delivering the drug to the entire tumor.

In vitro and in vivo suppression of interleukin-2-activated killer cell activity by chimeric proteins between interleukin-2 and Pseudomonas exotoxin.

The biological effects of IL-2 are mediated through high (complex of alpha and beta chain) or intermediate (beta chain) affinity IL-2 receptors. Previously, chimeric proteins composed of IL-2 and Pseudomonas exotoxin (IL-2-PE) were shown to be specifically cytotoxic to cells bearing IL-2 receptors. It has also been shown that IL-2-PE chimeric proteins can abrogate T cell-mediated immune response in vitro. In the current study, we have investigated the effects of IL-2-PE on LAK activity both in vivo and in vitro. We administered either IL-2-PE40 (comprised of IL-2 and 40-kDa portion of PE) or IL-2-PE66 (comprised of IL-2 and 66-kDa molecule of PE) to normal C57BL/6 mice for 3 or 8 days and LAK activity was assessed in various organs of mice. We found that IL-2-PE40 generated LAK activity in various compartments of mice and the level of activity was slightly lower than that observed with an equivalent amount of recombinant (r) IL-2 alone. However, IL-2-PE66 failed to generate LAK activity which would have been induced due to an equivalent concentration of rIL-2. IL-2-PE66 also did not induce LAK activity from the splenocytes during in vitro culture while IL-2-PE40 generated good LAK activity. An equivalent amount of IL-2 also generated potent LAK activity. The suppression of LAK activity by IL-2-PE66 was also evident in cells preactivated with IL-2; however, this inhibition was partial. The suppressive activity of IL-2-PE66 was shown to be mediated through IL-2 receptor interactions as excess amounts of rIL-2 were able to abrogate its effect. Both IL-2 toxins were equivalently cytotoxic to IL-2 receptor-bearing HUT 102 cells and both were able to compete from high and intermediate affinity IL-2 receptors. Taken together, our data indicate that IL-2-PE66 is highly cytotoxic to LAK cells while IL-2-PE40 is less cytotoxic. Thus, data from our study and from other published reports indicate that IL-2-PE66 is more potent immunosuppressive agent than IL-2-PE40.