Identification, characterization, and targeting of IL-4 receptor by IL-4-Pseudomonas exotoxin in mouse models of anaplastic thyroid cancer

Thyroid cancer is a rapidly increasing endocrine cancer. Since interleukin-4 receptor (IL-4R) is overexpressed in human solid cancer, we examined expression of IL-4R in 50 cases of anaplastic thyroid cancer (ATC), 37 well-differentiated papillary cancer (WDPC), 35 well-differentiated follicular cancer of thyroid (WDFC), and 37 normal thyroid specimens by immunohistochemistry (IHC) and in-situ hybridization (ISH) techniques. We demonstrated that IL-4Rα was overexpressed in 36/50 (72%) ATC, 20/35 (57%) WDFC, and 11/37 (30%) WDPC tumors. Other two subunits of IL-4R, interleukin-13 receptor α1 (IL-13Rα1) and interleukin-2 receptor gamma (IL-2RγC), were either weakly expressed or absent. As ATC is a highly aggressive cancer with higher incidence of IL-4Rα expression, we characterized IL-4R in 3 ATC cell lines. RT-qPCR and IFA results showed that IL-4Rα is overexpressed while IL-13Rα1 is weakly expressed. Control human umbilical vein endothelial cell line (HUVEC) showed weak expression of IL-4Rα. Binding and competition studies with 125I-IL-4 in ATC cell lines demonstrated that IL-4 specifically bound to IL-4Rα on cell surface. ATC cell lines were highly sensitive to a chimeric fusion cytotoxin consisting of circularly permuted IL-4 and truncated Pseudomonas exotoxin (IL-4-PE), which killed them in a concentration dependent manner. IL-4-PE also blocked colony formation of ATC cell lines in clonogenic assays. IL-4-PE mediated a significant antitumor activity in mouse models of ATC. Intratumoral administration of IL-4-PE caused significant regression of established tumors in a dose dependent manner and increased the overall survival without any visible toxicity. Thus, IL-4Rα in ATC may represent a novel therapeutic target and IL-4-PE may serve as an investigational therapeutic option for ATC.

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.