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 alpha (IL-4R alpha) is over-expressed 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-4R alpha 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-4R alpha 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-4R alpha 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-2R gamma C and IL-13R alpha 1, 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-4R alpha overexpression in vivo. Analysis of tumor biopsy specimens in TMAs revealed significantly higher IL-4R alpha 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-4R alpha (>= 2+) compared to 84% stage II (P <= 0.0001) and 100% stages III-IV tumors (P <= 0.0001). IL-13R alpha 1 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-2R gamma C was not expressed. Ten normal bladder specimens demonstrated <= 1+ staining for IL-4R alpha and IL-13R alpha 1 and no staining for IL-2R gamma C. These results demonstrate that IL-4R alpha is overexpressed in human bladder cancer, which correlates with advanced grade and stage of the disease. Thus, IL-4R alpha may be a bladder tumor-associated protein and a prognostic biomarker.