Interleukin-13 receptor alpha2 is a novel therapeutic target for human adrenocortical carcinoma.

BACKGROUND: Adrenocortical carcinoma (ACC) is a relatively rare but aggressive malignancy with limited therapeutic options. Previous genome-wide expression studies have demonstrated the overexpression of interleukin-13 receptor alpha2 (IL13Rα2) in some human malignancies.
METHODS: The authors evaluated IL13Rα2 mRNA and protein expression in 21 normal samples, 78 benign samples, 10 primary malignant samples, and 25 metastatic/recurrent samples and performed functional analyses with IL13 ligand and IL13 Rα2 knockdown in vitro. The sensitivity of 2 ACC cell lines (NCI-H295R [high IL13Rα2 expression] and SW13 [low IL13Rα2 expression]) to a highly specific IL-13 conjugated with Pseudomonas exotoxin (IL-13-PE) also was evaluated in both in vitro and in vivo models.
RESULTS: IL13Rα2 was overexpressed in malignant tumors compared with benign and normal samples (15-fold higher; P < .05). Immunohistochemistry also confirmed higher protein expression in malignant and benign tumors than in normal adrenocortical tissues (P < .05). The half-maximal inhibitory concentration for IL-13-PE was 1.3 ng/mL in the NCI-H295R cell line and 1000 ng/mL in the SW13 cell line. Mice that received intratumoral or intraperitoneal IL-13-PE injection had a significant reduction in tumor size and increased tumor necrosis compared with control groups (P < .05) and also had prolonged survival (P < .05). IL13Rα2 protein expression increased in cells that were treated with IL-13 ligand along with cell invasion (P < .05). Direct IL13Rα2 knockdown decreased cellular proliferation and invasion (P < .05).
CONCLUSIONS: The current results indicated that IL13Rα2 is overexpressed in ACC and regulates cell invasion and proliferation. IL13Rα2 is a novel therapeutic target for the treatment of human ACC.