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Antiapoptotic Activity of Autocrine Interleukin-22 and Therapeutic Effects of Interleukin-22-Small Interfering RNA on Human Lung Cancer Xenografts

Authors' Affiliations: ¹ Institute of Immunology, Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, People's Republic of China and ² Institute of Immunopharmacology and Immunotherapy, School of Pharmaceutical Sciences, Shandong University, Jinan, People's Republic of China

Requests for reprints: Zhigang Tian, School of Life Sciences, University of Science and Technology of China, 443 Huangshan Road, Hefei, Anhui 230027, People's Republic of China. Phone: 86-551-360-7379; Fax: 86-551-360-6783; E-mail: tzg{at}ustc.edu.cn.

Purpose: Non–small cell lung carcinoma (NSCLC) is one of most common malignant diseases and usually is resistant against apoptosis-inducing chemotherapy. This study is to explore the antiapoptotic mechanisms of interleukin (IL)-22 in human lung cancer.

Experimental Design: Nineteen cases with stage I to III NSCLC were collected to determine the expression of IL-22. Stable transfection of human IL-22 cDNA into A549 and PG cells and transfection of IL-22-RNA interference (RNAi) into these cancer cell lines were done to reveal the molecular mechanisms of IL-22.

Results: It was found that IL-22 was highly expressed in primary tumor tissue, malignant pleural effusion, and serum of patients with NSCLC. IL-22R1 mRNA was also detected in lung cancer tissues as well as lung cancer cell lines. Overexpression of IL-22 protected lung cancer cell lines from serum starvation-induced and chemotherapeutic drug-induced apoptosis via activation of STAT3 and its downstream antiapoptotic proteins such as Bcl-2 and Bcl-xL and inactivation of extracellular signal-regulated kinase 1/2. Exposure to blocking antibodies against IL-22R1 or transfection with the IL-22-RNAi plasmid in vitro resulted in apoptosis of these lung cancer cells via STAT3 and extracellular signal-regulated kinase 1/2 pathways. Furthermore, an in vivo xenograft study showed that administration of IL-22-RNAi plasmids significantly inhibited the human tumor cell growth in BALB/c nude mice.

Conclusions: Our study indicates that autocrine production of IL-22 contributes to human lung cancer cell survival and resistance to chemotherapy through the up-regulation of antiapoptotic proteins.