The cytomegalovirus protein UL138 induces apoptosis of gastric cancer cells by binding to heat shock protein 70

// Wenjing Chen 1, * , Kezhi Lin 2, * , Liang Zhang 1 , Gangqiang Guo 3 , Xiangwei Sun 1 , Jing Chen 4 , Lulu Ye 3 , Sisi Ye 3 , Chenchen Mao 1 , Jianfeng Xu 1 , Lifang Zhang 4 , Lubin Jiang 3, 5 , Xian Shen 1 , Xiangyang Xue 3 1 Department of General Surgery, First Affiliated Hospital, Wenzhou Medical University, Wenzhou, China 2 Experimental Center, Wenzhou Medical University, Wenzhou, China 3 Department of Microbiology and Immunology, Institute of Molecular Virology and Immunology, Institute of Tropical Medicine, Wenzhou Medical University, Wenzhou, China 4 Department of Rheumatology, First Affiliated Hospital, Wenzhou Medical University, Wenzhou, China 5 Key Laboratory of Molecular Virology and Immunology, Unit of Pathogen-Host Interaction and Epigenetics, Institut Pasteur of Shanghai, Shanghai, China * These authors contributed equally to this work Correspondence to: Xiangyang Xue, e-mail: wzxxy001@163.com Xian Shen, e-mail: shenxian5166@gmail.com Lubin Jiang, e-mail: lbjiang@ips.ac.cn Keywords: gastric cancer, cytomegalovirus, UL138, apoptosis, HSP70 Received: July 21, 2015      Accepted: December 05, 2015      Published: December 30, 2015 ABSTRACT It has been hypothesized that human cytomegalovirus (HCMV) could act as a tumor promoter and play an “oncomodulatory” role in the neoplastic process of several human malignancies. However, we demonstrate for the first time that UL138, a HCMV latency-associated gene, could act as a tumor inhibitor in gastric cancer (GC). The expression of UL138 is down-regulated in HCMV positive gastric adenocarcinoma tissues, especially in poorly or none differentiated tumors. Overexpression of UL138 in several human GC cell lines inhibits cell viability and induces apoptosis, in association with the reduction of an anti-apoptotic Bcl-2 protein and the induction of cleaved caspase-3 and caspase-9. Moreover, protein array analysis reveals that UL138 interacts with a chaperone protein, heat shock protein 70 (HSP70). This interaction is confirmed by immunoprecipitation and immunostaining in situ in GC cell lines. In addition, this UL138-mediated cancer cell death could efficiently lead to suppression of human tumor growth in a xenograft animal model of GC. In conclusion, these results uncover a previously unknown role of the cytomegalovirus protein UL138 in inducing GC cells apoptosis, which might imply a general mechanism that viral proteins inhibit cancer growth in interactions with both chaperones and apoptosis-related proteins. Our findings might provide a potential target for new therapeutic strategies of GC treatment.