IL-2 augments the therapeutic efficacy of adoptively transferred B cells which directly kill tumor cells via the CXCR4/CXCL12 and perforin pathways

// Yang Xia 1, 2, * , Huimin Tao 1, 3, 8, * , Yangyang Hu 1, 3, * , Quanning Chen 1, 4, * , Xin Chen 1, 5 , Leiming Xia 1, 2 , Li Zhou 1, 6 , Yi Wang 2 , Yangyi Bao 2 , Shiang Huang 3 , Xiubao Ren 6 , Steven K. Lundy 7 , Fu Dai 2, ** , Qiao Li 1, ** , Alfred E. Chang 1, ** 1 Department of Surgery, University of Michigan, Ann Arbor, Michigan, USA 2 The No.1 People’s Hospital of Hefei, Hefei, China 3 Hubei Province Stem Cell Research & Appling Center, Wuhan Union Hospital, Wuhan, China 4 Department of General Surgery, Tongji Hospital of Tongji University, Shanghai, China 5 Department of Oncology, Wuhan University, Renmin Hospital, Wuhan, China 6 Department of Biotherapy, Tianjin University Cancer Institute and Hospital, National Clinical Research Center of Cancer, Key laboratory of Cancer Immunology and Biotherapy, Tianjin, China 7 Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA 8 Current address: Fuda Cancer Hospital, Jinan University School of Medicine and Fuda Cancer Institute, Guangzhou, China * These authors have contributed equally to this work ** Joint senior authors Correspondence to: Qiao Li, email: qiaoli@umich.edu Alfred E. Chang, email: aechang@umich.edu Fu Dai, email: hfsyydf@sina.com Keywords: B cells, adoptive immunotherapy, IL-2, CXCR4/CXCL12, perforin Abbreviations: TDLN, tumor-draining lymph node; CM, complete medium; s.c., subcutaneous; i.v., intravenously; i.p., intraperitoneal Received: December 06, 2015     Accepted: July 26, 2016     Published: August 09, 2016 ABSTRACT We previously reported that antitumor B cells directly kill tumor cells via the Fas/FasL pathway and are regulated by IL-10. In this study, we defined additional mechanisms involved in B cell antitumor immunity. Administration of IL-2 significantly augmented the therapeutic efficacy of adoptively transferred tumor-draining lymph node (TDLN) B cells which express IL- 2R. Culture supernatant of purified B splenocytes harvested from the mice that received adoptive transfer of 4T1 TDLN B cells plus IL-2 administration produced larger amounts of IgG which bound to 4T1, resulting in 4T1 lysis. Furthermore, we detected CXCR4 expression on 4T1 TDLN B cells, and 4T1 tumor cells produced its ligand CXCL12. Transwell experiments demonstrated the chemoattraction of CXCR4-expressing 4T1 TDLN B cells towards CXCL12- producing 4T1 cells. Blockade of CXCR4 using a CXCR4-specific inhibitor, AMD3100, significantly reduced the killing of 4T1 tumor cells by 4T1 TDLN B cells. Blockade of FasL and CXCR4 concurrently inhibited B cell-mediated direct killing of tumor cells in an additive manner, indicating that both Fas/FasL and CXCL12/CXCR4 pathways are involved in the direct killing of 4T1 cells by 4T1 TDLN B cells. TDLN B cells produced perforin. Additional transwell experiments showed that effector B cells could directly kill tumor cells in cell-cell contact via the Fas/FasL and CXCR4/CXCL12 pathways as well as perforin, while without cell contact, perforin secreted by B cells led to tumor cell cytotoxicity. These findings underscore the diversity of function by which B cells can play an important role in the host immune response to tumor.