CD47 is expressed in normal activated cells as well as in several tumors. It also has been implicated as having antiangiogenic and antimetastatic properties, but its roles in Epstein-Barr virus (EBV)-transformed B cells are still not fully understood. Herein, we report that EBV infection induced CD47 surface expression on B cells, and CD47 ligation with anti-CD47 mAb (B6H12) reduced cell proliferation and induced G1 arrest. CD47-induced G1 arrest was mediated through increased cyclin-dependent kinase inhibitors (CDKi) and a simultaneously decreased CDK/cyclins, and p38 MAPK/JNK activation preceded binding of CDKi-CDK. Moreover, reactive oxygen species (ROS) generation and upregulation of both TAp73 and ER stress sensor proteins were detected after CD47 ligation, and p38 inhibitor SB203580 and JNK inhibitor SP600125 blocked upregulation of TAp73 and cell cycle arrest. We investigated whether ROS generation is the initial event of CD47-mediated G1 arrest because ROS scavenger NAC effectively abrogated the majority of CD47-mediated responses but SB203580 and SP600125 did not block ROS production. Taken together, we concluded that CD47 ligation on EBV-transformed B cells led to G1 arrest by ROS generation and, subsequently, there was p38 MAPK/JNK pathway activation, ER stress triggering, and TAp73 upregulation. Our findings provide data supporting CD47 as a feasible target for EBV-associated tumor therapy.
*Department of Anatomy and Research Center for Tumor Immunology, Inje University College of Medicine
‡Department of Internal Medicine, Inje University Busan Paik Hospital, Busan
†Department of Anesthesiology, Inje University Seoul Paik Hospital
§Department of Anesthesiology, Samsung Medical Center, Sungkyunkwan University, Seoul , Republic of Korea
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G.B.P. and S.R.B. contributed equally.
Reprints: Dae Young Hur and Yeong Seok Kim, Department of Anatomy and Tumor Immunology, Inje University College of Medicine, 633-165 Kaekum-2-dong, Jin-gu, Busan 614-735, Republic of Korea (e-mail: firstname.lastname@example.org or email@example.com).
Received September 10, 2012
Accepted March 19, 2014