A20 is a negative regulator of the NF-κB pathway and was initially identified as being rapidly induced after tumour-necrosis factor-α stimulation1. It has a pivotal role in regulation of the immune response and prevents excessive activation of NF-κB in response to a variety of external stimuli2,3,4,5,6,7; recent genetic studies have disclosed putative associations of polymorphic A20 (also called TNFAIP3) alleles with autoimmune disease risk8,9. However, the involvement of A20 in the development of human cancers is unknown. Here we show, using a genome-wide analysis of genetic lesions in 238 B-cell lymphomas, that A20 is a common genetic target in B-lineage lymphomas. A20 is frequently inactivated by somatic mutations and/or deletions in mucosa-associated tissue lymphoma (18 out of 87; 21.8%) and Hodgkin’s lymphoma of nodular sclerosis histology (5 out of 15; 33.3%), and, to a lesser extent, in other B-lineage lymphomas. When re-expressed in a lymphoma-derived cell line with no functional A20 alleles, wild-type A20, but not mutant A20, resulted in suppression of cell growth and induction of apoptosis, accompanied by downregulation of NF-κB activation. The A20-deficient cells stably generated tumours in immunodeficient mice, whereas the tumorigenicity was effectively suppressed by re-expression of A20. In A20-deficient cells, suppression of both cell growth and NF-κB activity due to re-expression of A20 depended, at least partly, on cell-surface-receptor signalling, including the tumour-necrosis factor receptor. Considering the physiological function of A20 in the negative modulation of NF-κB activation induced by multiple upstream stimuli, our findings indicate that uncontrolled signalling of NF-κB caused by loss of A20 function is involved in the pathogenesis of subsets of B-lineage lymphomas.
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This work was supported by the Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, by the 21st century centre of excellence program ‘Study on diseases caused by environment/genome interactions’, and by Grant-in-Aids from the Ministry of Education, Culture, Sports, Science and Technology of Japan and from the Ministry of Health, Labor and Welfare of Japan for the 3rd-term Comprehensive 10-year Strategy for Cancer Control. We also thank Y. Ogino, E. Matsui and M. Matsumura for their technical assistance.
Author Contributions M.Ka., K.N. and M.S. performed microarray experiments and subsequent data analyses. M.Ka., Y.C., K.Ta., J.T., J.N., M.I., A.T. and Y.K. performed mutation analysis of A20. M.Ka., S.Mu., M.S., Y.C. and Y.Ak. conducted functional assays of mutant A20. Y.S., K.Ta., Y.As., H.M., M.Ku., S.Mo., S.C., Y.K., K.To. and Y.I. prepared tumour specimens. I.K., K.O., A.N., H.N. and T.N. conducted in vivo tumorigenicity experiments in NOG/SCID mice. T.I., Y.H., T.Y., Y.K. and S.O. designed overall studies, and S.O. wrote the manuscript. All authors discussed the results and commented on the manuscript.
This file contains Supplementary Tables 1-6, Supplementary Figures 1-10 with Legends, and a Supplementary Reference.