ATM-deficient B cell lymphomas

Ataxia-telangiectasia mutated (ATM) kinase plays a central role in maintaining genomic integrity. In both humans and mice, ATM deficiency is associated with an increased incidence of lymphoid cancers that are primarily T cell in origin. We demonstrate here that when T cells are removed as targets for lymphomagenesis and as mediators of immune surveillance, ATM-deficient mice exclusively develop early onset IgM+ B cell lymphomas that by histology and gene expression profiling resemble the activated B cell-like (ABC) subset of human diffuse large B cell lymphomas (DLBCL). These ATM-deficient B cell tumors show considerable chromosomal instability and a recurrent genomic amplification of a 4.48 Mb region on chromosome 18 that contains Malt1 and is orthologous to a region similarly amplified in human ABC-DLBCL. Further, the amplification of Malt1 in these lymphomas correlates with their dependence on NF-kB, MALT1, and BCR signaling for survival, paralleling human ABC-DLBCL. This study reveals that ATM protects against development of B cell lymphomas that model human ABC-DLBCL and identifies a role for T cells in preventing the emergence of these tumors. We performed gene expression profiling on nine ATMKO.CD3epsilonKO lymphoma cell lines (n=12, 3 technical repeats). We analyzed gene expression of anti-IgM stimulated primary B cells from both ATMKO.CD3epsilonKO (n=7, 5 technical repeats) and ATMWT.CD3epsilonKO mice (n=2), and GC B cells isolated from SRBC-immunized ATMWT mice (n=3, 1 biological repeat and 2 technical repeats). We analyzed gene expression following treatment of two ATMKO.CD3epsilonKO lymphoma cell lines with the BTK inhibitor, PCI-32765, at time points (1, 3, 6, and 24 hours) as compared to time points with vehicle (DMSO) (n=8).