Microarray analysis of mouse TRAF3-/- premalignant splenic B cells

Specific deletion of the tumor suppressor gene TRAF3 from B lymphocytes (B-TRAF3-/-) in mice leads to prolonged survival of mature B cells and expanded B cell compartment in secondary lymphoid organs. To understand the metabolic basis of the prolonged survival of TRAF3-/- B cells, we performed LC-MS-based metabolome and lipidome screening with resting splenic B cells of young adult B-TRAF3-/- and littermate control (LMC) mice. Our metabolome screening data showed that phosphocholine (P-Cho) and phosphoethanolamine, two small metabolites and precursors of phospholipids, were significantly increased in TRAF3-/- B cells. Consistently, our lipidome screening revealed markedly elevated levels of multiple species of phosphatidylcholine (PC) and phosphatidylethanolamine in TRAF3-/- B cells. Interestingly, our transcriptome profiling identified Chka, the rate-limiting enzyme of choline metabolism, as a significantly up-regulated gene in TRAF3-/- B cells. To investigate the functional importance of elevated choline metabolism, we examined the effects of two Chka inhibitors, MN58B and RSM932A. We found that both MN58B and RSM932A potently induced cell apoptosis in TRAF3-/- mouse B lymphoma and human multiple myeloma cell lines in vitro. Furthermore, in vivo administration of MN58B and RSM932A partially decreased the spleen size and B cell compartment in B-TRAF3-/- mice. Together, our results indicate that TRAF3 specifically re-engineers the P-Cho-PC-PE metabolic pathways to regulate mature B cell survival. Our findings also suggest that the P-Cho-PC-PE metabolic pathways have diagnostic and therapeutic value for B cell malignancies with TRAF3 deletion or relevant mutations. Three control (normal splenic B cells) and three TRAF3-/- (premalignant splenic B cells) samples were collected to identify mechanisms altered in the absence of TRAF3.