Epstein-Barr Virus-Encoded Latent Membrane Protein 1 and B-Cell Growth Transformation Induce Lipogenesis through Fatty Acid Synthase

Abstract

Latent membrane protein 1 (LMP1) is the major transforming protein of Epstein-Barr virus (EBV) and is critical for EBV-induced B-cell transformation in vitro. Several B-cell malignancies are associated with latent LMP1-positive EBV infection, including Hodgkin’s and diffuse large B-cell lymphomas. We have previously reported that promotion of B cell proliferation by LMP1 coincided with an induction of aerobic glycolysis. To further examine LMP1-induced metabolic reprogramming in B cells, we ectopically expressed LMP1 in an EBV-negative Burkitt’s lymphoma (BL) cell line preceding a targeted metabolic analysis. This analysis revealed that the most significant LMP1-induced metabolic changes were to fatty acids. Significant changes to fatty acid levels were also found in primary B cells following EBV-mediated B-cell growth transformation. Ectopic expression of LMP1 and EBV-mediated B-cell growth transformation induced fatty acid synthase (FASN) and increased lipid droplet formation. FASN is a crucial lipogenic enzyme responsible for de novo biogenesis of fatty acids in transformed cells. Furthermore, inhibition of lipogenesis caused preferential killing of LMP1-expressing B cells and significantly hindered EBV immortalization of primary B-cells. Finally, our investigation also found that USP2a, a ubiquitin-specific protease, is significantly increased in LMP1-positive BL cells and mediates FASN stability. Our findings demonstrate that ectopic expression of LMP1 and EBV-mediated B-cell growth transformation leads to induction of FASN, fatty acids and lipid droplet formation, possibly pointing to a reliance on lipogenesis. Therefore, the use of lipogenesis inhibitors could potentially be used in the treatment of LMP1+ EBV associated malignancies by targeting a LMP1-specific dependency on lipogenesis. Importance Despite many attempts to develop novel therapies, EBV-specific therapies currently remain largely investigational and EBV-associated malignancies are often associated with a worse prognosis. Therefore, there is a clear demand for EBV-specific therapies for both prevention and treatment of viral-associated malignancies. Non-cancerous cells preferentially obtain fatty acids from dietary sources whereas cancer cells will often produce fatty acids themselves by de novo lipogenesis, often becoming dependent on the pathway for cell survival and proliferation. LMP1 and EBV-mediated B-cell growth transformation leads to induction of FASN, a key enzyme responsible for the catalysis of endogenous fatty acids. Preferential killing of LMP1-expressing B cells following inhibition of FASN suggests that targeting LMP-induced lipogenesis could be an effective strategy in treating LMP1-positive EBV-associated malignancies. Importantly, targeting unique metabolic perturbations induced by EBV could be a way to explicitly target EBV-positive malignancies and distinguish their treatment from EBV-negative counterparts.

Epstein–Barr virus oncoprotein–driven B cell metabolism remodeling

“…EBNA2, MYC, and sterol response element binding protein 2 (SREBP2) are each critical for ACACA and FASN induction. LMP1 further supports FASN up-regulation [ 39 ]. Similarly, LMP1 induces sterol response element binding protein 1 (SREBP1) in NPCs to up-regulate FASN and promote tumor progression, and LMP1 and FASN levels correlate in primary NPC samples [ 40 ].…”

Hallmarks of Metabolic Reprogramming and Their Role in Viral Pathogenesis

“…FASN is responsible for the conversion of acetyl-CoA to long-chain fatty acids through the direct induction by the viral protein BRLF1 [ 172 , 173 ]. Further, the EBV latent membrane protein 1 (LMP1) increases the fatty acid synthesis and induces FASN, resulting in increased fatty acids and lipid droplets in EBV-negative Burkitt’s lymphoma (BL) cells [ 174 ]. The replication of varicella-zoster (VZV) depends on lipid synthesis.…”

EBNA2 driven enhancer switching at the CIITA-DEXI locus suppresses HLA class II gene expression during EBV infection of B-lymphocytes

“…For proteomic study, deidentified human B cells were obtained from the Human Immunology Core of the University of Pennsylvania under an Institutional Review Board-approved protocol, as previously described [ 74 ]. Briefly, primary B cells (25 x 10 6 for each donor) were purified from donor plasma using the RosetteSep human B-cell enrichment cocktail (StemCell Technologies) and cultured in RPMI 1640 supplemented with fetal bovine serum (FBS, final concentration 15%), and 1% penicillin/streptomycin cocktail.…”