Abstract 3838: Upregulation of DLEU1 significantly prolongs survival in a rituximab-treated DLEU1 knockout human Burkitt lymphoma (BL) xenograft NSG mouse model: DLEU1 may act as a tumor suppressor gene in pediatric BL

Abstract

Abstract BACKGROUND: Burkitt lymphoma (BL) is the most common histological subtype of non-Hodgkin lymphoma (NHL) in children and adolescents (Cairo et al., Blood 2007; Miles/Cairo., BJHaem 2012). We identified that pediatric BL patients with chromosome 13q deletion, particularly 13q14.3, had significantly poorer outcome and inferior overall survival despite aggressive short, intensive multi-agent chemotherapy (Poirel/Cairo et al., Leuk 2009; Nelson/Cairo/Sanger et al., BJH 2009). Deleted in lymphocytic leukemia 1 (DLEU1) is a BL classifier gene in the 13q14.3 region (Dave et al., NEJM 2006) and interacts with C-MYC, TUBB2C and UBR1 (Stelzl et al., Cell 2005). We have previously reported a regulated DLEU1 expression significantly associated with changes in BL proliferation in vitro (Lee/Cairo et al., AACR 2015). We hypothesize that DLEU1 may have function as a tumor suppressor gene; however, functions and mechanisms underlying DLEU1 expression in the BL are poorly understood. OBJECTIVES: We hypothesize that DLEU1 may act as a tumor suppressor gene in BL and therefore examined whether up-regulation of DLEU1 results in changes in survival following targeted immunotherapy. METHODS: DLEU1 stably overexpressing Raji BL cells (Lee/Cairo et al., ASH 2013) were transfected with a firefly luciferase expression plasmid, kindly provided by Laurence Cooper MD, PhD. Four- to six- week-old female NSG (NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ) mice from The Jackson Lab. Tumor burden and tumor progression were monitored by bioluminescence imaging system. Mice were treated with either rituximab (30 mg/kg) or cyclophosphamide (25 mg/kg) by intraperitoneal injection at 7 day intervals. Survival rates were analyzed by the Kaplan-Meier method using the Prism Version 6.0 software. RESULTS: We observed that DLEU1 stably overexpressing Raji BL cells xenografted (GFP-DLEU1) mice had significantly extended survival compared to GFP control mice following treatment rituximab (59 vs 51 days, p<0.05, n = 8), cyclophosphamide (50.5 vs 37.5 days, p<0.0001, n = 12) and in combination treatment (60.5 vs 53 days, p<0.05, n = 12) whereas there were no significant differences in survival between WT and DLEU1-KO mice with PBS treatment. We observed that there were no significant differences of luciferase intensity in between GFP and GFP-DLEU1 mice following rituximab, cyclophosphamide or in combination treatment. CONCLUSIONS: We demonstrated that the upregulation of DLEU1 expression significantly improved the survival in DLEU1 overexpressing BL cells xenografted NSG mice following rituximab, cyclophosphamide and in combination treatment. Therefore, the up-regulation of DLEU1 expression in BL may in part result in sensitizing to chemoimmunotherapy induced survival and may result in a consideration of potential therapeutic strategies Citation Format: Sanghoon Lee, Changhong Yin, Tishi Shah, Janet Ayello, Erin Morris, Carmella van de Ven, Mitchell S. Cairo. Upregulation of DLEU1 significantly prolongs survival in a rituximab-treated DLEU1 knockout human Burkitt lymphoma (BL) xenograft NSG mouse model: DLEU1 may act as a tumor suppressor gene in pediatric BL. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3838.