Abstract 2077: DLEU1 significantly alters programmed cell death in chemoimmunotherapy-treated TALENs-induced DLEU1 knockout and DLEU1 overexpressing Burkitt Lymphoma (BL): DLEU1 may act as a tumor suppressor gene in pediatric BL

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA BACKGROUND: Burkitt Lymphoma (BL) is the most common histological subtype of childhood and adolescent Non Hodgkin Lymphoma (Cairo et al, Blood 2007; Miles/Cairo, BJH 2012). Pediatric patients with BL with a 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, Leukemia 2009; Nelson/Cairo/Sanger et al, BJH 2009). Deleted in Lymphocytic Leukemia 1 (DLEU1) is a BL classifier gene in the 13q14.3 (Dave et al, NEJM 2006) and it has been implicated in regulating programmed cell death in patients. Sequence-specific Transcription Activator-Like Effector Nucleases (TALENs) have been developed for precision targeted genome editing in in vitro and in vivo (Sander et al, Nat Bio 2011). OBJECTIVES: We hypothesize that DLEU1 may act as a tumor suppressor gene and therefore investigated whether DLEU1 expression results in changes in gene expression profiles, cell viability, apoptosis induced by chemoimmunotherapy regimens in DLEU1 knockout and/or DLEU1 overexpressing Raji BL cells. METHODS: TALEN-mediated DLEU1 knockout (DLEU1-KO) and DLEU1 overexpressing Raji BL cells (DLEU1-OE) were treated with Rituximab (RTX) and/or Cyclophosphamide (CTX). MTS, Caspase assay, qRT-PCR, western blot, and gene expression profiling using Affymetrix HG-133+ 2.0 arrays were performed. RESULTS: A significant decrease of apoptosis in DLEU1-KO (32.5±11.8%, p 2 fold, p<.05) and 79.8% of genes including signaling pathways and anti-apoptosis related genes including ATK1, ikBa and Bcl-2 were upregulated in DLEU1-KO.. There was a significant decrease in apoptosis with RTX, CTX and in combination (0.85±0.05, 0.76±0.09, and 0.65±0.17, p<.05, respectively) in DLEU1-KO whereas a significant increase with RTX (11.5%, p<.05), CTX (13.9%, p<.05) in DLEU1-OE. A significant increase in cell proliferation was observed with RTX, CTX and combination (1.14±0.06, 1.1±0.06, and 1.09±0.02, p<.05) in DLEU1-KO whereas a significant decrease with RTX, CTX and in combination (0.92±0.01, 0.89±0.04, and 0.87±0.04, p<.05, respectively) in DLEU1-OE vs control. CONCLUSIONS: We demonstrate that 1) DLEU1 knockout resulted in significant changes of ikBa and Akt1 expression, inhibition of apoptosis and increase of viability in RTX and CTX treatment; 2) DLEU1 overexpression significantly inhibited cell viability and increased apoptosis in RTX and CTX treatment. We hypothesize that deletion of DLEU1 in pediatric BL may in part result in chemotherapy resistance secondarily to a loss of a tumor suppressor gene. Citation Format: Sanghoon Lee, Changhong Yin, Janet Ayello, Carmella van de Ven, Mitchell S. Cairo. DLEU1 significantly alters programmed cell death in chemoimmunotherapy-treated TALENs-induced DLEU1 knockout and DLEU1 overexpressing Burkitt Lymphoma (BL): DLEU1 may act as a tumor suppressor gene in pediatric BL. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2077. doi:10.1158/1538-7445.AM2015-2077