NOD-Scid (NOD.CB17-Prkdcscid/NCrHsd) mice (five weeks of age, approximately 20 g body weight; Harlan Laboratory, S. Pietro al Natisone, Udine, Italy) were subcutaneously engrafted with 15 x106 cells of the human ABC-DLBCL cell line SU-DHL-2, and randomly divided into 10 groups of six mice each. Treatment with OTX015 (50 mg/kg once daily, oral, qdx7/w x5w; Oncoethix GmbH, a wholly owned subsidiary of Merck Sharp & Dohme Corp, Lucerne, Switzerland; formerly Oncoethix SA) was initiated three days after the engraftment, while treatment with ibrutinib (5 mg/kg PO; qdx2/w x5w), everolimus (1 mg/kg PO; qdx2/w x5w), vorinostat (15 mg/kg PO; qdx2/w x5w; Selleckchem, Houston, TX, USA) or rituximab (3 mg/kg IV; qdx1/w x5w; Roche, Basel, Switzerland) was initiated when mice developed palpable tumors (100 mm3). Tumor size was measured twice weekly using a digital caliper. Tumor volumes were calculated as previously described . Mice maintenance and animal experiments were performed with study protocols approved by the local Swiss Cantonal Veterinary Authority (No. 10/2014). Tumor specimens were collected at the end of treatment. Necrosis was semi-quantitatively assessed on hematoxylin-eosin stained slides. The percentage of necrotic cells on the total amount of the neoplastic tissue was evaluated on the whole section in 3 mice per each group. Differences in tumor volumes and percentage of necrosis were calculated using the Wilcoxon rank-sum test (Stata/SE 12.1 for Mac, Stata Corporation).