In vivo antineoplastic activity of hIFN-α₂b-LV. (A) Survival curves for CRO-AP/3–injected SCID mice treated with hIFN-α₂b-LV. Data were obtained from 2 separate experiments with 16 animals each (6 mice per hIFN-α₂b-LV group, 6 mice per EGFP-LV group, and 4 mice per medium group in each experiment). hIFN-α₂b-LV–treated mice showed a statistically significant increase in the survival time compared with control mice. (B) Photograph of representative SCID mice after intraperitoneal injection of CRO-AP/3 cells and subsequent control or therapeutic treatments. Left and middle panels show ascites-bearing mice after control (medium or EGFP-LV) treatments; neoplastic ascites were characterized by a marked abdomen expansion and absence of subcutaneous lymph node involvement. Right panel shows a hIFN-α₂b-LV–treated mouse bearing a lymphomatous subcutaneous mass on the left flank. (C) Proliferative capability of ex vivo PEL cells. Analysis of [³H]-thymidine uptake was performed on PEL cells recovered from an ascites (○) and 2 peritoneal washings (■ and ▿) of 3 hIFN-α₂b-LV–treated animals; the CRO-AP/3 cell line (♦) was used as control. Data are expressed as counts per minute. A direct correlation between the expression of the therapeutic gene and the antiproliferative activity exerted on PEL cells recovered from mice was observed.