In vivo therapeutic effects of atiprimod on established MCL in SCID mouse models. CB-17 SCID mice were inoculated subcutaneously in the right flank with 5 × 106 SP53 cells or Grant 519 cells. Three to 4 weeks later when palpable tumors (≥ 5 mm in diameter) developed, mice (10 per group) were treated with intraperitoneal injections of PBS or atiprimod (25 mg per kg per day) for 6 consecutive days. Tumor burdens were measured as (A) tumor volumes and (B) levels of circulating human β2M in SP53-SCID mouse sera detected by ELISA. (C) Survival of tumor-bearing SCID mice (survival times: atiprimod group versus PBS group: P < .05 in both SP53 and Grant 519 models). Arrows indicate injections of atiprimod or PBS.