Combination of low doses of NPI-0052 plus bortezomib inhibits human plasmacytoma growth in immunodeficient beige-nude-xid (BNX) mice. (A) Average and standard deviation of tumor volume (mm3) from group of mice (n = 3/group) versus time (days) when tumor was measured. Mice were treated with vehicle, NPI-0052 (intravenously), bortezomib (intravenously), or NPI-0052 plus bortezomib (intravenously) at the indicated doses on a twice-a-week schedule for 30 days. A significant delay in tumor growth in NPI-0052 plus bortezomib–treated mice was noted compared with vehicle-treated control mice (P = .04). Bars indicate means plus or minus SE. Inset shows tumors resected from control (vehicle) and NPI-0052 (0.025 mg/kg) plus or minus bortezomib (0.25 mg/kg)–treated mice. (B-D) Micrographs show apoptotic cells in tumors sectioned on day 30 (endpoint) from untreated or NPI-0052 (0.025 mg/kg) plus bortezomib (0.25 mg/kg)–treated mice as identified by a TUNEL assay (TUNEL-positive cells are dark brown) and caspase-3 cleavage (dark brown cells), as well as H&E and Ki-67 staining. Shown photographs are representative of similar observations in 3 different mice receiving same treatment. (B,C) Bar graphs show the quantification of TUNEL-positive cells and caspase-3 cleavage activity in tumors from NPI-0052 plus bortezomib–treated mice. Apoptotic tumor cells were enumerated in nonnecrotic areas of each section using light microscopy (magnification, 40×/0.75 NA oil). Eror bars represent standard deviation. Arrows: Immunostained tumor section of mice receiving indicated combined doses of agents.
