IPI-504 plus bortezomib synergistically inhibits the growth of bortezomib-resistant tumors in severe combined immunodeficient mice. (A) JBR cells (107 cells per mouse) were subcutaneously inoculated into the right flank of CB17–severe combined immunodeficient mice. Tumor-bearing mice received intraperitoneal injections of 50 mg/kg IPI-504 or 0.15 mg/kg bortezomib or both (n = 6), or equal volume of vehicle (n = 9), twice a week for ≤ 3 weeks. Arrows indicate the days of injection and tumor size recording (*P < .05, **P < .01). (B) Immunohistochemical staining of consecutive sections from tumor mass of representative specimen (magnification ×200). Specific anti–human antibodies were used to stain phospho-histone H3, activated caspase-3, and BiP/Grp78 in the whole tumor samples from each treated group. (C) Three representative fields from each phospho-Histone H3 and activated (act.) caspase-3 tumor staining were recounted for the presence of positive cells, and the mean percentages of positive cells in each treated group were compared (*P < .05). (D) BiP/Grp78 levels were evaluated by Western blot analysis of BiP/Grp78 expression and densitometric quantification of BiP/β-actin ratio in 3 representative specimens per tumor group. Shown are immunoblots from 4 representative tumor samples.
