Administration of APMS-MB-DOX microparticles (0.05 mg/kg) decreases proliferation in spheroid tumors. (A) Sections were stained for Ki-67 to assess cell proliferation. Quantification of Ki-67-positive cells per total cells counted from the same tumors (Mean +/- SEM) was scored by two individuals evaluating 5 regions at 40× magnification and counting 200 cells/region for each tumor section using a blind coding system. Treatment with APMS-MB-DOX (0.05 mg/kg) significantly decreased Ki-67-positive cells in spheroid MMs compared to saline controls (*) or groups receiving a comparable dose of DOX alone (†) (p ≤ 0.05). (B) Representative images of tissues stained for Ki-67 (4× objective); scale bar represents 100 μM. (C) Higher magnification micrographs were acquired with a 40× objective. Scale bar represents 50 μM.