Figure 4.

Histopathologic Analysis of Treated Tumors

Tumors were ranked according to intratumoral necrosis from most to least in a blinded fashion, and representative sections from each treatment group are shown in the figure. (A) Two H&E sections representative of tumors in each treatment group are shown, with a trichrome stain to highlight fibrosis. Only capular fibrosis is present in each treatment group, with the exception of ^MPγP₂₁₀, which showed intratumoral necrosis (H&E) and dense intratumoral fibrosis (Trichrome 6) in some animals, consistent with tumor regression immediately following treatment. Mice were sacrificed on day 3 after treating with 6 mg nanoparticles. Scale bars represent 5 μm. (B) Photomicrographs of representative tumors and corresponding special stains to highlight apoptosis and proliferative index. H&E examination demonstrated areas of tumor necrosis in all treatment groups, but was most pronounced in the ^MPγP₂₁₀ treatment group. The tumor necrosis present is due to apoptosis, as demonstrated by caspase-3 staining. The proliferative index of all treatment groups is low and comparable in the viable tumor cells (1 out of 4 or about 10%–15% of total tumor cells), but due to the extensive necrosis in the ^MPγP₂₁₀ treatment group, the overall proliferative index of the tumor ^MPγP₂₁₀ is reduced (less than 2% to 3%). Mice were sacrificed on day 3 after treating with 6-mg nanoparticles. Scale bars represent 5 μm.