Figure 2

GD2 expression on a subset of tumor cells in primary prostate cancer tissue with higher expression in metastatic lesions. Tissue microarrays (TMAs) composed of paired normal prostate and prostate cancer Gleason grades (3, 4 and 5) (n = 320) or 45 cases of bone and visceral metastatic samples (both obtained from the Prostate Cancer Biorepository Network) were analyzed by IHC staining for GD2. Histoscores were calculated by multiplying the staining intensity (0, negative; 1, low; 2, moderate positive; 3, strong positive) by the % tumor cells staining positive. (A, B) Representative examples of negative, low, moderate, and high GD2 staining in (A) primary, (B) bone metastatic and (C) visceral metastatic tumor samples. (D) Scattered plot shows histoscore distribution of primary tumors and normal prostate. GD2 expression is significantly higher in primary tumors than normal prostate. Data represents 34 cases of GD2 expression in tumors vs 24 in normal tissue, considering histoscore > 25 as positive. Mann–Whitney unpaired t-test used as statistical analysis; *, P < 0.05. (E) Pie charts displaying the % of cases that were GD2⁺ or GD2^- in primary and metastatic tumors samples. Histoscores of 0–5 were considered negative while scores higher than 5 were considered positive. (F, G) Frequency distribution plots histoscores plotted against (F) percentage of patients and (G) number of patients. The indicated histoscore grouping are: 0–5 (negative); 5–25 (low), 25–50 (moderate); and > 50 (strong).