MT (n = 4) PyV-mT (n = 4) CT26 (n = 4) CT26 (n =

MT (n = 4) PyV-mT (n = 4) CT26 (n = 4) CT26 (n = 6) Tumor size 0.982 ?0.958 cm
MT (n = 4) PyV-mT (n = 4) CT26 (n = 4) CT26 (n = 6) Tumor size 0.982 ?0.958 cm3 0.279 ?0.086 cm3 0.15 – 0.50 cm3 0.5 – 1.5 cm3 > 1.5 cm3 < 0.15 PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/27766426 cm3 0.15 – 0.50 cm3 1 h p.i. 1.31 ?0.71 1.53 ?0.43 1.47 ?0.89 1.22 ?0.59 1.15 ?0.41 1.37 ?0.41 1.58 ?0.45 2 h p.i. 1.06 ?0.69 1.14 ?0.37 1.13 ?0.83 1.05 ?0.61 0.86 ?0.36 0.92 ?0.38 1.22 ?0.35 3 h p.i. 0.92 ?0.61 0.84 ?0.26 0.97 ?0.70 0.91 ?0.56 0.76 ?0.42 0.68 ?0.38 0.90 ?0.Data are presented as ID/cc ?SD. h: hour, p.i.: post injection. PyV-mT n = 9 mice, n = 20 tumors.Histology and immunohistochemistryFor the assessment of tumor hypoxia, pimonidazole (60 mg/kg, Chemicon PD325901 custom synthesis International, Temecula, CA, USA) was injected in some CT26 colon carcinoma bearing mice intraperitoneally 1 h before the mice were sacrificed. Tumors were fixed in 4 formalin, embedded in paraffin and cut into 5 m slices with a manual rotary microtome (RM2235; Leica, Nussloch, Germany). Slices were analyzed using the HypoxyprobeTM-1 Kit for the detection of tissue hypoxia (Chemicon International, Temecula, CA, USA) with a confocal microscope (DM 5000B, Leica, Wetzlar, Germany) and FITC-fluorescence (primary antibody: Hypoxyprobe-1Mab1). A control stain was performed with PBS instead of the primary antibody. Hematoxylin and eosin (H E) stains were performed on subsequent slices according to standard procedures [33].StatisticsDifferences in [18F]FAZA tumor type-dependent uptake were compared using a two-sample Student’s t-test. Differences in [18F]FAZA uptake according to the breathing protocol were analyzed using the Wilcoxon test and the JMP software package (SAS Institute Inc, Cary, NC, USA). Data were represented as the mean ?standard deviation (SD). A value for p < 0.05 was considered to be statistically significant, and a value for p < 0.01 was highly statistically significant.ResultsEvaluation of tumor type-dependent [18F]FAZA uptakePyV-mT mammary carcinoma and CT26 colon carcinoma-bearing mice were imaged 1 h, 2 h and 3 h after injection of 12.3 ?1.0 MBq [18F]FAZA using breathing protocol P0 (Figure 1A and 1B; P0 breathing protocol). Absolute tracer uptake decreased in the PyV-mT mammary carcinomas from 1.31 ?0.71 ID/cc at 1 h to 0.92 ?0.61 ID/cc at 3 h and decreased in the CT26 colon carcinomas from 1.53 ?0.43 ID/cc at 1 h to 0.84 ?0.26 ID/cc at 3 h (Figure 2, Table 1). Absolute tracer uptake in muscle tissue in both mouse strains (C57BL/6, BALB/c) decreased much more pronounced than incarcinomas. No statistically significant differences in [18F]FAZA uptake were found between the endogenous PyV-mT mammary carcinomas and the exogenous subcutaneous CT26 colon carcinomas (p = 0.29; Figure 2, Table 1). Figure 3 represents the dynamics of the [18F] FAZA uptake in a CT26 colon carcinoma-bearing mouse over 3 h (breathing protocol P0), indicating that the peak uptake was achieved 20 min post injection (p. i.), whereas the T/M is highest at 3 h p.i. The [ 18 F]FAZA-PET data from PyV-mT mammary carcinomas and CT26 colon carcinomas were further analyzed according to tumor sizes (Table 1). Endogenous PyV-mT mammary carcinomas were classified into three groups: 1) tumors that were smaller than 0.5 cm3; 2) tumors that were between 0.5 cm3 and 1.5 cm3 and 3) tumors that were larger than 1.5 cm3. Statistical analysis did not reveal any significant differences at any scan time between small, medium sized, and large PyVmT mammary carcinomas. Similar to the PyV-mT mammary carcinomas, the CT26 colon carcinomas were classified into tum.