In Vivo Distribution and Therapeutic Efficacy of Radioiodine-Labeled pH-Low Insertion Peptide Variant 3 in a Mouse Model of Breast Cancer

Figure 4

In vivo micro-SPECT/CT imaging and distribution of ¹²⁵I-labeled pHLIPs in MDA-MB-231, SK-BR-3, and 4T1 breast cancer xenografts. (a) Tumor-to-background ratio (TBR) of ¹²⁵I-labeled variant 3 (Var3)-pHLIP and ¹²⁵I-labeled wild-type (WT)-pHLIP in xenografts peaked at 24-48 h after injection. The TBR of ¹²⁵I-Var3-pHLIP was significantly higher than that of ¹²⁵I-WT-pHLIP at 48 h in MDA-MB-231 xenografts ( vs. , ) but was not significantly different in 4T1 ( vs. , ) and SK-BR-3 ( vs. , ) xenografts. (b) In vivo micro-SPECT/CT imaging of ¹²⁵I-Var3-pHLIP (upper) and ¹²⁵I-WT-pHLIP (lower) in mice-bearing MDA-MB-231 tumors (red arrow). (c) The radioactive count of ¹²⁵I-Var3-pHLIP and ¹²⁵I-WT-pHLIP in xenografts peaked at 2 h after injection. Compared with ¹²⁵I-WT-pHLIP, the uptake of ¹²⁵I-Var3-pHLIP was significantly higher in MDA-MB-231 xenografts at 2 h pi () but not in 4 T1 () or SK-BR-3 xenografts ().

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