Characterization of TCP-1 probes for molecular imaging of colon cancer

Zhonglin Liu, Brian D. Gray, Christy Barber, Michael Bernas, Minying Cai, Lars R. Furenlid, Andrew Rouse, Charmi Patel, Bhaskar Banerjee, Rongguang Liang, Arthur F. Gmitro, Marlys H. Witte, Koon Y. Pak, James M. Woolfenden

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

Molecular probes capable of detecting colorectal cancer (CRC) are needed for early CRC diagnosis. The objective of this study was to characterize c[CTPSPFSHC]OH (TCP-1), a small peptide derived from phage display selection, for targeting human CRC xenografts using technetium-99m (99mTc)-labeled TCP-1 and fluorescent cyanine-7 (Cy7)-labeled form of the peptide (Cy7-TCP-1). 99mTc-TCP-1 was generated by modifying TCP-1 with succinimidyl-6-hydrazino-nicotinamide (S-HYNIC) followed by radiolabeling. In vitro saturation binding experiments were performed for 99mTc-TCP-1 in human HCT116 colon cancer cells. SCID mice with human HCT116 cancer xenografts were imaged with 99mTc-TCP-1 or control peptide using a small-animal SPECT imager: Group I (n = 5) received no blockade; Group II (n = 5) received a blocking dose of non-radiolabeled TCP-1. Group III (n = 5) were imaged with 99mTc-labeled control peptide (inactive peptide). SCID mice with human PC3 prostate cancer xenografts (Group IV, n = 5) were also imaged with 99mTc-TCP-1. Eight additional SCID mice bearing HCT116 xenografts in dorsal skinfold window chambers (DSWC) were imaged by direct positron imaging of 18F-fluorodeoxyglucose (18F-FDG) and fluorescence microscopy of Cy7-TCP-1. In vitro 99mTc-HYNIC-TCP-1 binding assays on HCT 116 cells indicated a mean Kd of 3.04 ± 0.52 nM. In cancer xenografts, 99mTc-TCP-1 radioactivity (%ID/g) was 1.01 ± 0.15 in the absence of blockade and was reduced to 0.26 ± 0.04 (P < 0.01) with blockade. No radioactive uptake was observed in the PC3 tumors with 99mTc-TCP-1 or HCT116 tumors with inactive peptide. Cy7-TCP-1 activity localized not only in metabolically active tumors, as defined by 18F-FDG imaging, but also in peritumoral microvasculature. In conclusion, TCP-1 probes may have a distinct targeting mechanism with high selectivity for CRC and tumor-associated vasculature. Molecular imaging with TCP-1 probes appears promising to detect malignant colorectal lesions.

Original languageEnglish (US)
Pages (from-to)223-230
Number of pages8
JournalJournal of Controlled Release
Volume239
DOIs
StatePublished - Oct 10 2016

Keywords

  • Colorectal cancer
  • Molecular imaging
  • Mouse xenograft models
  • Peptide
  • SPECT
  • Tc

ASJC Scopus subject areas

  • Pharmaceutical Science

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