Theranostics 2011; 1:363-370. doi:10.7150/thno/v01p0363

Research Paper

Transforming a Targeted Porphyrin Theranostic Agent into a PET Imaging Probe for Cancer

Jiyun Shi1,2,3 *, Tracy W.B. Liu1,2 *, Juan Chen2, David Green2, David Jaffray1,2, Brian C. Wilson1,2, Fan Wang3, Gang Zheng1,2 ✉

1. Department of Medical Biophysics, University of Toronto, Toronto, Canada;
2. Ontario Cancer Institute, University Health Network, Toronto, Canada;
3. Medical Isotopes Research Center, Peking University, Beijing, China.
* J. Shi and T. Liu contributed equally to this work.

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Citation:
Shi J, Liu TWB, Chen J, Green D, Jaffray D, Wilson BC, Wang F, Zheng G. Transforming a Targeted Porphyrin Theranostic Agent into a PET Imaging Probe for Cancer. Theranostics 2011; 1:363-370. doi:10.7150/thno/v01p0363. Available from http://www.thno.org/v01p0363.htm

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Abstract

Porphyrin based photosensitizers are useful agents for photodynamic therapy (PDT) and fluorescence imaging of cancer. Porphyrins are also excellent metal chelators forming highly stable metallo-complexes making them efficient delivery vehicles for radioisotopes. Here we investigated the possibility of incorporating 64Cu into a porphyrin-peptide-folate (PPF) probe developed previously as folate receptor (FR) targeted fluorescent/PDT agent, and evaluated the potential of turning the resulting 64Cu-PPF into a positron emission tomography (PET) probe for cancer imaging. Noninvasive PET imaging followed by radioassay evaluated the tumor accumulation, pharmacokinetics and biodistribution of 64Cu-PPF. 64Cu-PPF uptake in FR-positive tumors was visible on small-animal PET images with high tumor-to-muscle ratio (8.88 ± 3.60) observed after 24 h. Competitive blocking studies confirmed the FR-mediated tracer uptake by the tumor. The ease of efficient 64Cu-radiolabeling of PPF while retaining its favorable biodistribution, pharmacokinetics and selective tumor uptake, provides a robust strategy to transform tumor-targeted porphyrin-based photosensitizers into PET imaging probes.

Keywords: Copper-64, Porphyrin, PET, Folate receptor, Peptides