Targeted Photodynamic Therapy Agent with a Built-In Apoptosis Sensor for in Vivo Near-Infrared Imaging of Tumor Apoptosis Triggered by its Photosensitization in Situ

Imaging apoptotic cells or tissues after cancer therapy in situ would be a very useful tool for assessing proper treatment conditions and therapeutic outcome. By combining therapeutic and imaging functions, we have designed a multifunctional, membrane-permeable, and cancer-specific agent that triggers and images apoptosis in targeted cells. We chose photodynamic therapy (PDT) as an appropriate cancer treatment modality and caspase 3 as an apoptosis-specific imaging target. This targeted photodynamic therapy agent with a built-in apoptosis sensor (TaBIAS) induces photodamage only to target cells and simultaneously identifies those that are apoptotic by its near-infrared fluorescence. It contains a fluorescent photosensitizer used as an anticancer drug and a cancer-associated folate receptor homing molecule connected to a caspase 3 cleavable peptide linker that has a fluorescence quencher on the opposing site. We demonstrated that PDT-triggered cleavage of the peptide linker by caspase 3, one of the key executioner caspases, results in a detectable increase in fluorescence in folate receptor–overexpressing cancer cells and tumors. The presence of apoptosis was confirmed in vitro by flow cytometry and ex vivo by Apoptag assay, supporting the ability of TaBIAS to specifically induce and image apoptosis in situ.

[1]  N. Oleinick,et al.  Dissociation of mitochondrial depolarization from cytochrome c release during apoptosis induced by photodynamic therapy , 2001, British Journal of Cancer.

[2]  R. Weissleder,et al.  Near-infrared fluorescent imaging of tumor apoptosis. , 2003, Cancer research.

[3]  R. Weissleder,et al.  In vivo imaging of S-TRAIL-mediated tumor regression and apoptosis. , 2005, Molecular therapy : the journal of the American Society of Gene Therapy.

[4]  R. Weissleder,et al.  An azulene dimer as a near-infrared quencher. , 2002, Angewandte Chemie.

[5]  D. Kessel,et al.  The Role of Subcellular Localization in Initiation of Apoptosis by Photodynamic Therapy , 1997, Photochemistry and photobiology.

[6]  Amy L. Gryshuk,et al.  Methyl pyropheophorbide-a analogues: potential fluorescent probes for the peripheral-type benzodiazepine receptor. Effect of central metal in photosensitizing efficacy. , 2005, Journal of medicinal chemistry.

[7]  D. Harrison,et al.  Apoptosis and carcinogenesis. , 1999, British journal of cancer.

[8]  S. Yonehara,et al.  Caspases Are Activated in a Branched Protease Cascade and Control Distinct Downstream Processes in Fas-induced Apoptosis , 1998, The Journal of experimental medicine.

[9]  G. Salvesen,et al.  Internally quenched fluorescent peptide substrates disclose the subsite preferences of human caspases 1, 3, 6, 7 and 8. , 2000, The Biochemical journal.

[10]  N. Thornberry,et al.  The Caspase-3 Precursor Has a Cytosolic and Mitochondrial Distribution: Implications for Apoptotic Signaling , 1998, The Journal of cell biology.

[11]  K. Schulze-Osthoff,et al.  New Approaches and Therapeutics Targeting Apoptosis in Disease , 2005, Pharmacological Reviews.

[12]  Britton Chance,et al.  Protease-triggered photosensitizing beacon based on singlet oxygen quenching and activation. , 2004, Journal of the American Chemical Society.

[13]  N. Thornberry Caspases: key mediators of apoptosis. , 1998, Chemistry & biology.

[14]  M. Brauer In vivo monitoring of apoptosis , 2003, Progress in Neuro-Psychopharmacology and Biological Psychiatry.

[15]  X. Sun,et al.  Photodynamic Therapy with Pyropheophorbide‐a Methyl Ester in Human Lung Carcinoma Cancer Cell: Efficacy, Localization and Apoptosis ¶ , 2002, Photochemistry and photobiology.

[16]  C. Reutelingsperger,et al.  Flow cytometry of apoptotic cell death. , 2000, Journal of immunological methods.

[17]  T. Dougherty,et al.  Subcellular Localization Patterns and Their Relationship to Photodynamic Activity of Pyropheophorbide‐a Derivatives , 1999, Photochemistry and photobiology.

[18]  J C Reed,et al.  Mitochondria and apoptosis. , 1998, Science.

[19]  K. Bullok,et al.  Synthesis and characterization of a small, membrane-permeant, caspase-activatable far-red fluorescent peptide for imaging apoptosis. , 2005, Journal of medicinal chemistry.

[20]  R. Voll,et al.  Viable, apoptotic and necrotic monocytes expose phosphatidylserine: cooperative binding of the ligand Annexin V to dying but not viable cells and implications for PS-dependent clearance , 2005, Cell Death and Differentiation.

[21]  Boyd C. Pratt,et al.  The Federal Presence: Architecture, Politics, and Symbols in United States Government Building , 1978 .

[22]  Britton Chance,et al.  Pyropheophorbide 2-deoxyglucosamide: a new photosensitizer targeting glucose transporters. , 2003, Bioconjugate chemistry.

[23]  T. Tsuruo,et al.  Imaging of caspase‐3 activation in HeLa cells stimulated with etoposide using a novel fluorescent probe , 1999, FEBS letters.

[24]  D. Kessel,et al.  Photodynamic therapy: A mitochondrial inducer of apoptosis , 1999, Cell Death and Differentiation.

[25]  Philip S Low,et al.  Folate receptor-mediated drug targeting: from therapeutics to diagnostics. , 2005, Journal of pharmaceutical sciences.

[26]  Virginia McAlester,et al.  A Field Guide to American Houses , 1984 .

[27]  Cynthia de Miranda National Register of Historic Places , 2006 .

[28]  J. Hakumäki,et al.  Molecular imaging of apoptosis in cancer. , 2005, European journal of radiology.

[29]  D L Evans,et al.  Analysis and discrimination of necrosis and apoptosis (programmed cell death) by multiparameter flow cytometry. , 1992, Biochimica et biophysica acta.

[30]  M S Patterson,et al.  The physics of photodynamic therapy. , 1986, Physics in medicine and biology.

[31]  Y. Lazebnik,et al.  Caspases: enemies within. , 1998, Science.

[32]  N. Thornberry,et al.  Inhibition of Human Caspases by Peptide-based and Macromolecular Inhibitors* , 1998, The Journal of Biological Chemistry.

[33]  A. Moor,et al.  Signaling pathways in cell death and survival after photodynamic therapy. , 2000, Journal of photochemistry and photobiology. B, Biology.

[34]  Q. Peng,et al.  Photodynamic Therapy , 1988, Methods in Molecular Biology.

[35]  Nancy L Oleinick,et al.  The role of apoptosis in response to photodynamic therapy: what, where, why, and how , 2002, Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology.