No abstract

This study was designed to provide more detailed information on the subcellular sites of binding of the porphycene, termed 9-capronyloxytetrakis (methoxyethyl) porphycene (CPO), with a fluorescence resonance energy transfer (FRET) technique. The proximity of CPO to two fluorescent probes was determined: nonyl acridine orange (NAO), a dye with specific affinity for the mitochondrial lipid cardiolipin, and dihexaoxacarbocyanine iodide (DiOC 6 ), an agent that labels the endoplasmic reticulum (ER). FRET spectra indicated energy transfer between DiOC 6 and CPO but no significant transfer between NAO and CPO. These results confirm data obtained by fluorescence microscopy, suggesting a similar pattern of subcellular localization by CPO and DiOC 6 but not by CPO and NAO. However, when cells containing CPO were irradiated and then loaded with NAO, FRET between the two fluorophores was observed. Hence, a relocalization of CPO can occur during irradiation. These data provide an explanation for recent studies on CPO-catalyzed photodamage to both ER and mitochondrial Bcl-2.

According to the National Cancer Institute, an estimated 102,900 (colon) and 39,670 (rectal) new cases were obtained in 2010. An estimated 51,370 people have died from colon and rectal cancers combined. This makes colorectal cancer (CRC) the second leading cause of cancer-related deaths in the United States. Consequently, the development of an in-vivo imaging agent that is selective for CRC has long been needed. Much of the detection for tumorigenesis relies on the efficacy in detecting small tumors. Current agents are not selective and often stain tissue not associated with the cancer cells making it difficult to delineate between viable and tumorigenic entities. This project introduces a novel macrocycle conjugated to polyethylene glycol linker, which we hypothesize will serve as the template for a selective molecule with high fluorescence yields that greatly increases earlier detection. Our targeted remedy is a porphyrin that is conjugated to a peptide with an affinity for the Epidermal Growth Factor Receptor (EGFR). Porphyrins are characteristically aromatically stable, contain trademark absorption bands in the visible and near-IR range, and have fluorescence quantum yields much above the current fluorophores. This makes the macrocycle optimal for confocal laser endomicroscopy (CLE) agent production. Consequently, we use a polyethylene glycol linker in order to increase water solubility, retain low toxicity, and to achieve high fluorescence quantum yields, as well as high conjugation yields. In this research, we were able to produce both precursors to the porphyrin-peptide conjugate, MesoPOR-(mono)-3PEG and MesoPOR-(di)-3PEG. These molecules were synthesized successfully with the use of peptide conjugation mechanisms. Molecular weights were confirmed using Matrix Assisted Laser Desorption Ionization Mass Spectrometry (MALDI-MS). Characterization was performed using 1H Nuclear Magnetic Resonance (1H-NMR) and Ultraviolet-Visible Spectroscopy (UV-Vis) of the intended molecules. The synthesized molecules, MesoPOR-(mono) 3PEG and MesoPOR-(di) 3PEG, will be useful in peptide conjugation that targets EGFR. These peptide ligands will increase selectivity and detect CRC via CLE. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5735. doi:1538-7445.AM2012-5735