CRTpep solution (2.0 mg, 2.235 μmol) in borate buffer (pH 8.5, 0.1 M) was added to evaporated 18F-SFB and incubated for 30 min at 40☌. A fraction of the 18F-SFB solution in high-performance liquid chromatography eluent was added to a reaction vessel and evaporated. First, 18F-SFB was synthesized to an approximately 30%−40% (non–decay-corrected) radiochemical yield the radiochemical purity was more than 98%. 18F-CRTpep was synthesized using modifications of previously reported methods ( 15, 16). N-succinimidyl 4-fluorobenzoate (SFB) and ethyl 4-(trimethyl-ammonium) benzoate ( 18F-SFB precursor) were prepared as previously described ( 13, 14), with some modifications. 1–3 supplemental materials are available at ). We labeled the KLGFFKR peptide sequence (CRT peptide ) with fluorescein isothiocyanate (FITC) or 18F and evaluated its ability to detect dying cancer cells in vitro and in vivo after treatment with chemotherapeutic drugs or radiation.ĬRT peptide (CRTpep), CRTpep-FITC (KLGFFKR and KLGFFKR-FITC), and 19F-CRTpep (reference compound) were synthesized by Anygen Co. The KLGFFKR peptide motif in the cytoplasmic domain of an integrin that interacts with CRT to induce Ca 2+ binding has potential as an imaging probe for targeting ecto-CRT ( 12). Thus, molecular imaging technologies that can characterize and measure biologic processes at the cellular and molecular levels in living subjects ( 10, 11) are eagerly anticipated. However, modern medical imaging such as CT and PET requires several weeks to months to predict responsiveness. In cancer therapy, the ability to predict the response to treatment as early as possible is highly desirable. By contrast, lethal stimuli that fail to elicit sufficient endoplasmic reticulum stress, such as the nonimmunogenic drugs gemcitabine, mitomycin C, and cisplatin, do not induce the immunogenic exposure of CRT on the cell surface unless an exogenous source of endoplasmic reticulum stress is provided ( 8, 9). Surface exposure of CRT (ecto-CRT) can be induced by certain chemotherapeutic agents (e.g., oxaliplatin, mitoxantrone, and doxorubicin) and ionizing radiation and occurs within 1–4 h from the induction of immunogenic cell death, before the cells become apoptotic ( 2– 7).
Conclusion: The present results indicate that the CRT-specific peptide would enable the prediction of therapeutic response, thereby facilitating early decisions on continuation or discontinuation of immunogenic treatment.Ĭalreticulin (CRT) is a Ca 2+-binding protein located mainly in the lumen of the endoplasmic reticulum ( 1). Results: In vitro flow cytometry, immunofluorescence staining, and in vivo small-animal PET imaging results showed that CRTpep detected preapoptotic cells treated with immunogenic drugs or radiation but not those treated with the nonimmunogenic drug or a nontherapeutic dose of immunogenic drug. Methods: A synthetic CRT-specific peptide, KLGFFKR (CRTpep), was labeled with fluorescein isothiocyanate or 18F, and the characteristics of ecto-CRT were evaluated in a colon cancer cell line in vitro and in vivo. We assessed the use of a CRT-specific binding peptide for imaging ecto-CRT during immunogenic cell death and its utility for early prediction of treatment response. JSON - JSON formatted file with the same subset of the data available in the TSV-fileĬustom - Custom dataset defined by the user in TSV or JSON format.Surface-exposed calreticulin (ecto-CRT) is a well-known “eat-me” signal exhibited by dying cells that contributes to their recognition and destruction by the immune system. TSV - Tab-separated file with a subset of the data available in the XML-file RDF - Structured nanopublication data for the tissue annotations XML - An XML-file with more extensive data (including antigen sequences, protein expression, transcriptomics data, external references and more (see XSD)) for up to 10000 genes.
The show/hide columns function can be used to customize the columns in the search result list.The search result lists the genes found by the search function.