Real-time molecular optical micro-imaging of EGFR mutations using a fluorescent erlotinib based tracer.

BACKGROUND: EGFR mutations are routinely explored in lung adenocarcinoma by sequencing tumoral DNA. The aim of this study was to evaluate a fluorescent-labelled erlotinib based theranostic agent for the molecular imaging of mutated EGFR tumours in vitro and ex vivo using a mice xenograft model and fibred confocal fluorescence microscopy (FCFM). METHODS: The fluorescent tracer was synthesized in our laboratory by addition of fluorescein to an erlotinib molecule. Three human adenocarcinoma cell lines with mutated EGFR (HCC827, H1975 and H1650) and one with wild-type EGFR (A549) were xenografted on 35 Nude mice. MTT viability assay was performed after exposure to our tracer. In vitro imaging was performed at 1 µM tracer solution, and ex vivo imaging was performed on fresh tumours excised from mice and exposed to a 1 µM tracer solution in PBS for 1 h. Real-time molecular imaging was performed using FCFM and median fluorescence intensity (MFI) was recorded for each experiment. RESULTS: MTT viability assay confirmed that addition of fluorescein to erlotinib did not suppress the cytotoxic of erlotinib on tumoral cells. In vitro FCFM imaging showed that our tracer was able to distinguish cell lines with mutated EGFR from those lines with wild-type EGFR (p < 0.001). Ex vivo FCFM imaging of xenografts with mutated EGFR had a significantly higher MFI than wild-type (p < 0.001). At a cut-off value of 354 Arbitrary Units, MFI of our tracer had a sensitivity of 100% and a specificity of 96.3% for identifying mutated EGFR tumours. CONCLUSION: Real time molecular imaging using fluorescent erlotinib is able to identify ex vivo tumours with EGFR mutations.

A novel sulfonated prosthetic group for [18F]-radiolabelling and imparting water solubility of biomolecules and cyanine fluorophores.

Synthesis and some applications of a novel [(18)F]-fluorinated prosthetic group based on the promising sultone radiochemistry and suitable for the labelling of amine-containing (bio)chemical compounds are described. The combined sequential use of two easy and efficient conjugation reactions namely the fluoride ring-opening of a 1,3-propanesultone moiety and the aminolysis of an N-hydroxysuccinimidyl ester is the key component of this original radiolabelling strategy. The mild reaction conditions and the release of a free sulfonic acid moiety as a result of the [(18)F]-induced sultone ring-opening reaction, both make this [(18)F]-conjugation method suitable for the radiofluorination of fragile and hydrophobic biomolecules and fluorophores, particularly by making the separation of the targeted [(18)F]-tagged sulfonated compound from its starting precursor easier and thus faster. The ability of this unusual prosthetic group to readily introduce the radioisotope within complex (bio)molecular architectures has been demonstrated by (1) the preparation of the first [(18)F]-labelled cyanine 5.5 (Cy 5.5) dye, a suitable precursor for the construction of hybrid positron emission tomography/near-infrared fluorescence (PET/NIRF) imaging probes and (2) the radiolabelling of a biologically relevant peptide bearing a single lysine residue.

Synthesis of polysubstituted 3-hydroxypyridines via the revisited hetero-Diels-Alder reaction of 5-alkoxyoxazoles with dienophiles.

A general and single-step access to polysubstituted 3-hydroxypyridine scaffolds via hetero-Diels-Alder (HDA) reactions between readily prepared 5-ethoxyoxazoles and dienophiles is reported. The HDA reaction, run in the presence of Nd(OTf)(3) at room temperature, was successfully applied to various 5-ethoxyoxazoles showing good functional group tolerance, and led to a straightforward process to obtain useful building-blocks.