Browsing by Author "Kirby, L"

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    Improved detection of regional melanoma metastasis using 18F-6-Fluoro-N-[2-(Diethylamino)Ethyl] Pyridine-3-Carboxamide, a Melanin-specific PET probe, by perilesional administration
    (Society of Nuclear Medicine, 2011-01-01) Denoyer, D; Potdevin, T; Roselt, P; Neels, OC; Kirby, L; Greguric, I; Katsifis, A; Dorow, DS; Hicks, RJ
    The efficacy of differing routes of administration of 18F-6-fluoro-N-[2-(diethylamino)ethyl] pyridine-3-carboxamide (18F-MEL050), a new benzamide-based PET radiotracer for imaging regional lymph node metastasis in melanoma, was assessed. Methods: B16-Black/6 metastatic melanoma cells harboring an mCherry transgene were implanted into the left-upper-foot surface of 49 C57 Black/6 mice as a model of popliteal lymph node (PLN) metastasis. Ultrasound scanning of the left PLN was performed at baseline and in combination with 18F-MEL050 PET on days 5, 9, and 14. Mice were divided into 2 groups to compare the results of tracer administration either subcutaneously at the tumor site (local) or in the lateral tail vein (systemic). After PET on each imaging day, 5 mice per group—including any with evidence of metastasis—were sacrificed for ex vivo validation studies including assessment of retained radioactivity and presence of the mCherry transgene as a surrogate of nodal tumor burden. Results: Nine mice were judged as positive for PLN metastasis by ultrasound at day 5, and 8 PLNs were positive on 18F-MEL050 PET, 3 after systemic and 5 after local administration. Ex vivo analysis showed that ultrasound correctly identified 90% of positive PLNs, with 1 false-positive. 18F-MEL050 PET correctly identified 60% of positive PLNs after systemic administration and 100% after local administration with no false-positive results by either route. The average node-to-background ratio for positive PLNs was 6.8 in the systemic-administration group and correlated with disease burden. In the local-administration group, the mean uptake ratio was 48, without clear relation to metastatic burden. Additional sites of metastatic disease were also correctly identified by 18F-MEL050 PET. Conclusion: In addition to its potential for systemic staging, perilesional administration of 18F-MEL050 may allow sensitive and specific, noninvasive identification of regional lymph node metastasis in pigmented malignant melanomas. © 2011, Society of Nuclear Medicine
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    Preclinical characterization of 18FD-FPHCys, a new amino acid-based PET tracer
    (Springer, 2012-04-01) Denoyer, D; Kirby, L; Waldeck, K; Roselt, P; Neels, OC; Bourdier, T; Shepherd, R; Katsifis, A; Hicks, RJ
    The imaging potential of a new F-18-labelled methionine derivative, S-(3-[F-18]fluoropropyl)-d-homocysteine (F-18-D-FPHCys), and its selectivity for amino acid transporter subtypes were investigated in vitro and by imaging of human tumour xenografts. Expression of members of the system L (LAT isoforms 1-4 and 4F2hc) and ASCT (ASCT isoforms 1 and 2) amino acid transporter subclasses were assessed by quantitative real-time PCR in four human tumour models, including A431 squamous cell carcinoma, PC3 prostate cancer, and Colo 205 and HT-29 colorectal cancer lines. The first investigations for the characterization of F-18-D-FPHCys were in vitro uptake studies by comparing it with [1-C-14]-l-methionine (C-14-MET) and in vivo by PET imaging. In addition, the specific involvement of LAT1 transporters in F-18-D-FPHCys accumulation was tested by silencing LAT1 mRNA transcription with siRNAs. To determine the proliferative activity in tumour xenografts ex vivo, Ki-67 staining was used as a biomarker. A431 cells showed the highest F-18-D-FPHCys uptake in vitro and in vivo followed by Colo 205, PC3 and HT-29. A similar pattern of retention was observed with C-14-MET. F-18-D-FPHCys retention was strongly correlated with LAT1 expression both in vitro (R (2) = 0.85) and in vivo (R (2) = 0.99). Downregulation of LAT1 by siRNA inhibited F-18-D-FPHCys uptake, demonstrating a clear dependence on this transporter for tumour uptake. Furthermore, F-18-D-FPHCys accumulation mirrored cellular proliferation. The favourable properties of F-18-D-FPHCys make this tracer a promising imaging probe for detection of tumours as well as for the noninvasive evaluation and monitoring of tumour growth.© 2012, Springer.