Dataset Information

PET imaging of very late antigen-4 in melanoma: comparison of 68Ga- and 64Cu-labeled NODAGA and CB-TE1A1P-LLP2A conjugates.

ABSTRACT: Melanoma is a malignant tumor derived from epidermal melanocytes, and it is known for its aggressiveness, therapeutic resistance, and predisposition for late metastasis. Very late antigen-4 (VLA-4; also called integrin ?4?1) is a transmembrane noncovalent heterodimer overexpressed in melanoma tumors that plays an important role in tumor growth, angiogenesis, and metastasis by promoting adhesion and migration of cancer cells. In this study, we evaluated 2 conjugates of a high-affinity VLA-4 peptidomimetic ligand, LLP2A, for PET/CT imaging in a subcutaneous and metastatic melanoma tumor.LLP2A was conjugated to 1,4,8,11-tetraazacyclotetradecane-1-(methane phosphonic acid)-8-(methane carboxylic acid) (CB-TE1A1P) and 2-(4,7-bis(carboxymethyl)-1,4,7-triazonan-1-yl)pentanedioic acid (NODAGA) chelators for (68)Ga and (64)Cu labeling. The conjugates were synthesized by solid-phase peptide synthesis, purified by reversed-phase high-performance liquid chromatography, and verified by liquid chromatography mass spectrometry. Saturation and competitive binding assays with B16F10 melanoma cells determined the affinity of the compounds for VLA-4. The biodistributions of the LLP2A conjugates were evaluated in murine B16F10 subcutaneous tumor-bearing C57BL/6 mice. Melanoma metastasis was induced by intracardiac injection of B16F10 cells. PET/CT imaging was performed at 2, 4, and 24 h after injection for the (64)Cu tracers and 1 h after injection for the (68)Ga tracer.(64)Cu-labeled CB-TE1A1P-PEG4-LLP2A and NODAGA-PEG4-LLP2A showed high affinity to VLA-4, with a comparable dissociation constant (0.28 vs. 0.23 nM) and receptor concentration (296 vs. 243 fmol/mg). The tumor uptake at 2 h after injection was comparable for the 2 probes, but (64)Cu-CB-TE1A1P-PEG4-LLP2A trended toward higher uptake than (64)Cu-NODAGA-PEG4-LLP2A (16.9 ± 2.2 vs. 13.4 ± 1.7 percentage injected dose per gram, P = 0.07). Tumor-to-muscle and tumor-to-blood ratios from biodistribution and PET/CT images were significantly higher for (64)Cu-CB-TE1A1P-PEG4-LLP2A than (64)Cu-NODAGA-PEG4-LLP2A (all P values < 0.05). PET/CT imaging of metastatic melanoma with (68)Ga-NODAGA-PEG4-LLP2A and (64)Cu-NODAGA-PEG4-LLP2A showed high uptake of the probes at the site of metastasis, correlating with the bioluminescence imaging of the tumor.These data demonstrate that (64)Cu-labeled CB-TE1A1P/NODAGA LLP2A conjugates and (68)Ga-labeled NODAGA-LLP2A are excellent imaging agents for melanoma and potentially other VLA-4-positive tumors. (64)Cu-CB-TE1A1P-PEG4-LLP2A had the most optimal tumor-to-nontarget tissue ratios for translation into humans as a PET imaging agent for melanoma.

SUBMITTER: Beaino W

PROVIDER: S-EPMC4277817 | biostudies-literature | 2014 Nov

REPOSITORIES: biostudies-literature

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PET imaging of very late antigen-4 in melanoma: comparison of 68Ga- and 64Cu-labeled NODAGA and CB-TE1A1P-LLP2A conjugates.

Beaino Wissam W Anderson Carolyn J CJ

Journal of nuclear medicine : official publication, Society of Nuclear Medicine 20140925 11

<h4>Unlabelled</h4>Melanoma is a malignant tumor derived from epidermal melanocytes, and it is known for its aggressiveness, therapeutic resistance, and predisposition for late metastasis. Very late antigen-4 (VLA-4; also called integrin α4β1) is a transmembrane noncovalent heterodimer overexpressed in melanoma tumors that plays an important role in tumor growth, angiogenesis, and metastasis by promoting adhesion and migration of cancer cells. In this study, we evaluated 2 conjugates of a high-a ...[more]

PMID: 25256059

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Project description:Lung cancer accounts for 17% of cancer-related deaths worldwide, and most patients present with locally advanced or metastatic disease. Novel PET imaging agents for assessing vascular endothelial growth factor receptor-2 (VEGFR-2) expression can be used for detecting VEGFR-2-positive malignancies and subsequent monitoring of therapeutic response to VEGFR-2-targeted therapies. Here, we report the synthesis and characterization of an antibody-based imaging agent for PET imaging of VEGFR-2 expression in vivo.Ramucirumab (named RamAb), a fully humanized IgG1 monoclonal antibody, was conjugated to 2-S-(4-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid (p-SCN-Bn-NOTA) and labeled with (64)Cu. Flow cytometry analysis and microscopy studies were performed to compare the VEGFR-2 binding affinity of RamAb and NOTA-RamAb. PET imaging and biodistribution studies were performed in nude mice bearing HCC4006 and A549 xenograft tumors. Ex vivo histopathology was performed to elucidate the expression patterns of VEGFR-2 in different tissues and organs to validate in vivo results.Flow cytometry examination revealed the specific binding capacity of fluorescein isothiocyanate-RamAb to VEGFR-2, and no difference in VEGFR-2 binding affinity was seen between RamAb and NOTA-RamAb. After being labeled with (64)Cu, PET imaging revealed specific and prominent uptake of (64)Cu-NOTA-RamAb in VEGFR-2-positive HCC4006 tumors (9.4 ± 0.5 percentage injected dose per gram at 48 h after injection; n = 4) and significantly lower uptake in VEGFR-2-negative A549 tumors (4.3 ± 0.2 percentage injected dose per gram at 48 h after injection; n = 3). Blocking experiments revealed significantly lower uptake in HCC4006 tumors, along with histology analysis, further confirming the VEGFR-2 specificity of (64)Cu-NOTA-RamAb.This study provides initial evidence that (64)Cu-NOTA-RamAb can function as a PET imaging agent for visualizing VEGFR-2 expression in vivo, which may also find potential applications in monitoring the treatment response of VEGFR-2-targeted cancer therapy.

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Dataset Information

PET imaging of very late antigen-4 in melanoma: comparison of 68Ga- and 64Cu-labeled NODAGA and CB-TE1A1P-LLP2A conjugates.

Publications

PET imaging of very late antigen-4 in melanoma: comparison of 68Ga- and 64Cu-labeled NODAGA and CB-TE1A1P-LLP2A conjugates.

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