Dataset Information

Comparison of two cross-bridged macrocyclic chelators for the evaluation of 64Cu-labeled-LLP2A, a peptidomimetic ligand targeting VLA-4-positive tumors.

ABSTRACT: Integrin ?(4)?(1) (also called very late antigen-4 or VLA-4) plays an important role in tumor growth, angiogenesis and metastasis, and there has been increasing interest in targeting this receptor for cancer imaging and therapy. In this study, we conjugated a peptidomimetic ligand known to have good binding affinity for ?(4)?(1) integrin to a cross-bridged macrocyclic chelator with a methane phosphonic acid pendant arm, CB-TE1A1P. CB-TE1A1P-LLP2A was labeled with (64)Cu under mild conditions in high specific activity, in contrast to conjugates based on the "gold standard" di-acid cross-bridged chelator, CB-TE2A, which require high temperatures for efficient radiolabeling. Saturation binding assays demonstrated that (64)Cu-CB-TE1A1P-LLP2A had comparable binding affinity (1.2 nM vs 1.6 nM) but more binding sites (B(max)=471 fmol/mg) in B16F10 melanoma tumor cells than (64)Cu-CB-TE2A-LLP2A (B(max)=304 fmol/mg, p<0.03). In biodistribution studies, (64)Cu-CB-TE1A1P-LLP2A had less renal retention but higher uptake in tumor (11.4±2.3 %ID/g versus 3.1±0.6 %ID/g, p<0.001) and other receptor-rich tissues compared to(64)Cu-CB-TE2A-LLP2A. At 2h post-injection, (64)Cu-CB-TE1A1P-LLP2A also had significantly higher tumor:blood and tumor:muscle ratios than (64)Cu-CB-TE2A-LLP2A (CB-TE1A1P=19.5±3.0 and 13.0±1.4, respectively, CB-TE2A=4.2±1.4 and 5.5±0.9, respectively, p<0.001). These data demonstrate that (64)Cu-CB-TE1A1P-LLP2A is an excellent PET radiopharmaceutical for the imaging of ?(4)?(1) positive tumors and also has potential for imaging other ?(4)?(1) positive cells such as those of the pre-metastatic niche.

SUBMITTER: Jiang M

PROVIDER: S-EPMC3563241 | biostudies-literature | 2013 Feb

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Comparison of two cross-bridged macrocyclic chelators for the evaluation of 64Cu-labeled-LLP2A, a peptidomimetic ligand targeting VLA-4-positive tumors.

Jiang Majiong M Ferdani Riccardo R Shokeen Monica M Anderson Carolyn J CJ

Nuclear medicine and biology 20121223 2

Integrin α(4)β(1) (also called very late antigen-4 or VLA-4) plays an important role in tumor growth, angiogenesis and metastasis, and there has been increasing interest in targeting this receptor for cancer imaging and therapy. In this study, we conjugated a peptidomimetic ligand known to have good binding affinity for α(4)β(1) integrin to a cross-bridged macrocyclic chelator with a methane phosphonic acid pendant arm, CB-TE1A1P. CB-TE1A1P-LLP2A was labeled with (64)Cu under mild conditions in ...[more]

PMID: 23265977

Similar Datasets

Project description:UnlabelledMelanoma 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-affinity VLA-4 peptidomimetic ligand, LLP2A, for PET/CT imaging in a subcutaneous and metastatic melanoma tumor.MethodsLLP2A 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.Results(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.ConclusionThese 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.

Project description:UnlabelledVery-late-antigen-4 (VLA-4, α4β1 integrin, CD49d/CD29) is a transmembrane adhesion receptor that plays an important role in cancer and immune responses. Enhanced VLA-4 expression has been observed in multiple myeloma (MM) cells and surrounding stroma. VLA-4 conformational activation has been associated with MM pathogenesis. VLA-4 is a promising MM imaging and therapeutic biomarker.MethodsSpecificity of (64)Cu-LLP2A ((64)Cu-CB-TE1A1P-PEG4-LLP2A), a high-affinity VLA-4 peptidomimetic-based radiopharmaceutical, was evaluated in α4 knock-out mice and by competitive blocking in wild-type tumor-bearing mice. (64)Cu-LLP2A PET/CT (static and dynamic) imaging was conducted in C57BL6/KaLwRij mice bearing murine 5TGM1-GFP syngeneic tumors generated after intravenous injection via the tail. Blood samples were collected for serum protein electrophoresis. Bone marrow and splenic cells extracted from tumor-bearing and control mice (n= 3/group) were coincubated with the optical analog LLP2A-Cy5 and mouse B220, CD4, Gr1, and Mac1 antibodies and analyzed by fluorescence-activated cell sorting. Human radiation dose estimates for (64)Cu-LLP2A were extrapolated from mouse biodistribution data (6 time points, 0.78 MBq/animal, n= 4/group). Ten formalin-fixed paraffin-embedded bone marrow samples from deceased MM patients were stained with LLP2A-Cy5.Results(64)Cu-LLP2A and LLP2A-Cy5 demonstrated high specificity for VLA-4-positive mouse 5TGM1-GFP myeloma and nonmalignant inflammatory host cells such as T cells and myeloid/monocytic cells. Ex vivo flow cytometric analysis supported a direct effect of myeloma on increased VLA-4 expression in host hematopoietic microenvironmental elements. SUVs and the number of medullar lesions detected by (64)Cu-LLP2A PET corresponded with increased monoclonal (M) protein (g/dL) in tumor-bearing mice over time (3.29 ± 0.58 at week 0 and 9.97 ± 1.52 at week 3). Dynamic PET with (64)Cu-LLP2A and (18)F-FDG demonstrated comparable SUV in the prominent lesions in the femur. Human radiation dose estimates indicated urinary bladder wall as the dose-limiting organ (0.200 mGy/MBq), whereas the dose to the red marrow was 0.006 mGy/MBq. The effective dose was estimated to be 0.017 mSv/MBq. Seven of the ten human samples displayed a high proportion of cells intensely labeled with LLP2A-Cy5 probe.Conclusion(64)Cu-LLP2A and LLP2A-Cy5 demonstrated binding specificity for VLA-4 in an immune-competent murine MM model. (64)Cu-LLP2A displayed favorable dosimetry for human studies and is a potential imaging candidate for overexpressed VLA-4.

Dataset Information

Comparison of two cross-bridged macrocyclic chelators for the evaluation of 64Cu-labeled-LLP2A, a peptidomimetic ligand targeting VLA-4-positive tumors.

Publications

Comparison of two cross-bridged macrocyclic chelators for the evaluation of 64Cu-labeled-LLP2A, a peptidomimetic ligand targeting VLA-4-positive tumors.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets