15 research outputs found
Dual-Labeling Strategies for Nuclear and Fluorescence Molecular Imaging: A Review and Analysis
Molecular imaging is used for the detection of biochemical processes through the development of target-specific contrast agents. Separately, modalities such as nuclear and near-infrared fluorescence (NIRF) imaging have been shown to non-invasively monitor disease. More recently, merging of these modalities has shown promise owing to their comparable detection sensitivity and benefited from the development of dual-labeled imaging agents. Dual-labeled agents hold promise for whole-body and intraoperative imaging and could bridge the gap between surgical planning and image-guided resection with a single, molecularly targeted agent. In this review, we summarized the literature for dual-labeled antibodies and peptides that have been developed and have highlighted key considerations for incorporating NIRF dyes into nuclear labeling strategies. We also summarized our findings on several commercially available NIRF dyes and offer perspectives for developing a toolkit to select the optimal NIRF dye and radiometal combination for multimodality imaging
Molecular inhibition of prostaglandin E2 with GW627368X: Therapeutic potential and preclinical safety assessment in mouse sarcoma model
Prostaglandin E2, the major COX-2 product, acts via 4 functionally distinct prostanoid receptors, EP(1-4). PGE-2, through its receptors, feeds back to positively increase COX-2 expression augmenting its own synthesis thereby driving angiogenesis, while suppressing apoptosis and innate immunity. In addition to the well characterized PGE2/EP4/cAMP/PKA/CREB, EP4 activation increases GSK3 phosphorylation via PI3K and Akt consequently reducing β-catenin phosphorylation. EP4 induces angiogenesis by enhancing VEGF production via ERK activation. These effects of EP4 are asserted either directly or via EGFR transactivation depending on the type of cancer. In view of the safety concerns regarding long term use of COX-2 inhibitors and to find more effective alternatives, we evaluated the potential of EP4 prostanoid receptor as a target for treating cancer progression using a highly selective EP4 antagonist, 4-(4,9-diethoxy-1,3-dihydro-1-oxo-2H-benz[f]isoindol-2-yl)-N-(phenylsulfonyl)-benzeneacetamide. Oral administration of GW627368X showed significant tumor regression characterized by tumor reduction and induction of apoptosis. Reduction in prostaglandin E2 synthesis also led to reduced level of VEGF in plasma. Regulation of multiple pathways downstream of EP4 was evident by down regulation of COX-2, p-Akt, p-MAPK and p-EGFR. Considering wide distribution of the EP4 prostanoid receptor in major organs and the array of physiological processes it contributes to, the safety profile of the drug was analyzed. No major organ toxicity, immunosupression, behavioral change or change in blood parameters attributable to the drug was observed. The results assert the significance of EP4 prostanoid receptor as a therapeutic target as well as the safety of EP4 blockade by GW627368X
Molecular Landers as Probes for Molecular Device-Metal Surface Interactions
Specifically designed series of molecules (landers), comprising a central rigid polyaromatic core and several spacers that decouple the board from the metallic surface, have been synthesized. UHV-STM studies, on one hand, have shown important distortions of the molecule by interaction with the substrate. On the other hand, surface restructuring results from the presence of the molecules
Hyaluronic Acid-Paclitaxel: Antitumor Efficacy against CD44(+) Human Ovarian Carcinoma Xenografts1
Numerous human tumor types, including ovarian cancer, display a significant expression of the CD44 family of cell surface proteoglycans. To develop tumor-targeted drugs, we have initially evaluated whether the CD44 ligand hyaluronic acid (HA) could serve as a backbone for paclitaxel (TXL) prodrugs. HA-TXL was prepared by modification of previous techniques. The in vitro cytotoxicity of HA-TXL against the CD44(+) human ovarian carcinoma cell lines SKOV-3ip and NMP-1 could be significantly blocked by preincubation with a molar excess of free HA. Female nude mice bearing intraperitoneal implants of NMP-1 cells were treated intraperitoneally with a single sub-maximum tolerated dose dose of HA-TXL or with multiple-dose regimens of paclitaxel (Taxol; Mead Johnson, Princeton, NJ) to determine the effects of these regimens on host survival and intraperitoneal tumor burden, with the latter being assessed by magnetic resonance imaging. NMP-1 xenografts were highly resistant to Taxol regimens, as host survival was only nominally improved compared to controls (T//C ∼ 120), whereas single-dose HA-TXL treatment significantly improved survival in this model (T//C ∼ 140; P = .004). In both NMP-1 and SKOV-3ip models, MR images of abdomens of HA-TXL-treated mice obtained shortly before controls required humane sacrifice revealed markedly reduced tumor burdens compared to control mice. This study is among the first to demonstrate that HA-based prodrugs administered locoregionally have antitumor activity in vivo
Targeted Dual-Modal PET/SPECT-NIR Imaging: From Building Blocks and Construction Strategies to Applications
Molecular imaging is an emerging non-invasive method to qualitatively and quantitively visualize and characterize biological processes. Among the imaging modalities, PET/SPECT and near-infrared (NIR) imaging provide synergistic properties that result in deep tissue penetration and up to cell-level resolution. Dual-modal PET/SPECT-NIR agents are commonly combined with a targeting ligand (e.g., antibody or small molecule) to engage biomolecules overexpressed in cancer, thereby enabling selective multimodal visualization of primary and metastatic tumors. The use of such agents for (i) preoperative patient selection and surgical planning and (ii) intraoperative FGS could improve surgical workflow and patient outcomes. However, the development of targeted dual-modal agents is a chemical challenge and a topic of ongoing research. In this review, we define key design considerations of targeted dual-modal imaging from a topological perspective, list targeted dual-modal probes disclosed in the last decade, review recent progress in the field of NIR fluorescent probe development, and highlight future directions in this rapidly developing field
Comparison of HER2-Targeted Antibodies for Fluorescence-Guided Surgery in Breast Cancer
Background. Although therapeutic advances have led to enhanced survival in patients with human epidermal growth factor receptor 2 (HER2)-positive breast cancer, detection of residual disease remains challenging. Here, we examine two approved anti-HER2 monoclonal antibodies (mAbs), trastuzumab and pertuzumab, as potential candidates for the development of immunoconjugates for fluorescence-guided surgery (FGS). Methods. mAbs were conjugated to the near-infrared fluorescent (NIRF) dye, IRDye800, and for quantitative in vitro assessment, to the radiometal chelator, desferrioxamine, to enable dual labeling with 89Zr. In vitro binding was evaluated in HER2-overexpressing (BT474, SKBR3) and HER2-negative (MCF7) cell lines. BT474 and MCF7 xenografts were used for in vivo and ex vivo fluorescence imaging. Results. In vitro findings demonstrated HER2-mediated binding for both fluorescent immunoconjugates and were in agreement with radioligand assays using dual-labeled immunoconjugates. In vivo and ex vivo studies showed preferential accumulation of the fluorescently-labeled mAbs in tumors and similar tumor-to-background ratios. In vivo HER2 specificity was confirmed by immunohistochemical staining of resected tumors and normal tissues. Conclusions. We showed for the first time that fluorescent trastuzumab and pertuzumab immunoconjugates have similar NIRF imaging performance and demonstrated the possibility of performing HER2-targeted FGS with agents that possess distinct epitope specificity
Synthesis of a Fluorescently Labeled <sup>68</sup>Ga-DOTA-TOC Analog for Somatostatin Receptor Targeting
Fluorescently labeled
imaging agents can identify surgical margins
in real-time to help achieve complete resections and minimize the
likelihood of local recurrence. However, photon attenuation limits
fluorescence-based imaging to superficial lesions or lesions that
are a few millimeters beneath the tissue surface. Contrast agents
that are dual-labeled with a radionuclide and fluorescent dye can
overcome this limitation and combine quantitative, whole-body nuclear
imaging with intraoperative fluorescence imaging. Using a multimodality
chelation (MMC) scaffold, IRDye 800CW was conjugated to the clinically
used somatostatin analog, <sup>68</sup>Ga-DOTA-TOC, to produce the
dual-labeled analog, <sup>68</sup>Ga-MMC(IRDye 800CW)-TOC, with high
yield and specific activity. <i>In vitro</i> pharmacological
assays demonstrated retention of receptor-targeting properties for
the dual-labeled compound with robust internalization that was somatostatin
receptor (SSTR) 2-mediated. Biodistribution studies in mice identified
the kidneys as the primary excretion route for <sup>68</sup>Ga-MMC(IRDye
800CW)-TOC, along with clearance via the reticuloendothelial system.
Higher uptake was observed in most tissues compared to <sup>68</sup>Ga-DOTA-TOC but decreased as a function of time. The combination
of excellent specificity for SSTR2-expressing cells and suitable biodistribution
indicate potential application of <sup>68</sup>Ga-MMC(IRDye 800CW)-TOC
for intraoperative detection of SSTR2-expressing tumors
Evaluation of Anti-LGR5 Antibodies by ImmunoPET for Imaging Colorectal Tumors and Development of Antibody–Drug Conjugates
Leucine-rich repeat-containing G-protein
coupled receptor 5 (LGR5)
is highly expressed in colorectal tumors and marks colon cancer stem
cells that drive tumor growth and metastasis. Recently, we showed
that LGR5 is a promising target for antibody–drug conjugate
(ADC) therapy. However, it is important to identify LGR5-positive
tumors that would respond to ADC treatment. Prior to drug conjugation,
we evaluated two different anti-LGR5 monoclonal antibodies (mAbs),
8F2 and 9G5, using <sup>89</sup>Zr-immunoPET to select the optimal
mAb for ADC development and tumor imaging. Binding, specificity, and
internalization were compared, and mAbs were prescreened as ADC candidates
against colon cancer cells using secondary ADCs. Both mAbs demonstrated
strong, specific binding in 293T-LGR5 cells but not 293T-vector cells.
In DLD-1 colorectal cancer cells, which express high levels of LGR5,
the mAbs rapidly internalized into lysosomes and promoted ADC-induced
cytotoxicity, with 8F2 exhibiting slightly higher potency. No binding
was detected in DLD-1-shLGR5 (LGR5 knockdown) cells. <sup>89</sup>Zr-DFO-LGR5 mAbs were generated and shown to retain high affinity
and LGR5-dependent uptake in vitro. PET/CT imaging of DLD-1 tumors
was performed 5 days postinjection of <sup>89</sup>Zr-DFO-LGR5 mAbs,
and findings were consistent with biodistribution data, which showed
significantly higher tumor uptake (%ID/g) for <sup>89</sup>Zr-DFO-8F2
(17.9 ± 2.2) compared to <sup>89</sup>Zr-DFO-9G5 (5.5 ±
1.2) and <sup>89</sup>Zr-DFO-IgG (3.8 ± 1.0). No significant
uptake was observed in DLD-1-shLGR5 tumors. This study identifies
8F2 as the optimal candidate for ADC development and provides initial
evidence that <sup>89</sup>Zr-DFO-LGR5 mAbs may be utilized to stratify
tumors which would respond best to LGR5-targeted ADC therapy