Multifactorial diagnostic NIR imaging of CCK2R expressing tumors

Abstract

Optical imaging-based diagnostics identify malignancies based on molecular changes instead of morphological criteria in a non-invasive, irradiation free process. The aim of this study was to improve imaging efficiency by the development of a new Cholecystokinin-2-receptor targeted fluorescent peptide that matches the clinical needs regarding biodistribution and pharmacokinetics while displaying superior target specificity. Furthermore we performed multifactorial imaging of Cholecystokinin-2-receptor and tumor metabolism, since simultaneous targeting of various tumor biomarkers could intensely increase tumor identification and characterization. Affinity and specificity of the fluorescent Cholecystokinin-2-receptor targeted minigastrin (dQ-MG-754) were tested in vitro. We conducted in vivo imaging of the dQ-MG-754 probe alone and in a multifactorial approach with a GLUT-1 targeted probe (IR800 2-DG) on subcutaneous xenograft bearing athymic nude mice up to 24 h after intravenous injection (n = 5/group), followed by ex vivo biodistribution analysis and histological examination. We found specific, high affinity binding (Kd = 1.77 nM ± 0.6 nM) of dQ-MG-754 to Cholecystokinin-2-receptor expressing cells and xenografts as well as favorable pharmacokinetics for fluorescence-guided endoscopy. We successfully performed multifactorial imaging for the simultaneous detection of the Cholecystokinin-2-receptor and GLUT-1 targeted probe. Prominent differences in uptake patterns of the two contrast agents could be detected. The results were validated by histological examinations. The multifactorial imaging approach presented in this study could facilitate cancer detection in diagnostic imaging and intraoperative and endoscopic applications. Especially the dQ-MG-754 probe bears great potential for translation to clinical endoscopy imaging, because it combines specific high affinity binding with renal elimination and a favorable biodistribution.

Multifunctional calcium phosphate nanoparticles for combining near-infrared fluorescence imaging and photodynamic therapy

“…NP-DY682 offered just a short tumoral accumulation and a fast elimination thereafter, suggesting an enrichment due to the EPR effect (enhanced permeation and retention effect). The same accumulation kinetics was shown previously for the free dye DY-754 in A431 tumors (human epidermoid carcinoma cells) [44]. Thus, despite the different size of nanoparticles and free dye, the same favorable accumulation kinetics were obtained.…”

“…Because the free dye is rarely found in the lung [44,45], this is a real signal based on the nanoparticles. We assume that the strong signal in the lung is a result of the uptake of nanoparticles by cells of the mononuclear phagocyte system and transportation thereby to this organ.…”

Influence of d-glutamine and d-glutamic acid sequences in optical peptide probes targeted against the cholecystokinin-2/gastrin-receptor on binding affinity, specificity and pharmacokinetic properties

“…Our group recently showed that a minigastrin consisting of a six d -glutamine spacer showed promising in vitro and in vivo characteristics for optical imaging applications [20]. In detail, we found a low nanomolar affinity ( K d  = 1.8 nM), high binding specificity and selective fluorescence accumulation in CCK2R-expressing tumours in mice.…”

“…Firstly, to assess the influence of amino acid charge and hydrophilicity, we introduced a spacer of three neutral d -glutamines and three negatively charged d -glutamic acids; this strategy reduces the negative charges compared to the recently published probe [20]. Secondly, we investigated the targeting and imaging properties of a dimerized minigastrin, where a spacer of three neutral d -glutamines preceded each minigastrin molecule to gain further insight into the influence of multimerization and spacer lengths on affinity, specificity and stability.…”

Fluorescent chemical probes for accurate tumor diagnosis and targeting therapy

“…107 The 6 -Ala-Tyr-Gly-TrpMet-Asp-Phe-amid via a hydrophilic linker. 108 The binding assay demonstrated a high binding affinity for CCK2R-expressing A431 cells. After intravenous injection of the probe, a fast and longlasting accumulation in tumors was observed.…”