Tumor Imaging Agent Research Articles

Role of thyroid scintigraphy vs. fine needle aspiration cytology in the clinical evaluation of solitary thyroid nodule a clinicoradiopathologic study

To asses the value of qualitative and quantitative analysis of the radioisotopes 99m Tc tetrofosmin (Myoview) and 99m Tc (V) DMSA in the evaluation of malignant solitary thyroid cold nodule pre-operatively and to verify their exact value in diagnosis of differentiated thyroid carcinoma. In general there is a 5%-10% chance of malignancy in all thyroid nodules for the total population with higher incidence in single cold nodule than in multinodular goiter. The main role of 99m Tc (V) DMSA as a tumor imaging agent is in the diagnosis and follow-up of patients with medullary cancer thyroid. This work included 103 patients, 88 females and 15 males with a mean age of (37.86±13.59 years). All studied were subjected to history taking, proper clinical examination, thyroid function test profile, thyroid radioisotope imaging ( 99m Tc pertechnetate, 99m Tc tetrofosmin and 99m Tc (V) DMSA thyroid scans) and cytologic assessment of thyroid nodule proved to be cold on conventional thyroid scan. The current study combined both 99m Tc tetrofosmin and 99m Tc (V) DMSA to evaluate thyroid cold nodules and to verify possibility to differentiate between benign and malignant lesions preoperatively and as confirmed on cytology of lesions obtained by fine needle aspiration cytology (FNAC) modality. Our results showed that 99m Tc pertechnetate scan alone is not a reliable diagnostic tool to differentiate between benign and malignant thyroid nodules and that high early myoview uptake in the cold nodule is not specific for malignancy, it is also concluded that both 99m Tc tetrofosmin and 99m Tc (V) DMSA thyroid scans are valuable diagnostic tools when combined together.

Metabolic stability and biological evaluation of 99mTc-HYNIC-Tyr3-Octreotide as somatostatin receptor positive tumor imaging agent

In this study, metabolic stability and biological evaluation of 99mTc labelled 6-hydrazinopyridine-3-carboxylic-acid (HYNIC)-Tyr3-Octreotide was reported as a candidate for imaging somatostatin-receptor (SSTR)-positive tumors. The metabolic stability analysis did not show any evidence of breaking of the labeled compound and formation of free 99mTc. In biodistribution and scintigraphy imaging study, radiopeptide have showed high and receptor-specific uptake in the SSTR2 positive organs, tumor with rapid renal excretion from non-target tissues, illustrating the excellent properties of this agent for SSTR tumor imaging.

Synthesis and evaluation of novel Tc-99m labeled NGR-containing hexapeptides as tumor imaging agents.

Asparagine-glycine-arginine (NGR)-containing peptides targeting aminopeptidase N (APN)/CD13 can be an excellent candidate for targeting ligands in molecular tumor imaging. In this study, we developed two NGR-containing hexapeptides, and evaluated the diagnostic performance of Tc-99m labeled hexapeptides as molecular imaging agents in an HT-1080 fibrosarcoma-bearing murine model. Peptides were synthesized using Fmoc solid-phase peptide synthesis. Radiochemical purity of Tc-99m was evaluated using instant thin-layer chromatography. The uptake of two NGR-containing hexapeptides within HT-1080 cells was evaluated in vitro. In HT-1080 fibrosarcoma tumor-bearing mice, gamma images were acquired. A biodistribution study was performed to calculate percentage of the injected dose per gram of tissue (%ID/g). Two hexapeptides, glutamic acid-cysteine-glycine (ECG)-NGR and NGR-ECG were successfully synthesized. After radiolabeling procedures with Tc-99m, the complexes Tc-99m hexapeptides were prepared in high yield. The uptake of Tc-99m ECG-NGR within the tumor cells had been assured by in vitro studies. The gamma camera imaging in the murine model showed that Tc-99m ECG-NGR was accumulated substantially in the subcutaneously engrafted tumor. However, Tc-99m NGR-ECG was accumulated minimally in the tumor. Two NGR-containing hexapeptides, ECG-NGR and NGR-ECG were developed as molecular imaging agents to target APN/CD13 in HT-1080 fibrosarcoma. Tc-99m ECG-NGR showed a significant uptake in the tumor, and it is a good candidate for tumor imaging.

Comparison of BTSE-RGD with DOTA-RGD as a potential imaging agent for tumors

RGD and its analogues are very important compounds and can be used as potential tumor-targeting agents.

Synthesis and preliminary evaluation of a new (99m)tc labeled substance p analogue as a potential tumor imaging agent.

Neurokinin 1 receptors (NK1R) are overexpressed on several types of important human cancer cells. Substance P (SP) is the most specific endogenous ligand known for NK1Rs. Accordingly,a new SP analogue was synthesized and evaluated for detection of NK1R positive tumors.[6-hydrazinopyridine-3-carboxylic acid (HYNIC)-Tyr(8)-Met(O)(11)-SP] was synthesized and radiolabeled with (99m)Tc using ethylenediamine-N,N'-diacetic acid (EDDA)and Tricine as coligands. Common physicochemical properties of radioconjugate were studied and in-vitro cell line biological tests were accomplished to determine the receptor mediated characteristics. In-vivo biodistribution in normal and tumor bearingnude mice was also assessed. The cold peptide was prepared in high purity (>99%) and radiolabeled with (99m)Tc at high specific activities (84-112GBq/µmol) with an acceptable labeling yield (>95%). The radioconjugate was stable in-vitro in the presence of human serum and showed 44% protein binding to human serumalbumin. In-vitro cell line studies on U373MG cells showed an acceptable uptake up to 4.91 ± 0.22% with the ratio of 60.21 ± 1.19% for its specific fraction and increasing specific internalization during 4 h. Receptor binding assays on U373MG cells indicated a mean Kd of 2.46 ± 0.43 nM and Bmax of 128925 ± 8145 sites/cell. In-vivo investigations determined the specific tumor uptake in 3.36 percent of injected dose per gram (%ID/g) for U373MG cells and noticeable accumulations of activity in the intestines and lung. Predominant renal excretion pathway was demonstrated. Therefore, this new radiolabeled peptide could be a promising radiotracer for detection of NK1R positive primary or secondary tumors.

Perylene-diimide-based nanoparticles as highly efficient photoacoustic agents for deep brain tumor imaging in living mice.

In order to promote preclinical and clinical applications of photoacoustic imaging, novel photoacoustic contrast agents are highly desired for molecular imaging of diseases, especially for deep tumor imaging. Here, perylene-3,4,9,10-tetracarboxylic diiimide-based near-infrared-absorptive organic nanoparticles are reported as an efficient agent for photoacoustic imaging of deep brain tumors in living mice with enhanced permeability and retention effect.

GPER-Targeted, 99mTc-Labeled, Nonsteroidal Ligands Demonstrate Selective Tumor Imaging and In Vivo Estrogen Binding

Our understanding of estrogen (17β-estradiol, E2) receptor biology has evolved in recent years with the discovery and characterization of a 7-transmembrane-spanning G protein-coupled estrogen receptor (GPER/GPR30) and the development of GPER-selective functional chemical probes. GPER is highly expressed in certain breast, endometrial, and ovarian cancers, establishing the importance of noninvasive methods to evaluate GPER expression in vivo. Here, we developed (99m)Tc-labeled GPER ligands to demonstrate the in vivo status of GPER as an estrogen receptor (ER) and for GPER visualization in whole animals. A series of (99m)Tc(I)-labeled nonsteroidal tetrahydro-3H-cyclopenta[c]quinolone derivatives was synthesized utilizing pyridin-2-yl hydrazine and picolylamine chelates. Radioligand receptor binding studies revealed binding affinities in the 10 to 30 nmol/L range. Cell signaling assays previously demonstrated that derivatives retaining a ketone functionality displayed agonist properties, whereas those lacking such a hydrogen bond acceptor were antagonists. In vivo biodistribution and imaging studies performed on mice bearing human endometrial and breast cancer cell xenografts yielded significant tumor uptake (0.4-1.1%ID/g). Blocking studies revealed specific uptake in multiple organs (adrenals, uterus, and mammary tissue), as well as tumor uptake with similar levels of competition by E2 and G-1, a GPER-selective agonist. In conclusion, we synthesized and evaluated a series of first-generation (99m)Tc-labeled GPER-specific radioligands, demonstrating GPER as an estrogen-binding receptor for the first time in vivo using competitive binding principles, and establishing the utility of such ligands as tumor imaging agents. These results warrant further investigation into the role of GPER in estrogen-mediated carcinogenesis and as a target for diagnostic/therapeutic/image-guided drug delivery. These studies provide a molecular basis to evaluate GPER expression and function as an ER through in vivo imaging.

Are there differences between macrocyclic gadolinium contrast agents for brain tumor imaging? Results of a multicenter intraindividual crossover comparison of gadobutrol with gadoteridol (the TRUTH study).

Gadobutrol (Gadavist) and gadoteridol (ProHance) have similar macrocyclic molecular structures, but gadobutrol is formulated at a 2-fold higher (1 mol/L versus 0.5 mol/L) concentration. We sought to determine whether this difference impacts morphologic contrast-enhanced MR imaging. Two hundred twenty-nine adult patients with suspected or known brain tumors underwent two 1.5T MR imaging examinations with gadoteridol or gadobutrol administered in randomized order at a dose of 0.1 mmol/kg of body weight. Imaging sequences and T1 postinjection timing were identical for both examinations. Three blinded readers evaluated images qualitatively and quantitatively for lesion detection and for accuracy in characterization of histologically confirmed brain tumors. Data were analyzed by using the Wilcoxon signed rank test, the McNemar test, and a mixed model. Two hundred nine patients successfully completed both examinations. No reader noted a significant qualitative or quantitative difference in lesion enhancement, extent, delineation, or internal morphology (P values = .69-1.00). One hundred thirty-nine patients had at least 1 histologically confirmed brain lesion. Two readers found no difference in the detection of patients with lesions (133/139 versus 135/139, P = .317; 137/139 versus 136/139, P = .564), while 1 reader found minimal differences in favor of gadoteridol (136/139 versus 132/139, P = .046). Similar findings were noted for the number of lesions detected and characterization of tumors (malignant/benign). Three-reader agreement for characterization was similar for gadobutrol (66.4% [κ = 0.43]) versus gadoteridol (70.3% [κ = 0.45]). There were no significant differences in the incidence of adverse events (P = .199). Gadoteridol and gadobutrol at 0.1 mmol/kg of body weight provide similar information for visualization and diagnosis of brain lesions. The 2-fold higher gadolinium concentration of gadobutrol provides no benefit for routine morphologic imaging.

Development of (111)In-labeled porphyrins for SPECT imaging.

The aim of this research was the development of (111)In-labeled porphyrins as possible radiopharmaceuticals for the imaging of tumors. Ligands, 5, 10, 15, 20-tetrakis (3, 5-dihydroxyphenyl) porphyrin) (TDHPP), 5, 10, 15, 20-tetrakis (4-hydroxyphenyl) porphyrin (THPP) and 5, 10, 15, 20-tetrakis (3,4-dimethoxyphenyl) porphyrin) (TDMPP) were labeled with (111)InCl3 (produced from proton bombardment of natCd target) in 60 min at 80 ºC. Quality control of labeled compounds was performed via RTLC and HPLC followed by stability studies in final formulation and presence of human serum at 37 ºC for 48 h as well as partition coefficient determination. The biodistribution studies performed using tissue dissection and SPECT imaging up to 24h. The complexes were prepared with more than 99% radiochemical purity (HPLC and RTLC) and high stability to 48 h. Partition coefficients (calculated as log P) for (111)In-TDHPP, (111)In-THPP and (111)In-TDMPP were 0.88, 0.8 and 1.63 respectively. Due to urinary excretion with fast clearance for (111)In-TDMPP, this complex is probably a suitable candidate for considering as a possible tumor imaging agent.

Abstract 4923: Gallium-68- and Copper-64-labeled LLP2A conjugates for PET-CT imaging of integrin α4β1 in melanoma

Abstract Introduction: Melanoma is a malignant tumor derived from epidermal melanocytes, and it is known for its therapeutic resistance, aggressive clinical behavior, and predisposition for late metastasis. Integrin α4β1 is a transmembrane non-covalent heterodimer overexpressed in melanoma tumors that plays an important role in tumor growth, angiogenesis and metastasis by promoting adhesion and migration of cancer cells. There has been increasing interest in targeting this receptor for cancer imaging and therapy. In this study we evaluated three conjugates of a peptidomimetic ligand, LLP2A known to have high binding affinity for α4β1 for PET-CT imaging and potential radiotherapy. Methods: LLP2A was conjugated to three different chelators, CB-TE1A1P, NODAGA and DOTA, for 68Ga and 64Cu labeling. The conjugates were synthesized by solid phase peptide synthesis, purified by RP-HPLC and verified by LC-MS mass spectrometry. 68Ga and 64Cu labeling was done in acetate buffer pH 4 for 68Ga and pH 6.5 for 64Cu at 70°C for 20 min. High Specific activity (1 mCi/µg) and radiopurity (>98%) were achieved. Saturation binding and competitive binding assays with B16F10 melanoma cells determined the binding affinity of the compounds. The biodistributions of the LLP2A conjugates were evaluated in B16F10 subcutaneous tumor bearing C57BL/6 mice. PET-CT imaging was performed at 2, 4 and 24 h post-injection for the 64Cu tracers and 1h post-injection for 68Ga tracer. Results: The competitive binding assay indicated that Ga-NODAGA-PEG4-LLP2A had higher affinity (IC50 = 0.68, Ki = 0.11 nM) compared to Ga-DOTA-PEG4-LLP2A (IC50 = 9.37, Ki = 1.56 nM); however, biodistribution showed similar tumor uptake for 68Ga-NODAGA-PEG4-LLP2A and 68Ga-DOTA-PEG4-LLP2A (8.7 ± 1.3 %ID/g and 9.1 ± 0.9 %ID/g respectively) but less renal and liver retention for the DOTA conjugate. Both 64Cu-labeled CB-TE1A1P-PEG4-LLP2A and NODAGA-PEG4-LLP2A showed high affinity to α4β1 integrin with a comparable Kd (0.28 nM vs 0.23 nM) and Bmax (296 fmol/mg vs 243 fmol/mg). The tumor uptake at 2 h post-injection was comparable for the two probes but 64Cu-CB-TE1A1P-PEG4-LLP2A had higher uptake compared to 64Cu-NODAGA-PEG4-LLP2A (16.9 ± 2.2 %ID/g vs13.4 ± 1.7 %ID/g). Tumor to muscle and tumor to blood ratios from biodistribution and PET-CT images were significantly higher for 64Cu-CB-TE1A1P-PEG4-LLP2A compared to 64Cu-NODAGA-PEG4-LLP2A. In addition, liver and kidney uptake was 2-fold lower for 64Cu-CB-TE1A1P-PEG4-LLP2A. Conclusion: These data demonstrate that 68Ga-labeled DOTA, NODAGA and 64Cu-labeled CB-TE1A1P, NODAGA LLP2A conjugates are excellent imaging agents for melanoma or other α4β1-positive tumors, with 64Cu-CB-TE1A1P-PEG4-LLP2A being the best. These data also suggest the potential for radiotherapy and radiotheranostics using radioisotopes like Lu-177, Y-90 and Cu-67. Citation Format: Wissam Beaino, Carolyn J. Anderson. Gallium-68- and Copper-64-labeled LLP2A conjugates for PET-CT imaging of integrin α4β1 in melanoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4923. doi:10.1158/1538-7445.AM2014-4923

Abstract CT224: Pilot study in patients with advanced solid tumors to evaluate feasibility of ferumoxytol (FMX) as tumor imaging agent prior to MM-398, a nanoliposomal irinotecan (nal-IRI)

Abstract Introduction MM-398, a stable nanoliposomal irinotecan (nal-IRI), is designed to exploit leaky tumor vasculature for enhanced drug delivery to tumors. Tumor deposition of nal-IRI and subsequent irinotecan conversion by CES enzymes in both neoplastic cells and tumor associated macrophages (TAM) may positively correlate with activity. Predictive biomarkers to measure tumor deposition could identify patients likely to benefit from nal-IRI. FMX is a 30nm iron-oxide, superparamagnetic nanoparticle with MRI contrast properties. The particle size, its propensity for uptake by TAMs and similar distribution patterns to nal-IRI in preclinical models led to a clinical study evaluating the feasibility of correlating FMX-based MRI (Fe-MRI) acquisition with tissue drug metabolite levels and other biomarkers to estimate drug delivery to tumor. Patients and methods Eligible patients (n=12) with refractory solid tumors with at least two metastatic lesions >2cm accessible for a percutaneous biopsy were enrolled from one institution. Fe-MRI scans were performed on a 1.5T MRI using T2* iron sensitive sequences prior to and following FMX infusion (0.5h, 24h, 72h). MR images were used to direct biopsies at 72h to FMX high or low regions, permitting intra- and inter-patient comparisons of FMX and nal-IRI tumor levels. Patients continued on nal-IRI at 80mg/m2 q2w until progression. Tissue iron and TAM distribution were assessed by IHC, tissue-bound metabolite levels by mass-spectrometry. T2* signal was used to calculate FMX levels in total lesions along with FMX estimates on biopsy images derived from fused MRI-CT biopsy images. The first 9 patients (2M 7F; median age 57 years, range 28-71 years) are reported. Results There were no safety-related or other potential interactions with nal-IRI and FMX. Adverse events of nal-IRI were consistent with previous studies. FMX levels, quantified in 36 tumor lesions from the first 9 subjects, showed mean FMX accumulation of 37.9 mcg/mL [3.3-101.2 mcg/mL] and 13.2 mcg/mL [0.1-41.0 mcg/mL] at 24h and 72h, respectively. Lesions were localized mostly in liver (67%) and lymph nodes/peritoneal sites (25%). A mechanistic PK model indicated that tissue permeability to FMX contributed to Fe-MRI signals at 24h, while FMX binding contributed at 72h. Levels of irinotecan and SN-38 were 3.59mcg/g [2.29-4.89mcg/g] and 11.43ng/g [4.04-18.8ng/g], respectively, at 72h in biopsies from the first 6 patients. Conclusions This study is one of the first to measure active metabolite SN-38 levels in patient tumors. FMX can be used as a tumor contrast agent prior to nal-IRI treatment. T2* MRI sequences allowed for quantitation of FMX concentrations in tumor and reference tissue. A mechanistic model provided an estimation of FMX tumor tissue permeability and binding that may be useful as a predictive biomarker of nanotherapeutics such as nal-IRI. Citation Format: Ramesh K. Ramanathan, Ronald L. Korn, Jasgit C. Sachdev, Gerald J. Fetterly, Katie Marceau, Vickie Marsh, John M. Neil, Ronald G. Newbold, Natarajan Raghunand, Joshua Prey, Stephan G. Klinz, Eliel Bayever, Jonathan B. Fitzgerald. Pilot study in patients with advanced solid tumors to evaluate feasibility of ferumoxytol (FMX) as tumor imaging agent prior to MM-398, a nanoliposomal irinotecan (nal-IRI). [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr CT224. doi:10.1158/1538-7445.AM2014-CT224

Synthesis, physicochemical and biological evaluation of technetium-99m labeled lapatinib as a novel potential tumor imaging agent of Her-2 positive breast cancer

Tumors that are Her-2-positive tend to grow and spread more quickly than other types of breast cancer. Overexpression of Her-2 can be a predictive biomarker for stratification of patients for therapy with Herceptin (containing humanized IgG1 monoclonal antibody trastuzumab) or Tykerb (containing lapatinib di-p-toluenesulfonate) drug. Usually, Her-2 status is determined by immunohistochemical (IHC) as well as fluorescent or chromogenic in situ hybridisation (FISH or CISH) analysis of biopsy material. The objective of the present work was to standardize the conjugation of anti-cancer drug lapatinib (which recognizes selectively the Her-2 extracellular domain) with technetium-99m complex, of type ‘4+1’, to obtain 99mTc(NS3)(CN-lapatinib) conjugate for use as in vivo tracer of the Her-2 expression in breast cancer. The conjugate 99mTc(NS3)(CN-lapatinib) was formed with high yield, high radiochemical purity and specific activity within the range 25–30 GBq/μmol. The biological in vitro and in vivo studies of the conjugate showed its high affinity to Her-2 receptor (Kd = 3.5 ± 0.4 nM, Ki = 2.9 ± 0.5 nM, Bmax = 2.4 ± 0.3 nM, approximate number of 2.4 × 106 binding sites per cell, IC50 = 41.2 ± 0.4 nM) and also pointed out to the clearance through the hepatic and renal route in comparable degree. Basing on these results one can conclude that 99mTc(NS3)(CN-lapatinib) conjugate could be a promising radiopharmaceutical for in vivo diagnosis of the Her-2 status in breast with impact on treatment planning.

Emerging roles of metal solute carriers in cancer mechanisms and treatment.

The literature concerning the roles of metal transporting solute carriers in the development and progression of human cancer, and in the delivery of metal-containing anticancer drugs, chemical carcinogens and imaging agents, is reviewed. A range of different solute carrier families, including members from the SLC2A, SLC11A, SLC22A, SLC25A, SLC30A, SLC31A, SLC39A, SLC40A, SLC47A and SLCO1B families, and various metal substrates, including arsenic, copper, gadolinium, iron, platinum and zinc, have been implicated in these cancer-related transport processes. For example, the transport of platinum-based anticancer drugs has been reported to be influenced by the expression and activities of OCT1-3 (SLC22A1-3), OCTN1/2 (SLC22A4/5), CTR1/2 (SLC31A1/2) and MATE1/2 (SLC47A1/2) solute carriers. As another example, solute carriers mediate control over the availability of endogenous metal ions, such as copper, iron and zinc, may have key roles in regulating tumour angiogenesis, cell proliferation, epithelial-to-mesenchymal transition and aberrant MAPK and STAT-3 signal transduction in cancer. In conclusion, emerging mechanisms involving metal transporting solute carriers are being defined and seem likely to make major contributions to cancer development and progression, and to the delivery of anticancer and tumour imaging agents.

Development of human serum albumin conjugated with near-infrared dye for photoacoustic tumor imaging.

Photoacoustic (PA) imaging has emerged as a noninvasive diagnostic method which detects ultrasonic waves thermoelastically induced by optical absorbers irradiated with laser. For tumor diagnosis, PA contrast agent has been proposed to enhance the PA effect for detecting tumors sensitively. Here, we prepared a human serum albumin (HSA) conjugated with indocyanine green (ICG) as a PA contrast agent allowing enhanced permeability and retention effect for sensitive tumor imaging. The feasibility of PA imaging with HSA-ICG to detect allografted tumors was evaluated in tumor-bearing mice. In vivo fluorescence imaging and radiolabeled biodistribution study showed that the biodistribution dramatically changed as the number of ICG bound to HSA increased, and the maximum accumulation of ICG was achieved when around three ICG molecules were loaded on an HSA. In vivo PA imaging demonstrated a tumor-selective and dose-dependent increase of PA signal intensity in mice injected with HSA-ICG (R2 = 0.88, 387% increase for HSA-ICG, 104 nmol ICG). In conclusion, HSA-ICG clearly visualized the allografted tumors with high tumor-to-background ratios having high quantitative and spatial resolution for the sensitive PA imaging of tumors. HSA-ICG could be useful as a favorable contrast agent for PA tumor imaging for the management of cancer.

Intraoperative Tumor Imaging with Indocyanine Green in Head and Neck Cancer Patients

Objectives: (1) Describe the effectiveness of indocyanine green (ICG) as an imaging agent for head and neck tumors. (2) Illustrate the potential of near-infrared imaging for intraoperative visualization of cancers. Methods: Patients underwent intravenous administration of 7.5mg ICG during the surgical procedure. The SPY/LUNA (Novadaq) near-infrared intraoperative imaging system was used prior to resection and the Pearl (LICOR) and Odyssey (LICOR) systems for ex-vivo tumor imaging. Tumor-to-background ratio (TBR) was defined as tumor fluorescence divided by normal tissue fluorescence. Histologic analysis was performed with a head and neck cancer board-certified pathologist. Results: Five patients were enrolled into this study between August and September 2013. Three patients had pharyngeal cancer, one had laryngeal cancer, and one had cutaneous cancer. TBR values of confirmed cancer tissue varied among patients (LUNA TBR 3-9, Pearl TBR 3-18). However, in 2 patients, areas of highest fluorescence were found to be absent of carcinoma on histological analysis. The epidermal portions of the cutaneous SCC lesion were highly fluorescent, but the tumor did not penetrate this layer in multiple sections. Histologic analysis of these tissues confirmed significant areas of acute and chronic inflammation at areas of high fluorescence intensity. Skin, mucosal surfaces, and perivascular areas were most prone to false-positive high fluorescence. Conclusions: While intravenous ICG does accumulate in head and neck tumors sufficiently to distinguish them from normal tissue, it is not specific enough to serve as a tumor visualization agent. Targeted fluorescent probes will likely be needed for image-guided surgery.

LAT-1 based primary breast cancer detection by [99m]Tc-labeled DTPA-bis-methionine scintimammography: first results using indigenously developed single vial kit preparation.

To evaluate the diagnostic utility of a single vial ready to label with [99m]Tc kit preparation of DTPA-bis-methionine (DTPA-bis-MET) for the detection of primary breast cancer. The conjugate (DTPA-bis-MET) was synthesized by covalently conjugating two molecules of methionine to DTPA and formulated as a single vial ready to label with [99m]Tc lyophilized kit preparations. Thirty female patients (mean age=47.5±11.8 years; range=21-69 years) with radiological/clinical evidence of having primary breast carcinoma were subjected to [99m]Tc-methionine scintigraphy. The whole body (anterior and posterior) imaging was performed on all the patients at 5 minutes, 10 minutes, 1 hour, 2 hours, and 4 hours following an intravenous administration of 555-740 MBq radioactivity of [99m]Tc-methionine. In addition, scintimammography (static images; 256×256 matrix) at 1, 2, and 4 hours was also performed on all the patients. The resultant radiolabel, that is, [99m]Tc-DTPA-bis-MET, yielded high radiolabeling efficiency (>97.0%), radiochemical purity (166-296 MBq/μmol), and shelf life (>3 months). The radiotracer primarily gets excreted through the kidneys and localizes in the breast cancer lesions with high target-to-nontarget ratios. The mean±SD ratios on the scan-positive lesions acquired at 1, 2, and 4 hours postinjection were 3.6±0.48, 3.10±0.24, and 2.5±0.4, respectively. [99m]Tc-methionine scintimammography demonstrated an excellent sensitivity and positive predictive value of 96.0% each for the detection of primary breast cancer. Ready to label single vial kit formulations of DTPA-bis-MET can be easily synthesized as in-house production and conveniently used for the scintigraphic detection of breast cancer and other methionine-dependent tumors expressing the L-type amino acid transporter-1 receptor. The imaging technique thus could be a potential substitute for the conventional single-photon emission computed tomography (SPECT)-based tumor imaging agents, especially for tracers with nonspecific mitochondrial uptake. However, the diagnostic efficacy of [99m]Tc-methionine needs to be evaluated in a large cohort of patients through further multicentric trials.

Physico-chemical and toxicological characterization of iron-containing albumin nanoparticles as platforms for medical imaging.

Iron oxide-containing magnetic nanoparticles (MNPs) have certain advantages over currently used contrast agents for tumor imaging by magnetic resonance imaging (MRI) as they offer the possibility of functionalization with ligands and tracers. Functionalized MNPs also may be used for targeted tumor therapy. In the current study nanoparticles (NPs) consisting of recombinant human serum albumin (rHSA) with incorporated hydrophilic (NH4)2Ce(IV)(NO3)6-γ-Fe2O3 particles (CAN maghemite particles) for medical imaging were produced and characterized. For this purpose CAN maghemite particles were incorporated into an rHSA matrix to yield rHSA-NPs. The resulting NPs were analyzed by transmission electron microscopy, photon correlation spectroscopy, and atomic absorption. The sizes of the manufactured NP were 170 ± 10 nm, and the zeta-potential was -50 ± 3 mV. The NPs remained stable when stored after lyophilization with sucrose 3% [w/v] as a cryoprotector. They showed pro-inflammatory properties without cell and animal toxicity in vivo and were highly contrasting in MRI. In conclusion, this report introduces novel rHSA NP with favorable properties containing iron oxide for detection by MRI.

Synthesis and preliminary evaluation of 68Ga-NOTA-IF7 as a tumor imaging agent

With the aim of developing a new tumor imaging agent, the IFLLWQR (Ile-Phe-Leu–Leu-Trp-Glu-Arg, IF7) was conjugated with 1, 4, 7-triazacyclononane-N, N’, N’’-triacetic acid (NOTA) and labeled with 68Ga. In the optimal conditions, the whole radio-synthesis was accomplished within 20 min. The decay-corrected radiochemical yield was more than 92 %. The radiochemical purity of 68Ga-NOTA-IF7 was more than 95 %. MicroPET studies showed a high tumor uptake at 15 min post-injection with 7.52 ± 0.16 %ID/g. The ratios of tumor to muscle uptake were 20.61 ± 0.31, 13.14 ± 0.21, 2.39 ± 0.12 at 15 min, 30 min and 60 min post-injection, respectively. 68Ga-NOTA-IF7 is a promising radiopharmaceutical for tumor imaging.

18F](2S,4S)-4-(3-Fluoropropyl)glutamine as a Tumor Imaging Agent

Although the growth and proliferation of most tumors is fueled by glucose, some tumors are more likely to metabolize glutamine. In particular, tumor cells with the upregulated c-Myc gene are generally reprogrammed to utilize glutamine. We have developed new 3-fluoropropyl analogs of glutamine, namely [18F](2S,4R)- and [18F](2S,4S)-4-(3-fluoropropyl)glutamine, 3 and 4, to be used as probes for studying glutamine metabolism in these tumor cells. Optically pure isomers labeled with 18F and 19F (2S,4S) and (2S,4R)-4-(3-fluoropropyl)glutamine were synthesized via different routes and isolated in high radiochemical purity (≥95%). Cell uptake studies of both isomers showed that they were taken up efficiently by 9L tumor cells with a steady increase over a time frame of 120 min. At 120 min, their uptake was approximately two times higher than that of l-[3H]glutamine ([3H]Gln). These in vitro cell uptake studies suggested that the new probes are potential tumor imaging agents. Yet, the lower chemical yield of the precursor for 3, as well as the low radiochemical yield for 3, limits the availability of [18F](2S,4R)-4-(3-fluoropropyl)glutamine, 3. We, therefore, focused on [18F](2S,4S)-4-(3-fluoropropyl)glutamine, 4. The in vitro cell uptake studies suggested that the new probe, [18F](2S,4S)-4-(3-fluoropropyl)glutamine, 4, is most sensitive to the LAT transport system, followed by System N and ASC transporters. A dual-isotope experiment using l-[3H]glutamine and the new probe showed that the uptake of [3H]Gln into 9L cells was highly associated with macromolecules (>90%), whereas the [18F](2S,4S)-4-(3-fluoropropyl)glutamine, 4, was not (<10%). This suggests a different mechanism of retention. In vivo PET imaging studies demonstrated tumor-specific uptake in rats bearing 9L xenographs with an excellent tumor to muscle ratio (maximum of ∼8 at 40 min). [18F](2S,4S)-4-(3-fluoropropyl)glutamine, 4, may be useful for testing tumors that may metabolize glutamine related amino acids.

99mTc-labeled aminosilane-coated iron oxide nanoparticles for molecular imaging of ανβ3-mediated tumor expression and feasibility for hyperthermia treatment

HypothesisDual-modality imaging agents, such as radiolabeled iron oxide nanoparticles (IO-NPs), are promising candidates for cancer diagnosis and therapy. We developed and evaluated aminosilane coated Fe3O4 (10±2nm) as a tumor imaging agent in nuclear medicine through 3-aminopropyltriethoxysilane (APTES) functionalization. We evaluated this multimeric system of targeted 99mTc-labeled nanoparticles (NPs) conjugated with a new RGD derivate (cRGDfK-Orn3-CGG), characterized as NPs-RGD as a potential thermal therapy delivery vehicle. ExperimentsTransmission Electron Microscopy (TEM) and spectroscopy techniques were used to characterize the IO-NPs indicating their functionalization with peptides. Radiolabeled IO-NPs (targeted, non-targeted) were evaluated with regard to their radiochemical, radiobiological and imaging characteristics. In vivo studies were performed in normal and ανβ3-positive tumor (U87MG glioblastoma) bearing mice. We also demonstrated that this system could reach ablative temperatures in vivo. FindingsBoth radiolabeled IO-NPs were obtained in high radiochemical yield (>98%) and proved stable in vitro. The in vivo studies for both IO-NPs have shown significant liver and spleen uptake at all examined time points in normal and U87MG glioblastoma tumor-bearing mice, due to their colloidal nature. We have confirmed through in vivo biodistribution studies that the non-targeted 99mTc-NPs poorly internalized in the tumor, while the targeted 99mTc-NPs-RGD, present 9-fold higher tumor accumulation at 1h p.i. Accumulation of both IO-NPs in other organs was negligible. Blocking experiments indicated target specificity for integrin receptors in U87MG glioblastoma cells. The preliminary in vivo study of applied alternating magnetic field showed that the induced hyperthermia is feasible due to the aid of IO-NPs.