Magnetic/Upconversion Fluorescent Nanoparticle-Based Dual-Modal Molecular Probes for Imaging of  Lymph Node Metastasis From Pancreatic Cancer in vivo
Kai Cao1, Ruirui Qiao2, and Huimin Wei3

1Radiology, Changhai Hospital, Shanghai, China, People's Republic of, 2Chemistry, Chinese Academy of Sciences, Beijing, China, People's Republic of, 3Clinic and Translational Medicine Center, Changhai Hospital, Shanghai, China, People's Republic of


Construction of the specific pancreatic cancer probe based on upconversion nanoparticles. The probes taking biocompatibility upconversion nanoparticles with unique magnetic properties as a carrier, conjugated with ATF peptide specifically targeting the uPAR. Then, its effect of detection of tumor and lymph node metastasis would be further validated in an orthotopic human pancreatic cancer xenograft model by pathology and dual-modal imaging.


Molecular imaging have provided great hope for tiny tumors detection and staging upon acquisition of molecular and physiological information[1-2]. The anti-Stokes mechanism of the upconversion luminescence probes offers greater penetration of tissue by the NIR excitation and eliminates the interference of endogenous fluorescence, giving rise to an enhanced signal-to-noise ratio (SNR)[3-6]. Moreover, with the incorporation of gadolinium in the nanoparticle matrix, dual-modality imaging probes can be constructed with integrated magnetic and upconversion properties[7-10]. The culmination of these physical attributes provides unique opportunities in developing molecular probes for bioimaging, including the analysis of the tumor[11-14], blood pool[15], and lymph nodes[16]. Urokinase plasminogenactivator (uPA) is a serine protease that interacts with its receptor, uPAR, to regulate multiple pathways involved in matrix degradation, cell motility, metastasis, and angiogenesis[17]. Urokinase plasminogen activator receptor (uPAR), a cellular receptor that is highly expressed in pancreatic cancer cells and tumor stromal cells, is an excellent surface molecule for receptor-targeted imaging[18-20]. Studies have demonstrated that a high level of uPAR expression in tumor cells correlates with aggressive tumor types, tumor metastasis, and poorer prognosis[21,22]. Furthermore, in the majority of normal tissues or organs, the level of uPAR is very low or undetectable[23]. uPAR-targeted upconversion nanoparticles change the traditional single and down conversion luminescent imaging mode, as near-infrared excitation can better penetrate tissue than visible light while giving rise to greatly reduced background noise.


The uPAR-targeted probe is designed and prepared by conjugating amino-terminal fragment of the receptor binding domain of human urokinase plasminogen activator to the surface of upconversion nanoparticles. The orthotopic human pancreatic cancer xenograft model was established by a surgical procedure. A stably luciferase-expressing SW1990 cell line, which is a typical pancreatic cancer cell line, was used to enable constant monitoring of tumor development. Ten days after surgical implantation, the nude mice were screened by bioluminescence imaging to verify successful inoculation. Only mice exhibiting comparable bioluminescence intensities were chosen for parallel studies.


Targeted nanoparticles are able to specifically bind to uPAR-expressing tumor cells. The primary tumor and adjacent lymphatic metastasis site were clearly differentiated by upconversion luminescence imaging after the uPAR-specific probe was delivered through tail vein injection into tumor-bearing nude mice. Target specificity of nanoparticles is further confirmed by a clinical MRI scanner at a field strength of 3 Tesla. Furthermore, mice administered targeted nanoparticles exhibit lower uptake of the particles in the liver and lung compared to those receiving non-targeted upconversion nanoparticles.


Lymphatic status is a very important factor for the prognosis of cancer patients. With respect to the detection of LN metastasis, no imaging modality consistently achieves both high sensitivity and high specificity. In contrast, the sensitivity and specificity achieved by using the current UCNP-based probes are apparently superior to FDG-PET and other techniques for differentiating lymphatic metastasis from the primary cancer. In fact, MR imaging of lymph nodes enhanced by ultrasmall superparamagnetic iron oxide nanoparticles was reported quite some time ago. The mechanism largely relies on populating differences of macrophages between benign and malignant nodes, which makes detection of micrometatasis in LNs difficult. However, the current study provides a different mechanism for imaging only lymph nodes positive for metastases through active targeting of the malignant nodes via specific antibody antigen recognition. Although optical imaging offers an ultrasensitive tool for tumor detection, the limited tissue penetrationis widely accepted to be a flaw of optical imaging. However, the optical signal does not always need to penetrate through the whole abdominal wall to be detected during surgical lymphadenectomy.


Our results revealed that the probe could be useful for not only tiny tumor lesion diagnosis but also for lymphatic metastasis detections, indicating potential clinical applications in the early pancreatic cancer diagnosis and lymph node status evaluation.


No acknowledgement found.


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The current studies may pave a highly effective approach for pancreatic cancer diagnosis as well as provide a powerful tool for lymph node metastasis.

Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)