Specific targeting of angiogenesis in lung cancer with RGD-conjugated ultrasmall superparamagnetic iron oxide particles using a 4.7T magnetic resonance scanner / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Angiogenesis is an essential step for tumor development and metastasis. The cell adhesion molecule avβ3 integrin plays an important role in angiogenesis and is a specific marker of tumor angiogenesis. A novel avβ3 integrin- targeted magnetic resonance (MR) imaging contrast agent utilizing Arg-Gly-Asp (RGD) and ultrasmall superparamagnetic iron oxide particles (USPIO) (referred to as RGD-USPIO) was designed and its uptake by endothelial cells was assessed both in vitro and in vivo to evaluate the angiogenic profile of lung cancer.</p><p><b>METHODS</b>USPIO were coated with -NH3+ and conjugated with RGD peptides. Prussian blue staining was performed to evaluate the specific uptake of RGD-USPIO by human umbilical vein endothelial cells (HUVECs). Targeted uptake and subcellular localization of RGD-USPIO in HUVECs were confirmed by transmission electron microscopy (TEM). The ability of RGD-USPIO to noninvasively assess avβ3 integrin positive vessels in lung adenocarcinoma A549 tumor xenografts was evaluated with a 4.7T MR scanner. Immunohistochemistry was used to detect avβ3 integrin expression and vessel distribution in A549 tumor xenografts.</p><p><b>RESULTS</b>HUVECs internalized RGD-USPIO significantly more than plain USPIO. The uptake of RGD-USPIO by HUVECs could be competitively inhibited by addition of free RGD. A significant decrease in T2 signal intensity (SI) was observed at the periphery of A549 tumor xenografts at 30 minutes (P < 0.05) and 2 hours (P < 0.01) after RGD-USPIO was injected via the tail vein. Angiogenic blood vessels were mainly distributed in the periphery of tumor xenografts with positive avβ3 integrin expression.</p><p><b>CONCLUSIONS</b>RGD-USPIO could specifically label avβ3 integrin and be taken up by HUVECs. This molecular MR imaging contrast agent can specifically evaluate the angiogenic profile of lung cancer using a 4.7T MR scanner.</p>

Epidermal growth factor receptor-targeted ultra-small superparamagnetic iron oxide particles for magnetic resonance molecular imaging of lung cancer cells in vitro / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Magnetic resonance (MR) molecular imaging can detect abnormalities associated with disease at the level of cell and molecule. The epidermal growth factor receptor (EGFR) plays an important role in the development of lung cancer. This study aimed to explore new MR molecular imaging targeting of the EGFR on lung cancer cells.</p><p><b>METHODS</b>We attached ultra-small superparamagnetic iron oxide (USPIO) particles to cetuximab (C225) anti-human IgG using the carbodiimide method. We made the molecular MR contrast agents C225-USPIO and IgG-USPIO, the latter as a control reagent, and determined concentrations according to the Fe content. Lung cancer A549 cells were cultured and immunocytochemistry (SP) was used to detect the expression of EGFR on cells. We detected the binding rate of C225-USPIO to A549 cells with immunofluorescence staining and flow cytometry. We cultured A549 cells with C225-USPIO at a Fe concentration of 50 µg/ml and assayed the binding of C225-USPIO after 1 hour with Prussian blue staining and transmission electron microscopy (TEM). We determined the effects on imaging of the contrast agent targeted to cells using a 4.7T MRI. We did scanning on the cells labeled with C225-USPIO, IgG-USPIO, and distilled water, respectively. The scanning sequences included axial T1WI, T2WI.</p><p><b>RESULTS</b>Immunocytochemical detection of lung cancer A549 cells found them positive for EGFR expression. Immunofluorescence staining and flow cytometry after cultivation with different concentrations of C225-USPIO showed the binding rate higher than the control. Prussian blue staining and transmission electron microscopy revealed that in the C225-USPIO contrast agent group of cells the particle content of Fe in cytoplasmic vesicles or on surface was more than that in the control group. The 4.7T MR imaging (MRI) scan revealed the T2WI signal in the C225-USPIO group of cells decreased significantly more than in unlabeled cells, but there was no significant difference between the time gradients.</p><p><b>CONCLUSIONS</b>We successfully constructed the molecular imaging agent C225-USPIO targeting the EGFR of A549 lung cancer cells. The imaging agent showed good targeting effect and specificity, and reduced MRI T2 value significantly, thus such molecular contrast agents could provide a new way to measure EGFR levels.</p>