Spatial Homogeneity of Superparamagnetic Nanoparticles and the Relationship to Relaxivity for Magnetic Resonance Imaging

The contribution of spatial homogeneity of magnetic nanofluids to the r2-relaxivity (1/T2 relaxation time) has been widely investigated for the past decade as a crucial scientific approach to enhance the resolution of T2-weighted magnetic resonance imaging (MRI). However, the correlation has not been comprehensively understood, and there are still controversies regarding the interpretation of the correlation. Here, the effects of spatial homogeneity, which is systematically controlled by the PDI (polydispersity index) and Dh (hydrodynamic diameter), of SPIONP (superparamagnetic iron oxide nanoparticle) nanofluids on the r2-relaxivity were experimentally and theoretically studied to provide scientific clues for solving the unsettled controversies on the correlation between the spatial homogeneity and r2-relaxivity. According to the analyzed results, the spatial homogeneity of nanofluids critically affects the r2-relaxivity and accordingly the T2-weighted MR contrast efficiency due to its contribution to the m(M) (or Hc ≈ HK) change of the nanofluids. Moreover, it was demonstrated that the magnetic energy competition model and water accessibility model depending on the degree of spatial homogeneity are critical to interpret the effects of spatial homogeneity on the r2-relaxivity for T2-weighted MR imaging

Significance of the several parameters in the response rate (RR) and disease control rate (DCR).

Significance of the several parameters in the response rate (RR) and disease control rate (DCR).</p

The patient characteristics according to the RAI therapy response.

The patient characteristics according to the RAI therapy response.</p

The response rate (RR) and disease control rate (DCR) at lesion-based analysis.

The response rate (RR) and disease control rate (DCR) at lesion-based analysis.</p

Glycosylation of Sodium/Iodide Symporter (NIS) Regulates Its Membrane Translocation and Radioiodine Uptake

<div><p>Purpose</p><p>Human sodium/iodide symporter (hNIS) protein is a membrane glycoprotein that transports iodide ions into thyroid cells. The function of this membrane protein is closely regulated by post-translational glycosylation. In this study, we measured glycosylation-mediated changes in subcellular location of hNIS and its function of iodine uptake.</p><p>Methods</p><p>HeLa cells were stably transfected with hNIS/tdTomato fusion gene in order to monitor the expression of hNIS. Cellular localization of hNIS was visualized by confocal microscopy of the red fluorescence of tdTomato. The expression of hNIS was evaluated by RT-PCR and immunoblot analysis. Functional activity of hNIS was estimated by radioiodine uptake. Cyclic AMP (cAMP) and tunicamycin were used to stimulate and inhibit glycosylation, respectively. In vivo images were obtained using a Maestro fluorescence imaging system.</p><p>Results</p><p>cAMP-mediated Glycosylation of NIS resulted in increased expression of hNIS, stimulating membrane translocation, and enhanced radioiodine uptake. In contrast, inhibition of glycosylation by treatment with tunicamycin dramatically reduced membrane translocation of intracellular hNIS, resulting in reduced radioiodine uptake. In addition, our hNIS/tdTomato fusion reporter successfully visualized cAMP-induced hNIS expression in xenografted tumors from mouse model.</p><p>Conclusions</p><p>These findings clearly reveal that the membrane localization of hNIS and its function of iodine uptake are glycosylation-dependent, as our results highlight enhancement of NIS expression and glycosylation with subsequent membrane localization after cAMP treatment. Therefore, enhancing functional NIS by the increasing level of glycosylation may be suggested as a promising therapeutic strategy for cancer patients who show refractory response to conventional radioiodine treatment.</p></div

Generation of HeLa cells expressing the hNIS/tdTomato fusion gene.

<p>(A) Schematic representation of the hNIS/tdTomato fusion gene reporter construct (upper). RT-PCR (lower left) and Immunoblot analysis (lower right) showed stable expression of hNIS/tdTomato gene in HeLa cells. (B) Fluorescence microscope image shows the hNIS/tdTomato fusion protein expression in HeLa-hNIS/tdTomato cells. Cellular hNIS proteins were imaged using a time-lapse live cell imaging system (upper) and confocal microscopy (lower). (C) Red fluorescence from HeLa-hNIS/tdTomato cells increased with increasing cell number. (D) Function of hNIS/tdTomato in HeLa cells was measured by I-uptake and iodine uptake shows cell number dependency.</p

Flow chart of enrollment of study participants.

Flow chart of enrollment of study participants.</p

Membrane translocation of hNIS protein by cAMP after inhibition of de novo protein synthesis.

<p>To inhibit cAMP-induced protein synthesis, AMD (5 ng/mL) or CHX (1 μg/ml) were pretreated 24h before treatment of 100 μM cAMP. (A) Enhanced expression of hNIS/tdTomato proteins by cAMP was visualized after blocking de novo protein synthesis. (B) Enhanced membrane localization of hNIS/tdTomato proteins by cAMP was visualized after blocking de novo protein synthesis. Red fluorescent intensity was analyzed with MetaMorph software. An arbitrary threshold that represented the cytosolic compartment was designated. Threshold intensity of fluorescence was adjusted to show membrane-localized hNIS/tdTomato protein only. Signals over or under the threshold were depicted as red or gray, respectively. (C) The upper threshold of red fluorescent intensity was measured to quantify the membrane localized hNIS/tdTomato protein. Confocal images were collected from at least three different regions of each sample. Bars represent mean ± SD (*, P<0.05; **, P<0.01; N = 3).</p

Membrane localization of glycosylated hNIS/tdTomato protein.

<p>(A) HeLa-hNIS/tdTomato cells were treated with tunicamycin (1.2 μM) or cAMP (100 μM), and the red fluorescent signals were photographed using confocal microscopy. Based on a cross-sectional analysis using fluorescence profiling of MetaMorph software, an arbitrary threshold that represented the cytosolic compartment was designated. Signals over the threshold were considered to be from the membrane compartment. (B) NIS expression was observed by immunoblot analysis with cellular protein extracts (20 μg) from tunicamycin- and cAMP-treated HeLa-hNIS/tdTomato cells. β-actin was used as an internal control. (C) NIS expression was observed by immunoblot analysis with membrane proteins isolated from cAMP-treated cells. Caveolin was used as an internal control.</p

The representative cases showing the predictive role of FDG uptake in RAI therapy.

A. The patient who has lung metastasis from papillary thyroid cancer was done RAI therapy after total thyroidectomy. After first therapy, there was quite amount of RAI in the metastatic lesion, expecting therapeutic effect of RAI. However, initial FDG PET scan showed there are also substantial FDG uptake in the metastasis. At the time of 2nd therapy, the RAI uptake was gone and the anatomical size of lung metastasis was not changed during serial follow-up CT scan. Even the unstimulated Tg level as well as stimulated Tg level was subsequently increased. B. The patient who has recurred metastatic lung nodules from papillary thyroid cancer after total thyroidectomy 10 years ago. The metastatic nodules had a significant amount of RAI uptake in the post-therapy scan, but did not show significant uptake in the FDG PET scan performed at the same time. At the time of 2nd therapy, the size of lesions was significantly decreased and stimulated Tg level was also lowered.</p