Characteristics of AU-rich elements and involvement of the poly-(A) tail in stress-induced mRNA stabilization

[no abstract

Assessment of tumor redox status through (S)-4-(3-[18F]fluoropropyl)-L-glutamic acid positron emission tomography imaging of system xc- activity

The cell's endogenous antioxidant system is vital to maintenance of redox homeostasis. Despite its central role in normal and pathophysiology, no non-invasive tools exist to measure this system in patients. The cystine/glutamate antiporter system xc- maintains the balance between intracellular reactive oxygen species and antioxidant production through the provision of cystine, a key precursor in glutathione biosynthesis. Here we show that tumor cell retention of a system xc--specific positron emission tomography radiotracer, (S)-4-(3-[18F]fluoropropyl)-L-glutamic acid ([18F]FSPG), decreases in proportion to levels of oxidative stress following treatment with a range of redox-active compounds. The decrease in [18F]FSPG retention correlated with a depletion of intracellular cystine resulting from increased de novo glutathione biosynthesis, shown through [U-13C6, U-15N2]cystine isotopic tracing. In vivo, treatment with the chemotherapeutic doxorubicin decreased [18F]FSPG tumor uptake in a mouse model of ovarian cancer, coinciding with markers of oxidative stress but preceding tumor shrinkage and decreased glucose utilization. Having already been used in pilot clinical trials, [18F]FSPG PET could be rapidly translated to the clinic as an early redox indicator of tumor response to treatment

GLUT 5 Is Not Over-Expressed in Breast Cancer Cells and Patient Breast Cancer Tissues

F18 2-Fluoro 2-deoxyglucose (FDG) has been the gold standard in positron emission tomography (PET) oncologic imaging since its introduction into the clinics several years ago. Seeking to complement FDG in the diagnosis of breast cancer using radio labeled fructose based analogs, we investigated the expression of the chief fructose transporter-GLUT 5 in breast cancer cells and human tissues. Our results indicate that GLUT 5 is not over-expressed in breast cancer tissues as assessed by an extensive immunohistochemistry study. RT-PCR studies showed that the GLUT 5 mRNA was present at minimal amounts in breast cancer cell lines. Further knocking down the expression of GLUT 5 in breast cancer cells using RNA interference did not affect the fructose uptake in these cell lines. Taken together these results are consistent with GLUT 5 not being essential for fructose uptake in breast cancer cells and tissues

Imaging Target mRNA and siRNA-Mediated Gene Silencing In Vivo with Ribozyme-Based Reporters

Noninvasive imaging of specific mRNAs in living subjects promises numerous biological and medical applications. Common strategies use fluorescently or radioactively labelled antisense probes to detect target mRNAs through a hybridization mechanism, but have met with limited success in living animals. Herewe present a novel molecular imaging approach based on the group I intron of Tetrahymena thermophila for imaging mRNA molecules in vivo. Engineered trans-splicing ribozyme reporters contain three domains, each of which is designed for targeting, splicing, and reporting. They can transduce the target mRNA into a reporter mRNA, leading to the production of reporter enzymes that can be noninvasively imaged in vivo. We have demonstrated this ribozyme-mediated RNA imaging method for imaging a mutant p53 mRNA both in single cells and noninvasively in living mice. After optimization, the ribozyme reporter increases contrast for the transiently expressed target by 180-fold, and by ten-fold for the stably expressed target. siRNA-mediated specific gene silencingof p53 expression has been successfully imaged in real time in vivo. This newribozyme-ba sed RNA reporter system should open up newavenues for in vivo RNA imaging and direct imaging of siRNA inhibition

Investigation of 6-[¹⁸F]-Fluoromaltose as a Novel PET Tracer for Imaging Bacterial Infection

<div><p></p><p>Despite advances in the field of nuclear medicine, the imaging of bacterial infections has remained a challenge. The existing reagents suffer from poor sensitivity and specificity. In this study we investigate the potential of a novel PET (positron emission tomography) tracer that overcomes these limitations.</p><p>Methods</p><p>6-[¹⁸F]-fluoromaltose was synthesized. Its behavior <i>in vitro</i> was evaluated in bacterial and mammalian cultures. Detailed pharmacokinetic and biodistribution profiles for the tracer were obtained from a murine model.</p><p>Results</p><p>6-[¹⁸F]-fluoromaltose is taken up by multiple strains of pathogenic bacteria. It is not taken up by mammalian cancer cell lines. 6-[¹⁸F]-fluoromaltose is retained in infected muscles in a murine model of bacterial myositis. It does not accumulate in inflamed tissue.</p><p>Conclusion</p><p>We have shown that 6-[¹⁸F]-fluoromaltose can be used to image bacterial infection <i>in vivo</i> with high specificity. We believe that this class of agents will have a significant impact on the clinical management of patients.</p></div

<i>In vitro</i> characterization of 6-[¹⁸F]-fluoromaltose.

<p>A) Uptake of 6-[¹⁸F]-fluoromaltose in the indicated strains of bacteria for 60 minutes. B) 1 hour uptake of 6-[¹⁸F]-fluoromaltose in the mammalian cell lines, MDA MB231 and HeLa and its uptake in <i>E.coli</i> in the presence of 1 mM maltose. C) Bioluminescence imaging of a macrophage cell line J774 infected with a bioluminescent strain of <i>Listeria monocytogenes.</i> D) 1 hour uptake of 6-[¹⁸F]-fluoromaltose in the bioluminescent strain of <i>Listeria monocytogenes</i> and in macrophage cell line J774 with and without intracellular <i>Listeria</i> infections.</p

<i>In vivo</i> characterization of 6-[¹⁸F]-fluoromaltose.

<p>A) 3D color map from a PET/CT scan of a mouse bearing <i>E.coli</i> induced infection on the left thigh (red arrow) 1 hr after tail-vein injection of 7.4MBq of 6-[¹⁸F]-fluoromaltose. B) Region of interest analysis (ROIs) from PET/CT images at the indicated time points (n = 4 for each time point) * indicates statistical significance with p<0.05. C) Time activity curve showing accumulation of 6-[¹⁸F]-fluoromaltose in the infected muscle (n = 3).</p