Biomedical subjects

Shi Ke

Publications and source records attributed to Shi Ke.

15 recordsLinked to original sources

PubMed2006

Dual optical and nuclear imaging in human melanoma xenografts using a single targeted imaging probe.

INTRODUCTION: Dual-labeled imaging agents that allow both nuclear and optical imaging after a single injection would be advantageous in certain applications. In this study, we synthesized and characterized a dual-labeled RGD (Arg-Gly-Asp) peptide and compared nuclear and optical images obtained with this agent. METHODS: 111In-DTPA-Lys(IRDye800)-c(KRGDf) composed of both the 111In chelator diethylenetriaminepentaacetic acid (DTPA) and the near-infrared (NIR) fluorescent dye IRDye800 (excitation/emission, 765/792 nm) was synthesized. The probe was characterized with regard to in vitro biological activity and in vivo pharmacokinetics and the ability to target integrin alphavbeta3. Tumors of mice injected with the dual-labeled probe were imaged both by gamma scintigraphy and NIR fluorescence optical camera. RESULTS: DTPA-Lys(IRDye800)-c(KRGDf), DTPA-Lys-c(KRGDf) and c(KRGDf) inhibited the adhesion of melanoma M21 cells to vitronectin-coated surface with the similar biological activity. Both 111In-DTPA-Lys(IRDye800)-c(KRGDf) and 111In-DTPA-Lys-c(KRGDf) had significantly higher uptakes in alphavbeta3-positive M21 melanoma than in alphavbeta3-negative M21-L melanoma at 4-48 h after their injection. Side-by-side comparison of images obtained using 111In-DTPA-Lys(IRDye800)-c(KRGDf) revealed that in living mice, both optical imaging and gamma scintigraphy enabled noninvasive detection of the bound probe to alphavbeta3-positive tumors, with optical images providing improved resolution and sensitive detection of the superficial lesions and gamma images providing sensitive detection of deeper structures. CONCLUSION: The dual-labeled imaging probe 111In-DTPA-Lys(IRDye800)-c(KRGDf) was found to specifically bind to alphavbeta3 in melanoma tumor cells. Employing both nuclear and optical imaging with a single imaging probe may facilitate translation of NIR fluorescence optical imaging into clinical applications.

Animals↗

PubMed2006

Antimetastatic activity of insulin-like growth factor binding protein-3 in lung cancer is mediated by insulin-like growth factor-independent urokinase-type plasminogen activator inhibition.

Insulin-like growth factor binding protein-3 (IGFBP-3), a major IGF-binding protein in human serum, regulates the growth of non-small cell lung cancer (NSCLC) cells through IGF-dependent and IGF-independent mechanisms. However, the role of IGFBP-3 in lung cancer metastasis is not well known. In the present study, we showed that noncytotoxic doses of adenoviral or recombinant IGFBP-3 significantly decreased the migration and invasion of H1299 and A549 NSCLC cells. Furthermore, treatment of human lung fibroblasts with recombinant IGFBP-3 suppressed their ability to stimulate the invasion of H1299 cells. Overexpression of IGFBP-3 markedly reduced lung metastasis of A549 cells in an experimental animal model system and prolonged the survival time of the animals. Urokinase-type plasminogen activator (uPA) inhibitor treatment or uPA small interfering RNA transfection of A549 and H1299 cells resulted in a significant decrease in invasion. Corresponding ELISA, Western blot, gelatin zymogram, and semiquantitative reverse transcription-PCR analyses revealed that IGFBP-3 reduced the expression of uPA mRNA through IGF-independent mechanisms. The specific role of uPA in anti-invasive activity of IGFBP-3 was further confirmed in NSCLC cells, in which uPA expression/activity was suppressed by the transfection with synthetic small interfering RNA or by the treatment with uPA inhibitor or induced by the infection with an adenoviral vector. IGFBP-3 also decreased the expression/activity of matrix metalloproteinase-2 through IGF-dependent but uPA-independent pathways. Taken together, our data suggest that IGFPB-3 effectively block uPA- and matrix metalloproteinase-2-stimulated invasion pathways, ultimately reducing lung cancer cell metastasis. Our findings indicate that IGFBP-3 may be a promising anti-invasive and antimetastatic therapeutic agent in lung cancer.

Animals↗

PubMed2005

Antibacterial chemoprophylaxis in the prevention of traveler's diarrhea: evaluation of poorly absorbed oral rifaximin.

The use of antibacterial drugs was first shown to effectively reduce the occurrence of traveler's diarrhea nearly 50 years ago. The approach was not encouraged for general use by a Consensus Development Conference in 1985 because of concerns about adverse effects of the drugs and the possible development of resistance against systemically absorbed drugs. When therapy with poorly absorbed rifaximin was shown to be as effective as therapy with systemically absorbed drugs in shortening the duration of traveler's diarrhea, without the development of resistant coliform flora, the use of rifaximin for the prevention of traveler's diarrhea was studied. In the present study, rifaximin provided 72% protection against the development of diarrhea and 77% protection against active or treated diarrhea during 2 weeks of drug administration to United States students in Mexico. Rifaximin offers a potentially useful approach for preventing traveler's diarrhea. Potential areas of future study include use of the drug to prevent diarrhea due to mucosally invasive bacteria, including ciprofloxacin-resistant Campylobacter species, and to reduce the occurrence of postinfectious irritable bowel syndrome.

Adolescent↗

PubMed2005

A randomized, double-blind, placebo-controlled trial of rifaximin to prevent travelers' diarrhea.

BACKGROUND: Travelers' diarrhea causes substantial morbidity and postinfectious irritable bowel syndrome. OBJECTIVE: To evaluate nonabsorbable rifaximin for prevention of travelers' diarrhea. DESIGN: Randomized, double-blind, placebo-controlled clinical trial. SETTING: Guadalajara, Mexico. PARTICIPANTS: U.S. students. INTERVENTION: On arrival in Guadalajara, Mexico, 210 U.S. adults received rifaximin (200 mg/d, 200 mg twice daily, or 200 mg 3 times daily) or placebo for 2 weeks. MEASUREMENTS: Participants were followed daily for 3 weeks for enteric disease and symptoms and daily for 5 weeks for drug side effects. Changes in intestinal coliform flora were studied. RESULTS: Travelers' diarrhea developed in 14.74% of participants taking rifaximin and 53.70% of those taking placebo (rate ratio, 0.27 [95% CI, 0.17 to 0.43]). Rifaximin provided 72% and 77% protection against travelers' diarrhea and antibiotic-treated travelers' diarrhea, respectively (P < 0.001 for both), and all rifaximin doses were superior to placebo. In the groups that did not report travelers' diarrhea, rifaximin significantly reduced the occurrence of mild diarrhea (P = 0.02) and moderate and severe intestinal problems (P = 0.009 for pain or cramps; P = 0.02 for excessive gas). Rates of adverse events were comparable in the rifaximin and placebo groups. Minimal changes in coliform flora were found during rifaximin therapy. LIMITATIONS: Rifaximin safely prevented travelers' diarrhea in Mexico, where most cases are caused by diarrhea-producing Escherichia coli. A study is needed in Asia to determine whether rifaximin can prevent diarrhea caused by invasive bacterial pathogens. CONCLUSIONS: Rifaximin prevents travelers' diarrhea with minimal changes in fecal flora, and more liberal chemoprophylaxis against this disease should be considered. Future studies should evaluate whether rifaximin is effective in preventing postinfectious irritable bowel syndrome.

Adult↗

PubMed2004

Enteroaggregative Escherichia coli diarrhea in travelers: response to rifaximin therapy.

BACKGROUND AND AIMS: We have recently shown that enteroaggregative Escherichia coli (EAEC) strains commonly cause travelers' diarrhea. The study was designed to determine whether U.S. travelers with EAEC diarrhea responded to rifaximin therapy. METHODS: In a multicenter placebo-controlled clinical trial of travelers' diarrhea without non-EAEC pathogens we evaluated 2 doses of rifaximin. EAEC was sought in stool samples in enrolled subjects by HEp-2 cell assay. Response to rifaximin (both groups combined) and placebo were evaluated in EAEC-positive and EAEC-negative patient groups. RESULTS: Compared with placebo, rifaximin shortened the postenrollment illness in travelers with EAEC diarrhea (median, 22 vs. 72 hours; P = 0.03). In subjects with EAEC-negative diarrhea, the median duration of post-treatment diarrhea was shorter with rifaximin (33 hours) than with placebo (52 hours), but this difference was not significantly different (P = 0.14). CONCLUSIONS: Improvement of EAEC-mediated diarrhea with antibiotic treatment supports the pathogenicity of this organism in travelers to developing countries. The study provides information on the value of the poorly absorbed drug rifaximin in therapy of travelers' diarrhea.

Anti-Infective Agents↗

PubMed2004

Near-infrared optical imaging of integrin alphavbeta3 in human tumor xenografts.

In vivo optical imaging is potentially useful for evaluating the presence of tumor markers that are targets of molecular medicine. Here we report the synthesis and characterization of integrin alphavbeta3-targeted peptide cyclo(Lys-Arg-Gly-Asp-Phe) [c(KRGDf )] labeled with fluorescence dyes with wavelength spanning from the visible/near infrared (Cy5.5) to the true near infrared (IRDye800) for optical imaging. In vitro, the peptide-dye conjugates bound specifically to tumor cells expressing alphavbeta3. When administered intravenously into mice at a dose of 6 nmol /mouse, the conjugates accumulated in tumors expressing alphavbeta3. The tumor-to-background ratios for human KS1767 Kaposi's sarcoma in mice injected with Cy5.5-c(KRGDf ) and Cy5.5 were 5.5 and 1.5, respectively. Preinjection of c(KRGDf ) blocked the uptake of Cy5.5-c(KRGDf ) in tumors by 89%. In alphavbeta3-positive M21 and alphavbeta3-negative M21-L human melanoma, fluorescence intensity in the tumor of mice injected with IRDye800 - c(KRGDf ) was 2.3 and 1.3 times that in normal tissue, respectively. Dynamic imaging revealed that Cy5.5- c(KRGDf ) was rapidly taken up by KS1767 tumor immediately after bolus injection. The rate of its uptake in the tumor was reduced by preinjection of c(KRGDf ) in an interval time-dependent manner. Our data suggest that near-infrared fluorescence imaging may be applied to the detection of tumors expressing integrin alphavbeta3 and to the assessment of the optimal biological dose and schedule of targeted therapies.

Animals↗

PubMed2004

Imaging taxane-induced tumor apoptosis using PEGylated, 111In-labeled annexin V.

UNLABELLED: 99mTc-Labeled annexin V has been used for the imaging of tumor apoptosis induced by chemotherapy. However, owing to the short half-life of annexin V, multiple injections of the radiotracer are necessary to capture the peak apoptotic activity. In this study, we evaluated the imaging properties of an (111)In-labeled, long-circulating annexin V. METHODS: Both polyethylene glycol (PEG) and the metal chelator diethylenetriaminepentaacetic acid (DTPA) were simultaneously introduced to annexin V or ovalbumin through the use of a heterofunctional PEG precursor. Imaging studies were performed in mice bearing subcutaneously inoculated human mammary MDA-MB-468 tumors. The mice were treated with poly(L-glutamic acid)-paclitaxel, monoclonal antibody C225, or a combination of poly(L-glutamic acid)-paclitaxel and C225, followed by intravenous injection of (111)In-DTPA-PEG-annexin V. Images were acquired 48 h after the injection of the radiotracer. Autoradiography and TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling) staining were performed on adjacent tumor slices for the localization of apoptotic cells. The imaging properties of unPEGylated annexin V and PEGylated ovalbumin were also determined to permit assessment of the specificity of (111)In-DTPA-PEG-annexin V. RESULTS: Tumor apoptotic index increased from 1.67% +/- 0.31% at baseline to 7.60% +/- 0.72% and 11.07% +/- 1.81%, respectively, 4 d after treatment with poly(L-glutamic acid)-paclitaxel or combined poly(L-glutamic acid)-paclitaxel and C225. Tumor uptake (percentage of injected dose per gram of tumor [%ID/g]) of PEGylated (111)In-DTPA-PEG-annexin 4 d after treatment was significantly higher in tumors treated with poly(L-glutamic acid)-paclitaxel (10.76 +/- 1.38 %ID/g; P = 0.001) and with combined poly(L-glutamic acid)-paclitaxel and C225 (9.84 +/- 2.51 %ID/g; P = 0.029) than in nontreated tumors (6.14 +/- 0.67 %ID/g), resulting in enhanced visualization of treated tumors. (111)In-DTPA-PEG-annexin V distributed into the central zone of tumors, whereas (111)In-DTPA-annexin V was largely confined to the tumor periphery. Furthermore, uptake of (111)In-DTPA-PEG-annexin V by tumors correlated with apoptotic index (r = 0.87, P = 0.02). Increase in tumor uptake of the nonspecific PEGylated protein (111)In-DTPA-PEG-ovalbumin was also observed after poly(L-glutamic acid)-paclitaxel treatment (55.6%), although this increase was less than that observed for (111)In-DTPA-PEG-annexin V (96.7%). CONCLUSION: Increased uptake of and improved visualization with (111)In-DTPA-PEG-annexin V in solid tumors after chemotherapy are mediated through both specific binding to apoptotic cells and nonspecific retention of macromolecular contrast agents in the tumors. (111)In-Labeled, PEGylated annexin V may be used to assess tumor response to chemotherapy.

Animals↗

PubMed2003

Near-infrared optical imaging of epidermal growth factor receptor in breast cancer xenografts.

The specificity of a novel epidermal growth factor (EGF)-Cy5.5 fluorescent optical probe in the detection of EGF receptor (EGFr) was assessed using continuous-wave fluorescence imaging accomplished via an intensified charge-coupled device (CCD) camera. Human mammary MDA-MB-468 (EGFr+) and MDA-MB-435 (EGFr-) cancer cells were incubated with Cy5.5, EGF-Cy5.5, or the anti-EGFr monoclonal antibody C225 or EGF followed by EGF-Cy5.5 and examined under a fluorescence microscope. In vivo imaging was performed on mice with s.c. MDA-MB-468 and MDA-MB-435 tumors. Images were obtained every 6 s for 20 min after i.v. injection of each agent and every 24 h after injection for up to 192 h. Additionally, mice with MDA-MB-468 tumors were injected i.v. with C225 24 h before injection of EGF-Cy5.5. EGF-Cy5.5, but not Cy5.5 or indocyanine green dye (ICG), bound to MDA-MB-468 cells. Binding of EGF-Cy5.5 was blocked by C225 and by EGF. In contrast, binding of EGF-Cy5.5 to MDA-MB-435 cells was not observed. Monitoring of the time-fluorescence intensity in mice confirmed that ICG and Cy5.5 had no favorable binding to tumor regardless of EGFr expression level. In contrast, EGF-Cy5.5 accumulated only in MDA-MB-468 tumors. Moreover, tumor uptake of EGF-Cy5.5 was blocked by C225. ICG and Cy5.5 fluorescence was completely absent from the tumor site, regardless of EGFr expression level, 24 h after injection. Little EGF-Cy5.5 fluorescence was detected in MDA-MB-435 tumors 24 h after injection. In MDA-MB-468 tumors, our data suggest that EGF-Cy5.5 may be used as a specific NIR contrast agent for noninvasive imaging of EGFr expression and monitoring of responses to molecularly targeted therapy.

Adenocarcinoma↗

PubMed2003

Targeting doxorubicin to epidermal growth factor receptors by site-specific conjugation of C225 to poly(L-glutamic acid) through a polyethylene glycol spacer.

PURPOSE: Targeted delivery of chemotherapeutic agents through antibody-polymer conjugates has met with limited success. One of the limiting factors is the loss of antibody's binding affinity upon conjugation with polymeric carriers because of lack of control over the number and site of attachment. This study aims to synthesize monovalent polymeric immunoconjugates through site-specific conjugation and to evaluate the in vitro binding activities of the resulting construct. METHODS: Antibody C225 against epidermal growth factor receptors was coupled to the terminus of a doxorubicin-bound block copolymer, poly(L-glutamic acid)-co-polyethylene glycol (PG-PEG). Western blot analysis, confocal fluorescent microscopy, and cytotoxicity assay were performed to confirm the specific binding of C225-PEG-PG-Dox to EGFR. RESULTS: C225 was conjugated to PEG-PG-doxorubicin conjugates by reacting sulfhydryl group introduced to C225 with vinylsulfone group introduced at the terminus of PEG-PG block copolymer. Polymeric immunoconjugate C225-PEG-PG-Dox, but not control (i.e., conjugate without antibody), selectively bound to human vulvar squamous carcinoma A431 cells that overexpress epidermal growth factor receptors. Receptor-mediated uptake of C225-PEG-PG-Dox occurred rapidly (within 5 min), whereas nonspecific uptake of PEG-PG-Dox required an extended period of time (24 h) to internalize. Binding of C225-PEG-PG-Dox to A431 cells could be blocked by pretreatment with C225 antibody. C225-PEG-PG-Dox was more potent than free doxrubicin in inhibiting the growth of A431 cells after a 6-h exposure period. CONCLUSION: Site-specific conjugation of a monoclonal antibody to the terminus of a polymeric carrier enhances receptor-mediated delivery of anticancer agents.

Antibodies, Monoclonal↗

PubMed2003

Improved radiolabeling of PEGylated protein: PEGylated annexin V for noninvasive imaging of tumor apoptosis.

We have developed a one-step procedure to introduce both polyethylene glycol (PEG) and the metal chelator diethylenetriaminepentaacetic acid (DTPA) to proteins through a heterofunctional PEG precursor. The PEG precursor contains DTPA at one end and an amine-reactive isothiocyanate (SCN-) functional group at the other end. It was obtained as lyophilized powder and could be stored at 4 degrees C for several months. Protein conjugation was achieved by simply mixing the proteins and the PEG precursor SCN-PEG-DTPA in an aqueous solution. As exemplified by the PEGylation and radiolabeling of annexin V, the resulting conjugate 111In-DTPA-PEG-annexin V showed selective binding to apoptotic cells in vitro and increased blood half-life in vivo. The PEGylated, radiolabeled annexin V may be useful in the noninvasive imaging of apoptosis.

Animals↗

PubMedDate not supplied

Quantifying molecular specificity of alphavbeta3 integrin-targeted optical contrast agents with dynamic optical imaging.

Dynamic fluorescence images were obtained from a subcutaneous human Kaposi's sarcoma tumor (KS1767) model immediately following the intravenous injection of an integrin-targeting cyanine dye conjugate, Cy5.5-c(KRGDf). The fluorescence images, acquired via an intensified charge-coupled device detection system, were used in conjunction with a pharmacokinetic (PK) model to determine kinetic properties of target binding in the presence and absence of a competitive ligand, free c(KRGDf). The results indicate that the conjugate dye behaves similarly in normal tissue to the free Cy5.5 dye while it possesses increased uptake in tumor tissue. The change in pharmacokinetic parameters obtained from dynamic imaging of Cy5.5-c(KRGDf) after administration of c(KRGDf) as a competitive ligand to the integrin receptor suggests that (i) the increased uptake of Cy5.5-c(KRGDf) is molecularly specific and that (ii) receptor turnover occurs within 24 h. In addition, PK analysis enables quantification of an in vivo c(KRGDf) binding constant attributable to integrin binding. In vivo pharmacokinetic analysis based on rapid and dynamic optical imaging may be potentially useful for evaluating the presence and turnover rate of disease markers that are potential targets of molecular medicine.

Animals↗

PubMedDate not supplied

Quality analysis of in vivo near-infrared fluorescence and conventional gamma images acquired using a dual-labeled tumor-targeting probe.

The cyclic peptide, cyclopentapeptide cyclo(lys-Arg-Gly-Asp-phe) (c(KRGDf)), which is known to target alpha(v)beta3 integrin, is dual-labeled with a radiotracer, (111)indium, for gamma scintigraphy as well as with a near-infrared dye, IRDye800, for continuous-wave (cw) imaging of alpha(v)beta3 positive human M21 melanoma in xenografts. Twenty-four hours after administration of the dual-labeled peptide at a dose equivalent to 90 microCi of (111)In and 5 nmol of near-infrared (NIR) dye, whole-body gamma scintigraphy and cw imaging was conducted. Image acquisition time was 15 min for the gamma scintigraphy images and 800 ms for the optical images acquired using an NIR sensitive intensified charge-coupled device. The results show that while the target-to-background ratio (TBR) of nuclear and optical imaging were similar for surface regions of interest and consistent with the origin of gamma and NIR radiation from a common targeted peptide, the signal-to-noise ratio (SNR) was significantly higher for optical than nuclear imaging. Furthermore, an analysis of SNR versus contrast showed greater sensitivity of optical over nuclear imaging for the subcutaneous tumor targets. While tomographic reconstructions are necessary to probe TBR, SNR, and contrast for interior tissues, this work demonstrates for the first time the direct comparison of molecular optical and planar nuclear imaging for surface and subsurface cancers.

Animals↗

PubMedDate not supplied

Near-infrared fluorescence optical imaging and tomography.

The advent of recent advances in near-infrared laser diodes and fast electro-optic detection has spawned a new research field of diagnostic spectroscopy and imaging based on targeting and reporting exogenous fluorescent agents. This review seeks to concisely address the physics, instrumentation, advancements in tomography, and near-infrared fluorescent contrast agent development that promises selective and specific molecular targeting of diseased tissues. As an example of one area of the field, recent work focusing on pharmacokinetic analysis of fluorophores targeting the epidermal growth factor receptor (EGFR) is presented in a human breast cancer xenograft mouse model to demonstrate specificity of molecularly targeted contrast agents. Finally, a critical evaluation of the limitations and the opportunities for future translation of fluorescence-enhanced optical imaging of deep tissues is presented.

Animals↗

PubMedDate not supplied

Imaging dose-dependent pharmacokinetics of an RGD-fluorescent dye conjugate targeted to alpha v beta 3 receptor expressed in Kaposi's sarcoma.

Dynamic fluorescence images were obtained from xenografts bearing a subcutaneous human Kaposi's sarcoma (KS1767) immediately following the intravenous injection of an integrin-receptor targeting Cy5.5-c(KRGDf) at a dose ranging from 0.75 to 6 nmol/mouse. The fluorescence images were acquired using an intensified charge-coupled device system and were analyzed with a three-compartment pharmacokinetic (PK) model to determine uptake parameters in the tumor and normal tissue regions of interest as a function of administered dose. Our results show that the uptake of Cy5.5-c(KRGDf) in tumor regions were: (i) significantly greater than the contralateral normal tissue regions; (ii) linearly increased with dose of Cy5.5-c(KRGDf) up to 1.5 nmol/mouse; and (iii) blocked by preinjection of c(KRGDf). Above doses of 1.5 nmol/mouse, the uptake no longer increased with dose, suggesting integrin receptor saturation. In normal tissues, the PK uptake parameters were not influenced by Cy5.5-c(KRGDf) dose nor by the preadministration of c(KRGDf).

Animals↗

PubMedDate not supplied

Improved excitation light rejection enhances small-animal fluorescent optical imaging.

Small-animal fluorescence-enhanced imaging involves the detection of weak fluorescent signals emanating from nanomolar to picomolar concentrations of exogenous or endogenously produced fluorophore concurrent with the rejection of an overwhelmingly large component of backscattered excitation light. The elimination of the back-reflected excitation light of the collected signal remains a major and often unrecognized challenge for further reducing the noise floor and increasing sensitivity of small-animal fluorescence imaging. Herein, we show that the combination of three-cavity interference and holographic super notch filters with appropriate imaging lenses to collimate light improves rejection of excitation light, enabling more accurate imaging. To assess excitation leakage, the "out-of-band (S(lambda x))" to "in-band (S(lambda m) - S(lambda x))" signal ratio from phantom studies and the target-to-background ratio (TBR) from in vivo animal imaging was acquired with and without collimating optics. The addition of collimating optics resulted in a 51% to 75% reduction in the ratio of (S(lambda x))/(S(lambda m) - S(lambda x)) for the phantom studies and an improvement of TBR from 11% to 31% and of signal-to-noise ratio from 11% to 142% for an integrin-targeting conjugate in human glioma xenografts.

Animals↗