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Molecular imaging of matrix metalloproteinases expression…
80 Molecular Imaging and Biology, Volume 6, Number 2
No. 40
No. 42
124I POSITRON EMISSION TOMOGRAPHY/COMPUTED TOMOGRAPHY IMAGING OF NIS GENE EXPRESSION IN MYELOMA XENOGRAFTS AFTER INTRAVENOUS INJECTION OF A REPLICATING VIRUS D. Dingli, B. J. Kemp, V. Lowe, J. C. Morris, S. J. Russell Mayo Clinic, Rochester, MN.
MOLECULAR IMAGING OF MATRIX METALLOPROTEINASES EXPRESSION IN METASTATIC TUMORS USING A RADIOLABELED INHIBITOR AND MICROPET W. P. Li, J. E. Sprague, J. Rutlin, S. Achilefu, C. J. Anderson The Mallinckrodt Institute of Radiology and Siteman Cancer Center, Washington University School of Medicine, St. Louis, MO.
With the advent of replication competent viruses for cancer gene therapy, it has become imperative to monitor the biodistribution, expression and replication of these vector systems in living organisms. This study was conducted to explore the feasibility of using 124I positron emission tomography (PET)/computed tomography (CT) imaging to demonstrate sodium iodide symporter (NIS) expression from a replicating virus. The replication competent measles virus engineered to express NIS in infected cells (MV-NIS) and its parent virus, derived from the Edmonston vaccine strain (MV-Edm) were used. CB17 SCID mice were implanted in the right flank with the myeloma cell line MMI and the mice injected with MV-Edm (control) or MV-NIS (2x106 pfu) intravenously when the tumors reached a mean diameter of 0.8cm. Nine days after virus administration, the mice were injected intraperitoneally with 3.4 MBq 124I and imaged using the GE Discovery LS PET/CT scanner. PET/CT images allowed accurate demarcation of mouse anatomy and visualization of the tumors. Quantification of PET images showed a mean iodide uptake of 25.6% in thyroid, 37.5% in stomach, 6.0% in bladder and 7.1% in tumor. Tumors infected with the control virus MV-Edm had only 0.3% uptake which was essentially background. 124I PET resolution was acceptable using a clinical scanner and the urinary bladder and tumor could be clearly demarcated despite their close proximity. 124I PET/CT imaging can demonstrate MV-NIS induced gene expression and biodistribution in a mouse myeloma tumor model after intravenous administration of virus. This method may provide a means to evaluate MVNIS gene expression and biodistribution in clinical trials.
New imaging technologies have developed over the last few years providing novel tools to examine extracellular matrix (ECM) remodeling and protease activity in vivo. Among the enzymes involved in proteolytic degradation of the ECM, which is required for tumor growth, tumor angiogenesis, and metastasis, are the matrix metalloproteinases (MMPs). MMPs are a family of zinc-dependent endopeptidases produced by host and tumor cells, and elevated secretion of MMP 2 and MMP 9, (also called gelatinase A and B) were shown to be correlated with the rapid progression of a variety of cancers. We tested the hypothesis that gelatinase expression may provide a target for monitoring tumor metastatic potential in two tumorbearing mouse models. A bifunctional chelator DOTA (1,4,7,10-tetraazacyclotetradecane-N,N',N'',N'''-tetraacetic acid) was conjugated to a synthetic cyclic peptide, CTTHWGFTLC (CTT), which has been reported as a selective inhibitor of MMP-2/9, and the conjugate was radiolabeled with Cu-64 for biodistribution and microPET imaging. High resolution microPET images as well as traditional biodistribution showed significant tumor uptake from one to four hours post-injection in both MDA-MB-435 breast cancer tumor-bearing mice as early as five-week post-implantation and B16F10 murine melanoma tumor mice at 10 days post-implantation. However, high levels of radioactivity accumulation in the liver were observed, as well as a reduction of tumor uptake over time (from four to 24 hours). Gelatin electrophoresis (zymography) of excised MDA-MB435 and B16F10 tumors from mice confirmed the presence of MMP-2 and MMP-9. These data suggest the possibility of radiolabeled cyclic peptide inhibitors for imaging the metastatic capability of cancers by positron emission tomography (PET).
No. 41 No. 43 PULSED X-RAY IMAGING USING A CARBON NANOTUBE BASED X-RAY SOURCE Y. Z. Lee, J. Zhang, Y. Cheng, J. Lu, O. Zhou, W. Lin University of North Carolina Chapel Hill, Chapel Hill, NC. Introduction: Recently, it has been demonstrated that carbon nanotubes may serve as field emitters for a cold cathode X-ray source, allowing simple and precise control of the X-ray flux. This ability may allow triggered X-ray imaging for small animals. We examined the capability of the nanotube based source to achieve pulsed X-ray imaging and for performing gated planar imaging. Method and Materials: A tungsten-target nanotube based X-ray source was implemented chamber. The source could be operated in two modes, continuously on or pulsed, where pulse durations as short as 100 nanoseconds have been achieved. A Hamamatsu C7921 detector was fixed opposite the source, with 50 x 50 mm field-of-view. Continuous and pulsed imaging was performed on biological and mechanical systems, including the rotation of a fan blade, contrast agent infusion and rat respiration. Triggered imaging was performed on a ventilated rat, with the trigger signal from the ventilator. Results: The maximum frame rate was limited by the detector readout speed (15 fps). X-ray pulses as short as 1 msec were used. The pulsed Xrays were able to prevent the blur induced by the mechanical and biological motions. Gating allowed the acquisition of repeated images with the lungs at fixed positions throughout the respiratory cycle. Conclusions: We demonstrate the first pulsed and gated biological imaging using a carbon nanotube based source. While efforts are ongoing to refine the technique and extend it to tomographic imaging, the ability to freeze biological motion should significantly improve studies of non-stationary tissues
DETECTING PHOSPHOLIPASE A2 ACTIVITY WITH OPTICAL IMAGING AND MAGNETIC RESONANCE SPECTROSCOPY M. Milkevitch, G. Zheng, J. D. Glickson, E. J. Delikatny University of Pennsylvania, Philadelphia, PA. A continuing challenge in the use of imaging for biochemical and physiological information is one of interpretation. Our approach has been to verify biochemical information obtained by magnetic resonance spectroscopy (MRS)/magnetic resonance imaging (MRI) with self-quenching reporter probes that release fluorescent moieties upon enzymatic phospholipase cleavage, with the goal of correlating specific processes with MR-observable metabolic changes. Phospholipases are a series of enzymes that catalyze phospholipid breakdown and perform a number of critical regulatory functions within cells and tissues. Phospholipase A2 (PLA2) levels are increased during inflammation, hyperproliferation and apoptosis. PLA2 has been implicated in a number of diseases including cancer, arthritis and Alzheimer’s disease. NMR studies of cells and tumors have shown increases in glycerophosphocholine (GPC) levels associated with chemo- or radiotherapy that has been proposed to arise from increased phospholipid catabolism and phospholipase activation. In this study, DU145 prostate cancer cells were treated with the differentiating agent phenylbutyrate (PB) and examined using 31P and diffusion-weighted 1H NMR spectroscopy. The self-quenching fluorescent phospholipid analogue, PED-6, was used to detect PLA2 activity. PB caused a dramatic time-dependent increase in 1H mobile fatty acyl chain, total choline and 31P GPC resonances. This was accompanied by significant increases in fluorescence released from PED-6 liposomes in PB-treated cells relative to controls. The combination of these two imaging modalities provides strong evidence that metabolic
No. 40
No. 42
124I POSITRON EMISSION TOMOGRAPHY/COMPUTED TOMOGRAPHY IMAGING OF NIS GENE EXPRESSION IN MYELOMA XENOGRAFTS AFTER INTRAVENOUS INJECTION OF A REPLICATING VIRUS D. Dingli, B. J. Kemp, V. Lowe, J. C. Morris, S. J. Russell Mayo Clinic, Rochester, MN.
MOLECULAR IMAGING OF MATRIX METALLOPROTEINASES EXPRESSION IN METASTATIC TUMORS USING A RADIOLABELED INHIBITOR AND MICROPET W. P. Li, J. E. Sprague, J. Rutlin, S. Achilefu, C. J. Anderson The Mallinckrodt Institute of Radiology and Siteman Cancer Center, Washington University School of Medicine, St. Louis, MO.
With the advent of replication competent viruses for cancer gene therapy, it has become imperative to monitor the biodistribution, expression and replication of these vector systems in living organisms. This study was conducted to explore the feasibility of using 124I positron emission tomography (PET)/computed tomography (CT) imaging to demonstrate sodium iodide symporter (NIS) expression from a replicating virus. The replication competent measles virus engineered to express NIS in infected cells (MV-NIS) and its parent virus, derived from the Edmonston vaccine strain (MV-Edm) were used. CB17 SCID mice were implanted in the right flank with the myeloma cell line MMI and the mice injected with MV-Edm (control) or MV-NIS (2x106 pfu) intravenously when the tumors reached a mean diameter of 0.8cm. Nine days after virus administration, the mice were injected intraperitoneally with 3.4 MBq 124I and imaged using the GE Discovery LS PET/CT scanner. PET/CT images allowed accurate demarcation of mouse anatomy and visualization of the tumors. Quantification of PET images showed a mean iodide uptake of 25.6% in thyroid, 37.5% in stomach, 6.0% in bladder and 7.1% in tumor. Tumors infected with the control virus MV-Edm had only 0.3% uptake which was essentially background. 124I PET resolution was acceptable using a clinical scanner and the urinary bladder and tumor could be clearly demarcated despite their close proximity. 124I PET/CT imaging can demonstrate MV-NIS induced gene expression and biodistribution in a mouse myeloma tumor model after intravenous administration of virus. This method may provide a means to evaluate MVNIS gene expression and biodistribution in clinical trials.
New imaging technologies have developed over the last few years providing novel tools to examine extracellular matrix (ECM) remodeling and protease activity in vivo. Among the enzymes involved in proteolytic degradation of the ECM, which is required for tumor growth, tumor angiogenesis, and metastasis, are the matrix metalloproteinases (MMPs). MMPs are a family of zinc-dependent endopeptidases produced by host and tumor cells, and elevated secretion of MMP 2 and MMP 9, (also called gelatinase A and B) were shown to be correlated with the rapid progression of a variety of cancers. We tested the hypothesis that gelatinase expression may provide a target for monitoring tumor metastatic potential in two tumorbearing mouse models. A bifunctional chelator DOTA (1,4,7,10-tetraazacyclotetradecane-N,N',N'',N'''-tetraacetic acid) was conjugated to a synthetic cyclic peptide, CTTHWGFTLC (CTT), which has been reported as a selective inhibitor of MMP-2/9, and the conjugate was radiolabeled with Cu-64 for biodistribution and microPET imaging. High resolution microPET images as well as traditional biodistribution showed significant tumor uptake from one to four hours post-injection in both MDA-MB-435 breast cancer tumor-bearing mice as early as five-week post-implantation and B16F10 murine melanoma tumor mice at 10 days post-implantation. However, high levels of radioactivity accumulation in the liver were observed, as well as a reduction of tumor uptake over time (from four to 24 hours). Gelatin electrophoresis (zymography) of excised MDA-MB435 and B16F10 tumors from mice confirmed the presence of MMP-2 and MMP-9. These data suggest the possibility of radiolabeled cyclic peptide inhibitors for imaging the metastatic capability of cancers by positron emission tomography (PET).
No. 41 No. 43 PULSED X-RAY IMAGING USING A CARBON NANOTUBE BASED X-RAY SOURCE Y. Z. Lee, J. Zhang, Y. Cheng, J. Lu, O. Zhou, W. Lin University of North Carolina Chapel Hill, Chapel Hill, NC. Introduction: Recently, it has been demonstrated that carbon nanotubes may serve as field emitters for a cold cathode X-ray source, allowing simple and precise control of the X-ray flux. This ability may allow triggered X-ray imaging for small animals. We examined the capability of the nanotube based source to achieve pulsed X-ray imaging and for performing gated planar imaging. Method and Materials: A tungsten-target nanotube based X-ray source was implemented chamber. The source could be operated in two modes, continuously on or pulsed, where pulse durations as short as 100 nanoseconds have been achieved. A Hamamatsu C7921 detector was fixed opposite the source, with 50 x 50 mm field-of-view. Continuous and pulsed imaging was performed on biological and mechanical systems, including the rotation of a fan blade, contrast agent infusion and rat respiration. Triggered imaging was performed on a ventilated rat, with the trigger signal from the ventilator. Results: The maximum frame rate was limited by the detector readout speed (15 fps). X-ray pulses as short as 1 msec were used. The pulsed Xrays were able to prevent the blur induced by the mechanical and biological motions. Gating allowed the acquisition of repeated images with the lungs at fixed positions throughout the respiratory cycle. Conclusions: We demonstrate the first pulsed and gated biological imaging using a carbon nanotube based source. While efforts are ongoing to refine the technique and extend it to tomographic imaging, the ability to freeze biological motion should significantly improve studies of non-stationary tissues
DETECTING PHOSPHOLIPASE A2 ACTIVITY WITH OPTICAL IMAGING AND MAGNETIC RESONANCE SPECTROSCOPY M. Milkevitch, G. Zheng, J. D. Glickson, E. J. Delikatny University of Pennsylvania, Philadelphia, PA. A continuing challenge in the use of imaging for biochemical and physiological information is one of interpretation. Our approach has been to verify biochemical information obtained by magnetic resonance spectroscopy (MRS)/magnetic resonance imaging (MRI) with self-quenching reporter probes that release fluorescent moieties upon enzymatic phospholipase cleavage, with the goal of correlating specific processes with MR-observable metabolic changes. Phospholipases are a series of enzymes that catalyze phospholipid breakdown and perform a number of critical regulatory functions within cells and tissues. Phospholipase A2 (PLA2) levels are increased during inflammation, hyperproliferation and apoptosis. PLA2 has been implicated in a number of diseases including cancer, arthritis and Alzheimer’s disease. NMR studies of cells and tumors have shown increases in glycerophosphocholine (GPC) levels associated with chemo- or radiotherapy that has been proposed to arise from increased phospholipid catabolism and phospholipase activation. In this study, DU145 prostate cancer cells were treated with the differentiating agent phenylbutyrate (PB) and examined using 31P and diffusion-weighted 1H NMR spectroscopy. The self-quenching fluorescent phospholipid analogue, PED-6, was used to detect PLA2 activity. PB caused a dramatic time-dependent increase in 1H mobile fatty acyl chain, total choline and 31P GPC resonances. This was accompanied by significant increases in fluorescence released from PED-6 liposomes in PB-treated cells relative to controls. The combination of these two imaging modalities provides strong evidence that metabolic