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Pinhole micro-SPECT/CT for noninvasive monitoring and quantitation of oncolytic virus dispersion and percent infection in solid tumors.

Penheiter AR, Griesmann GE, Federspiel MJ, Dingli D, Russell SJ, Carlson SK - Gene Ther. (2011)

Bottom Line: The purpose of our study was to validate the ability of pinhole micro-single-photon emission computed tomography/computed tomography (SPECT/CT) to: 1) accurately resolve the intratumoral dispersion pattern and 2) quantify the infection percentage in solid tumors of an oncolytic measles virus encoding the human sodium iodide symporter (MV-NIS).We reliably resolved multiple distinct intratumoral zones of infection from non-infected regions.Pinhole micro-SPECT/CT imaging using the NIS reporter demonstrated precise localization and quantitation of oncolytic MV-NIS infection, and can replace more time-consuming and expensive analyses (for example, autoradiography and IHC) that require animal killing.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Medicine, Mayo Clinic, Rochester, MN 55905, USA.

ABSTRACT
The purpose of our study was to validate the ability of pinhole micro-single-photon emission computed tomography/computed tomography (SPECT/CT) to: 1) accurately resolve the intratumoral dispersion pattern and 2) quantify the infection percentage in solid tumors of an oncolytic measles virus encoding the human sodium iodide symporter (MV-NIS). Sodium iodide symporter (NIS) RNA level and dispersion pattern were determined in control and MV-NIS-infected BxPC-3 pancreatic tumor cells and mouse xenografts using quantitative, real-time, reverse transcriptase, polymerase chain reaction, autoradiography and immunohistochemistry (IHC). Mice with BxPC-3 xenografts were imaged with (123)I or (99)TcO(4) micro-SPECT/CT. Tumor dimensions and radionuclide localization were determined with imaging software. Linear regression and correlation analyses were performed to determine the relationship between tumor infection percentage and radionuclide uptake (% injected dose per gram) above background and a highly significant correlation was observed (r(2)=0.947). A detection threshold of 1.5-fold above the control tumor uptake (background) yielded a sensitivity of 2.7% MV-NIS-infected tumor cells. We reliably resolved multiple distinct intratumoral zones of infection from non-infected regions. Pinhole micro-SPECT/CT imaging using the NIS reporter demonstrated precise localization and quantitation of oncolytic MV-NIS infection, and can replace more time-consuming and expensive analyses (for example, autoradiography and IHC) that require animal killing.

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Quantitation of Percent Tumor Cell Infection and Correlation with NIS-Mediated Ex Vivo 123I Uptake. A, Representative tumor is divided into 10 equally spaced, immunohistochemically stained sections. B, 123I uptake for 5 BXPC-3 tumors infected with MV-NIS and 3 control tumors (no MV-NIS) was plotted against percentage of infected BxPC-3 cells (determined by automated threshold pixel analysis). The solid line is a linear fit to the data (r2 = 0.947; P<.0001); the dashed line is a simulation using values for percentage of infected cells determined by NIS RNA analysis. NIS denotes sodium iodide symporter; MV-NIS, measles virus expressing NIS.
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Figure 4: Quantitation of Percent Tumor Cell Infection and Correlation with NIS-Mediated Ex Vivo 123I Uptake. A, Representative tumor is divided into 10 equally spaced, immunohistochemically stained sections. B, 123I uptake for 5 BXPC-3 tumors infected with MV-NIS and 3 control tumors (no MV-NIS) was plotted against percentage of infected BxPC-3 cells (determined by automated threshold pixel analysis). The solid line is a linear fit to the data (r2 = 0.947; P<.0001); the dashed line is a simulation using values for percentage of infected cells determined by NIS RNA analysis. NIS denotes sodium iodide symporter; MV-NIS, measles virus expressing NIS.

Mentions: Automated threshold pixel analysis was then performed on 10 equally spaced, whole-tumor, IHC-stained sections (Figure 4A) to determine the percentage of infected BxPC-3 tumor cells. In this representative tumor, the total area of the 10 sections was 209.941 mm2. When corrected for stromal content (multiplying by 0.70), the area occupied by BxPC-3 cells was calculated to be 146.96 mm2. With automated threshold pixel analysis, the infected area was measured as 12.965 mm2; after correction with the recovery coefficient (dividing by 0.396), the area was 32.79 mm2. Therefore, the percentage of BxPC-3 cells infected with MV-NIS was 22.3%. The measured 123I uptake for the tumor was 13.1 %ID/g. Applying the linear regression equation calculated above (Figure 1B), 13.1 %ID/g corresponded to a predicted 24.2% infection of BxPC-3 cells. This technique was performed on 8 additional tumors (in total, 5 infected, 3 control tumors). Figure 4B shows the relationship between the infection rates predicted by IHC quantitation and measured by 123I uptake. The close agreement between the 2 methods (NIS RNA–based prediction and MV-NIS–based IHC quantitation with automated threshold pixel analysis) validates the quantitative NIS-mediated radionuclide accumulation method to predict the percentage of infected tumor cells.


Pinhole micro-SPECT/CT for noninvasive monitoring and quantitation of oncolytic virus dispersion and percent infection in solid tumors.

Penheiter AR, Griesmann GE, Federspiel MJ, Dingli D, Russell SJ, Carlson SK - Gene Ther. (2011)

Quantitation of Percent Tumor Cell Infection and Correlation with NIS-Mediated Ex Vivo 123I Uptake. A, Representative tumor is divided into 10 equally spaced, immunohistochemically stained sections. B, 123I uptake for 5 BXPC-3 tumors infected with MV-NIS and 3 control tumors (no MV-NIS) was plotted against percentage of infected BxPC-3 cells (determined by automated threshold pixel analysis). The solid line is a linear fit to the data (r2 = 0.947; P<.0001); the dashed line is a simulation using values for percentage of infected cells determined by NIS RNA analysis. NIS denotes sodium iodide symporter; MV-NIS, measles virus expressing NIS.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3198860&req=5

Figure 4: Quantitation of Percent Tumor Cell Infection and Correlation with NIS-Mediated Ex Vivo 123I Uptake. A, Representative tumor is divided into 10 equally spaced, immunohistochemically stained sections. B, 123I uptake for 5 BXPC-3 tumors infected with MV-NIS and 3 control tumors (no MV-NIS) was plotted against percentage of infected BxPC-3 cells (determined by automated threshold pixel analysis). The solid line is a linear fit to the data (r2 = 0.947; P<.0001); the dashed line is a simulation using values for percentage of infected cells determined by NIS RNA analysis. NIS denotes sodium iodide symporter; MV-NIS, measles virus expressing NIS.
Mentions: Automated threshold pixel analysis was then performed on 10 equally spaced, whole-tumor, IHC-stained sections (Figure 4A) to determine the percentage of infected BxPC-3 tumor cells. In this representative tumor, the total area of the 10 sections was 209.941 mm2. When corrected for stromal content (multiplying by 0.70), the area occupied by BxPC-3 cells was calculated to be 146.96 mm2. With automated threshold pixel analysis, the infected area was measured as 12.965 mm2; after correction with the recovery coefficient (dividing by 0.396), the area was 32.79 mm2. Therefore, the percentage of BxPC-3 cells infected with MV-NIS was 22.3%. The measured 123I uptake for the tumor was 13.1 %ID/g. Applying the linear regression equation calculated above (Figure 1B), 13.1 %ID/g corresponded to a predicted 24.2% infection of BxPC-3 cells. This technique was performed on 8 additional tumors (in total, 5 infected, 3 control tumors). Figure 4B shows the relationship between the infection rates predicted by IHC quantitation and measured by 123I uptake. The close agreement between the 2 methods (NIS RNA–based prediction and MV-NIS–based IHC quantitation with automated threshold pixel analysis) validates the quantitative NIS-mediated radionuclide accumulation method to predict the percentage of infected tumor cells.

Bottom Line: The purpose of our study was to validate the ability of pinhole micro-single-photon emission computed tomography/computed tomography (SPECT/CT) to: 1) accurately resolve the intratumoral dispersion pattern and 2) quantify the infection percentage in solid tumors of an oncolytic measles virus encoding the human sodium iodide symporter (MV-NIS).We reliably resolved multiple distinct intratumoral zones of infection from non-infected regions.Pinhole micro-SPECT/CT imaging using the NIS reporter demonstrated precise localization and quantitation of oncolytic MV-NIS infection, and can replace more time-consuming and expensive analyses (for example, autoradiography and IHC) that require animal killing.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Medicine, Mayo Clinic, Rochester, MN 55905, USA.

ABSTRACT
The purpose of our study was to validate the ability of pinhole micro-single-photon emission computed tomography/computed tomography (SPECT/CT) to: 1) accurately resolve the intratumoral dispersion pattern and 2) quantify the infection percentage in solid tumors of an oncolytic measles virus encoding the human sodium iodide symporter (MV-NIS). Sodium iodide symporter (NIS) RNA level and dispersion pattern were determined in control and MV-NIS-infected BxPC-3 pancreatic tumor cells and mouse xenografts using quantitative, real-time, reverse transcriptase, polymerase chain reaction, autoradiography and immunohistochemistry (IHC). Mice with BxPC-3 xenografts were imaged with (123)I or (99)TcO(4) micro-SPECT/CT. Tumor dimensions and radionuclide localization were determined with imaging software. Linear regression and correlation analyses were performed to determine the relationship between tumor infection percentage and radionuclide uptake (% injected dose per gram) above background and a highly significant correlation was observed (r(2)=0.947). A detection threshold of 1.5-fold above the control tumor uptake (background) yielded a sensitivity of 2.7% MV-NIS-infected tumor cells. We reliably resolved multiple distinct intratumoral zones of infection from non-infected regions. Pinhole micro-SPECT/CT imaging using the NIS reporter demonstrated precise localization and quantitation of oncolytic MV-NIS infection, and can replace more time-consuming and expensive analyses (for example, autoradiography and IHC) that require animal killing.

Show MeSH
Related in: MedlinePlus