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Changes in vascular permeability and expression of different angiogenic factors following anti-angiogenic treatment in rat glioma.

Ali MM, Janic B, Babajani-Feremi A, Varma NR, Iskander AS, Anagli J, Arbab AS - PLoS ONE (2010)

Bottom Line: The findings were validated with histochemical and western blot studies.Dynamic contrast-enhanced MRI (DCE-MRI) using a high molecular weight contrast agent albumin-(GdDTPA) showed significantly increased K(trans) at the rim of the treated tumors compared to that of the central part of the treated as well as the untreated (vehicle treated) tumors.These findings indicate that PTK787 treatment induced over expression of VEGF as well as the Flk-1/VEGFR2 receptor tyrosine kinase, especially at the rim of the tumor, as proven by DCE-MRI, SPECT imaging, immunohistochemistry and western blot.

View Article: PubMed Central - PubMed

Affiliation: Cellular and Molecular Imaging Laboratory, Department of Radiology, Henry Ford Hospital, Detroit, Michigan, United States of America.

ABSTRACT

Background: Anti-angiogenic treatments of malignant tumors targeting vascular endothelial growth factor receptors (VEGFR) tyrosine kinase are being used in different early stages of clinical trials. Very recently, VEGFR tyrosine kinase inhibitor (Vetanalib, PTK787) was used in glioma patient in conjunction with chemotherapy and radiotherapy. However, changes in the tumor size, tumor vascular permeability, vascular density, expression of VEGFR2 and other angiogenic factors in response to PTK787 are not well documented. This study was to determine the changes in tumor size, vascular permeability, fractional plasma volume and expression of VEGFR2 in PTK787 treated U-251 glioma rat model by in vivo magnetic resonance imaging (MRI) and single photon emission computed tomography (SPECT). The findings were validated with histochemical and western blot studies.

Methodologies and principal findings: Seven days after implantation of U251 glioma cells, animals were treated with either PTK787 or vehicle-only for two weeks, and then tumor size, tumor vascular permeability transfer constant (K(trans)), fractional plasma volume (fPV) and expression of VEGFR2 and other relevant angiogenic factors were assessed by in vivo MRI and SPECT (Tc-99-HYNIC-VEGF), and by immunohistochemistry and western blot analysis. Dynamic contrast-enhanced MRI (DCE-MRI) using a high molecular weight contrast agent albumin-(GdDTPA) showed significantly increased K(trans) at the rim of the treated tumors compared to that of the central part of the treated as well as the untreated (vehicle treated) tumors. Size of the tumors was also increased in the treated group. Expression of VEGFR2 detected by Tc-99m-HYNIC-VEGF SPECT also showed significantly increased activity in the treated tumors. In PTK787-treated tumors, histological staining revealed increase in microvessel density in the close proximity to the tumor border. Western blot analysis indicated increased expression of VEGF, SDF-1, HIF-1alpha, VEGFR2, VEGFR3 and EGFR at the peripheral part of the treated tumors compared to that of central part of the treated tumors. Similar expression patters were not observed in vehicle treated tumors.

Conclusion: These findings indicate that PTK787 treatment induced over expression of VEGF as well as the Flk-1/VEGFR2 receptor tyrosine kinase, especially at the rim of the tumor, as proven by DCE-MRI, SPECT imaging, immunohistochemistry and western blot.

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Related in: MedlinePlus

SPECT analysis of in vivo accumulation of Tc-99m-HYNIC-VEGF-c.VEGF-c (which targets both VEGFR2 and VEGFR3) was tagged with HYNIC chelators and then labeled with Tc-99m-pertechnetate (Tc-99m) and injected intravenously in PTK787 and vehicle treated rats. One hour after injection, SPECT images were obtained using dedicated animal scanner. All PTK787 treated rats showed increased accumulation of Tc-99m-HYNIC-VEGF-c in the tumors (lower panel, arrows) compared to that of vehicle treated tumors (upper panel, arrows).
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pone-0008727-g003: SPECT analysis of in vivo accumulation of Tc-99m-HYNIC-VEGF-c.VEGF-c (which targets both VEGFR2 and VEGFR3) was tagged with HYNIC chelators and then labeled with Tc-99m-pertechnetate (Tc-99m) and injected intravenously in PTK787 and vehicle treated rats. One hour after injection, SPECT images were obtained using dedicated animal scanner. All PTK787 treated rats showed increased accumulation of Tc-99m-HYNIC-VEGF-c in the tumors (lower panel, arrows) compared to that of vehicle treated tumors (upper panel, arrows).

Mentions: To determine whether there were any changes in the expression of VEGFRs in the PTK787 and vehicle treated tumors, animals underwent SPECT scanning with Tc-99m tagged VEGF-c. All the animals that were treated with PTK787 showed higher activity of Tc-99-VEGF-c in the tumors (Figure 3) compared to that of the animals that were treated with vehicle. The higher expression of VEGFRs was also confirmed by western blotting and immunohistochemical studies (see below).


Changes in vascular permeability and expression of different angiogenic factors following anti-angiogenic treatment in rat glioma.

Ali MM, Janic B, Babajani-Feremi A, Varma NR, Iskander AS, Anagli J, Arbab AS - PLoS ONE (2010)

SPECT analysis of in vivo accumulation of Tc-99m-HYNIC-VEGF-c.VEGF-c (which targets both VEGFR2 and VEGFR3) was tagged with HYNIC chelators and then labeled with Tc-99m-pertechnetate (Tc-99m) and injected intravenously in PTK787 and vehicle treated rats. One hour after injection, SPECT images were obtained using dedicated animal scanner. All PTK787 treated rats showed increased accumulation of Tc-99m-HYNIC-VEGF-c in the tumors (lower panel, arrows) compared to that of vehicle treated tumors (upper panel, arrows).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2806917&req=5

pone-0008727-g003: SPECT analysis of in vivo accumulation of Tc-99m-HYNIC-VEGF-c.VEGF-c (which targets both VEGFR2 and VEGFR3) was tagged with HYNIC chelators and then labeled with Tc-99m-pertechnetate (Tc-99m) and injected intravenously in PTK787 and vehicle treated rats. One hour after injection, SPECT images were obtained using dedicated animal scanner. All PTK787 treated rats showed increased accumulation of Tc-99m-HYNIC-VEGF-c in the tumors (lower panel, arrows) compared to that of vehicle treated tumors (upper panel, arrows).
Mentions: To determine whether there were any changes in the expression of VEGFRs in the PTK787 and vehicle treated tumors, animals underwent SPECT scanning with Tc-99m tagged VEGF-c. All the animals that were treated with PTK787 showed higher activity of Tc-99-VEGF-c in the tumors (Figure 3) compared to that of the animals that were treated with vehicle. The higher expression of VEGFRs was also confirmed by western blotting and immunohistochemical studies (see below).

Bottom Line: The findings were validated with histochemical and western blot studies.Dynamic contrast-enhanced MRI (DCE-MRI) using a high molecular weight contrast agent albumin-(GdDTPA) showed significantly increased K(trans) at the rim of the treated tumors compared to that of the central part of the treated as well as the untreated (vehicle treated) tumors.These findings indicate that PTK787 treatment induced over expression of VEGF as well as the Flk-1/VEGFR2 receptor tyrosine kinase, especially at the rim of the tumor, as proven by DCE-MRI, SPECT imaging, immunohistochemistry and western blot.

View Article: PubMed Central - PubMed

Affiliation: Cellular and Molecular Imaging Laboratory, Department of Radiology, Henry Ford Hospital, Detroit, Michigan, United States of America.

ABSTRACT

Background: Anti-angiogenic treatments of malignant tumors targeting vascular endothelial growth factor receptors (VEGFR) tyrosine kinase are being used in different early stages of clinical trials. Very recently, VEGFR tyrosine kinase inhibitor (Vetanalib, PTK787) was used in glioma patient in conjunction with chemotherapy and radiotherapy. However, changes in the tumor size, tumor vascular permeability, vascular density, expression of VEGFR2 and other angiogenic factors in response to PTK787 are not well documented. This study was to determine the changes in tumor size, vascular permeability, fractional plasma volume and expression of VEGFR2 in PTK787 treated U-251 glioma rat model by in vivo magnetic resonance imaging (MRI) and single photon emission computed tomography (SPECT). The findings were validated with histochemical and western blot studies.

Methodologies and principal findings: Seven days after implantation of U251 glioma cells, animals were treated with either PTK787 or vehicle-only for two weeks, and then tumor size, tumor vascular permeability transfer constant (K(trans)), fractional plasma volume (fPV) and expression of VEGFR2 and other relevant angiogenic factors were assessed by in vivo MRI and SPECT (Tc-99-HYNIC-VEGF), and by immunohistochemistry and western blot analysis. Dynamic contrast-enhanced MRI (DCE-MRI) using a high molecular weight contrast agent albumin-(GdDTPA) showed significantly increased K(trans) at the rim of the treated tumors compared to that of the central part of the treated as well as the untreated (vehicle treated) tumors. Size of the tumors was also increased in the treated group. Expression of VEGFR2 detected by Tc-99m-HYNIC-VEGF SPECT also showed significantly increased activity in the treated tumors. In PTK787-treated tumors, histological staining revealed increase in microvessel density in the close proximity to the tumor border. Western blot analysis indicated increased expression of VEGF, SDF-1, HIF-1alpha, VEGFR2, VEGFR3 and EGFR at the peripheral part of the treated tumors compared to that of central part of the treated tumors. Similar expression patters were not observed in vehicle treated tumors.

Conclusion: These findings indicate that PTK787 treatment induced over expression of VEGF as well as the Flk-1/VEGFR2 receptor tyrosine kinase, especially at the rim of the tumor, as proven by DCE-MRI, SPECT imaging, immunohistochemistry and western blot.

Show MeSH
Related in: MedlinePlus