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. 2012 Dec;29(12):3312-24.
doi: 10.1007/s11095-012-0823-4. Epub 2012 Jul 14.

Mechanisms of tumor vascular priming by a nanoparticulate doxorubicin formulation

Tista Roy Chaudhuri  1 , Robert D Arnold, Jun Yang, Steven G Turowski, Yang Qu, Joseph A Spernyak, Richard Mazurchuk, Donald E Mager, Robert M Straubinger
Affiliations

Mechanisms of tumor vascular priming by a nanoparticulate doxorubicin formulation

Tista Roy Chaudhuri et al. Pharm Res. 2012 Dec.

Abstract

Purpose: Tumor vascular normalization by antiangiogenic agents may increase tumor perfusion but reestablish vascular barrier properties in CNS tumors. Vascular priming via nanoparticulate carriers represents a mechanistically distinct alternative. This study investigated mechanisms by which sterically-stabilized liposomal doxorubicin (SSL-DXR) modulates tumor vascular properties.

Methods: Functional vascular responses to SSL-DXR were investigated in orthotopic rat brain tumors using deposition of fluorescent permeability probes and dynamic contrast-enhanced magnetic resonance imaging. Microvessel density and tumor burden were quantified by immunohistochemistry (CD-31) and quantitative RT-PCR (VE-cadherin).

Results: Administration of SSL-DXR (5.7 mg/kg iv) initially (3-4 days post-treatment) decreased tumor vascular permeability, k(trans) (vascular exchange constant), vascular endothelial cell content, microvessel density, and deposition of nanoparticulates. Tumor vasculature became less chaotic. Permeability and perfusion returned to control values 6-7 days post-treatment, but intratumor SSL-DXR depot continued to effect tumor vascular endothelial compartment 7-10 days post-treatment, mediating enhanced permeability.

Conclusions: SSL-DXR ultimately increased tumor vascular permeability, but initially normalized tumor vasculature and decreased tumor perfusion, permeability, and nanoparticulate deposition. These temporal changes in vascular integrity resulting from a single SSL-DXR dose have important implications for the design of combination therapies incorporating nanoparticle-based agents for tumor vascular priming.

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Figures

Fig. 1
Fig. 1
Temporal effects of SSL-DXR administration on intracranial 9L tumor vascular perfusion and permeability. Fisher 344male rats (n=8–10/treatment group) bearing intracranial 9L tumors were treated iv with a single dose of SSL-DXR (5.7 mg DXR/kg) when tumors reached a volume of 3–5 mm3 (7–9 days after implantation). Controls received saline. Tumor volume was estimated from high-resolution T2-weighted images and DCE-MRI with Gd-DTPA contrast agent was performed for vascular permeability and perfusion measurements. T1 relaxation rate measurements were acquired before, during, and after Gd-DTPA infusion. (a) Tumor concentration-time profile of Gd-DTPA 3 days after SSL-DXR (circles, solid line) or saline (squares, dashed line) treatment. Concentration of Gd-DTPA was determined from T1 relaxation rates (Methods). Lines through the data represent the best fit of the Michaelis-Menten equation. (b) Gd-DTPA exposure of treated vs. control tumors on different days after SSL-DXR treatment. Open bars: SSL-DXR-treated animals; hatched bars: control animals. Ordinate: AUC0–50 (area under Gd-DTPA concentration-time curve) determined for the 50 min following infusion. The 2-fold reduction in AUC for SSL-DXR-treated animals was significant (*, P<0.05) on day 3. (c) The tumor:vasculature exchange constant ktrans was calculated for Gd-DTPA using a population PK model (Methods). The 3-fold lower value of ktrans in treated animals differed significantly (*, P<0.05) from controls on day 3. (d) ve (extracellular volume available to Gd-DTPA) was significantly (**, P<0.01) lower on day 3 in tumors of treated animals compared to controls.
Fig. 2
Fig. 2
Effect of single SSL-DXR treatment on permeability of intracranial 9L tumors to fluorescently-labeled sterically-stabilized liposomes. Three and 6 days after treatment with SSL-DXR, animals were injected iv with 85–110 nm SSL labeled with 0.1 mole% of the non-exchangeable fluorophore DiIC18(5)-DS and sacrificed at 24 h. The brain was rapidly removed, frozen, and 10 µm sections were cut. Panoramas encompassing the entire tumor region were acquired using constant exposure conditions (Methods). (a) Tumors of saline-treated controls or (b) SSL-DXR-treated animals injected iv with fluorescent SSL 3 days after treatment and imaged 1 day later. Accretions of fluorescent DiI-SSL in tumors of SSL-DXR-treated animals were smaller and less numerous than in control animals, but contained a larger number of strand-like features resembling perfused vessels. (c) Tumors of controls or (d) treated animals injected iv with DiI-SSL 6 days after SSL-DXR treatment and imaged 1 day later. The tumor core of both control- and treated animals showed decreased overall DiI-SSL deposition on day 6–7 compared to day 3–4, but were similar to each other. Bar: 50 µm. Image intensity in (c) and (d) was increased to reveal patterns of deposition.
Fig. 3
Fig. 3
Quantification of SSL-DXR effects on intracranial 9L tumor vascular permeability to sterically-stabilized probe liposomes. Tumor deposition of fluorescent DiI-SSL was quantified from images of 10 µm frozen tissue sections encompassing the entire tumor of control- and SSL-DXR-treated animals (cf. Fig. 2) using ImageJ. (a) Deposition of DiI-SSL in the tumor core region of SSL-treated-(open bars) or control (hatched bars) animals. Ordinate: arbitrary fluorescence units per unit area over equal-sized regions-of-interest (ROI). The difference between SSL-DXR-treated and control groups was significant for animals injected on day 3 post treatment with DiI-SSL (*, P<0.05), but not in animals probed on day 6 after treatment. (b) Deposition of DiI-SSL in the invasive peripheral tumor region at varying times after SSL-DXR treatment. The difference between SSL-DXR-treated and control animals was significant for animals injected on day 3 post treatment with DiI-SSL (**, P<0.01), but not on day 6. (c) The uniformity of intratumor deposition of DiI-SSL was quantified for animals injected with the probe liposomes on day 3 or 6 after SSL-DXR treatment or control (saline) administration (Methods). A higher variability of fluorescence (ordinate) indicates less uniform deposition in the control group. SSL-DXR treatment reduced the covariance of fluorescent intensity significantly (**, P<0.01), indicating more uniform intratumor deposition.
Fig. 4
Fig. 4
Changes in tumor microvessel density and morphology mediated by SSL-DXR. Microvessel density and morphology were evaluated by CD31 immunostaining of frozen tumor sections obtained at the same times that tumor vasculature was probed for permeability (cf. Figs. 2 and 3). (a) Control animals showed chaotic, disorganized tumor microvasculature 4 days after saline treatment. (b) SSL-DXR-treated animals showed fewer but larger organized, intensely-staining CD31-positive structures 4 days after treatment. Bar represents 50 µm.
Fig. 5
Fig. 5
Effect of SSL-DXR treatment on tumor content of vascular endothelial cells. Changes in tumor content of vascular endothelial cells or tumor cells mediated by a single dose of SSL-DXR were quantified by RT-PCR. On days 2, 4, 7, 9 and 11 after SSL-DXR treatment, groups of 3–5 animals treated with SSL-DXR or saline (controls) were sacrificed. Tumor burden (eGFP expression) and endothelial cell content (VE-cadherin, PECAM-1) were determined by qRT-PCR analysis. (a) VE-cadherin expression in tumor as a function of time after treatment with SSL-DXR (filled circles, solid line) or saline (control; filled squares, dashed line). Ordinate: data were normalized against multiple ‘house-keeping’ genes (Methods) and axis represents relative copy number. Treatment with a single dose of SSL-DXR abrogated the expansion of tumor endothelial cell content that was observed in control animals. The difference between control- and treated animals was significant on day 7 (*, P<0.05). (b) Tumor cell density in harvested tissue samples based on 9L-eGFP cells included in tumor inoculum. Relative abundance of tumor cells increased as tumors grew more dense, excluding normal brain cells. (c) Vascular endothelium:tumor cell ratio in tissue samples. VE-cadherin expression (a) was normalized for each individual animal by its corresponding eGFP (tumor) content (b). The 7-fold suppression of VE-cadherin:eGFP ratio in SSL-DXR-treated animals relative to controls was statistically significant (*, P<0.05). The data are the results of one complete, representative experiment. The experiment was performed twice, with at least 5 time points and n=3–5 animals per treatment group at each time point. The effect of SSL-DXR treatment to suppress peak endothelial cell expansion was statistically significant in both experiments (*, P<0.05).
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References

    1. Jemal A, Siegel R, Ward E, Hao Y, Xu J, Thun MJ. Cancer statistics, 2009. CA Cancer J Clin. 2009;59:225–249. - PubMed
    1. Ries LAG, Kosary CL, Hankey BF, Miller BA, Clegg L, Edwards BK. Surveillance epidemiology end result (SEER) cancer statistics review 1973–1996. Bethesda: National Cancer Institute. 1999
    1. Packer RJ. Brain tumors in children. Arch Neurol. 1999;56:421–425. - PubMed
    1. Fathallah-Shaykh H. New molecular strategies to cure brain tumors. Arch Neurol. 1999;56:449–453. - PubMed
    1. Demuth T, Rennert JL, Hoelzinger DB, Reavie LB, Nakada M, Beaudry C, et al. Glioma cells on the run—the migratory transcriptome of 10 human glioma cell lines. BMC Genomics. 2008;9:54. - PMC - PubMed

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