Differential mechanisms associated with vascular disrupting action of electrochemotherapy: intravital microscopy on the level of single normal and tumor blood vessels.

Bostjan Markelc,Gregor Sersa,Maja Cemazar,Boris Rubinsky

doi:10.1371/journal.pone.0059557

Bostjan Markelc, Gregor Sersa + Show 2 more

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https://doi.org/10.1371/journal.pone.0059557

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Journal: PloS one	Publication Date: Mar 26, 2013
Citations: 141	License type: CC BY 4.0

Affiliation: Institute of Oncology Ljubljana

Abstract

Electropermeabilization/electroporation (EP) provides a tool for the introduction of molecules into cells and tissues. In electrochemotherapy (ECT), cytotoxic drugs are introduced into cells in tumors, and nucleic acids are introduced into cells in gene electrotransfer. The normal and tumor tissue blood flow modifying effects of EP and the vascular disrupting effect of ECT in tumors have already been determined. However, differential effects between normal vs. tumor vessels, to ensure safety in the clinical application of ECT, have not been determined yet. Therefore, the aim of our study was to determine the effects of EP and ECT with bleomycin on the HT-29 human colon carcinoma tumor model and its surrounding blood vessels. The response of blood vessels to EP and ECT was monitored in real time, directly at the single blood vessel level, by in vivo optical imaging in a dorsal window chamber in SCID mice with 70 kDa fluorescently labeled dextrans. The response of tumor blood vessels to EP and ECT started to differ within the first hour. Both therapies induced a vascular lock, decreased functional vascular density (FVD) and increased the diameter of functional blood vessels within the tumor. The effects were more pronounced for ECT, which destroyed the tumor blood vessels within 24 h. Although the vasculature surrounding the tumor was affected by EP and ECT, it remained functional. The study confirms the current model of tumor blood flow modifying effects of EP and provides conclusive evidence that ECT is a vascular disrupting therapy with a specific effect on the tumor blood vessels.

Highlights

Electrochemotherapy (ECT) is a widely used treatment modality for the treatment of cancer, predominantly melanoma metastases in the skin
For the maximal anti-tumor effect of ECT, the drug must be injected 3 min before EP [37], the filling kinetics of the tumor blood vessels were determined after the injection of fluorescein isothiocyanate-labeled dextran (FD)
When only EP was performed, the leakage of FD began with a short delay of 2 min and thereafter remained present throughout the observation period, but it was limited only to the tumor blood vessels, which were re-perfused after EP (Figs. 2, 3)

Summary

Introduction

Electrochemotherapy (ECT) is a widely used treatment modality for the treatment of cancer, predominantly melanoma metastases in the skin. Its merits are increasingly exploited in other tumor types, and the technology is being adopted for the treatment of deep-seated tumors like liver, bone and brain metastases, and oesophageal and colon tumors [1,2]. EP is increasingly used for the delivery of different nucleic acids (plasmid DNA, siRNA etc.) into the cells in vitro and different tissues in vivo. This application of EP is termed gene electrotransfer (GET) and can be used in DNA vaccination [5,6] or in the treatment of cancer [7,8,9,10,11]

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