Intravital Monitoring of Vasculature After Targeted Gene Therapy Alone or Combined With Tumor Irradiation

Vascular-targeted therapies exhibit radiosensitizing effects by remodeling tumor vasculature, thus facilitating the increased oxygenation of the remaining tumor tissue. To examine these phenomena, the effects of antiendoglin gene therapy alone and in combination with irradiation were monitored for 5 consecutive days on a murine mammary adenocarcinoma (TS/A) tumor model growing in a dorsal window chamber. The vascularization of the tumors was assessed by the determination of the tumor vascular area and by measurement of tumor perfusion by using laser Doppler flowmetry to provide insight into intratumoral gene electrotransfer effects. The changes in the vascular area after this specific therapy correlated with laser Doppler measurements, indicating that either of the methods can be used to demonstrate the induced changes in the vascularization and perfusion of tumors. Gene electrotransfer with an endothelial-specific promoter resulted in a vascular-targeted effect on tumor vasculature within the first 24 hours and did not restore within 5 days. The combination with the irradiation did not result in a more pronounced vascular effect, and irradiation alone only abrogated the formation of new vessels and prevented an increase in the tumor perfusion over time. The results indicate that tumors grown in a dorsal window chamber facilitate intravital measurements of the vascularization of tumors and blood perfusion, enabling the monitoring of the antiangiogenic or vascular disruptive effects of different therapies.