Abstract 85: Noninvasive imaging of tumor hypoxia during radiation-induced tumor vascular disruption
Authors: Kelada Olivia J. , Kunjachan Sijumon , Virani Needa A. , Detappe Alexandre , Hayashi Jennifer , Ireland Thomas , Biancur Douglas E. , Kumar Rajiv , Sridhar Srinivas , Makrigiorgos Mike , Berbeco Ross I. 
Published: August 2019

Purpose Tumor vascular targeted gold nanoparticles induce tumor vascular disruption when combined with external beam radiation therapy. Although effective in suppressing tumor growth and improving progression-free survival, tumor hypoxia may be a potential challenge in this anti-vascular therapy. Here, we investigate, the dynamic changes in tumor hypoxia pre- and post-radiation therapy using a gold nanoparticle-based tumor vascular disrupting agent.

Materials and methods 4-6 weeks old female nude-FOXn1 mice were subcutaneously inoculated with human A549 cells (~3×106) into the left flank. Functionalized gold nanoparticles (AuNP) were used to target the tumor blood vessels and tumor vascular disruption was induced via radiation. 10 Gy radiation treatment was delivered using a clinical radiation beam (6 MV) and HypoxiSense680 based in vivo fluorescence imaging was performed to visualize changes in tumor hypoxia at 24 h, 48 h and an extended period of 10 days. Tumor hypoxia was confirmed via immunohistochemistry. Mice were divided into four treatment groups: control, AuNP only, IR only, and AuNP+IR. Following treatment, tumor progression and overall survival was measured. Further analysis of nanoparticle biodistribution and toxicity were accessed using TEM Imaging, IC-PMS, and immunohistochemistry.

Results Longitudinal changes in tumor hypoxia were observed in all radiation-based treatment conditions. Combining gold nanoparticle and radiation resulted in an increase in tumor hypoxia at 48 h (p &lt; 0.05) and a return to baseline in 10 days. In contrast, the ‘radiation only’ group showed an increase in tumor hypoxia by a factor of 0.5 at 48 h post-IR compared to baseline while 10 days later the tumor hypoxia remained stable. Quantitative variation in the hypoxia blood factor, CA9 increased 24 h post IR in the AuNP+IR, followed by a decrease in hypoxic by day 10 in accordance with in vivo imaging data. No change was observed with the IR only group. These findings were confirmed with representative pimonidazole staining that showed an increase in tumor hypoxia a few hours after AuNP+IR treatment. The mean relative reduction in tumor size post-treatment was a factor of 5.2 (p &lt; 0.05) in the AuNP+IR group compared to the control and 3.5 compared to the IR only group, nearly 80 days post-treatment. Overall survival showed an average gain of up to 24 days in the AuNP+IR group compared to all other treatments. Almost 100 days post-treatment, 50% survival was observed in the AuNP+IR group compared to 20% in the IR-only groups (p &lt; 0.05).

Conclusions Noninvasive imaging showed that AuNP+IR results in a transient increase and subsequent decline in mean tumor hypoxia, leading to substantial tumor regression and an overall increase in tumor survival. High radiation-induced vascular damage may lead to better tumor reduction and prolonged survival in the human non-small cell lung cancer model.

Citation Format: Olivia J. Kelada, Sijumon Kunjachan, Needa A. Virani, Alexandre Detappe, Jennifer Hayashi, Thomas Ireland, Douglas E. Biancur, Rajiv Kumar, Srinivas Sridhar, Mike Makrigiorgos, Ross I. Berbeco. Noninvasive imaging of tumor hypoxia during radiation-induced tumor vascular disruption [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 85.