Abstract A08: Investigating tumor vasculature development and the effects of OXi4503 by non-invasive photoacoustic imaging

Abstract

Abstract Vasculature-targeted cancer therapies, such as vascular disrupting or anti-angiogenic agents, interact directly with tumor blood vessels. Direct longitudinal assessment of vascular response, as opposed to indirect measures of tumor volume, would aid clinical translation for these targeted therapies, but novel treatment strategies require adequate biomarkers of response. OXi4503 (Combretastatin-A1 phosphate, CA1P) is a vascular disrupting agent (VDA) known to have significant antitumor effects against a wide range of pre-clinical human tumor model systems, and in the clinic. OXi4503 causes disruption of the central tumor vasculature within an hour of administration, followed by thrombosis and vessel occlusion, resulting in massive central tumor necrosis 24 hours after treatment but leaving a thin viable rim of tumor cells. Photoacoustic imaging (PAI) is a novel non-ionising and non-invasive technique, that provides 3D images of the vascular microenvironment with high spatial resolution. Structural information of blood vessel location, and potentially functional data as well, can therefore be obtained in a longitudinal manner. It is thus ideally suited to assess preclinical models of subcutaneous tumors with regard to vascular targeted therapies. We have used PAI to investigate the development of tumor blood vessels, and the effects of OXi4503 (40mg/kg) on the vasculature of 2 human colorectal xenografts grown in nude mice. Results: The human colorectal tumor cell lines SW1222 and LS174T were established as subcutaneous models in nude mice, by the injection of 5X106 tumor cells. Using PAI we were able to: Determine the extent and pattern of tumor vascularization, non-invasively, over time Differentiate between the pathophysiologies of different tumor types Follow the response to vascular targeted therapy Determine the length of time to tumor regrowth following therapy Conclusion: The data suggest that PAI could prove invaluable in providing imaging biomarkers of response to treatment for vascular targeted therapies, with potential for clinical translation. Citation Format: Sean Peter Johnson, Ollie Ogunlade, Edward Zhang, Mark Lythgoe, Paul Beard, Rosamund Barbara Pedley. Investigating tumor vasculature development and the effects of OXi4503 by non-invasive photoacoustic imaging. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr A08. doi:10.1158/1538-7445.CHTME14-A08