Abstract 6151: A 3-dimentional in vitro preclinical model of oncologic cryoablation
Authors: Hesh Christopher A. , Qiu Yongzhi , Schnepp Robert R. , Lam Wilbur A. 
Published: September 2020

Abstract
Cryoablation is a form of percutaneous image-guided thermal ablation employed by interventional radiologists in the treatment and palliation of solid tumors. It achieves tumor cell death by inducing an osmotic gradient through extracellular ice formation, resulting in cellular protein damage, enzymatic impairment, and disruption of the plasma membrane. Due in part to lack of robust preclinical models, however, evidence-based protocols of oncologic cryoablation are limited. These preclinical models, which have focused uniformly on the treatment of solid tumors of adulthood, have consisted primarily of 2D cell cultures and animal models, both of which harbor significant disadvantages. For instance, 2D cell cultures take place on a plastic surface bathed in media, requiring heat transport through a substance with thermal characteristics and a structural complexity that poorly recapitulates in vivo tumor. Animal models, on the other hand, are costly, lack flexibility for carrying out reductionist experimentation, do not accurately recapitulate human pathophysiology, and have poor throughput potential. Both models, therefore, have basic translational limitations. Furthermore, because these models lack the capability of targeted modification of the physical tumor microenvironment, an important driver of malignancy, they leave a significant unmet need in the preclinical evaluation of cryoablation, a need compounded in children where cryoablation has served a palliative role but low incidence of rare tumor phenotypes requires robust preclinical investigation before translation to the bedside.
The objective of this study is therefore to develop a preclinical model that recapitulates the in vivo spatial relationship of tumor cells within a biologically relevant, tunable extracellular matrix (ECM) substitute that better recapitulates the in vivo process of heat transport during cryoablation, and evaluate the impact of this therapeutic modality on osteosarcoma, an aggressive solid tumor of childhood. Here we present preliminary results from in situ experiments using this model, evaluating freeze time and number of freeze/thaw cycles, both altered routinely in cryoablative therapy, on cell death. In addition, we investigate how cellular and collagen density, both variables with reported prognostic significance in some solid tumors, influence cell death. These experiments demonstrate that increasing the freezing duration and the number of freeze/thaw cycles results in increased cell death, while increasing collagen density has an inverse effect, possibly due to impaired heat transport or limited formation of an osmotic gradient. These data highlight the unique capabilities of a 3D hydrogel-based model for the evaluation of cryoablation, which recapitulates known behaviors of cryoablative therapy and provides the first data on the inverse relationship between ECM collagen density and cryoablation-induced cell death.
Citation Format: Christopher A. Hesh, Yongzhi Qiu, Robert R. Schnepp, Wilbur A. Lam. A 3-dimentional in vitro preclinical model of oncologic cryoablation [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6151.