Abstract 1915: In vivo prostate tumor tissue stiffness differs by tumor region and can be recapitulated in bioengineered prostate tumor tissues
Authors: Habbit Nicole L. , Anbiah Benjamin , Anderson Luke S. , Suresh Joshita , Hassani Iman , Eggert Matthew , Jasper Shanese L. , Prabhakarpandian Balabhaskar , Arnold Robert D. , Lipke Elizabeth A. 
Published: August 2019

Abstract
Throughout the tumorigenic process, locational heterogeneities in tumor tissue microarchitecture develop as a result of aberrant angiogenesis and a subsequently induced oxygen and nutrient gradient within the three-dimensional (3D) mass. This phenomenon often results in differential tissue stiffness between the necrotic, quiescent, and proliferative tumor regions. In vitro, strong correlations have been found to exist between cell culture platform stiffness and acquired chemoresistance and varied drug response. Therefore, to accurately recapitulate the tumor microenvironment, biomimetic models must provide a mechanically similar scaffold. This study reports novel quantification of the in vivo prostate tumor stiffness and the ensuing development of tunable 3D bioengineered tumor tissue (BioTT) to successfully recapitulate in vivo mechanical cues in vitro.
In vivo samples were generated by subcutaneously injecting Matrigel-suspended metastatic prostate cancer cells (PC-3) into the flank of athymic NCr nude mice. Resultant tumors (300 – 1,500 mm3) were excised from the murine host and geometrically dissected to provide samples from the tumor core, midpoint, and periphery. The Young’s modulus was quantified via parallel plate compression under physiological conditions. The 3D BioTT model is comprised of poly(ethylene glycol)-fibrinogen (PF) with varying amounts of excess poly(ethylene glycol) diacrylate (PEGDA) to modulate the mechanical properties of the scaffold. PC-3 cancer cells and BJ-5ta human fibroblasts were encapsulated within the covalently crosslinkable biomaterial and co-cultured for 29 days in vitro. Cell viability was assessed by LIVE/DEAD staining and cellular morphology was visualized with Hoechst 33342, Phalloidin, and the anti-fibroblast immunomarker, TE-7. Temporal variations in cell populations were quantified by flow cytometry and mechanical stiffness characterization was again performed by parallel plate compression.
In vivo prostate cancer tumors presented a wide range of tissue stiffness heterogeneity (200 – 5,750 Pa), characterized by an increasing modulus with respect to locational progression from the core to the periphery (n = 48 per tumor region). The BioTT model successfully recapitulated the full tumor stiffness range through biomaterial composition modulation; the addition of excess PEGDA significantly stiffened the PF scaffold (p ≤ 0.05, n = 3). PC-3 and BJ-5ta cells survived the encapsulation process and remained viable throughout long-term co-culture. Visualization of the 3D cellular microenvironment revealed both cancer and stromal cells maintained characteristic morphology. In future studies, the BioTT will be extended to a microfluidic chip platform, thus augmenting the physiological relevancy of the model by incorporating dynamic shear conditions and the ability to monitor cancer cell metastasis.
Citation Format: Nicole L. Habbit, Benjamin Anbiah, Luke S. Anderson, Joshita Suresh, Iman Hassani, Matthew Eggert, Shanese L. Jasper, Balabhaskar Prabhakarpandian, Robert D. Arnold, Elizabeth A. Lipke. In vivo prostate tumor tissue stiffness differs by tumor region and can be recapitulated in bioengineered prostate tumor tissues [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 1915.