Abstract 2097: Desmoplasia-mimetic gels with modular and temporal properties for modeling pancreatic cancer progression
Authors: Liu Hung-Yi , Lin Chien-Chi 
Published: August 2018

Abstract
Tumor microenvironment (TME) governs all aspects of cancer progression, and in vitro 3D culture platforms are increasingly developed to emulate the interactions between stromal tissues and cancer cells. To mimic the complex compositions and dynamically changing matrix mechanics in TME, we developed a dynamic hydrogel via integrating modular thiol-ene photopolymerization and enzyme-triggered matrix stiffening. Gelatin was dually modified with norbornene (NB) and 4-hydroxyphenylacetic acid (4-HPA). The former renders gelatin photo-crosslinkable and the later affords responsiveness to tyrosinase (TYR)-triggered stiffening. In addition, hyaluronic acid was covalently incorporated into gels. We characterized macromer modification, as well as enzyme-triggered stiffening and degradation. We also evaluated the influence of matrix compositions and dynamic stiffening on pancreatic ductal adenocarcinoma (PDAC) cell in 3D. Methods: Gelatin-norbornene (GelNB) was modified with 4-HPA via carbodiimide chemistry to yield GelNB-HPA. Gels were prepared by reacting NB moieties (GelNB, GelNB-HPA) with thiol motifs on PEG4SH or THA via photopolymerization (1mM LAP, 365nm light 5 mW/cm2, 2 min). Next, gels were swollen for a day, followed by incubating in TYR solution (1 kU/mL) for 6 hours. To study the influences of matrix compositions on PDAC cells, COLO-357 cells were encapsulated in gels, 1) GelNB with PEG4SH (Gel/PEG), 2) GelNB with THA (Gel/HA), 3) GelNB-HPA with PEG4SH (GelHPA/PEG), and 4) GelNB-HPA with THA (GelHPA/HA). Live/dead staining was used to evaluate cell viability and morphology. At day 14, total RNA was extracted from cell-laden gels for mRNA expression analyses using Taqman® array. Results: After TYR treatment, gels with HPA moieties formed additional crosslinks and exhibited higher moduli. Live/dead staining showed high cell viability after cell encapsulation process and throughout 14 days culture. Cells grew into spheroids but were visibly larger in Gel/PEG gels. However, cluster sizes were significantly smaller when the gels were soft and contained HA (i.e., Gel/HA) or stiffened but contained no HA (i.e., GelHPA/PEG). Interestingly, the morphology of the spheroids in GelHPA/HA gels became highly irregular. Results in TaqMan® array revealed changes unique to the presence of HA, to a stiffened microenvironment, or to the combination of both. We characterized mRNA expression from cells in GelHPA/HA gels. Results showed that these cells underwent epithelial-mesenchymal transition (EMT), as evidenced by downregulation of E-cadherin and upregulation of mesenchymal markers as N-cadherin, SNAIL-1 and vimentin. In sum, we designed a biomimetic hydrogel capable of mimicking the diverse biochemical compositions and dynamic biophysical environment of pancreatic desmoplasia, providing a diverse platform for studying pancreatic cancer.
Citation Format: Hung-Yi Liu, Chien-Chi Lin. Desmoplasia-mimetic gels with modular and temporal properties for modeling pancreatic cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2097.