Development of a Novel 3D Tumor-tissue Invasion Model for High-throughput, High-content Phenotypic Drug Screening

While much progress has been made in the war on cancer, highly invasive cancers such as pancreatic cancer remain difficult to treat and anti-cancer clinical trial success rates remain low. One shortcoming of the drug development process that underlies these problems is the lack of predictive, pathophysiologically relevant preclinical models of invasive tumor phenotypes. While present-day 3D spheroid invasion models more accurately recreate tumor invasion than traditional 2D models, their shortcomings include poor reproducibility and inability to interface with automated, high-throughput systems. To address this gap, a novel 3D tumor-tissue invasion model which supports rapid, reproducible setup and user-definition of tumor and surrounding tissue compartments was developed. High-cell density tumor compartments were created using a custom-designed fabrication system and standardized oligomeric type I collagen to define and modulate ECM physical properties. Pancreatic cancer cell lines used within this model showed expected differential invasive phenotypes. Low-passage, patient-derived pancreatic cancer cells and cancer-associated fibroblasts were used to increase model pathophysiologic relevance, yielding fibroblast-mediated tumor invasion and matrix alignment. Additionally, a proof-of-concept multiplex drug screening assay was applied to highlight this model's ability to interface with automated imaging systems and showcase its potential as a predictive tool for high-throughput, high-content drug screening.

3D collagen fibrillar microstructure guides pancreatic cancer cell phenotype and serves as a critical design parameter for phenotypic models of EMT

Pancreatic cancer, one of the deadliest cancers, is characterized by high rates of metastasis and intense desmoplasia, both of which are associated with changes in fibrillar type I collagen composition and microstructure. Epithelial to mesenchymal transition (EMT), a critical step of metastasis, also involves a change in extracellular matrix (ECM) context as cells detach from basement membrane (BM) and engage interstitial matrix (IM). The objective of this work was to develop and apply an in-vitro three-dimensional (3D) tumor-ECM model to define how ECM composition and biophysical properties modulate pancreatic cancer EMT. Three established pancreatic ductal adenocarcinoma (PDAC) lines were embedded within 3D matrices prepared with type I collagen Oligomer (IM) at various fibril densities to control matrix stiffness or Oligomer and Matrigel combined at various ratios while maintaining constant matrix stiffness. Evaluation of cell morphology and protein expression at both the cellular- and population-levels revealed a spectrum of matrix-driven EMT phenotypes that were dependent on ECM composition and architecture as well as initial PDAC phenotype. In general, exposure to fibrillar IM was sufficient to drive EMT, with cells displaying spindle-shaped morphology and mesenchymal markers, and non-fibrillar BM promoted more epithelial behavior. When cultured within low density Oligomer, only a subpopulation of epithelial BxPC-3 cells displayed EMT while mesenchymal MiaPaCa-2 cells displayed more uniform spindle-shaped morphologies and mesenchymal marker expression. Interestingly, as IM fibril density increased, associated changes in spatial constraints and matrix stiffness resulted in all PDAC lines growing as tight clusters; however mesenchymal marker expression was maintained. Collectively, the comparison of these results to other in-vitro tumor models highlights the role of IM fibril microstructure in guiding EMT heterogeneity and showcases the potential of standardized 3D matrices such as Oligomer to serve as robust platforms for mechanistic study of metastasis and creation of predictive drug screening models.

Abstract 5783: In vitro modeling of patient derived bladder cancer cell lines in 3D culture systems

Background: Drug screening is a key component for drug development and optimizing anti-tumor therapies. Traditionally, in vitro drug testing has been conducted in monolayer systems that are not capable of recapitulating the tumor complexity. Recently, the field has witnessed the rise of interest in 3D culture systems which are capable of reproducing tumor complexity while circumventing the cost associated with in vivo drug testing. Our access to fresh patient samples has enabled us to establish a novel 3D culture system consisting of bladder cancer patient derived cell lines. Using a wide range of matrices and co-culture conditions with tumor associated stromal cells we were able to establish a unique high throughput drug testing tool.

Methods: Matrigel and collagen based matrices were used to establish 3D culture systems of bladder cancer patient derived cells. Tumor cells were cultured in 3D conditions either alone or in coculture with tumor associated stromal cells. Response to Cisplatin and PI3K pathway targeted agents (i.e. LY LY3023414) was tested in both conditions. High throughput imaging via Thermo ArrayScan XTI was used to assess the biological behavior of spheroids as well as their response to therapies overtime. Confocal microscopy was used to validate the biological mimicry of tumor derived spheroids to the original patient tumors. Integration of RNA-seq data from the patient-derived tumor cells with the biological behavior and therapeutic response in 3D culture is ongoing for the purpose of characterizing the 3D model

Results: In 3D culture conditions; bladder cancer derived cells were able to re-express E-cadherin that was suppressed upon propagation in monolayer. The re-expression of the epithelial marker (E-cadherin) observed in 3D accurately mirrors the original tumors; which are of epithelial origin. Phenotypic differences were observed across different matrix conditions and also among different tumor derived cells. Bladder 3D organoids of luminal origin were more sensitive to both cisplatin and PI3K pathway inhibitors as compared to those of basal origin. This drug response profile was reminiscent of what we observed in vivo using patient derived xenograft (PDX) models derived from the same tumors. The phenotypic as well as the drug response variations observed in our 3D culture correlated with variable gene expression profiles (luminal vs basal) that were detected in our RNA-seq data.

Conclusion: As compared to monolayer, 3D culture is more capable of recapitulating tumor complexity and accurately reflects the drug resistance / sensitivity profiles that are observed in PDX models in vivo. Therefore, a 3D culture system provides an invaluable tool for high throughput screening of drugs in bladder cancer and providing a better understanding of tumor biology in the search of more effective treatments for bladder cancer patients.

Citation Format: May Elbanna, Sreenivasulu Chintala, Eric Ciamporcero, Remi Adelayie, Ashley Orillion, Sreevani Arisa, Nur Damayanti, Michelle Grimard, TJ Puls, Sherry Harbin, Melissa Fishel, Roberto Pili. In vitro modeling of patient derived bladder cancer cell lines in 3D culture systems [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5783. doi:10.1158/1538-7445.AM2017-5783

Abstract A57: Novel 3D tumor-stromal model highlights the importance of ECM composition and biophysical properties in pancreatic cancer EMT and drug resistance

Introduction: Epithelial to mesenchymal transition (EMT), where cells detach from basement membrane (BM) and invade interstitial matrix (IM), plays a significant role in tumor metastasis and drug resistance. Mechanobiological mechanisms of such tumor-stroma interactions are poorly understood largely due to inherent limitations of current preclinical tumor models (e.g. 2D cell culture and spheroids). The objective of this work was to apply a novel in-vitro 3D tumor-stromal model to define how extracellular matrix (ECM) composition and biophysical properties modulate EMT.

Methods: This work involved pancreatic cancer cells representing different EMT phenotypes (BxPc-3: epithelial; Panc-1: intermediate; MiaPaCa-2: mesenchymal). Matrigel was used to represent BM, while tunable type I collagen Oligomers represented IM. Cells were encapsulated within 3D matrices composed of Matrigel, Oligomer of varied fibril density (matrix stiffness), or Oligomer and Matrigel combined at varied ratios. Cell phenotype was characterized based on morphology and EMT protein immunostaining (i.e., E-cadherin and vimentin). Dose response curves to gemcitabine (standard of care) were used to define relative IC50. ECM microstructure was visualized using confocal reflection microscopy, and matrix stiffness (G') was determined using rheometric oscillatory shear testing.

Results: Oligomer enhanced the mesenchymal phenotype with decreasing stiffness (vimentin expression; spindle-shaped cells), while Matrigel downregulated mesenchymal properties and encouraged an epithelial phenotype (E-cadherin expression; rounded, grouped cells). While maintaining vimentin expression in all matrices, Panc-1 and MiaPaCa-2 grew as tight clusters within Matrigel and the highest stiffness Oligomer, where they showed the greatest gemcitabine resistance. BxPc-3 were most sensitive in intermediate stiffness Oligomer where they appeared most proliferative. They also showed relatively high drug resistance in Matrigel and matched-stiffness Oligomer despite each matrix supporting opposite phenotypes. Cells were also cultured within matrices of varied Oligomer:Matrigel ratio to define how BM and IM engagement guides EMT. In matrices with high Oligomer content (>50%), MiaPaCa-2 generated a notably more invasive, mesenchymal phenotype, while BxPc-3 only transitioned to a mesenchymal phenotype in pure Oligomer. Since stiffness and fibril density were similar in the 75:25 and 100:0 ratios, the presence of BM components appears to mediate the phenotypic transition between these matrices.

Collectively, these results emphasize the importance of ECM composition and biophysical properties in guiding EMT. Findings suggest that epithelial tumor cells (BxPc-3) may require engagement with a low stiffness IM to undergo EMT and reduce drug sensitivity. For already transitioned cells (Panc-1 and MiaPaCa-2), decreasing stiffness enhances their mesenchymal nature but increases drug sensitivity. Together these observations align with the idea that EMT increases drug resistance, yet challenge the view that increasing matrix stiffness mediates this transition. Also, engagement with both matrix types promotes invasiveness of mesenchymal cells while exposure to BM suppresses EMT of epithelial cells. Finally, Matrigel promotes a drug resistant, epithelial phenotype which highlights its limitations for studying EMT mechanisms.

Conclusion: This work represents the first use of type I collagen oligomers for mechanistic study of EMT mechanobiology and provides new insight into how IM fibril microstructure and mechanical properties guide EMT. These results challenge correlations between stromal properties and EMT established using conventional preclinical models and help identify critical parameters for engineering pathophysiologically relevant tumor-stromal models.

Citation Format: TJ Puls, Xiaohong Tan, Catherine Whittington, Sherry Voytik-Harbin. Novel 3D tumor-stromal model highlights the importance of ECM composition and biophysical properties in pancreatic cancer EMT and drug resistance. [abstract]. In: Proceedings of the AACR Special Conference on Engineering and Physical Sciences in Oncology; 2016 Jun 25-28; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2017;77(2 Suppl):Abstract nr A57.

Thrombin generation and fibrin formation under flow on biomimetic tissue factor-rich surfaces

BACKGROUND

Blood flow regulates coagulation and fibrin assembly by controlling the rate of transport of zymogens, enzymes and plasma proteins to and from the site of an injury.

OBJECTIVE

The objective of this work was to define the hemodynamic conditions under which fibrin can form under flow on tissue factor (TF)-rich substrates.

METHODS

TF-coated silica beads (~ 800 nm) were patterned into 18-85-μm spots. Normal pooled plasma and factors VIII, IX and XI deficient plasmas were perfused over the beads coated with 0.08, 0.8 and 8 molecules-TF μm(-2) at shear rates of 50-1000 s(-1) . Fibrin deposition and thrombin generation were measured by fluorescence microscopy in a hydrodynamic focusing microfluidic device.

RESULTS AND CONCLUSIONS

Fibrin deposition was supported on patterned bead spots, but not planar TF substrates at the same surface TF concentration. There was a threshold spot size and a shear rate dependent TF concentration that was necessary to support fibrin polymerization. FVIII and FIX had minor effects on fibrin dynamics at 8 molecules-TF μm(-2) , but were essential at 0.8 molecules-TF μm(-2) . The absence of FXI influenced thrombin generation and fibrin deposition at both 0.8 and 8 molecules-TF μm(-2) . These results show that fibrin deposition requires perturbations in the flow field that protect reactions from dilution by flow under venous and arterial conditions. FVIII and FIX have a modest effect on fibrin deposition at high TF concentrations, but are necessary for fibrin deposition at low TF concentrations. FXI amplifies thrombin generation under flow at both low and high TF concentrations.