Abstract B041: Investigating the impact of extracellular matrix stiffness on macrophage function and organoid growth in pancreatic ductal adenocarcinoma
Authors: Mahgoub Bayan , Xiao Weikun , Fung Eileen , Mumenthaler Shannon , Hill Reginald 
Published: November 2024

Abstract
Pancreatic ductal adenocarcinoma (PDAC) has a 5-year survival rate of only 11%. Current treatments mostly target the cancer cells themselves and have not been able to significantly improve survival rates, meaning there is an urgent need for novel therapies. PDAC is unique among solid tumors because it exhibits extensive desmoplasia that is characterized by an abundance of extracellular matrix (ECM) components. In recent years, an increasing body of work has shown that cancer tissue is stiffer than normal tissue by a factor of 3 or more. This increase in ECM stiffness has been shown to play an important role in affecting cell-to-cell communication as well as cancer progression and chemoresistance . However, how ECM stiffness affects tumor-associated macrophages, an important component of the pancreatic tumor microenvironment (TME), is still understudied. Previous studies have demonstrated that macrophages are highly responsive to mechanical cues, with the mechanical environment influencing macrophage polarization and function in a context- and disease-dependent manner. Elucidating these potential changes in PDAC can provide us with insights on how stiffness affects therapeutic outcome. Healthy pancreatic tissue typically exhibits a storage modulus of approximately 0.5-1 kPa, whereas PDAC tissue can range from 4-10 kPa. To study macrophage responses to varying stiffness, we cultured RAW264.7 mouse macrophage cell lines on 2D substrates with stiffness levels of 0.2, 2, and 8 kPa. We observed that macrophages cultured on stiffer matrices exhibited a trend toward a pro-inflammatory phenotype, with increased expression of M1 markers such as iNOS, IL-1β, and IL-6, compared to those cultured on softer matrices. However, conditioned media from macrophages cultured on both soft and stiff substrates similarly reduced the size of PDAC organoids, indicating a lack of functional difference between these groups. These findings suggest the need for more sophisticated models that better replicate the PDAC TME to fully capture the complex cell-to-cell interactions that are not evident in 2D cultures. To address this limitation, we developed a 3D tri-culture tunable biomimetic mouse model comprising PDAC organoids, host-matched cancer-associated fibroblasts (CAFs), and macrophages. This novel model allows us to modulate the stiffness of the 3D co-culture system through the addition of collagen I and CAFs. Rheometry data confirmed that the stiff tri-culture model had a significantly higher storage modulus than the soft tri-culture model. Using qPCR, we investigated the role of mechanosensitive ion channels, specifically Transient Receptor Potential Vanilloid-type 4 (TRPV4) and Piezo1, in mediating macrophage mechanosensing in response to varying levels of matrix stiffness. This study highlights the importance of 3D models that can recapitulate biophysical cues of cancer and will allow us to better understand how macrophages respond to stiffness, which may give rise to new therapeutic targets and development of new treatments in the future.
Citation Format: Bayan Mahgoub, Weikun Xiao, Eileen Fung, Shannon Mumenthaler, Reginald Hill. Investigating the impact of extracellular matrix stiffness on macrophage function and organoid growth in pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr B041.