Abstract 1303: Tunable ECM interfaces in microfluidic chips for interfacial metastatic studies of breast cancer spheroids

Abstract Background: Metastasis remains one of the most challenging aspects of cancer progression to study. Recent research highlights that the physical characteristics of the extracellular matrix (ECM)—such as stiffness, porosity, and microarchitecture—are critical regulators of cancer invasion and metastasis. Tumor cells often encounter heterogeneous microenvironments, including matrix-matrix interfaces (MMIs), which provide unique interfacial cues influencing invasion and dissemination. Despite growing recognition of these interfacial dynamics, the mechanisms by which MMIs modulate metastatic behaviors remain poorly understood. To address this, we developed a microfluidic chip with tunable ECM interfaces, enabling precise modulation of stiffness and structural heterogeneity. This platform facilitates the study of interfacial metastatic behaviors of breast cancer spheroids (BCS) in a controlled and reproducible in vitro setting. Methods: A tunable microfluidic chip was fabricated using polydimethylsiloxane (PDMS) via photolithography. The chip comprises three distinct channels: a central channel engineered to create defined MMIs with combinations of soft and stiff ECM regions, and two lateral channels designed for nutrient supply. Collagen type I hydrogels were employed as the ECM material, and their physical properties—stiffness and microarchitecture—were characterized using rheometry and scanning electron microscopy (SEM). MDA-MB-231 and MCF7 BCSs were placed near the MMIs formed by juxtaposing ECMs of varying stiffness to model interfacial metastatic behaviors. Spheroid dispersion, invasion, and single-cell migration were observed and recorded using bright-field microscopy after 24 and 48 hours of incubation. Results: The stiffness of the soft and stiff ECMs measured 5.18 ± 0.19 MPa and 6.58 ± 1.20 MPa, respectively, with porosity differing significantly between the inner regions of soft (6.56 ± 0.22) and stiff (2.71 ± 0.10) ECMs. In homogeneous environments, MDA-MB-231 spheroids exhibited enhanced dispersion and invasive behavior in soft ECM compared to stiff ECM. At MMIs, the presence of a stiff interface further enhanced MDA-MB-231 spheroid invasiveness, compared to soft-soft or homogeneous ECM conditions. In contrast, MCF7 spheroids showed minimal migration across all MMI conditions. Conclusion: This study underscores the importance of tunable ECM interfaces in understanding the role of physical and structural heterogeneity on the invasive behaviors of BCSs. The results demonstrate how MMIs modulate metastatic dynamics, particularly in response to stiffness variations, and highlight the utility of microfluidic platforms in investigating the interplay between mechanical and biochemical microenvironments. Citation Format: Hsiang-Pei Chen, Hwanseok Jang, Seung-Cheol Shin, Seok Chung. Tunable ECM interfaces in microfluidic chips for interfacial metastatic studies of breast cancer spheroids [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1303.