Abstract
The tumor microenvironment plays a critical role in the proliferation and chemoresistance of cancer cells. Growth factors (GFs) are known to interact with the extracellular matrix (ECM) via heparin binding sites, and these associations influence cell behavior. In the present study, we demonstrate the ability to define signals presented by the scaffold by pre-mixing growth factors, such as epidermal growth factor, into the heparin-based (HP-B) hydrogel prior to gelation. In the 3D biomimetic microenvironment, breast cancer cells formed spheroids within 24 hours of initial seeding. Despite higher number of proliferating cells in 2D cultures, 3D spheroids exhibited a higher degree of chemoresistance after 72 hours. Further, our RNA sequencing results highlighted the phenotypic changes influenced by solid-phase GF presentation. Wnt/β-catenin and TGF-β signaling were upregulated in the cells grown in the hydrogel, while apoptosis, IL2-STAT5 and PI3K-AKT-mTOR signaling were downregulated. With emerging technologies for precision medicine in cancer, this nature of fine-tuning the microenvironment is paramount for cultivation and downstream characterization of primary cancer cells and rare circulating tumor cells (CTCs), and effective screening of chemotherapeutic agents.
Highlights
The hanging-drop method,[7] the use of non-adhesive substrates,[8] and orbital shaking[9] have been previously used to form spheroids in aqueous culture
The cumulative percentage release of Epidermal growth factor (EGF) was less than 5% of the initial bound EGF over a period of 3 days. 96.73 ± 0.53% of the EGF was retained in the HP-B hydrogel over 72 hours (Fig. 2(A))
Heparin-based hydrogel was a suitable scaffold for solid-phase epidermal growth factor presentation and to support the formation of breast cancer cell spheroids
Summary
The hanging-drop method,[7] the use of non-adhesive substrates,[8] and orbital shaking[9] have been previously used to form spheroids in aqueous culture. None of these methods encourage self-assembly, but are rather focused on external physical stimuli to encourage cell aggregation. The use of hydrogels as a biomimetic niche have shown notable changes in cell behavior.[10,11,12,13,14,15,16,17] While previous studies have introduced novel natural and synthetic materials for controlling biological and mechanical properties, they are limited in their molecular characterization of tumor cells in their microenvironment.
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