Abstract
Here, we demonstrate the flexibility of peptide-functionalized poly(ethylene glycol) (PEG) hydrogels for modeling tumor progression. The PEG hydrogels were formed using thiol-ene chemistry to incorporate a matrix metalloproteinase-degradable peptide crosslinker (KKCGGPQG↓IWGQGCKK) permissive to proteolytic remodeling and the adhesive CRGDS peptide ligand. Tumor cell function was investigated by culturing WM239A melanoma cells on PEG hydrogel surfaces or encapsulating cells within the hydrogels, and either as monocultures or indirect (non-contact) cocultures with primary human dermal fibroblasts (hDFs). WM239A cluster size and proliferation rate depended on the shear elastic modulus for cells cultured on PEG hydrogels, while growth was inhibited by coculture with hDFs regardless of hydrogel stiffness. Cluster size was also suppressed by hDFs for WM239A cells encapsulated in PEG hydrogels, which is consistent with cells seeded on top of hydrogels. Notably, encapsulated WM239A clusters and single cells adopted invasive phenotypes in the hDF coculture model, which included single cell and collective migration modes that resembled invasion from human melanoma patient-derived xenograft tumors encapsulated in equivalent PEG hydrogels. Our combined results demonstrate that peptide-functionalized PEG hydrogels provide a useful platform for investigating aspects of tumor progression in 2D and 3D microenvironments, including single cell migration, cluster growth and invasion.
Highlights
Tumor progression and metastasis are dependent on reciprocal changes between tumor cells and the local microenvironment, which includes genetic changes, cell-cell interactions, soluble signaling, and biochemical and biophysical extracellular matrix (ECM) properties[1,2,3,4,5,6,7,8,9,10,11]
We demonstrate the versatility of thiol-ene poly(ethylene glycol) (PEG) hydrogels by studying the effects of different microenvironments on migration, growth and invasiveness for the human WM239A melanoma cell line, including stromal influences on tumor function using WM239A single cells and clusters cocultured with human dermal fibroblasts
By varying the –ene concentration, peptide functionalized PEG hydrogels were synthesized with shear storage moduli (G’) ranging from 520–1150 Pa (Fig. 1b), which spans a range of tissues that are commonly targeted by melanoma metastases[21,22], including lung tissue[53], which is a metastatic site for WM239A cells[54]
Summary
Cluster growth, and invasion of a metastatic melanoma cell line (WM239A) was investigated using poly(ethylene glycol) (PEG) hydrogels to provide a “modular” platform for controlling the 3D microenvironment. After one day of coculture, hDFs had contracted the collagen gel to form a dense stromal region surrounding the circumference of the PEG hydrogel disk containing WM239A clusters (Fig. 3a, “Collagen + hDFs”). These combined results identify microenvironments that are useful for investigating single cell migration, cluster growth, and invasion for WM239A cells or xenograft tumors encapsulated in PEG hydrogels. Our results demonstrated that WM239A cluster size and proliferation rate were dependent on matrix stiffness for cells cultured on PEG hydrogels, and that coculture with hDFs suppressed cluster growth for each of the moduli investigated (520–1150 Pa). Cocultured hDFs suppressed growth for WM239A clusters within PEG hydrogels, but induced transition to an invasive phenotype characterized by both single cell and collective migration modes. Our combined approach is modular in nature, allowing control over matrix properties and the timing of coculture with stromal cells, and provides a versatile tool for investigating the role for several critical components of the microenvironment during tumor progression
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