Peptide Functionalized Poly(ethylene glycol) Hydrogels Deconstruct the Tumor Microenvironment

Samir Paul Singh, University of Colorado Boulder

Alternate title: Investigating Tumor Progression and Migration Using a Synthetic Culture Platform to Quantitatively Control Biochemical and Biophysical Matrix Properties of the 3D Microenvironment


Tumor growth, progression, and metastasis are complex processes, which are poorly characterized. To design therapies capable of controlling the spread of cancer, a better understanding of tumor function is needed. There is a growing interest in developing synthetic three-dimensional poly(ethylene glycol) (PEG) hydrogel platforms to study the complex biochemical and biophysical processes related to tumor cell growth, progression, and migration. This thesis exploits PEG hydrogel systems to study various aspects of tumor progression, including cell-matrix and cell-cell interactions as well as the role of oncogene expression on cellular motility.

This thesis presents a method in which to deconstruct the tumor microenvironment to study cancer cell migration. Peptide functionalized PEG hydrogels were designed to tune biochemical and biophysical properties of the matrix and study the model cell line, HT-1080s, a human fibrosarcoma cancer line. HT-1080 speed varied with a complex dependene on both matrix modulus and adhesion, with regimes in which motility was increased, decreased, or was minimally altered. Additionally, HT-1080s were able to migrate across a mechanical interface from a stiff to soft environment, but not vice versa, indicating that cancer cells are capable of “reverse durotaxis”. Additionally, in determining influences of cell-cell interactions, the WM239a cell line (metastatic melanoma) was co-cultured with human Dermal Fibroblasts (hDFs). On short time scales, hDFs suppress the growth of melanoma tumors, and on long time scales, hDFs actually promote melanoma tumor invasion. This result is analogous to single cell cultures where hDFs promote an invasive and motile phenotype, but in monoculture conditions, melanoma cells were rounded and minimally motile. Finally, the effect of mutations was explored. NIH3T3 cells were transformed to overexpress oncoprotein in the Mitogen Activated Protein Kinase (MAPK) pathway. Cell lines overexressing Mitogen Activated Protein Kinase Kinase Kinase (MAPKKK) proteins exhibited highly motile behavior and were linked with higher MMP-9 expression over control cells in 3D culture conditions. There results demonstrate the utility of using peptide functionalized PEG hydrogels to simply the tumor microenvironment and study tumor growth and progression.