Date of Award

1-1-2013

Document Type

Open Access Thesis

Department

Chemical Engineering

First Advisor

Jabbari, Esmaiel

Abstract

Maintenance of cancer stem cells (CSCs) is regulated by their microenvironment. As cancer cells are affected by many factors in their microenvironment, a major challenge is to isolate the effect of a specific factor on cancer stem cells (CSCs) while keeping other factors unchanged. We have developed a synthetic inert 3D polyethylene glycol diacrylate (PEGDA) gel culture system as a unique tool to study the effect of microenvironmental factors on CSCs response. Synthetic hydrogels provide the flexibility to design three-dimensional (3D) matrices to isolate and study individual factors in the tumor microenvironment.

The objective of this work was to investigate the effect of matrix modulus on tumorsphere formation by breast cancer cells and maintenance of CSCs in an inert microenvironment without the interference of other factors. We have shown that the gel modulus had a strong effect on tumorsphere formation and CSCs formed in the inert PEGDA gel by encapsulation of breast cancer cells maintain their stemness within a certain range of gel stiffness. Tumorsphere formation and expression of CSC markers peaked after 8 days of culture. At day 8, as the matrix modulus was increased from 2 kPa to 5, 26, and 50 kPa, the average tumorsphere size changed from 37 ± 6 mm to 57± 6, 20 ± 4, and 12 ± 2 mm, respectively; The expression of CD44 breast CSC marker changed from 17 ± 4-fold to 38 ± 9-, 3 ±1 and 2 ± 1 fold increase compared with the initial level. Similar results were obtained with MCF7 human breast carcinoma cells. Mouse 4T1 and human MCF7 cells encapsulated in the gel with about 5 kPa modulus formed the largest tumorspheres and highest density of tumorspheres, and had highest expression of breast CSC markers CD44 and ABCG2. The inert polyethylene glycol hydrogel can be used as a model-engineered 3D matrix to study the role of individual factors in the tumor microenvironment on tumorigenesis and maintenance of CSCs without the interference of other factors.

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