Matrix Manipulation Affects Attachment And Growth Of Breast Cancer Cells In A Bone-like Microenvironment In Vitro

Open Access
Author:
Foster, Shelby Jean
Area of Honors:
Biochemistry and Molecular Biology
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • David Scott Gilmour, Thesis Supervisor
  • Andrea Marie Mastro, Honors Advisor
Keywords:
  • breast cancer
  • metastasis
  • bone
  • estrogen
  • osteoblast
Abstract:
Breast cancer is one of the most common and deadly cancers, but treatment of the primary tumor is usually very successful if the condition is realized early. The disease becomes more deadly once metastasis occur sand cancer cells spread from the primary tumor to secondary sites. One of the most common sites of breast cancer metastasis is the skeletal system. Breast cancer metastasis to bone is a painful process for a patient to endure, as breast cancer cells interrupt the healthy balance of buildup and breakdown of the bone. Introduction of breast cancer cells into the bone microenvironment causes an upregulation of bone degradation by increasing the activity of osteoclasts. Osteoblasts, bone forming cells, also are affected. They are unable to make up for the increased degradation, and the breast cancer invasion causes bones to become weak and more susceptible to trauma. It was hypothesized that specific changes to the bone microenvironment altered the attachment and growth of breast cancer cells within the bone. The aim was to determine the role of the bone extracellular matrix in breast cancer colonization. Experiments were conducted in vitro by differentiating mouse osteoblasts for four weeks until they created a bone matrix. In order to distinguish the osteoblasts from their secreted matrix, the cultures were altered through fixation and decellularization. Human metastatic breast cancer cells, MDA-MB-231 and an isologous line that carries a metastasis suppressor gene, MDA-MB-231 BRMS1 were added to the cultures of osteoblasts and attachment and growth of the cancer cells were Monitored. Most notably, breast cancer cells attached and proliferated more on a fixed osteoblast cultures than on decellurized or live osteoblast cultures. It was concluded that the growth was due to a change in the structure of the matrix after fixation. This result may correlate with a reduction of EPLIN, a protein responsible for fixation of surfaces, in metastatic cancer cells including MDA-MB-231. A second aim was to test another relevant modification of the bone environment, brought about by estrogen during osteoblast differentiation. Estrogen effects were important to test because breast cancer metastasis to bone occurs most often in women after menopause when less estrogen is produced in the body. Inhibiting estrogen receptors during osteoblast differentiation noticeably changed collagen fiber rearrangement and reduced the total amount of protein produced by the osteoblasts. Estrogen inhibition, however, did not affect breast cancer cell attachment or proliferation on a decellularized matrix, but significant changes in both attachment and proliferation were observed when the live osteoblasts were left intact. ELISA analysis also showed that more of the inflammatory and bone remodeling cytokine IL-6 is produced by MC3T3-E1 cells when they are grown with the estrogen inhibitor and exposed to the breast cancer cells. It was concluded that estrogen inhibition causes an inflammatory environment that is more supportive of breast cancer cells.