Impact Of Osteoblast-derived Bone Remodeling Cytokines On metastatic Breast Cancer Cell Dormancy

Open Access
Author:
Rutan, Emily Claire
Area of Honors:
Biochemistry and Molecular Biology
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Andrea Marie Mastro, Thesis Supervisor
  • Teh Hui Kao, Honors Advisor
  • Richard John Frisque, Faculty Reader
Keywords:
  • breast cancer
  • bone remodeling
  • cytokines
  • cancer
  • dormancy
  • metastasis
  • metastases
  • IL-6
  • IL-1beta
  • TNF-alpha
  • osteoblasts
Abstract:
It has been observed that patients in remission from breast cancer often have a reoccurrence of breast cancer at the site of a bone injury. Sometimes this reoccurrence as a metastases occurs many years after a “cure” has been declared. Thus the original cancer likely metastasized but remained dormant. Therefore, it would be beneficial to determine how certain factors in the bone-remodeling environment impact dormancy and metastatic breast cancer cell proliferation and morphology. The aspects of the bone-remodeling environment that make it unique as compared to the homeostatic bone microenvironment include the presence of bone-remodeling cytokines, inflammatory cytokines, and the increased activity for the osteoblasts and osteoclasts. It is proposed that by observing how certain bone-remodeling cytokines, inflammatory cytokines, and osteoblasts impact breast cancer cell dormancy in vitro, a better understanding of how breast cancer reoocurs will be gained. The inflammatory cytokines included IL-6, MCP-1, IL-8, VEG-F and Gro-α [1]. Bone Remodeling Cytokines included TGF-β, IL-6, IL-1β, and PGE2 [2]. Three breast cancer cell lines were used, MDA-MB 231, a highly aggressive line, MDA-MB 231 BRMS11, a metstatic-suppressed variant of the MDA-MB 231 cell line, and MCF7, a non-metastatic line. An MTT assay revealed that the bone remodeling cytokines stimulated more proliferation of breast cancer cells than inflammatory cytokines. In co-culture, MC3T3- E1s, or murine osteoblasts, were cultured for one month to allow them to lay down a matrix. At this point, some cultures were decellularized and breast cancer cells were added. Additionally, some of the cancer cells both with and without osteoblasts received bone-remodeling cytokines. Proliferation was measured either with a biochemical assay (MTT), or by quantitation of the expression of the green fluorescent protein expressed by the cancer cells. Morphology was examined using confocal microscopy. The bone remodeling cytokines clearly enhanced breast cancer cell proliferation, both on the charged plastic surface of standard tissue culture plates, and on the bone matrix in vitro. However, the same effect was not observed when the osteoblasts were present, indicating that these cells may play a key role in the cross-talk between cytokines and breast cancer cells.