The Role of Osteoblast-Derived Inflammatory Cytokines in Bone Metastatic Breast Cancer
Open Access
- Author:
- Bussard, Karen Marie
- Graduate Program:
- Pathobiology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- August 22, 2008
- Committee Members:
- Andrea Marie Mastro, Committee Chair/Co-Chair
Robert Paulson, Committee Chair/Co-Chair
Avery August, Committee Member
Pamela Hankey Giblin, Committee Member
Carol V Gay, Committee Member
Andrew Thomas Henderson, Committee Member - Keywords:
- MIP-2
GRO-alpha
osteoblast
osteoclast
breast cancer
MC3T3-E1
MDA-MB-231W
IL-6
MCP-1
VEGF
KC
IL-8 - Abstract:
- Breast cancer preferentially metastasizes to the skeleton. I hypothesized that: 1) osteoblasts in culture would increase the secretion of cytokines in the presence of metastatic breast cancer cells, act as chemoattractants for them, and enhance osteoclast formation; 2) treatment of osteoblasts with a bone-seeking metastatic breast cancer cell variant would elicit the greatest increase in osteoblast-derived cytokines; and 3) osteoblast-derived cytokines would be increased in the metaphyses of femurs of cancer-bearing mice. Osteoblasts were incubated with breast cancer cells or their conditioned media and assayed for cytokine expression. Femurs from mice inoculated via intracardiac injection with breast cancer cells were assayed ex vivo for bone-derived cytokines. Tumor localization within femurs was examined using µCT, densitometry, and MRI. IL-6, MCP-1, and VEGF expression were assayed via immunohistochemistry. The chemoattractant capability of IL-6, MCP-1, and VEGF on breast cancer cell migration was assessed in a transwell assay. The effect of culture supernatants from osteoblasts treated with breast cancer cells on osteoclast formation was examined via TRAP stain. Osteoblast-derived cytokine production of IL-6, KC, MIP-2, MCP-1, and VEGF increased with metastatic breast cancer cell treatment in vitro. Osteoblasts produced MCP-1, while cancer cells did not. Cancer cells colonized the trabecular bone and, trabecular bone volume was ~75% less in cancer-bearing mice. Bone-derived cytokine production of IL-6, KC, MIP-2, MCP-1, and VEGF was increased in cancer-bearing mice as measured ex vivo. MCP-1 and VEGF were localized in the matrix of trabecular bone, whereas IL-6 was found throughout the bone marrow. Murine MCP-1 and VEGF were not detected adjacent to tumor cells, but were present in increasing amounts extending away from the cancer cells. Human VEGF expression increased with increasing tumor size. Osteoblast conditioned medium was a potent chemoattractant for metastatic breast cancer cells in vitro, but IL-6, VEGF, or KC alone, or in combination, were not. The culture supernatant of osteoblasts treated with metastatic breast cancer cells facilitated osteoclast formation in vitro. This study suggested that osteoblast-derived cytokines are important in bone metastatic breast cancer. Metastatic breast cancer cells appear to co-opt osteoblasts into creating a niche supportive of breast cancer cell colonization.