The Effects of Combination Zoledronate and Docetaxel Therapy on Breast Cancer Colonization of Three-Dimensional Osteoblastic Tissue

Open Access
Author:
Miller, Genevieve Nicole
Area of Honors:
Bioengineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Erwin A Vogler, Thesis Supervisor
  • Andrea Marie Mastro, Thesis Supervisor
  • William O Hancock, Honors Advisor
Keywords:
  • breast cancer
  • bone metastasis
  • bisphosphonate
Abstract:
Breast cancer frequently metastasizes to bone, and most treatments for the disease involve both tumor-directed (such as chemotherapy agents) and bone-directed therapies. The family of drugs called bisphosphonates has been widely used clinically for the management and prevention of skeletal complications from bone metastases because bisphosphonates are targeted to the bone. The purpose of this study was to characterize the effects of a bisphosphonate, zoledronate, and a taxane, docetaxel, on an in vitro model of cancer-in-bone. Mineralized 3D osteoblastic tissue was grown from murine calvarial pre-osteoblasts (MC3T3-E1) in a specialized bioreactor based on the principle of simultaneous-growth-and-dialysis. This 3D bone model provides a unique test system in which cancer cell interactions with osteoblastic tissue at controlled phenotypic maturities can be microscopically monitored in real time. Human metastatic breast cancer cells (MDA-MB-231GFP) were co-cultured with osteoblastic tissue in the actively mineralizing phase. Cultures were either treated with zoledronate following cancer cell inoculation, pre-treated with zoledronate, or pre-treated with a combination of zoledronate and docetaxel. Osteoblastic tissue was stained with Cell Tracker Orange or AlexaFluor 568, and cultures were monitored daily using confocal microscopy. Without added drug treatments, breast cancer cells were observed to attach, penetrate, and colonize osteoblastic tissue in a continuous process that ultimately marshaled osteoblasts into linear files similar to that observed in authentic pathological tissue. A single dose of zoledronate following cancer cell inoculation delayed cancer-cell penetration and colony formation, with osteoblasts retaining the characteristic cuboidal shape observed in controls for the first 2 days of co-culture. Thereafter, cancer-cell colonization progressed to the filing stage. Pre-treatment of cultures with zoledronate also resulted in reduced breast cancer cell colony formation and a disruption of cancer cell aligment. Differences in the distribution of cancer cells within colonies were observed. Combined treatment with zoledronate and docetaxel completely inhibited cancer progression. These results indicate that concentrations of zoledronate that minimally affect osteoblast function are capable of delaying breast cancer progression throughout bone. Furthermore, administration of zoledronate adjuvant to the chemotherapy drug docetaxel results in synergistic antitumor effects. This study has shown that the bioreactor is a useful device for the study of drug effects on the early stages of breast cancer cell interactions with bone tissue.