Roles of Osteonecti in Breast Cancer Metastasis to Bone

摘要

Osteonectin is a secreted matrix protein that has a variety of functions, including cell adhesion modulation and chemoattraction. It has been implicated as a chemoattractant for breast cancer cells despite the evidence that some cancer cells secrete osteonectin. Other studies demonstrate the ability of osteonectin to permeabilize a vascular endothelial cell layer even though some endothelial cells also secrete osteonectin. We hypothesize that there are differences between cancer-derived osteonectin, bone-derived osteonectin, and vascular endothelial-derived osteonectin. Osteonectin was separated by SDS-PAGE under reducing and non-reducing conditions followed by immunoblotting; a small variance in molecular size between osteonectin from different sources is detected. Results suggest that breast cancer cells secrete two types of osteonectin with different configurations of disulfide linkages, whereas bone cells secrete osteonectin with a single pattern of disulfide links. No differences were observed from deglycosylation and phosphorylation as says while osteonectin-induced endothelial permeabiliztion was also not detected by interference reflection microscopy. The research completed in the last year has supported the hypothesis that there are structural differences between breast cancer-secreted and vascular/bone-secreted osteonectin.