Breast Osteoblast-like Cells: A Reliable Early Marker for Bone Metastases From Breast Cancer

The development of bone metastasis from breast cancer results from a functional interaction between tumor cells and osteoclasts or osteoblasts. The main aim of this study was therefore to test the hypothesis that the appearance of breast osteoblast-like cells (BOLCs) in primary mammary lesions is a precursor (and hence an early predictor) of the formation of breast cancer metastases to bone.

In this study, we collected 64 breast infiltrating carcinomas, 50 breast benignant lesions, and 10 biopsies of bone metastasis selected from patients with infiltrated carcinoma. Immunohistochemical, western blot, and ultrastructural analysis allowed us to investigate the presence of BOLCs in breast cancer lesions and metastatic sites.

We established the presence of a high amount of breast cancer cells that underwent mesenchymal transformation in infiltrating carcinomas. In addition, our results demonstrated that the microenvironment of breast cancer is very similar to the microenvironment of bone. We noted a significantly higher expression of BMP-2/4 and PTX3 in breast-infiltrating carcinomas compared with benign lesions. Moreover, we also identified numerous BOLCs positive to RANKL and Vitamin D receptor. Thanks to ultrastructural analysis, we also revealed the presence of BOLCs at the metastatic site.

The identification of breast cancer cells with high affinity for a bone environment opens new perspectives on prevention and therapy of bone metastases from breast.