Résumé
A typical consequence of breast cancer tumor progression is the colonization of the skeleton. Targeted immunotherapy is an option to specifically deliver cytotoxic agents to the malignant lesions. However, the identification of targetable systemically reachable cancer‐associated antigens precludes the development of novel and effective antibody‐based therapies. In this study, we had the unique opportunity to examine a breast cancer primary tumor and the corresponding bone metastatic lesion obtained simultaneously from a fresh autopsy performed on a patient who died from disseminated breast cancer. We were interested in identifying accessible protein biomarkers using a biotinylation procedure on fresh tissue. The biotinylated proteins are captured by streptavidin affinity chromatography and the peptides derived from tryptic digestion are analyzed using the 2D‐HPLC‐MS/MS technique. The comparison of the differential expression of the primary tumor and the bone metastase yielded 234 proteins of which 78 were found to be located in the extracellular matrix and/or in the plasma membrane and represented potential candidates for antibody targeting. Twenty nine of the potential biomarkers were found uniquely expressed in the primary breast cancer while 27 proteins were detected only in the bone metastasis lesion. In particular, several proteins belonging to small leucine rich proteoglycans and integrin families were found up‐regulated in the primary tumor. Our study identifies potential valuable biomarkers for the selective antibody‐based targeted eradication of bone metastases and indicates that bone metastases accessible biomarkers are significantly different from those corresponding to the primary breast tumor.