Abstract :
[en] The current work provides valuable insights into the novel proteins potentially implicated in metastatic progression. It is particularly important for the field of the bone metastasis development where there is a shortage of information. Cell surface and extracellular proteins have been implicated as having important roles in proliferation, migration and invasion. Using a comprehensive combination approach based on three sequential highly specific methods, we exploited the fact that cell surface and extracellular proteins can be labeled with biotin reagent and are predominantly glycosylated. Additionally, a last step involved analysis of the remaining peptides, which were neither biotinylated nor glycosylated, yielding a spectrum of interesting proteins. Moreover, a further in silico step that combines these remaining peptides with the identified glycopeptides brings extra value in terms of number of proteins identified and robustness of the method. Altogether, this strategy permitted the use of clinical material present in limited quantity and demonstrated its ability to identify a maximum number of cell surface and extracellular proteins starting from the same sample.Following a unique opportunity, a bone metastatic lesion and its corresponding breast primary tumor were collected simultaneously from the same patient. Subsequently, the newly developed strategy was used to identify novel cell surface and extracellular proteins potentially involved in the bone metastasis development. In terms of protein expression, the primary breast tumor and the bone metastasis were similar. Nevertheless, variations were detected in proteins potentially associated with aggressive phenotype and/or bone metabolism were highlighted. It is important to note that these proteins of interest identified by the proteomic analysis from one single pair of primary breast tumor and bone metastasis were also validated in a larger collection. One of the identified proteins was CD166, which was found as over-expressed in the cancer cells residing in the bone compared to the cancer cells in the primary breast tumor. Other proteins, such as SUSD2 and ASPN, were not expressed by the residing bone cancer cells. These observations generate novel hypotheses for their potential role in bone metastasis development. These hypotheses can be further validated using in vivo and/or in vitro assays. For that reason, it was essential to investigate the relevance of the MDA-MB-231/B02 bone metastasis model which is described to mimic the development of bone metastases. A high degree of similarity was observed between the cell line model and the clinical specimen. This is particularly relevant for the kinectin-1, which was found as up-regulated in the bone metastasis in both models. Therefore, the investigation of the role of CD166, SUSD2, and ASPN in the bone metastasis progression using the cell line model could be of particular interest, not only to better understand the in vivo scenario that leads to the bone metastasis development, but also in terms of developing novel diagnosis and therapeutic modalities.
