Author(s): Minafra IP
A major complication of advanced breast cancer is the frequent formation of bone metastases. To our knowledge, however, the information on the phenotypic properties of cancer cells able to survive and colonize the bone tissue is still fragmentary. We report here a proteomic study of breast cancer cells (SKBR3) collected after a colonization of bone fragments in a special model of co-culture, used to simulate the phenotype of breast cancer metastasizing cells. The scanning electron microscopy of the seeded cancer cells into the bone fragments, showed their peculiar traits of multilayered growth and spiny surface, typical of a very aggressive phenotype. The comparative proteomic profiling of the bone-conditioned cells (SKBR3-B1) versus the parental cell line (SKBR3-WT), performed by applying two-dimensional electrophoresis (2D-IPG) and mass spectrometry (Maldi / TOF) revealed the existence of an interesting differential proteomic profiling. Within this pattern, an increase of several members of the S100 protein family, not described before in relation to bone metastasis from breast cancer, was observed in the SKBR3-B1. Other up-regulated proteins belong to protein classes involved mainly in cytoskeleton dynamics, chaperone / folding, negative regulation of apoptosis and cell metabolism. These results suggest that, rather than individual proteins, a coordinated network of strategic proteins is able to determine or drive the invasive and metastatic phenotype of breast cancer cells, namely: proteins primarily strategic for the cell penetration and homing into the bone, and proteins coming into play to satisfy the modified metabolic needs of the cells. We believe that the present study represents an innovative approach of co-culture with fresh human bone fragments, and that it may contribute greatly to improve the knowledge of the molecular mechanisms underlying the propensity of breast cancer cells to colonize, survive and proliferate into the bone microenvironment.