Abstract B7: The bone metastasis secretome: Identification of potential therapeutic targets via high-throughput proteomics

Abstract

Abstract Secreted tumor proteins are critical for establishing the requisite tumor-stromal interactions in the process of metastasis and are superior therapeutic targets. Here we present a proteome-scale analysis to identify novel secreted proteins associated with bone metastasis. To characterize the complete set of secreted proteins involved in tissue-specific metastasis, we analyzed the secreted protein fractions from four sublines of the MDA-MB-231 breast cancer cell line which differ in bone metastasis ability. Using LC-MS/MS mass spectrometry technology, we identified 1153 total unique proteins from these fractions and filtered out those proteins predicted to be non-secreted using SignalP 3.0. This analysis yielded 206 unique secretory-predicted proteins, thus providing the first view of the MDA-MB-231 secretome. To determine potential therapeutic targets, we looked at which secreted proteins were found only in the highly bone metastatic cell lines. This 32-protein bone metastasis “secretome signature” contained several proteins already known to play a role in promoting bone metastasis (eg. MMP1, CTGF, and TGF-) as well as many novel proteins with no prior link to metastasis or cancer. GO categories significantly enriched in this signature included “extracellular region,” “calcium ion binding,” and “ IGF-binding,” further confirming its biological relevance. Oncomine database analysis indicated that 6 of 32 secretome signature proteins are strongly upregulated in multiple human cancers as compared to matched normal tissue. To narrow the secretome signature biologically, we repeated the LC-MS/MS analysis on two additional sets of matched parental vs. highly bone metastatic derivative cell lines. From the three total secretome analyses, 5 secreted proteins were found to be unique to bone metastatic derivatives in two of three cell types, and one protein was found in every bone metastatic derivative (and in none of the weakly bone metastatic lines). Oncomine analysis indicated that three of these five proteins were also strongly upregulated in multiple human cancers as compared to normal tissue. This analysis of the metastasis secretome and its associated bone metastasis-specific changes has identified multiple novel secreted proteins strongly implicated in clinical malignant progression. Following experimental and clinical validation, any could be considered for therapeutic targeting via monoclonal antibody. Citation Information: Clin Cancer Res 2010;16(7 Suppl):B7