Lectin capture strategy for effective analysis of cell secretome

Secreted proteins play important roles in physiological and pathological processes. However, effective proteomic detection of low-abundant secreted proteins is often shielded by the presence of a large amount of intracellular proteins released from unavoidable dead cells during cell culture. In the present study, we applied lectin affinity capture approach to enrich the secreted proteins in the conditioned media (CM) of three human breast cell lines (MCF-10A, MCF-7, and MDA-MB-231). Lectin capture showed efficient enrichment of the secreted proteins in CM of all three cell lines and significantly increased the number of secreted proteins detected: from 183 to 292 for MCF-10A, 196 to 325 for MCF-7, and 194 to 368 for MDA-MB-231. Based on more comprehensive profiling of the secreted proteins, we identified 92 secreted proteins which were both upregulated in MCF-7 and MDA-MB-231, with 82 only found in lectin-captured samples. It should be noted that among these 82 potential biomarkers, 59 were not reported in the previous proteomic studies of breast cancer. These data indicate that the lectin capture approach is a powerful means to move toward more comprehensive analysis and comparison of secretomes.