(210c) Integrated Single-Cell Analysis of Heterogeneous Secretory Profiles Exhibited by Human Primary Colorectal Tumor Cells

There is increasing evidence for genetic heterogeneity among individual tumor cells.  In colon cancer, multilineage differentiation and epigenetic regulation have also been shown to induce transcriptional heterogeneity, which may affect other complex functional behaviors such as secretion of growth factors or chemokines.  Since secreted factors produced by tumor and stromal cells can affect progression of disease, it is important to understand the functional heterogeneity that exists within the tumor microenvironment in order to begin mapping signaling networks.  Bulk methods such as ELISAs or protein microarrays lack the ability to resolve functional heterogeneity among single cells.  In this study, we employ quantitative microengraving, in combination with on-chip cytometry, to probe the secretomes of over 10,000 human primary colorectal tumor cells in parallel using arrays of subnanoliter wells (nanowells).  Starting with a panel of 21 cytokines, chemokines, and growth factors relevant to cancer biology, we examined protein production from six human primary tumors and identified common responses among the samples, including chemokines such as IL-8.  We show that individual cells from the tumors exhibit discrete secretory profiles, suggesting that functional heterogeneity is common among cells from a single tumor.  We also find evidence for intercellular bypass signaling via production of redundant chemokines that agonize the same receptor.