SINGLE-CELL SCREENING OF EXOSOME SECRETION IN BREAST CANCER

Exosomes mediate intercellular communication in health and disease. Conventional assays are limited in profiling exosomes secreted from large populations of cells and are unsuitable for studying the functional consequences of individual cells exhibiting varying propensity for exosome secretion. Here, we developed a high throughput single-cell technique that enabled the mapping of exosome secretion dynamics. By utilizing clinically relevant models of breast cancer, we established that non-metastatic cancer cells secrete more exosomes than metastatic cancer cells. We established isogenic clonal cell lines from nonmetastatic cells with differing propensities for exosome secretion and showed that exosome secretion is an inheritable property preserved during cell division. Combined in vitro and in vivo studies with these cell lines suggested that exosome secretion can impede tumor formation. In human non-metastatic breast tumors, tumors with the higher secretion of exosomes have a better prognosis compared to tumors with the lower secretion of exosomes. As another application for our technique and to identify markers relevant to exosome secretion in metastatic cell lines, we profiled the cellular transcriptome of isogenic metastatic cell lines with varied exosome secretion rates established with our method. The genes identified with the highest expression and correlation in the high secretor clone were significantly associated with poor survival and low CD8 T cell infiltration in breast cancer patients. Our single-cell methodology can become an essential tool that enables the direct integration of exosome secretion with multiple cellular functions.