Using Sound To Separate Circulating Tumor Cells.

Since 2010, Tony Huang, Ph.D., from the Acoustofluidics laboratory at Penn State University in University Park, Penn.; Ming Dao, Ph.D., from the Massachusetts Institute of Technology in Cambridge; and Subra Suresh, Ph.D., now president of Carnegie Mellon University in Pittsburgh, came up with the idea of using sound waves to tweeze out pathological cells from normal blood cells. Four years later, they showed that their sound-based device, named Acoustic Tweezers (AT), could separate MCF-7 breast cancer cells from normal white blood cells. This firstgeneration, dime-sized cell sorting device recovered about 71% of the MCF-7 cells from the white blood cells with 84% purity (Proc. Natl. Acad. Sci. USA 2014;111:12992– 7). Now their second-generation AT has been scaled up for performance, and it efficiently tweezed out circulating tumor cells (CTCs) from normal blood cells in patient samples with a higher throughput and recovery rate, recovering more than 83% of the CTCs (Proc. Natl. Acad. Sci. USA 2015;112:4970–5). CTCs are shed by a tumor, which then may lead to metastasis. They are rare cells: A 7.5 mL sample of blood may contain only 1–100 cells. “Looking for them in a blood sample is like looking for a needle in a haystack,” Huang said. But separating and culturing CTCs for analysis may serve as a “liquid biopsy,” allowing clinicians to screen for various biological signatures of cancer, such as probing mutations in tumor cells or examining their drug susceptibility.