Photoswitchable Flow Cytometry Directly Tracks Single Circulating Tumor Cells

A original method has been developed that allows investigators to label and track single tumor cells circulating in the blood and this advance could help to develop a better understanding of cancer spread and how to stop it.

The innovative method allows for labeling and tracking of individual circulating cancer cells throughout the body, thereby helping scientists to elucidate the pathways of single cells from start to finish, including invasion into nearby normal tissue, movement into the lymphatic system or the bloodstream.


An international team led by those at the University of Arkansas for Medical Sciences (Little Rock, AR, USA) used photoswitchable fluorescent proteins that change their color in response to light. When the first laser of light hits the circulating tumor cells, they appear to be fluorescent green. A second laser, using a different wavelength, makes the cells appear to be fluorescent red. To label individual cells, the scientists used a very thin violet laser beam aimed at small blood vessels. The fluorescence from each cell is collected, detected, and reproduced on a computer monitor as real-time signal traces, allowing the investigators to count and track individual cells in the bloodstream.

In tumor-bearing mice, the scientists could monitor the real-time dynamics of circulating cancer cells released from a primary tumor. They could also image the various final destinations of individual circulating cells and observe how these cells circulate and colonize healthy tissue, existing sites of metastasis, or the site of the primary tumor. The Multicolor Photoswitchable Flow Cytometry (PFC) Platform was based on an Olympus IX81 inverted microscope (Olympus America; Center Valley, PA, USA) with incorporated three continuous-wave lasers.

Ekaterina Galanzha, MD, PhD, the senior author of the study said, “This technology allows for the labeling of just one circulating pathological cell among billions of other normal blood cells by ultrafast changing color of photosensitive proteins inside the cell in response to laser light. Therefore, the approach may give oncologists knowledge on how to intervene and stop circulating cancer cell dissemination that might prevent the development of metastasis.” The study was published on May 8, 2014, in the journal Chemistry & Biology.

Related Links:
University of Arkansas for Medical Sciences
Olympus America