Caption: A mix of cells collected from an abdominal cancer. The cancer cells (green) are positive for a cell surface cancer marker called EpCAM. The red cell is a normal mesothelial cell. The nuclei of all the cells are stained blue. Each of the five rows in the red, orange, and yellow “heat map” in the corner represents one cell, and the intensity of the color in each of the ~30 narrow columns reflects the abundance of a particular protein. It is apparent that there is a lot of heterogeneity in this collection of cancer cells.
Credit: Ralph Weissleder, Center for Systems Biology, Massachusetts General Hospital, Boston
The proteins speckling the surface of a cancer cell reveal critical clues—the type of cancer cell and a menu of possible mutations that may have triggered the malignancy. Since these proteins are exposed on the outside of the cell, they are also ideal targets for so-called precision cancer therapies (especially monoclonal antibodies), optimized for the particular individual. But in the past, to analyze and identify these different proteins, large samples of tissue have been needed. Typically, these are derived from surgical biopsies. But biopsies are expensive and invasive. Furthermore, they aren’t a practical option if you want to monitor the effects of a drug in a patient closely over time.
Using a minimally invasive method of cell sampling called fine needle aspiration, physicians can collect miniscule cell samples frequently, cheaply, and safely. But, until now, these tiny samples only provided enough material to analyze a handful of cell surface proteins.
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