Cancer tumors shed cells that circulate through the blood steam. And, according to a Stanford study published today in PLoS ONE, those mobile cells have a high level of genetic diversity even within a single patient.
For the study, researchers here looked at circulating tumor cells (CTCs) first in mouse cell-lines and then in blood drawn from breast cancer patients. To find the very small number of CTCs in blood, the team used a device they developed in 2008 called the MagSweeper, which zeros in on specific protein on the surface of tumor cells. Next, they measured the levels of 95 different genes using another Stanford technology: real-time PCR microfluidic chips, developed by Stephen Quake, PhD, professor of bioengineering. They found as many as five different groups of cancer cells – all with different patterns of genes turned on or off.
The diversity, Jeffrey said, means that tumors may contain multiple types of cancer cells that may get into the bloodstream, and a single biopsy from a patient’s tumor doesn’t necessarily reflect all the molecular changes that are driving a cancer forward and helping it spread. Moreover, different cells may require different therapies. One breast cancer patient studied, for example, had some CTCs positive for the marker HER2 and others lacked the marker. When the patient was treated with a drug designed to target HER2-positive cancers, the CTCs lacking the molecule remained in her bloodstream.
These results don’t have immediate impacts for cancer patients in the clinic because more work is needed to discover whether different types of CTCs respond to different therapies and whether that will be clinically useful for guiding treatment decisions. But the finding is a step forward in understanding the basic science behind the bits of tumors that circulate in the blood