Detecting cancer, one CTC at a time

In honor of breast cancer awareness month, I've been scouring science headlines around the internet to find really interesting, clever, and unique approaches to fighting all sorts of cancer. I stumbled on some fantastic research this morning that really piqued my interest; I hope it does the same for you! The early diagnosis of cancer makes a dramatic difference in the prognosis of patients. Take, for example, breast cancer. Below is a chart showing 5 year survival rates of breast cancer patients relative to the stage at which the cancer was diagnosed:

Figure 1: The 5-year relative survival rates among breast cancer patients

The contrast between Stage I and IV survival is pretty stark, as you can see! The cause of this jump is a phenomenon known as metastasis, which is cancer's ability to spread its tumors from the primary site to remote organs. In fact, the majority of breast cancer fatalities occur due to these remote tumors (in the bone, liver, etc) rather than solely cancer in the breast. This is a defining feature of Stage IV cancers.

Detecting these metastatic tumors has been a challenge, but recent advances have allowed scientists and clinicians to detect circulating tumor cells (CTCs) in the blood. This allows us to study and monitor cancer in a noninvasive manner, which is critical in ensuring that the cancer treatment process is as painless as possible. Aceto et al. published a paper in Cell describing a very interesting discovery in the nature of these cells. As it turns out, the cells that are the most successful in establishing remote tumors travel in clusters, rather than in isolation.

Figure 2: A schematic showing CTC mediated tumor establishment. Credit: Aceto et al. 2014

These cells express a protein called plakoglobin, a cell adhesion protein which presumably allows the cells to remain in contact with one another until they reach their destination. Traveling in this way seems to provide a protective advantage, as the scientists also noted that solitary tumor cells suffered much higher rates of cell death. Patients with high levels of this protein in their cancer cells had a much shorter metastasis-free survival time.

Researchers hope that with this new knowledge, our monitoring of cancer patients will become much more effective. For example, if a clinician notices that levels of plakoglobin and/or clustered CTCs are rising in his/her patient, that may call for a more aggressive treatment regimen. It may also warrant a closer examination of the genetics of these clusters, as metastatic tumors are notorious for having different genetics than their parent tumors, which may partially explain why some chemotherapies eventually stop working.

For more information, check out the full paper in the first hyperlink above. The more you know!