Typically, breast cancer is identified once it becomes symptomatic—when swelling or a lump becomes noticeable. By that time, the cancer might have spread beyond the breast tissue and into lymph nodes en route to other places in the body.
Newer methods, like microRNA testing, seek to spot tumor growth before it becomes apparent. But, a new study led by researchers at Oxford University might make early detection easier than it’s ever been.
The research, recently published in the journal Metallomics, looked at the relationship between zinc and cancerous tissue and could one day lead to an early detection blood test based on a zinc biomarker. “What we have is an indication that a biomarker exists,” explains lead author Fiona Larner, a postdoctoral research associate in earth sciences at Oxford University.
Perhaps 10 or even 20 years from now, Larner envisions a blood test administered during regular physical exams to test for the biomarker. Doctors would use a positive result as an indication that further screening might be necessary.
The pilot study looked at zinc in the blood of 10 people—five healthy and five with breast cancer. Instead of simply detecting the concentration of zinc in a sample, as a standard hospital test would do, Larner’s test works at 100 times the resolution and detects differences in mass among zinc isotopes. Weight variations happen when atoms of an element have different numbers of neutrons. Cancer tissue might take on one type of isotope over another (a “light” or “heavy” version), leaving more of that one in the bloodstream. Larner’s team found that zinc isotopes in breast cancer tumors were lighter than those in the blood and breast tissue of healthy patients.
Imagine, for instance, a bowl of red and green M&Ms. If someone eats a few red ones, they’ve changed the ratio of candies left in the dish. While a standard hospital blood test might only see that there are fewer M&Ms overall, Larner’s test sees the colors and knows the altered ratio.
Larner and her co-authors borrowed the technique from earth science, which uses the method to study climate change and the formation of planets. Climate scientists, for instance, can analyze isotopes in ice cores to find isotopic signatures for long-past climate events, such as volcanic activity and atmospheric composition.
For over a decade, scientists have known that breast cancer tissue holds onto a lot of zinc, but until now it’s been impossible to understand the processes that lead to that behavior. By identifying the individual isotopes present in healthy versus cancerous tissues, Larner hopes to further understand how cancer-building proteins process zinc. She will then use that knowledge to isolate a biomarker that might detect cancer long before current methods, such as mammograms, can.
Research is already underway to drill deeper and study samples of zinc isotopes in blood from patients at different stages of cancer and metastasis—perhaps even subjects who have tested positive for the BCRA “breast cancer” gene but have not yet developed the disease. The process of isolating a zinc-based biomarker for breast cancer could take years, but Larner is optimistic. “I wouldn’t be doing this if I didn’t think it was totally possible,” she says.
At the same time, researchers could easily adapt these methods to test for other metals. For example, Larner has studied the relationship between copper and Parkinson’s, and NASA has dug into calcium’s role in osteoporosis. “We use a lot of metals in our body,” she explains, “and that shows we can stretch this net wide and approach different issues, find what is useful using our technique and leave behind the things that aren’t.”