Red Algae from the Sea Studied for Colon Cancer Prevention

Division of Cancer Prevention

Calcium is a mineral, the ionic form (Ca2+) of which moves in and out of cells and conveys important signals. It is an essential component of the diet, but calcium’s direct relationship with cancer is unclear. Evidence that calcium can prevent cancer is strongest in colorectal cancer compared to other cancers, although some studies have failed to show an impact. In contrast, there is some evidence that high calcium levels might even increase the risk of prostate cancer.

James Varani, Ph.D., professor of Pathology at the University of Michigan, sees these unclear effects of calcium on cancer as an opportunity. Because calcium is instrumental in a wide range of the body’s functions, figuring out how it works in different kinds of cancer cells could possibly lead to a number of useful insights, he believes. The calcium-sensing receptor (CaSR) in cells is a major avenue for calcium’s ability to regulate cell growth. Some studies have shown little or no expression of CaSR in colon cancer, Dr. Varani noted. “If we could find a way to more effectively deliver calcium by upregulating CaSR, we might be able to stop a lot of the early cellular changes that we know lead to colon cancer.”

NCI is funding* Dr. Varani’s lab to look at a new and promising way to deliver calcium to these CaSR-deficient cells. Red algae, known as Lithothamnion calcareum, extracts calcium from the sea and becomes progressively calcified as it grows. “The fronds accumulate minerals very effectively and eventually become so heavy they are just an organic matrix of minerals,” he explained. “Red algae can be harvested from shallow waters. It has been a ‘treasure chest’ for us, because more than 70 other trace minerals, in addition to calcium, have been identified.”

First, “we are trying to confirm that the red algae extract is effective against colon cancer,” Dr. Varani said. He and his colleagues are conducting animal studies using a xenograft model, where colon cancer cells are directly grown in mice. The researchers are feeding the mice a high-fat diet for 15 months. Some of the rodents will get either a “plain vanilla” inorganic calcium supplement, while other mice will receive the red algae extract, he explained.

“If the extract is more effective at inhibiting colon cancer and polyps,” said Dr. Varani, “it opens up an interesting question: is the high calcium content in the extract getting to the right prevention targets? If so, there must be something else among the many additional trace elements in the algae that is transporting calcium into the cells, compared to the calcium the control mice are getting.” Another possibility the researchers need to consider is the direct or synergistic impact of those additional minerals, especially magnesium. The experiments will also provide information about the CaSR receptor’s role, if any, in red algae’s impact on cancer cells.