Calcium carbonate could be key to stopping cancerous tumor growth – study

500-milligram calcium supplements made from calcium carbonate. © Ragesoss
Stopping the growth of cancerous tumors could be as easy as treating them with nano-sized calcium carbonate, the main ingredient in heartburn and indigestion tablets which can alter the pH of diseased cells according to a new study.

Scientists at Washington University in St. Louis intravenously injected nanoparticles of calcium carbonate – the main ingredient in antacids – into mice each day, in order to treat solid tumors.

The compound changed the pH tumor environment from acidic to alkaline, which consequently stopped the tumors from growing.

"Cancer kills because of metastasis," said MD and PhD student Avik Som in a press release, referring to the spread of cancer from one part of the body to another.

"The pH of a tumor has been heavily correlated with metastasis,” he added, stating that one of the methods that a tumor uses to spread is a decreased pH.

Som and his colleagues set out to find a way to raise the pH of the tumor environment. The answer was calcium carbonate, delivered in nanoparticle form. However, working with the compound came with numerous challenges.

"Calcium carbonate doesn't like to be small," Som said. "Calcium carbonate crystals are normally 10 to 1,000 times bigger than an ideal nanoparticle for cancer therapy. On top of that, calcium carbonate in water will constantly try to grow, like stalactites and stalagmites in a cave."

But the researchers were able to create two solutions to that problem. First, they developed a method using polyethyleneglycol-based diffusion to synthesize 20- and 300-nanometer-sized calcium carbonate.

Secondly, they created a solvent made of albumin to keep the calcium carbonate nanoparticles from growing. This allowed them to be injected into the mice intravenously.

Nanoparticles are often made with gold and silver, although that process comes with concerns since neither is naturally present in the human body. Both calcium and carbonate, however, are found heavily in the body and are generally non-toxic, according to Som.

"When calcium carbonate dissolves, the carbonate becomes carbon dioxide and is released through the lungs, and calcium is often incorporated into the bones,” he said.

The scientists, whose research was published in the journal Nanoscale, said the next step is to determine the optimal dose of calcium carbonate to prevent metastasis, as well as to improve targeting to tumors and determine if the compound could be used with chemotherapy drugs.