Smithsonian.com

Gold’s been used for thousands of years to treat disease. Credit: Flickr user covilha

Over thousands of years, gold has been used to treat rheumatoid arthritis, inner ear infections, facial nerve paralysis, fevers and syphilis. Now, preliminary findings suggest a new application for tiny grains of gold—destroying cancer cells.

Gold-carrying nanoparticles are capable of killing a common type of cancer that attacks antibody-making B cells in the blood, according to a study published today in the journal Proceedings of the National Academy of Sciences. This cancer, B-cell lymphoma, originates in the lymph glands and is the most common type of non-Hodgkin lymphoma. Last year, it resulted in nearly 19,000 deaths.

Developed by researchers at Northwestern University, the nanoparticle mimics the size, shape and surface chemistry of high-density lipoprotein—natural HDL—the preferred meal of these cancer cells. HDL is the “good” cholesterol that cruises through the bloodstream, removing dangerous buildups of LDL, the harmful, “bad” cholesterol.

The bits of gold tucked inside these particles are tiny—just five nanometers wide. A billionth of a meter, a nanometer is a measurement used to size bacteria, X-rays and DNA. The width of a double helix is about two nanometers.

Despite its microscopic size, the synthetic particle packs a big punch—more accurately, two of them. Recent research has shown that B-cell lymphoma is dependent on the uptake of natural HDL, from which it derives fat content, to spur cell proliferation. The nanoparticle cuts off its supply. Masquerading as natural HDL, the nanoparticle latched on to cholesterol receptors on deadly lymphoma cells. First, the nanoparticle’s spongy surface sucked out the cell’s cholesterol. Then, it plugged up the cancer cell, preventing it from absorbing natural HDL particles in the future. Deprived of this essential nutrient, the cell eventually died.

Natural HDL alone didn’t kill the cells or inhibit tumor growth in the study. The blinged-out particle was key to starving the lymphoma cell—and it did so without the help of cancer drugs.

It also didn’t appear to be toxic to other human cells normally targeted by HDL particles, to normal lymphocytes (a type of white blood cells) or to mice, in which the particle actually inhibited tumor growth. Developing a drug therapy using this nanoparticle depends on further extensive testing, but it could take chemotherapy off the table for the thousands of patients diagnosed with B-cell lymphoma.