There aren’t too many chemicals out there that grip the public’s imagination as much as arsenic does. Frequently employed in books, movies, and plays, slipping a little arsenic into a person’s coffee or tea is often the method of choice for characters in a story to eliminate an enemy or adversary.

In an interesting twist on this idea, doctors are looking to arsenic as a way to treat leukemia. In fact, arsenic has been used for centuries in Traditional Chinese Medicine (TCM) as a way combat psoriasis and sexually transmitted disease. It also appears to have a therapeutic effect on a certain forms of cancer, though the way that it works was never completely understood. Now, however, researchers have discovered key mechanisms by which the chemical targets cancer cells.

As it turns out, arsenic acts upon certain proteins that contribute to tumor growth, degrading them and thereby inhibiting their ability to encourage the growth of acute promyelocytic leukemia (APL) cells. APL is a subtype of acute myelogenous leukemia (AML), which is the most common form of leukemia in adults. Like AML, APL affects the blood and bone marrow and results in the abnormal and rapid growth of white blood cells that interfere with normal blood cell production.

The basis for APL lies in a genetic mutation that produces a fusion protein (PML-RARalpha) that is essential to the growth and development of the cancer cells. However, when this protein is exposed to arsenic, a chemical reaction occurs whereby another protein binds to the fusion protein and leads to its destruction. With the protein gone, the cancer cell can no longer survive, and eventually dies.

What the new findings, published in the journal Science, have uncovered is a clearer picture of how this occurs. Arsenic actually binds to a region of the protein that is referred to as the zinc fingers. The ensuing reaction results in the formation of insoluble proteins that bind to the cancer cell, thus leading to its death.

There are advantages to using arsenic because it has fewer side effects than conventional chemotherapy, which frequently results in hair loss and impairment of the immune system. It is currently used in many countries the world over to treat APL, though its reputation as a poison discourages some doctors from recommending it, as well as patients from accepting it as a form of treatment.

APL is a relatively rare disorder that was first characterized by the medical establishment in the late 1950s. Over the next 20 years, there were no effective treatments for the condition, and it essentially 100% fatal. Though modern forms of cancer treatment have improved this number, APL still has a high rate of relapse with standard chemotherapeutic regimens.

In the past 15 years, however, doctors in China began treating APL patients with arsenic, and as a result, over 90% of the patients in that country with APL survive for at least 5 years and show little to no symptoms of the disease.

For more information about APL, visit the website for the National Institutes of Health (NIH) and the American Cancer Society.