Arsenic increases breast cancer growth.

Ruiz-Ramos R, L López-Carrillo, A Albores, RU Hernández-Ramírez, and ME Cebrian. 2009. Sodium arsenite alters cell cycle and MTHFR, MT1/2, and c-Myc protein levels in MCF-7 cells. Toxicology and Applied Pharmacology 241:269-274.

Levels of arsenic that are observed in many people around the world alter cell signals and damage DNA in early stage breast cancer cells, according to a study published in the journal Toxicology and Applied Pharmacology. The changes increase cell growth and could potentially intensify the disease's progression.

Both DNA damage and tumor growth are bad news for those with cancer.

The authors find that arsenic changes how cells regulate DNA and cell growth to ways more commonly seen in later stage – and more deadly – breast cancers. Specifically, the results suggest that arsenic could make tumors grow more aggressively in women who have very early stage breast cancer. This would increase the chance that their breast cancer progresses rapidly and is detected after it has already become life-threatening.

While arsenic exposure is associated with many types of cancer – including skin, bladder, liver, lung and prostate – its influence on breast cancer is still far from known. This is one of the first studies to investigate how the metal may affect breast cancer initiation and growth.

The way arsenic causes any cancer is not well understood. But, it is important to know so scientists can identify who is most at risk for the disease and physicians can select the best treatment options.

Arsenic is found naturally in many places and is released from human activities. Arsenic levels are particularly high in parts of the United States, Bangladesh, Mexico, Argentina, Chile and China. People who live in these areas can have high levels of the metal in their bodies.

The amounts of arsenic used in this cell study are similar to the higher levels found in these locations. The researchers exposed the early stage breast cancer cells to arsenic levels comparable to amounts of arsenic found naturally in the water of Bangladesh – an area known to have high natural sources of arsenic.

The breast cancer cells of this study are frequently used in research to study breast cancer that is not yet deadly. In the study, the higher levels of arsenic tested during a short time period altered breast cancer cell DNA in ways that made the cells grow faster than unexposed cells.

Arsenic also increased DNA damage by causing oxidative stress. Oxidative stress occurs when certain molecules react with oxygen to produce substances that cause cancer. Many people choose foods with “anti-oxidants” to counteract these effects.

Further research will explore the breast cancer risk in women who are exposed to different levels of arsenic.

Many women do not know they have breast cancer until the cancer has already become deadly. Detecting breast cancer early, when it is easier to treat, is important to help women survive it. Although the medical recommendations recently changed, this research suggests that women who live in areas with high levels of arsenic may have a higher risk for the disease and should continue monthly breast examines and scheduled mammograms.