Key Protein May Explain Mens' Higher Liver Cancer Risk

IL-6 damages the organ, but estrogen helps prevent that injury, study finds

THURSDAY, July 5 (HealthDay News) -- Men produce more of a protein linked to liver cancer than women do, researchers report. The finding might explain why men have a higher rate of liver cancer than women, the U.S. team says.

The body produces the protein, called interleukin-6 (IL-6), in response to damage to the liver. IL-6, in turn, adds to the chronic liver inflammation that causes cancer.

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Not only do women produce less of the protein, but the University of California, San Diego, team found that estrogen keeps the amount of protein women do produce in check.

Liver cancers are caused by chronic liver disease, heavy alcohol use, hepatitis B or C infections, or a family history of cancer. Men are three to five times more likely to develop liver cancer than women.

In their study, the team first gave mice a cancer-causing agent. All of the male mice developed liver cancer, compared to one out of five of the females.

The researchers found higher levels of IL-6 in the males than in the females. And when they gave the cancer-causing agent to mice that were unable to produce IL-6, only one in 10 males developed cancer.

The researchers also treated a third group of male mice with estrogen and then gave them the cancer-causing agent. In this case, rates of liver cancer remained the same as in normal female mice.

A close analysis of the liver cells showed that estrogen helped cut the production of IL-6.

"While some organs, such as breasts, are clearly influenced by gender, others, like the liver, are not," said Willscott Naugler, clinical instructor in the department of medicine at UCSD, in a prepared statement. "So, it's quite interesting that liver inflammation is so markedly suppressed by estrogens. It raises the possibility that organs not usually associated with gender differences may be governed by the same principle. Bladder cancer, for example, occurs more frequently in males than females, and the differences may be a result of higher IL-6 levels and inflammation in male bladders."

In the article, published in the July issue of Science, the researchers suggest that either reducing the amount of IL-6 in men or giving men an estrogen-like compound might help reduce liver cancer rates.

More information

To learn about liver cancer, visit the U.S. National Cancer Institute.

-- Madeline Vann