July 21, 2006
A test developed by Tulane professor of biochemistry Diane Blake has helped show a strong correlation between levels of cadmium in the blood and pancreatic cancer. The results are significant, says Blake, because this is the first study, albeit a small one, to demonstrate a long-suspected relationship.
The research was published in a recent issue of Environmental Health Perspectives. Cadmium is a heavy metal present in the earth's crust and in plants humans consume. With a half-life of 15 years, the metal often accumulates over decades in the kidneys and the pancreas.
The human body has developed mechanisms to handle naturally occurring exposures to cadmium, says Blake, but higher levels due to pollution, worksite exposure or smoking are thought to be related to various diseases, including pancreatic cancer.
Traditionally, levels of cadmium in the blood could only be tested in fresh blood samples. Blake's team recently developed a way to measure cadmium levels in serum samples, which meant that samples could be frozen, stored and tested multiple times over months and years.
After she published the new testing method, Blake was contacted by Amr Soliman, then an epidemiologist at MD Anderson Cancer Center in Houston.
Soliman, a native of Egypt, had collected serum samples from 83 patients (32 with pancreatic cancer, 51 without) from the East Nile Delta region, which is known to be heavily polluted, says Blake. Although cadmium is regulated by the Environmental Protection Agency in the United States, countries worldwide continue to use cadmium-rich chemicals, such as pesticides and fertilizers.
Soliman and Blake wanted to know if there was a relationship between serum levels of cadmium and having pancreatic cancer. They were additionally concerned because pancreatic cancer is rare and typically occurs later in life, yet the cluster of pancreatic patients in Egypt was younger than the norm.
The results of the serum tests suggest a relationship between high levels of serum cadmium and pancreatic cancer, irregardless of age, gender or residence. Although the source of exposure is not identified in this study, Blake says there was also a correlation between having pancreatic cancer and working on a farm.
Despite the regulations in the U.S., Blake says this data, gathered halfway across the world, is important to Louisianans. Local residents also live in a delta region at the end of a long river that runs through farm country. Like the East Nile Delta Egyptians, Louisianans eat a lot of locally grown fish and rice, both of which absorb environmental cadmium.
Still, she says, this study raises more questions than it answers, which is typical of early studies. She and Soliman, who is now at the University of Michigan School of Public Health, are hoping to test 300 more blood samples to increase the overall sample size and explore the link between smoking, cadmium levels and pancreatic cancer.
They are also planning a study of pancreatic cancer patients in the United States and hope one day to explore the mechanism by which cadmium may trigger the growth of cancer cells. Cadmium is ubiquitous, says Blake, who has spent the past 13 years studying heavy metals, but there are ways to reduce exposure.
"Even though the levels of cadmium in this country are controlled, if it's in your diet and you smoke a lot, you will accumulate higher levels. So stop smoking," says Blake.
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