Cadmium Disrupts Ability of Cells to Fight Cancer

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http://ens-news.com/ens/jun2003/2003-06-09-10.asp

 

Cadmium Disrupts Ability of Cells to Fight Cancer

 

 

RESEARCH TRIANGLE PARK, North Carolina, June 9, 2003 (ENS) - Cadmium, a

naturally occurring metal found in food, water and cigarette smoke, disrupts a

DNA repair system that is important in preventing cancer, according to

researchers at the National Institute of Environmental Health Sciences (NIEHS).

The metal, primarily used to make batteries, is a known human carcinogen and has

long been known to cause human lung cancer in cadmium-related industries unless

strict safeguards are taken.

But unlike most carcinogens that work by attacking DNA directly, the NIEHS study

released today indicates that cadmium causes mutations in another way, explains

the study's senior author Dr. Dmitry Gordenin.

The NIEHS research team showed that cadmium causes mutations by inhibiting the

ability of cells to repair routine errors made when the DNA is copied to make

new cells.

" Unless cadmium is unique in its mechanism, it would seem that environmental

factors may cause genetic defects and cancer not only by attacking our DNA

directly but also by undermining the mechanisms by which faulty DNA replication

is repaired, " Gordenin said. Cadmium is a natural element and can be found in

air, water, soil and food. (Photo courtesy Royal Society of Chemistry)Cells must

duplicate their DNA in order to replace dying cells, but mistakes in this

duplication are frequently made. Most organisms correct these mistakes, Gordenin

explained, by " efficient mechanisms akin to a computer's 'spellcheck.' "

Without these corrective mechanisms, mutations would occur and multiply in cell

after cell, which could lead to cancer, reproductive problems, birth defects or

other ills.

The researchers found that cadmium blocks " post-replication mismatch repair " of

natural errors.

This increases mutations " as much as 2,000 fold, " said Dr. Michael Resnick, an

NIEHS senior scientist and a co-author of the report.

" Genetically, this can result in a vast increase in errors that could be

catastrophic, " Resnick said.

The researchers say that the amount of cadmium needed to inhibit repair and

increase mutations was remarkably small.

" We saw substantial effect from cadmium exposure from concentrations that may

well be environmentally relevant especially to cadmium-related industry workers

and smokers, " said Dr. Thomas Kunkel, another NIEHS senior scientist who worked

on the study.

Cadmium is a natural element, found in all soils and rocks, including coal and

fertilizers. Its natural presence in air, water, soil and foodstuffs results

mainly from mining and metal processing operations, gradual rock erosion and

abrasion, as well as from volcanic eruptions.

Cadmium is not mined, rather it is a byproduct of the smelting of other metals

such as zinc, lead and copper. The soft, silver-white metal has been used for

metal coatings, and in paint, plastics and batteries, because it does not

corrode easily, has a low melting point and excellent electrical conduction.

Scientists hope a better understanding of how carcinogens affect DNA will lead

to improvements in defining at risk populations. (Photo courtesy National

Institute of General Medical Sciences (NIGMS))Some seventy percent of its use is

in rechargeable nickel-cadmium batteries.

The primary health concerns are for industrial workers who may be exposed to

generation concentrations, but the general population can be exposed to cadmium

from breathing cigarette smoke, drinking contaminated water or eating foods that

contain it. Smoking doubles the average daily intake.

Cadmium disappears from organisms very slowly and its half-life in the human

body can be as long as 20 years.

Until banned by the EPA in 1997, cadmium carbonate and cadmium chloride were

used as fungicides for golf courses and home lawns.

The NIEHS studies, reported in today's online issue of the journal " Nature

Genetics, " were done in yeast cells - the living cells used to make bread rise -

which have proved a useful tool for studying cellular activities.

Previous work has demonstrated that what happens in yeast cells generally also

happens in more complex life forms. The researchers say that their studies with

extracts of human cells and initial studies in cultured human cells also suggest

a similar mechanism to the one found in the study of yeast cells.

 

 

 

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