Cancer is a major killer, but its cause is still a -pestering mystery. Now a recent study linking carcinogens and human bodies at the molecular level throws some light on this dark alley
CANCER remains a mystery in its aetiology even today. Death tolls from cancer
are gaining staggering proportions; the
us recorded 538)000 deaths from cancer
in 1994, which amounts to one-fifth of
the nation's population. The basic problem in cancer research is the unavailability of conclusive causative agents
The disease finds its way into existence
out of billions of complex interactions
that make up human cellular biochemistry. Some of these causes are inherited,
like the gene BRCA- 1, which causes
breast cancer. However, there are also
many environmental factors presumably avoidable: asbestos, tobacco, air
pollution, a diet low in vegetables and
fruits, alcohol and UV-radiations.
As researchers screen out more and more substances that have the potential to cause cancer, there has set in a certain cynicism about the potential hazards of persuing one's gastronornal indulgences. Peanut butter, mustard, mushrooms, root beer-all are said to be containing trace amounts of potential carcinogens. This raises the concern whether food that comes from the kitchen may turn out to be the destroyer.
Carcinogens are normally found through the detection of significant rise in malignancies in animals exposed to potentially carcinogenic test chemicals. The virtue of this system lies in the simplicity of the procedure. Unlike people, these laboratory animals have a rather uncomplicated life without exposure to thousands of foods, chemicals or obnoxious gases in the atmosphere. They can be subjected to carefully designed and tightly controlled experiments and the exclusion criteria is much more strictly regulated as compared to test models including human specimens. In short, the outcome of animal model studies can be confidently taken into account as the tell-tale story that it shows because of the lesser chances of unpredictable causes.
Some scientists including Bruce Ames at the University of California at Berkeley, us, have cited differences in 'animal models and those of humans saying that there is a vast gap between the generic configuration of the animals and human test systems despite the fact that both rodents and humans are mammals. A carcinogen mainly works by causing a mutation in an oncogene - a gene that, if it malfunctions, lays the groundwork for the uncontrolled proliferation of the cell where it resides.
Now a new development in the field of research called 'molecular epidemiology' addresses different questions in the sub-microscopic arena, where cells interact with foreign chemicals, It may even be able to establish distinction between lethal and insignificant doses of a potential carcinogen. And ultimately, may succeed in producing a simple blood test which shows that you are harboring a clinically dangerous amount of a cancer causing substance.
Frederica Perera and her colleagues at Columbia University began their work with humans rather than test animals. They amassed tissue and body fluid samples from volunteers, who either have cancer or have been exposed to suspect chemicals. They then combed through these tissues for tell-tale biomarkers - the chemical products that reveal interaction between a suspected carcinogen and human cell. In these cases investigators most often hunt for an 'adduct' - a suspicious chemical bond between the substance and human DNA. Carcinogen adducts can be the first stage in a process that disrupts DNA replication during cell division. So when an adduct forms an oncogene, the machinery of cellular replication can run haywire, setting the stage for malignancies. This can cause cancer. However, adducts are not the disease. Molecular epidemiologists may establish the link between the quantity of adducts and biomarkers in a person's tissue and the subsequent chances of carcinoma. The amount of personal risk can be calculated exactly by means of a simple blood test. If a person has high levels of adducts and biomarkers, his exposure to carcinogens can be restricted or eliminated (Discover, May 1996).
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