Letters

The real cause for cancer

This is with reference to the article by Anil Agarwal and Sunita Narain on the study published in New England Journal of Medicine which says that environment, and not genes, is the real cause of cancer, which recently appeared in the Business Standard (see also 'Dreams, genes and reality, Down To Earth , Vol 9, No 6; August 15).

Their conclusion -- that environment is the cause of most cancers and genes have little or no role -- is based on a common misunderstanding of the popular 'Nature-Nurture' controversy and about the role of genes. All animals, humans included, have what are called germ cells (sperm or egg) and somatic cells. Information is passed on from generation to generation by the dna ( deoxyribonucleic acid) of germ cells. Mutations in the dna of somatic cells are not passed on to our progeny. Cancer happens when the regulation in the cell goes awry. For this to happen at least 2-3 independent cellular accidents need to take place resulting in the regulatory circuitry breaking down and in uncontrolled proliferation of the cell. These cellular accidents are caused by the environment -- pollution, viruses, diet and lifestyle.

These must act in three different ways on the same cell and, at least in two of the three cases, by affecting the dna of the cell. Therefore, the study of how genes cause cancer has two meanings. One, the meaning used by Agarwal and Narain -- germline mutations. And the other -- the way in which the dna of somatic cells are affected by the environment to cause cancer. Cancer therapy is big business and the study of dna and cancers, caused as it is by the environment, is also big business.

It is quite possible that industry will oppose the link between environmental agents and specific cancers as it has for tobacco. But these cancer causing agents act on our dna. Thus, they are carcinogens which act by mutagenesis. When the environment acts on our germline and causes mutations that we transmit to our progeny, the agents are mutagens, which may or may not cause cancer, but could well cause inherited developmental disorders. Similarly, just as with carcinogens, teratogens in the environment can affect the mother or the developing foetus and cause developmental disorders. Here, unlike in cancer somatic dna damage may be less important.

The most common cancer among Indian women is cervical cancer. This is caused by the environment -- a virus called the human papilloma virus. There are many types of this virus which are sexually transmitted and most are harmless and cause mild warts. Some of them, including the hpv 16, are destructive and can affect the dna of cells in the cervix to cause cancer....

Green magazine

I am a professor of environmental engineering in the Datta Meghe College of Engineering, Airoli, Maharashtra, and a regular reader of Down To Earth.

Down To Earth is the one of the few magazines which presents the true picture of the environmental conditions in the world. I have always recommended this magazine to my students. Even my child finds your supplement, Gobar Times, very interesting. The articles by Anil Agarwal should be read by people from all walks of life. I have been a subscriber for two years or so and I have made year-wise bound volumes of your magazine....

Errata

The byline in the article 'Shifting blame' ( Down To Earth , Vol 9, No 8; September 15) was inadvertently left out. The article was written by Ghazala Shahabuddin. The error is regretted....

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