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All
life on Earth follows a code that is remarkably simple at its base, yet
complex in its adaptation. The code is of only four chemical
letters, A, C, G, and T, arranged in three-letter words on a very long
string called DNA. The code describes the order in which amino acids
must be connected to form the proteins that build the organism. Each
of the 20 amino acids is coded by a particular three-letter word on the
DNA. So four letters are used to make words that code for each of
the 20 amino acids, which build tens of thousands of proteins for life so
diverse as to defy enumeration. Yet the same word is used for each
amino acid in everything from bacteria to human beings.
A
bacterial cell fends for itself, struggling to multiply and outnumber any
other cellular competitors. Each human cell is part of a team that
must work together. In bacteria, if its DNA is damaged, it may die
or it may actually compete better with other cells for survival. In
a human cell, if its DNA is damaged it is supposed to have the discipline
to kill itself; this is called “Programmed Cell Death” or
“Apoptosis”.
Apoptosis
is currently a hot topic in cancer research because sometimes a damaged
cell refuses to kill itself, and decides it is no longer part of the
person. It begins to fend for itself, struggling to multiply and
outnumber any other cellular competitors. This, then, is cancer.
Our immune system finds and kills most invading bacteria. But cancer
cells look enough like ourselves that they may go unnoticed until it is
too late.
Cancer
is a disease beginning in a single cell, and results from damage to the
genetic code of DNA. The nature of this damage has become
increasingly well understood. First is damage causing the cell to
forget it is part of a community of cells working together, and second is
damage causing the cell to refuse its duty to kill itself. However,
the reasons why the damage occurs are not so clear. For some of the
common cancers, their causes have been at least partly explained: the rise
in lung cancer occurs because people pick up the habit of smoking, liver
cancer in Africa and Asia is caused by aflatoxin in moldy food and by
spread of hepatitis viruses, a fall in stomach cancer happens when people
start using refrigerators that prevent food spoilage, and more than half
the risk of colon cancer is explained by sedentary lifestyle and diet.
For
breast cancer, however, the cause of the epidemic as societies
industrialize is entirely unclear; breast cells in women in the modern
world are suffering the DNA damage leading to cancer in ever-increasing
numbers. We don’t know why. The international race to
find the causes of breast cancer is the subject of THE MYSTERY OF
BREAST CANCER, a one-hour documentary being developed for broadcast
on U.S. PBS stations and international channels..
Watch for more information coming soon.
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