About Cancer

What causes cancer?

Tobacco smoke, most people would say. Probably
too much alcohol, sunshine or grilled
meat; infection with cervical papillomaviruses;
asbestos. All have strong links to cancer, certainly.
But they cannot be root causes. Much
of the population is exposed to these carcinogens,
yet only a tiny minority suffers dangerous
tumors as a consequence.
A cause, by definition, leads invariably to
its effect. The immediate cause of cancer must
be some combination of insults and accidents
that induces normal cells in a healthy human
body to turn malignant, growing like weeds
and sprouting in unnatural places.
At this level, the cause of cancer is not entirely
a mystery. In fact, a decade ago many geneticists
were confident that science was homing
in on a final answer: cancer is the result of
cumulative mutations that alter specific locations
in a cell’s DNA and thus change the particular
proteins encoded by cancer-related
genes at those spots. The mutations affect two
kinds of cancer genes. The first are called tumor
suppressors. They normally restrain cells’
ability to divide, and mutations permanently
disable the genes. The second variety, known
as oncogenes, stimulate growth—in other
words, cell division. Mutations lock oncogenes
into an active state. Some researchers
still take it as axiomatic that such growthpromoting
changes to a small number of cancer
genes are the initial event and root cause of
every human cancer.