Cancer Related Videos

An accumulation of genetic defects can apparently

cause normal cells to become cancerous and cancerous

cells to become increasingly dangerous

by Webster K. Cavenee and Raymond L. White

Do the risks of aggressive treatment for early prostate cancer

outweigh the beneÞts? This question is one of several unresolved issues

faced by those who treat, and those who have, prostate cancer

by Marc B. Garnick

Charles Darwin

Natural selection lacks the power

to erase cancer from our species and,

some scientists argue, may even have

provided tools that help tumors grow

Charles Darwin, 1881

NATURAL SELECTION IS NOT NATURAL PERFECTION.
Living creatures have evolved some remarkably complex adaptations, but we are still very vulnerable to disease. Among the most tragic of those ills—and perhaps most enigmatic—is cancer. A cancerous tumor is exquisitely well adapted for survival in its own grotesque way. Its cells continue to divide long after ordinary cells would stop. They destroy surrounding tissues to make room for themselves, and they trick the body into supplying them with energy to grow even larger. But the tumors that afflict us are not foreign parasites that have acquired sophisticated strategies for attacking our bodies. They are made of our own cells, turned against us. Nor is cancer some bizarre rarity: a woman in the U.S. has a 39 percent chance of being diagnosed with some type of cancer in her lifetime. A man has a 45 percent chance.

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.