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What causes pancreatic cancer?
While it is virtually impossible to tell what caused a specific
person to develop pancreatic cancer, there are some important
principles of cancer biology that can help us understand why pancreatic
cancer develops, and large population-based studies help us understand
the many risk factors for this disease.
Pancreatic cancer is fundamentally a disease caused by damage
to the DNA (mutations). These mutations can be inherited from mom or
dad, or they can be acquired as we age. First, let us look at the
inherited mutations. Remember that we have two copies of each gene -
one copy we inherit from mom, the other copy we inherit from dad. Most
individuals with an inherited cancer syndrome inherit one mutant copy
(let us say from dad) and one intact (normal) copy (let us say from mom)
of a cancer associated gene. As they age, some of these people will
damage the good copy of the gene (the copy they got from mom) in a cell
in their pancreas. That cell will have two bad copies of the gene, and,
as a result, that cell in the pancreas will grow into a cancer. It
doesn’t mean that everyone with an inherited predisposition will get
cancer, it means that since they only have one copy of the gene, they
are more likely to get cancer. I like to think of it using the analogy
of the space shuttle, with the shuttle standing in for a person, and
computers on the space shuttle standing in for genes. Normally the
shuttle goes into space with a computer and a back-up for that computer.
Only if both computers break is there a problem. For people with a
genetic predisposition to pancreatic cancer, it is like going up into
space with one good computer and one bad computer. If something goes
wrong with the one good computer, they are in trouble.
The second way we can damage our DNA is with our behavior. The
carcinogens in cigarette smoke can damage our DNA. If the carcinogens
damage a key cancer-associated gene in a cell in the pancreas, then that
cell may grow into a cancer. Simply put, don’t smoke!
The third way our DNA gets damaged is by chance. This is probably the
least satisfying explanation, but it is true. Every cell in our body
(and there are trillions of them!) contains a 23 chromosomes and these
23 chromosomes contain 3 billion base-pairs of DNA. Every time a cell
divides it has to copy all of that DNA (so that it can make a daughter
cell with a full complement of DNA). The DNA copying machinery in cells
is pretty darn good, but it is not perfect. Occasionally mistakes are
made. On one hand, this is good from a population or species
perspective, because these mistakes allow for evolution to occur (if we
copied our DNA perfectly we would not evolve!). If one of these chance
errors in copying (DNA mutations) damage a key cancer-associated gene
in a cell in the pancreas, then that cell may grow into a cancer.
