Von Hippel-Lindau Disease, an Inherited Cancer Syndrome
The association between chromosome abnormalities and cancer is nearly 100 years old. Although the association between chromosomal abnormalities and human cancers was first made in the early 1900's, the first genetic marker for a cancer, the Philadelphia chromosome that occurs in chronic myelogenous leukemia, was not identified until 1960. Research that demonstrated the association of specific genes with certain cancers did not flourish until the 1990's. Although this seems like an incredibly slow progression of discoveries, we know a tremendous amount of information about cancer and chromosomes today. Much of this progress has been made through research in cancer genetics, with a major emphasis on identifying families in which members had a clear predisposition to developing certain types of cancer.
The
importance of understanding the
role that genetics has played in
the identification of cancer-associated
genes can be appreciated through
a comparison of lung and kidney
cancers. Each of these cancers has
a strong association with smoking,
and each exhibits common abnormalities
of human chromosome 3. Lung cancer,
with an estimated 170,000 new cases
diagnosed in the United States in
the year 2001, does not appear to
have a hereditary component. In
other words, families with a predisposition
to developing lung cancer in the
absence of smoking have not been
identified. On the other hand, about
2% of the ~31,000 new cases of kidney
cancer diagnosed in the U.S. in
2001 were hereditary cancers. These
kidney cancers occurred in patients
who were predisposed to developing
kidney cancer because of their family
history. Through the study of families
with cancer predisposition, researchers
have identified several genes associated
with the development of kidney cancer,
while lung cancer genes have not
been defined.
There are several types of inherited kidney cancer. One is kidney cancer associated with von Hippel-Lindau (VHL) disease. By analyzing genetic markers in many VHL patients, it was discovered in the late 1980's that the gene responsible for VHL disease occurs on human chromosome 3. The VHL gene was identified in 1993 and was found to be mutated in patients with VHL disease. In addition, patients with non-hereditary kidney cancer were found to have mutations in the VHL gene in their tumors but not in other cells in their body. Therefore, mutations in the VHL gene are closely associated with kidney cancer. This is an example where the identification of a gene responsible for a rare inherited cancer led to the understanding that the same gene is responsible for the more common, non-inherited form of the same cancer.
VHL
disease is a cancer syndrome. VHL
patients may develop cysts or tumors
in the kidneys, retinas, brain,
spinal cord, adrenals, pancreas,
inner ear, or the scrotum. Before
the VHL gene was identified in 1993,
diagnosis was determined by family
history and the presence of multiple
tumors. Because diagnoses were frequently
made in the late stages of cancer
growth, VHL patients had a significantly
shortened life expectancy. Today
a relatively simple DNA-based blood
test can identify VHL disease gene
carriers before any tumors are detected.
While we can readily identify patients
predisposed to developing VHL disease,
we cannot yet predict the full spectrum
of tumors these patients will develop
or at what age they will become
problematic. Therefore, VHL patients
require frequent and detailed medical
examinations to detect tumors and
follow their growth.
A VHL patient has a 50-50 chance of passing a mutated form of the VHL gene to each of his or her children. The VHL gene produces a protein that works as a tumor suppressor. Tumor suppressors control cell division, and when tumor suppressors are mutated, they lose their normal function and cells may exhibit uncontrolled growth. Since the VHL tumor suppressor is mutated in most cases of kidney cancer seen in the general population, gaining an understanding of how the VHL tumor suppressor works will help VHL patients as well as patients with non-inherited kidney cancer.
The
possibility of developing cancer
is something that every person fears
to some degree. For some, such as
VHL patients, it is not a matter
of if they will develop cancer but
rather when it will occur. With
genetic testing and close medical
surveillance, we expect that the
life expectancy of a VHL patient
diagnosed today will far exceed
the life expectancy of a patient
diagnosed as recently as 10 years
ago. It is the goal of future biomedical
research to develop and offer therapies
that are even more effective to
VHL and non-hereditary kidney cancer
patients.
Here are answers to some common questions regarding VHL Disease and other types of inherited cancer:
I'm 55 years
old, and after I went to the doctor
about having blood in my urine 7
years ago, I was diagnosed with
kidney cancer. If kidney cancer
can be inherited, should I have
my children tested to see if they
have a mutation in the VHL gene?
Probably not. If you have no family history of kidney cancer or any of the spectrum of tumors associated with VHL disease, if your kidney cancer was a single tumor in one kidney, and if you have no other tumors, then it is likely that your cancer was what we call a non-hereditary or sporadic cancer. This would mean that your children would have no greater likelihood of developing cancer than anyone in the general population.
My father
died of lung cancer when he was
56 years old and his brother died
of lung cancer when he was 60 years
old. If cancer can be inherited,
should I be concerned about developing
lung cancer too?
Yes, if you are a smoker. There is no indication that lung cancer is inherited, but it does have a very strong association with smoking. Researchers do not yet understand why some smokers develop lung cancer while others do not, or why in some very rare cases non-smokers develop lung cancer. Genes are almost certainly the determining factors in lung cancer predisposition, so you should be concerned about developing lung cancer if you smoke.
I
am a 23-year-old woman and my mother
recently died from kidney cancer
related to VHL disease. We did not
know she had VHL until just before
her death. I had genetic testing
done, and a VHL mutation was found
in my blood cells. When I had a
full medical work-up, I learned
I had several tumors in my brain
and in both kidneys. My family doctor
told me that I should not have children,
because they would be subjected
to the same cancers that I have.
Is this true?
Any VHL patient has a
50-50 chance of passing the mutated
gene onto their children. This is
a personal decision that you need
to make for yourself, but you can
help make a better decision with
some education about VHL. The VHL
Family Alliance (www.vhl.org) is
a patient support organization that
can provide information on VHL disease
and can put you in touch with other
VHL patients. Children can be tested
at any age to determine whether
they inherited a mutated form of
the VHL gene. If a child or other
family member has a mutated VHL
gene, careful, annual medical screening
will enable physicians to identify
tumors and follow their growth before
they become problematic. New surgical
techniques are continually being
developed, and drugs that may limit
tumor growth are currently being
tested. Through patient education
and biomedical research, VHL patients
may lead long, normal lives.
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