It has long been suspected that vitamin A may be linked to cancer
prevention. The mechanisms by which this may be happening, however,
have yet to be understood. Conversely, scientists have discovered
that a malfunction in the way the body processes vitamin A may be
the culprit behind the formation of breast cancer.
Vitamin A, or retinol, can be found in a number of food products,
such as cod liver oil, milk, eggs and fruits and vegetables; however,
too much vitamin A can be toxic to the body.
Vitamin A Processing
-
Once the vitamin enters the body, it is stored in the liver
and other tissues, including the breast
-
When it is needed, the vitamin is converted into retinoic acid,
activating the retinoic acid receptor in the cells
-
The receptor regulates the expression of a variety of genes,
most of which are associated with cell differentiation
-
When cell differentiation occurs, the genes turn into cells
with specific roles to play; cells that don't differentiate
can develop into tumors
If the cells don't get enough vitamin A stored, the retinoic acid
receptor doesn't get activated, cells don't differentiate and they
can turn cancerous.
Through working with human and mouse breast cells, scientists found
that the problem stemmed from the cellular retinol-binding protein
I (CRBP-I), which is involved in the process of storing the vitamin.
One scientist added, "We found that, in the early stages of
tumor formation, if you don't have CRBP or LRAT [another protein]
to store the retinol, it's likely the receptors will not work in
a normal way. This means that cells can't differentiate, and therefore
start to proliferate into tumors."
Journal
of the National Cancer Institute January 5, 2005;97(1):1
|