A derivative of vitamin A, known as retinoic acid,
found abundantly in sweet potato and carrots, helps turn pre-cancer cells back
to normal healthy breast cells, according to research published this month in
the International Journal of Oncology. The research could help explain why some
clinical studies have been unable to see a benefit of vitamin A on cancer: the
vitamin doesn’t appear to change the course of full-blown cancer, only
pre-cancerous cells, and only works at a very narrow dose.
Because cells undergo many changes before they
become fully aggressive and metastatic, Sandra V. Fernandez, Ph.D., Assistant
Research Professor of Medical Oncology at Thomas Jefferson University, and
colleagues, used a model of breast cancer progression composed of four types of
cells each one representing a different stage of breast cancer: normal,
pre-cancerous, cancerous and a fully aggressive model.
When the researchers exposed the four breast cell
types to different concentrations of retinoic acid – one of the chemicals that
the body converts vitamin A into – they noticed a strong change in the
pre-cancerous cells. Not only did the pre-cancerous cells begin to look more
like normal cells in terms of their shape, they also changed their genetic
signature back to normal. Dr. Fernandez’s pre-cancerous cells had 443 genes
that were either up or downregulated on their way to becoming cancerous. All of
these genes returned to normal levels after treatment with retinoic acid. “It
looks like retinoic acid exerts effects on cancer cells in part via the
modulation of the epigenome,” says Fernandez.
“We were able to see this effect of retinoic acid
because we were looking at four distinct stages of breast cancer,” says Dr.
Fernandez. “It will be interesting to see if these results can be applied to
patients.”
Interestingly, the cells that were considered fully
cancerous did not respond at all to retinoic acid, suggesting that there may be
a small window of opportunity for retinoic acid to be helpful in preventing
cancer progression. In addition, the researchers showed that only one
concentration of retinoic acid (about one micro Molar) produced the anti-cancer
effects. Lower concentrations gave no change, and higher concentrations
produced a smaller effect.
The next step will be to try to learn whether the
amount of retinoic acid required can be maintained in an animal model, and if
that concentration will have the same effects as Dr. Fernandez observed in
cells. If those studies show the same effect, the next step would be to test
whether these observations hold true in humans.
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