Researchers at Oregon State University (OSU) have for the
first time traced the actions of a known carcinogen in cooked meat to its
complex biological effects on microRNA and cancer stem cells.
The findings are part of a growing awareness of the role of
epigenetics in cancer, or the ways in which gene expression and cell behavior
can be changed even though DNA sequence information is unaltered.
The scientists also found that consumption of spinach can
partially offset the damaging effects of the carcinogen. In tests with
laboratory animals, it cut the incidence of colon tumors almost in half, from
58% to 32%.
The research at OSU’s Linus Pauling Institute was reported
in Molecular Nutrition and Food Research,
in work supported by the National Institutes of Health.
“Cancer development is a complex, multistep process, with
damaged cells arising through various means,” said Mansi Parasramka, a
postdoctoral scholar with LPI. “This study showed that alterations of microRNAs
affect cancer stem cell markers in colon cancer formation.
“MicroRNAs are very small factors that do very big things in
cells,” she said.
Traditionally, cancer was thought to be caused by changes in
DNA sequence, or mutations, that allowed for uncontrolled cell growth. That’s
still true. However, there’s also increasing interest in the role played by
epigenetics, in which such factors as diet, environmental toxins, and lifestyle
affect the expression of genes—not just in cancer, but also cardiovascular
disease, diabetes, and neurological disorders.
Included in this epigenetic equation is the formation of
microRNAs—once thought to be “junk DNA”—which researchers were at a loss to
understand. It’s now known that they influence which areas of DNA get expressed
There are hundreds of microRNAs, and the OSU scientists
monitored 679 in their experiments. When they don’t work right, bad things can
happen, including abnormal gene expression leading to cancer.
“Recent research is showing that microRNAs are one of the
key epigenetic mechanisms regulating cellular functions in normal and diseased
tissues,” said Rod Dashwood, the Helen P. Rumbel Professor for Cancer
Prevention and director of LPI’s Cancer Chemoprotection Program.
“But unlike mutations which are permanent genetic changes in
DNA,” he said, “the good news about epigenetics and microRNA alterations is
that we may be able to restore normal cell function, via diet and healthy life
style choices, or even drug treatments.”
Epigenetics essentially makes every person biologically
unique, Dashwood said, a product of both their genetics and their environment.
That includes even identical twins.
The findings of the new study should lead to advances in
understanding microRNAs, their effects on cancer stem cells, and the regulatory
processes disrupted in disease development, the OSU scientists said. This might
lead one day to tailored or “patient specific” therapies for cancer, Dashwood
Source: Oregon State University