The leading cause of death in all cancer patients continues to be the
resistance of tumor cells to chemotherapy, a form of treatment in which
chemicals are used to kill cells.
Now a study by UC Riverside biochemists that focuses on cancer cells reports
that ingesting apigenin ? a naturally occurring dietary agent found in
vegetables and fruit ? improves cancer cells? response to chemotherapy.

Xuan Liu, a professor of biochemistry, and Xin Cai, a postdoctoral
researcher working in her lab, found that apigenin localizes tumor
suppressor p53, a protein, in the cell nucleus ? a necessary step for
killing the cell that results in some tumor cells responding to
chemotherapy.

The study, published this week in the online early edition of the
Proceedings of the National Academy of Sciences, provides a novel approach
to conquer tumor resistance to chemotherapy, and suggests an avenue for
developing safe chemotherapy via naturally occurring agents.

Normally, cells have low levels of p53 diffused in their cytoplasm and
nucleus. When DNA in the nucleus is damaged, p53 moves to the nucleus where
it activates genes that stop cell growth and cause cell death. In this way,
p53 ensures that cells with damaged DNA are killed.

In many cancers, p53 is rendered inactive by a process called cytoplasmic
sequestration. Apigenin is able to activate p53 and transport it into the
nucleus, resulting in a stop to cell growth and cell death.

?In therapy you want to kill cancer cells,? explained Cai, the first author
of the research paper. ?But to stop cell growth and to kill the cell, p53
first needs to be moved to the cell?s nucleus to function. Apigenin is very
effective in localizing p53 this way.?

Apigenin is mainly found in fruit (including apples, cherries, grapes),
vegetables (including parsley, artichoke, basil, celery), nuts and
plant-derived beverages (including tea and wine). It has been shown by
researchers to have growth inhibitory properties in several cancer lines,
including breast, colon, skin, thyroid and leukemia cells. It has also been
shown to inhibit pancreatic cancer cell proliferation.

?Our study advocates the inclusion of vegetables and fruit in our daily diet
to help prevent cancer,? said Liu, the research paper?s coauthor.

The National Institutes of Health supported the five-year study.

Next in their research Liu and Cai plan to design therapies for cancer by
finding compounds that are like, but perform better than, apigenin.

About UCR
The University of California, Riverside is a doctoral research university, a
living laboratory for groundbreaking exploration of issues critical to
Inland Southern California, the state and communities around the world.
Reflecting California's diverse culture, UCR's enrollment of about 17,000 is
expected to grow to 21,000 students by 2020. The campus is planning a
medical school and has reached the heart of the Coachella Valley by way of
the UCR Palm Desert Graduate Center. The campus has an annual statewide
economic impact of more than $1 billion. To learn more, visit www.ucr.edu