ScienceDaily (Oct. 24, 2008) — 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 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.

Adapted from materials provided by University of California - Riverside

ScienceDaily (Jun. 28, 2007) — They’ve been said to stall aging, ward off disease and wage internal war against the harmful free radicals that pummel our bodies every day. But just how well do antioxidants—those all-powerful compounds often found in richly colored fruits and vegetables, such as blueberries, blackberries and red cabbage—actually perform inside the human body?

Nutritionists with the Agricultural Research Service (ARS), the U.S. Department of Agriculture’s chief scientific research agency, recently tackled this question. Their findings appear in the current issue of the Journal of the American College of Nutrition.

Led by Ronald Prior, an ARS chemist who works at the Arkansas Children’s Nutrition Center in Little Rock, the researchers investigated how the consumption of different fruits affected volunteers’ antioxidant status.

They did this by measuring the plasma (blood) antioxidant capacity (AOC) of volunteers who’d just ingested blueberries, cherries, dried plums, dried-plum juice, grapes, kiwis or strawberries.

The series of ARS studies confirmed what many antioxidant experts have long suspected: that the free-radical-busting compounds found in foods are quite complex, with some apparently being easier to absorb and utilize than others.

For instance, the researchers found that despite their high antioxidant content, plums did not raise plasma AOC levels in volunteers. According to Prior, one of the major phytochemicals in plums is chlorogenic acid, a compound not readily absorbed by humans.

As for the wild blueberry, a larger-than-average serving of this much-heralded antioxidant source was needed to boost plasma AOC levels. A noticeable climb in AOC wasn’t detected until volunteers consumed at least a half-cup serving of the berries.

The volunteers’ consumption of grapes and kiwifruit both led to noticeable spikes in plasma AOC. But it’s not clear yet which compounds were responsible for the increased levels.

Alternatively, when volunteers were asked to consume a shake containing protein, carbohydrates and fat, with no antioxidants, their blood antioxidant levels dropped.

While additional research is needed to determine if elevated plasma AOC levels translate to a lower risk for chronic degenerative disease, the current ARS study is an important first step in efforts to establish recommendations for antioxidants in the diet.

USDA/Agricultural Research Service (2007, June 28). Not All Antioxidants Are Created Equal. ScienceDaily. Retrieved December 4, 2007, from http://www.sciencedaily.com