The research at the department of chemistry and the Center for Advanced Food Technology (CAFT) may also have implications for other forms of cancer, such as skin, lung, colon, esophagus and mammary gland cancers.
The team's conclusions were highlighted in a paper presented today by lead researcher Kuang Yu Chen, professor of chemistry and chemical biology, at the 222nd national meeting of the American Chemical Society (ACS) in Chicago.
ACS, which holds two national meetings a year, is the world's largest scientific society. The Rutgers paper, "Effects of Polyphenolic Compounds in Black Tea and Grape on the Expression of Specific Genes in Normal and Cancerous Human Cells" summarizes the team's work on polyphenols, compounds in tea and other foods with antioxidative and other biochemical properties.
The researchers found that when a black tea polyphenol known as theaflavin-3'-monogallate (TF-2) was added to a pair of laboratory cultures of cancerous and normal human colorectal cells, it killed virtually all of the cancer cells without harming the normal ones.
"The TF-2 compound apparently caused the cancer cells to commit suicide," says Chen. "Their DNA was chopped into pieces and the cells died. But the compound had little or no effect on normal cells."
Several leading laboratories around the world, including the Laboratory for Cancer Research at Rutgers' College of Pharmacy and the Cancer Institute of New Jersey in New Brunswick, have shown that black tea extract is a powerful inhibitor of a variety of cancers in animal models, including skin, lung, colon, esophagus and mammary gland cancers.
To determine black tea's impact on cancer, Chen and his team focused on TF-2 and two other major black tea polyphenol compounds.
The first step in their investigation, says Chen, was to find out if the compounds inhibit cell growth, and if so, how they did it. For example, some cancer inhibitors work by causing a hole in the cell membrane (wall) to destroy it, and others can cause the cell to commit suicide, known as "apoptosis."
The researchers found that TF-2 was a powerful cancer inhibitor that causes the cell to become suicidal. What's more, it did it without harming healthy cells. "That's what makes TF-2 so amazing," notes Chen. "It kills only cancer cells."
Further examination of how the compound worked inside the cell showed that it not only causes apoptosis, but it suppresses a gene known as Cox 2 that is often associated with colon cancer, says Chen. Expression or activation of Cox 2 is known to cause inflammation, part of the chain of events that could turn normal cells into cancer cells, notes the researcher.
"We can't say that the Cox 2 gene directly causes cancer, but we can say that a high level of Cox 2 gene expression occurs in many cancer types," the scientist says. "And Cox 2 has been considered an important pharmacological target in cancer treatment."
In fact, notes Chen, for some anti-inflammatory drugs such as aspirin, their well-known protective effects against colorectal cancer probably stem from their ability to suppress Cox 2 activity. "The bottom line is that the TF-2 compound may be the reason, at least in part, for the chemopreventive activity (the ability to target and kill cancerous cells and not healthy ones) in black tea extracts," says Chen.
The Rutgers team did similar studies on polyphenols in green tea and grape skin, but with less dramatic results. However, by slightly modifying the polyphenols in grape skin, Chen and his fellow researchers were able to greatly strengthen its cancer-killing abilities without harming healthy cells.
"By rationally modifying the chemical structure of nutraceuticals, we can actually improve on nature," says Chen. "We can move from discovering nutraceuticals to making pharmaceuticals."
Chen and his team are busy assaying the hundreds of compounds and plant extracts in foods that remain to be studied for their cancer-fighting potential through a process they have developed and patented at Rutgers.
The process uses specially prepared tissue culture to determine if the compounds in a specific food have the ability to turn off a cancer-causing gene or, alternatively, turn on a gene that fights cancer.
Different foods can be tested on a panel of selected genes, allowing researchers to easily sift through many compounds to uncover those with therapeutic potential.
Rutgers licenses the process to WellGen, a New Jersey company spun off from Rutgers in 1998. The university is a major shareholder in WellGen, which develops and markets the compounds. Aside from black and green tea, and grapes, the company has found cancer-fighting properties in orange peel, Mexican bamboo, Vietnamese mint and licorice.
Other members of the research team are Geetha Ghai, assistant director at CAFT; Robert Rosen, associate director at CAFT; Chi-Tang Ho, professor of food science; and Jiebo Lu, Min Chen and Alexander Gosslau, postdoctoral fellows.