U. ILLINOIS (US) — The soy peptide lunasin is able to prevent highly metastatic colon cancer from attaching to the liver, particularly in patients who have developed a resistance to chemotherapy.
“When lunasin was used in combination with the chemotherapy drug oxaliplatin, we saw a six-fold reduction in the number of new tumor sites,” says Elvira de Mejia, associate professor of food chemistry and food toxicology at the University of Illinois.
Almost all colon cancer deaths are caused when cancer metastasizes—or spreads—to the liver, de Mejia says. Until now chemotherapy has targeted the primary tumor because the process of metastasis is not well understood.
“In this study, we have learned that lunasin can penetrate the cancer cell, cause cell death, and interact with at least one type of receptor in a cell that is ready to metastasize,” says Vermont P. Dia, a postdoctoral fellow in de Mejia’s lab and lead author of the study, published in the journal Cancer Letters.
A separate study, published in Molecular Nutrition & Food Research, showed lunasin induces cell death in highly metastatic human colon cancer cells.
When that receptor is blocked, new blood vessels cannot form and differentiate, which prevents cancer from spreading. Binding such receptors has emerged as a promising target for developing cancer therapies, he says.
In the Cancer Letters study, which mimicked the spread of colon cancer in humans, mice were separated into four groups: a control group; a group injected daily with lunasin; a group injected with the chemo drug oxaliplatin; and a group that received both lunasin and oxaliplatin. After 28 days, the mice were examined to learn the extent of cancer’s involvement in the liver.
“The group that received lunasin alone had 50 percent fewer metastatic sites. But an even more exciting result was seen in the group that received both lunasin and the chemotherapy drug—only 5 new cancer sites when compared with 28 in the control group,” de Mejia says.
“This huge reduction in metastasis was achieved with the amount of lunasin in only 25 daily grams of soy protein, the amount recommended in the FDA health claim,” Dia says.
The researchers recently analyzed commercial soy milks and all contained lunasin. However, the amount of lunasin depended on the type of soy product that was used to prepare the soy milk.
“Two glasses of soy milk a day generally provide half the amount of lunasin used in our study,” says de Mejia. “It certainly seems feasible to create a lunasin-enriched product that people could consume in a preventive way.”
The next step will be a colon cancer study in which lunasin is included as part of the animals’ diet—rather than injecting the peptide—to see if digestion and absorption alter its effectiveness. They soon hope to move to human trials.
Funding was provided by the USDA, the University of Illinois, and the Illinois Soybean Association.
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