In their quest for finding new therapies for treating cancers, researchers in the LSU AgCenter and the LSU Health Sciences Center have found several natural compounds that can reduce tumor development by inhibiting angiogenesis.
The AgCenter’s Zhijun Liu
and colleagues have recently added the extract of black raspberries to the list to study.
Long known for its antioxidant properties, black raspberries, not grown in Louisiana, were ordered frozen from Oregon to make an extract. Liu said an extract from black raspberries inhibited angiogenic initiation in a human-tissue model and reduced tumor growth by about half in preliminary laboratory animal studies. Angiogenesis is the process by which new blood vessels grow. All adult angiogenic processes are caused by disease with the exception of a few physiological processes like menses and placental formation.
Tumors cannot grow beyond the size of 0.08 inch without first inducing new blood vessel formation, Liu said. Inhibiting angiogenesis can thus prevent cancer from developing beyond the simple limits of diffusion for oxygen and nutrients.
“Inhibition of angiogenesis contributes to the inhibition of cancer. If you can inhibit angiogenesis, you can inhibit tumor growth. Therefore, the tumor will remain the same size because it can’t grow new blood vessels or obtain nutrients through other new blood vessels,” Liu said.
One of the apparent advantages of black raspberries is that the antioxidant compounds are available merely by eating the fruit. The scientists also know, however, that their hypothesis hasn’t been proved in clinical studies, probably because of enormous variations in the concentration of active compounds in the berries.
Liu said to produce a consistent biomedical effect, the berry compounds must be standardized before they can be effective in a person’s diet. Liu and his laboratory team used a chemical process to develop a standardized black raspberry extract that retains all the angiogenic inhibitors – likely three – in a concentrate that’s less than 7 percent of the volume of the initial extract.
“In its concentrated form, the extract completely inhibited angiogenic initiation and angiogenic growth at the same dose,” Liu said of the laboratory experiments.
The investigators took the product to the next step to discover whether blocking new blood vessel growth works in live tumors and if oral delivery of the extract is effective. Using rats implanted with human pancreatic tumors, the scientists divided them into two groups – one receiving black raspberry extract and the other not. Liu said black raspberry extract orally administered to tumor-bearing rats was effective in retarding tumor growth.
“The fact that oral administration was effective supports black raspberry extract’s use as a dietary supplement in the prevention and treatment of cancer,” Liu said. Liu is encouraged that the research team has proof of concept. The next stage, he said, is to identify the specific compound or combination of compounds that produce the effect.
“We need to reach a therapeutic, effective dose if we can concentrate the compound enough,” Liu said.
Knowing that blackberry works could lead to repeating the study to confirm the bioassay and protocol through animal models. A patent for raspberry extract as a cancer treatment is pending.
Read about Zhijun Liu's research in the winter 2005 issue of Louisiana Agriculture
, Noni Tree: Potential Cancer Treatment, Therapy
(This article was published in the winter 2006 issue of Louisiana Agriculture.)