Are Fish Better Than Mice for Cancer Research?

Cancer animal studies may be misleading

(RxWiki News) Most cancer research eventually involves animals - usually mice. Some researchers are suggesting that these types of studies are not only weaker, but may not be achieving the right answers.

A recent study involving rainbow trout reaffirmed that chlorophyll - the green pigment in plants and vegetables - is protective against cancer.

The authors of this research, say that if the study had involved mice, as is traditional, a different conclusion may have been reached.

"Eat lots of green vegetables."

Oregon State University researchers conducted the chlorophyll study, which they say not only confirms its value, but also raises sobering questions about the accuracy of traditional laboratory animal studies.

OSU has been a pioneer in using these fish as laboratory models because the trout react in much the same way rodents do. Experts say they can use thousands of fish instead of dozens or hundreds of mice and conduct experiments that would otherwise be impossible.

The trout are cheaper and more versatile to work with in laboratory experiments. In contrast, fewer mice must be tested against much higher levels of toxins.

The chlorophyll experiment illustrated the difference between using mice and trout. In one part of the study, the trout were given chlorophyll at the same time they were exposed to moderate levels of a known carcinogen. The chlorophyll reduced liver tumors by between 29-64 percent and stomach malignancies by  24-45 percent.

However, in another portion of the study in which the fish were exposed to much higher - unrealistic doses - of the same toxin, the chlorophyll increased the number of tumors substantially.

The study authors point out that in traditional research involving a limited number of mice exposed to these extremely high amounts of a carcingen, researchers may have drawn incorrect conclusions.

"The central assumption of such experiments is that intervention effects at high carcinogen dose will apply equally at lower carcinogen doses," the researchers wrote in their report. "Contrary to the usual assumption, the outcomes in the major target organ were strikingly dependent on carcinogen dose."

OSU scientists believe that some studies involving rainbow trout can produce superior, more accurate, real-world results than traditional rodent animal models. The fish are more relevant to humans, they propose, because many more specimens can be used and lower doses of toxins studied.

These scientists conclude that experiments done with fish may be as much as 20 times cheaper than mice studies and produce more valid results.

As for the chlorophyll anti-cancer benefits, dailyRx asked our Contributing Expert, Edward Giovannucci, M.D., Sc.D., professor of nutrition and epidemiology at the Harvard School of Public Health, who was not involved in this research.

"These findings are interesting, though the relationship between chlorophyll and cancer in humans has received minimal study from epidemiological studies," Dr. Giovannucci told dailyRx.

"The main sources of chlorophyll in the human diet (e.g. vegetables) have been associated with lower risk of some cancers in some studies, but this finding has not been consistent. Even so, it would be difficult to try to separate other potentially beneficial substances such as folate, carotenoids, from the chlorophyll in these studies," Dr. Giovannuci said

Study findings appeared in January, 2012 in the journal Food and Chemical Toxicology.

This research was supported by funds from the National Institutes of Health.

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Review Date: 
January 18, 2012