Targeting Spot 14 and CLA
Research Offers New Hope in the Battles Against Breast Cancer and Obesity
April 23, 2009
What if you could target a gene necessary for breast cancer proliferation? What if you could take a pill that stopped fat production? Could the two somehow be related? Every day, in research laboratories across the globe, the war against cancer, as well as obesity, rages on. Here at Dartmouth-Hitchcock, in the research laboratory of William B. Kinlaw, MD, perhaps the battle is just a little closer to being won.
In the early 1980s, while still at the University of Minnesota, Dr. Kinlaw's work as an endocrinologist was focused on how the thyroid controls various genes. What he and the team discovered was a previously undescribed gene that, because of its rapid response when given to rodents, was a perfect gene with which to try to unravel how thyroid hormone works. Dr. Kinlaw notes, "The gene was turned on within seconds and remains by far the most rapid thyroid response gene. If there were a lengthy delay between giving the hormone and seeing the gene turned on then you'd have no idea of how many steps are in-between. But this is so quick that it must be a direct effect." The gene was called Spot 14.
Targeting Spot 14
When Kinlaw returned to Dartmouth-Hitchcock, where he had done both his internship and his residency, he focused on where exactly in the body Spot 14 was turned on in rats. "The patterns strongly suggested that it was involved in turning on the pathway where the body makes sugar into fat-fat synthesis. It looked like Spot 14 was probably regulating that pathway," says Kinlaw. He remembers that at about that time a medical student agreed to work in the lab but only on human studies, instead of rodent experiments, so Kinlaw suggested he try to localize the gene-find out what chromosome it is on in humans. "This was before the genome had been sequenced. I thought if we were lucky it might land on some area of a chromosome where a lipid disease had been linked," says Kinlaw.
"Every single case of breast cancer that showed a recurrence after initial treatment showed the highest score for Spot 14 in the tumor. More importantly, of the ones that showed a zero score of Spot 14, not a single one recurred. "
The research showed that Spot 14 was localized to the long arm of chromosome 11, an area which had been extensively studied by groups in the U.S. and France because it is amplified in many breast cancers. "This means that basically breast cancers take that little area of the gene and make many extra copies of it. This is often a clue that the cancer has found this region of the chromosome to provide it with something that helps it to grow."
"Then we started thinking about the relationship of Spot 14 to fat synthesis. Well, what does that have to do with breast cancer?" Kinlaw says that was "when the light bulbs really went on" because a research group at Johns Hopkins had shown that "most cases of breast cancer make lots of fat. They're very active in converting glucose to fat and all the genes involved in that process are turned on in these cancers." He stresses that, "Most importantly, if you interrupt the process the breast cancer cells die, so they are actually dependent on a constant supply of fat."
The Role of Conjugated Linoleic Acid (CLA)
About this time a dairy scientist at Cornell, Dale Bauman, PhD, was studying a problem seen in cows. They were suffering from milk fat depression (MFD), a syndrome in which a cow's milk becomes completely devoid of fat and therefore commercially useless. Bauman thought this had to do with something in the cow's feed that is altered in the rumen-part of the bovine digestive tract. "There are bacteria that occur only in the rumen that can do some pretty strange things metabolically," says Kinlaw. One of these things is that they take a very common lipid found in plant material, linoleic acid, and shuffle the double bonds to turn it into fatty acids called conjugated linoleic acid (CLA)."
Bauman did an experiment: he fed his cows either normal grass or grass that would cause MFD. Then he did a biopsy of the cow's mammary gland and a gene chip analysis. "He analyzed the level of every gene-about 20,000 genes-and the biggest hit he got was Spot 14, which was turned off when cows were fed the grass that caused MFD. Additional experimentation with pure CLA provided the same results," explains Kinlaw. "Now the thing is he had never heard of Spot 14 before, so he called me up and said 'what is going on with this?'"
After several discussions, Bauman "said the obvious thing that was running through my mind too: 'if CLA can shut down lipid synthesis (fat production) in normal mammary cells, maybe it can also do it in breast cancer,'" says Kinlaw. "So we experimented and figured out how to deliver CLA into breast cancer cells. We found it does shut down Spot 14 gene expression, shuts down lipid synthesis, and it kills the cells. This work was recently accepted for publication in the international journal Nutrition and Cancer."
Approximately 75% of breast cancers seem to be dependent on a supply of fat. "That statement is equally applicable to prostate, ovarian, and colon cancers," says Kinlaw. CLA is readily available as a dietary supplement, and currently people are taking it primarily for weight loss. It is also used by body builders to minimize body fat content and increase lean body mass. However, Kinlaw points out, "It's a nutritional supplement, so it doesn't fall under the purview of the FDA. I would say that nobody yet knows the true beneficial and untoward effects of CLA."
According to Kinlaw, further research needs to be done. There are different types of breast cancer and it may be that some types are susceptible and others aren't. Further research shows that it may be that "dual inhibitors that can shut down both the making of new fat and the getting of fat out of the blood stream are going to be necessary." Yet, it would be a definite advantage if CLA is an effective tool against breast cancer because it is an already existing compound. There would be no need to start at square one with new drug development.
"We are trying now to get some seed money locally to do the necessary preliminary CLA studies in human beings. The idea is to enlist women who have just been diagnosed with breast cancer to take CLA pills between the time of their initial diagnostic biopsy and the hopefully definitive surgery," says Kinlaw. "We will then be able to take small amounts of the breast cancer tissue and stain it with antibody to see if the CLA actually shuts down the Spot 14 gene in tumors." Because of the highly responsive nature of the Spot 14 gene, the study would only take about 10 days. "It is either going to work or not," says Kinlaw. Because breast cancer arises in the mammary gland, which is basically a fat pad, normal fat is also excised with the tumor tissue. "We will then be able to compare the ability of CLA to shut down Spot 14 in normal fat as well."
Kinlaw wants to be clear; he does not think Spot 14 causes cancer. "But I do think it is a required component to be a nasty cancer. Nasty cancers have the metabolic equipment to survive some very difficult situations, such as establishing a metastasis from a single cell." Previously he, along with other Cancer Center staff, had an opportunity to take 90 tissue samples from breast cancers that were diagnosed at DHMC. Most importantly, says Kinlaw, they were diagnosed about 10 years ago, "so we had enough information over time to know whether they were cured or not and other characteristics related to tumor aggressiveness."
After staining all 90 cases with antibodies and scoring them based on how much Spot 14 was in each, they came out with an "unbelievable" result. "Every single case of breast cancer that showed a recurrence after initial treatment showed the highest score for Spot 14 in the tumor. More importantly, of the ones that showed a zero score of Spot 14, not a single one recurred." Kinlaw hopes that soon they will be able to increase the study size. "We have been trying, so far unsuccessfully, to locate a much larger group with all the clean, clear, clinical data that we had on our 90 cases to replicate this finding. More in-depth statistics would require at least 500, preferably 1000 cases. That is a major goal we are aiming for." But for now, he says, "At the very least Spot 14 is a pretty good biomarker for aggressive breast cancer," and CLA might offer one of the best chances to tame it.
-Reprinted from Skylight (Winter 2009; Volume 8, Number 1), the newsletter for Dartmouth-Hitchcock Medical Center.