Lars Porskjær Christensen’s research focus area is identification of natural products that can help prevent diseases such as cancer, inflammation and type 2 diabetes. His major focal point is small-molecule natural products occurring in plants, because traditionally, such substances have been shown to have beneficial effects on these diseases – for instance, taxol, a natural product from yew trees, is one of today's better known anticancer drugs that is widely used in chemotherapy. In recent years, a major part of his research has been focused on the cancer-preventive effects of a vegetable most of us consume on a regular basis: carrots.
IDENTIFYING THE BIOACTIVE COMPOUNDS IN CARROTS
We regularly hear in the media how eating specific plants may improve our health in one way or another, from herbs, spices and plants that may prevent diseases to “superfoods” that may improve our mental or physical performance in various ways. However, sometimes the wrong conclusions are made on which specific compounds in the plants are actually the cause of these effects. "We probably all remember how healthy eating was placed on the agenda in the 90s. Back then, when the conversation turned to carrots, beta-carotene and other antioxidants were hailed as the major health-promoting elements. However, from my early work in analytical chemistry and natural products chemistry, I knew this to be a false conclusion” Lars Porskjær Christensen explains. When the opportunity arose, he acquired funding for a PhD student, who could work on investigating exactly why studies showed that carrots and closely related root vegetables have preventive effects on cancer.
“We took the objective approach and included all small-molecule natural products in carrots in our research. In practice, we used the technique called bioassay-guided fractionation, in which we start by extracting all relevant compounds from the plant material and test this extract in a bioassay – in other words, examine what effect they have on living cells, in our case cancer cells. If their growth is inhibited when exposed to the extract, we know that the extract contains one or more compounds that has what is called a cytotoxic effect – they are toxic to certain kinds of living cells.”
Following this, the extract was separated into different types of compounds, called fractions, which were again tested to identify which specific compounds had this cytotoxic effect on the cancer cells. Here, the researchers identified two fractions of the carrot extract with a markedly high cytotoxic effect – and, as expected, it was not beta-carotene or other antioxidants, but two compounds called falcarinol and falcarindiol. Furthermore, a later study showed that not only did both compounds have this effect – in the right proportions, they also had a synergistic effect in the sense that when both substances were present, they increased each other’s effect, in essence causing a kind of 2+2 = 5 effect.
PROVING THE PREVENTIVE EFFECT ON COLON CANCER
The next step for Lars Porskjær Christensen was to test falcarinol and falcarindiol in living organisms.
“We tested the effect of the two compounds on rats who had been subjected to a cancer-causing substance that resulted in polyps in their colons. We tested both if falcarinol and falcarindiol had any effect, and what dose was the most effective” he explains.
- “We saw a very significant effect, not only on the number of polyps but also on the size of them. This means that these compounds not only prevent and slow the development of polyps that are precancerous; they also have a chemotherapeutic effect in that they minimize the size of the polyps when they do occur.”
In order to find out exactly how the compounds work on the cancer cells, the researchers did biopsies on the tumours in rats whose diets had been supplemented with falcarinol and falcarindiol as well as in a control group whose diet did not include the compounds. The purpose was to determine which biomarkers for inflammation and cancer were affected in the rats who had been given the compounds, as a lower expression level of these biomarkers would indicate that the cancer-preventive effect would most likely be due to the compounds having an inhibitory effect on these biomarkers.
One of the already-known drugs with a preventive effect on colon cancer is Aspirin, which has the effect of inhibiting enzymes called cycloxygenase 1 and 2 (also called COX-1 and COX-2). COX-2 is a well-known biomarker for cancer and inflammation, and as such inhibiting this biomarker is a way to prevent colon cancer. On the other hand, COX-1 has a number of crucial functions in our body, as it is involved in the regulation of many physiological processes such as gastric acid and phlegm in our lungs. This means that it is not possible to inhibit COX-1 to a large degree without causing severe side effects such as ulcers, bleeds in the stomach, cardiovascular diseases or blood clots. Therefore, as Aspirin inhibits both enzymes, it is not a viable preventive drug, as it cannot be consumed in larger doses.
- “What we found in our studies was that the expression level of the biomarkers for inflammation and cancer were significantly lower in the rats who had been given the rat diet supplemented with falcarinol and falcarindiol compared to the control group – but much more important was that the compounds turned out to inhibit COX-2 but NOT COX-1. So here we have two compounds in combination that inhibit an enzyme that is closely linked to the development of colon cancer – but which comes from a food product that has no known side effects” Lars Porskjær Christensen says.
GETTING READY FOR CLINICAL TRIALS
Now, the researchers are working to get ready for the next step: being able to perform clinical trials on human patients. Finding willing test persons, which is often an extensive and expensive process in clinical trials, will fortunately be no problem at all, as it will simply be a matter of offering the trial to those who get called in for an extra check-up on the basis of the colon cancer test that is already offered Danes over the age of 50. Rather, the challenge is how to give the compounds to the patients.
“We know that falcarinol and falcarindiol prevent colon cancer in rats, and we know to a large degree why they work. As the two compounds are present in a well-known vegetable that is consumed worldwide, there are no risks in giving them to patients. But this is the point where we meet our next challenge, because in order to get the necessary proportions of falcarinol and falcarindiol, they would have to consume the equivalent of around one pound of carrots a day.”
From an earlier experiment Lars Porskjær Christensen knows that the compounds are bioavailable, which means that when ingested via consumption of carrots or carrot products, they are easily absorbed in the body without the need for help from other substances.
- “We are testing different ways of concentrating the carrot extracts to enable giving the test persons the amount and proportion of the compounds that we know work on cancer cells. As mentioned, patients cannot consume the necessary amount of raw carrots, and juicing them is not a viable option either, because a certain amount of the compounds will stay in the drinking glass as residue” he explains. Instead, the researchers are looking at two other options: Either freeze-dried carrots turned into pills, or doing advanced extraction of the falcarinol and falcarindiol from carrots and turning the extract into capsules, tablets or pills. An interesting side project – with holds a further significant potential in terms of sustainability – that the researchers are looking into is whether they can actually use carrot waste from food or dye production as the base of extracting the compounds, because they are present in the peel and core of the carrots.
Once the extraction and pelleting process has been completed, all the pieces are in place for the clinical trials – except the final funding for the trial, which Lars Porskjær Christensen is currently working on acquiring in collaboration with a number of researchers, including medical doctors. He is hoping that within five years, the trial will have been completed with a successful outcome, and the next step, developing a drug that can be chemically produced in bulk, can be commenced. “There is no doubt in my mind that these compounds have a preventive effect on colon cancer in humans – and perhaps on other types of cancer as well. Our final goal is to use our findings to develop a drug for the prevention of colon cancer that is highly effective and at the same time has very few side effects. Just imagine if in the future we can simply take a capsule or pill to prevent getting colon cancer – and all because of a food plant we can all grow in our gardens or buy at the supermarket” Lars Porskjær Christensen finishes.