Can curry cure cancer? No, of course not...
Turmeric is a herbaceous perennial plant which is part of the ginger family. Its root-like rhizomes, when boiled and then dried, can be ground into a powder which is widely used in Asian cooking; not just Indian curries but also food from Malaysia, Thailand, Indonesia and other countries. As well as providing a hot, spicy flavour, turmeric is also a colouring agent, providing a mustard-yellow colour which gives it the alternative name ‘Indian saffron’. It can also be used as a dye for clothes and even has a sideline as a pH indicator.
The yellow colour of turmeric comes from three polyphenols (organic compounds containing multiple six-atom carbon rings) known as curcuminoids. These are desmethoxycurcumin, bis-desmethoxycurcumin and plain old curcumin (called E100 when used as a food additive) which is the subject of medical research in Leicester.
Turmeric has been used as a folk medicine in India for 4,000 years for a wide range of ailments and there is now a great deal of research into curcumin – which has been pegged as the active ingredient - to identify which conditions can genuinely benefit from the substance.
Curcumin as (possible) cancer therapy
There is some evidence that curcumin is capable of killing carcinogenic cells without harming adjacent healthy cells, which makes it potentially very useful in the treatment of cancer. But what is required of any potential cancer treatment, including naturally occurring substances such as curcumin, is solid evidence that not only is it beneficial but that such benefits more than outweigh any negative aspects of the treatment regime.
Researchers at Leicester, led by Dr Karen Brown and Dr Lynne Howells from our Department of Cancer Studies and Molecular Medicine, are looking into the use of curcumin as an adjunct or follow-up to chemotherapy in colorectal cancer, targeting the small groups of cells which can survive chemotherapy and cause the cancer to return. This research is funded by local charity Hope Against Cancer.
But, as the saying goes, it’s a bit more complicated than that. It’s certainly a lot more complicated than the simplistic ‘curry cures cancer’ media headlines suggest.
Curcumin research at Leicester
The Leicester research is concentrated on a chemical called oxaliplatin which is administered to cancer patients as part of a triple-treatment regime known as FOLFOX. This contains atoms of platinum, hence the name and hence the effect is ‘platination’. There is no doubt that oxaliplatin is effective (to some degree) and there is no suggestion that curcumin could or should replace it.
Doctors Brown and Howells and their colleagues have already done some research into whether curcumin and oxaliplatin together work better than oxaliplatin on its own and the results are promising. As is well known, chemotherapy is not a pleasant process and has many side effects so anything which could boost the effectiveness of oxaliplatin has the potential to reduce the amount of FOLFOX required for the same level of benefit.
The first problem to overcome was that curcumin, although very effective in vitro (ie. in a petri dish on a lab bench) is much less effective in vivo (inside a living being) simply because it doesn’t travel effectively beyond the gut wall. This was solved by using a proprietary medicine called Meriva which mixes 17% curcumin with a soy bean derivative. Tests have shown that dose of Meriva containing equivalent amounts of curcumin gives five times the levels in the blood of curcumin administered alone.
Four experimental groups were studied: one with oxaliplatin, one with Meriva, one with both substances and a control group with neither. But research like this involves more than just comparing which group does ‘better’ or ‘worse’ than the others.
Curcumin at a molecular level
This is molecular biology: understanding what is happening within cells at a molecular level. Oxaliplatin is known to affect several proteins which in turn have effects that are either cytotoxic (killing cells, a process known as apoptosis) or cytostatic (preventing cells from further dividing). These proteins have names like p53, p21, Notch and survivin and the precise arrangement of atoms in a molecule of each one is already known.
This structural knowledge helps our researchers to provide explanations for experimental results and thereby to understand not only what each protein does but how they affect each other. For example, we know that survivin inhibits p53-induced apoptosis - but it may also indirectly affect the cytotoxic effects of p53 by boosting the effect of another protein, Mdm2, which is a p53 suppressor.
The team measured a variety of outcomes including tumour size, protein expression, biological markers and platination of DNA. Tumour size in particular showed impressive results, with the Meriva+oxaliplatin group showing much greater reduction than either of the substances alone. Measuring a marker enzyme called ALDH1 produced an intriguing result: low concentrations of curcumin decreased ALDH1 expression but higher concentrations increased the amount of ALDH1. Also, the fact that there was no difference in DNA platination between the combined group and the oxaliplatin-only group suggests that the two substances are acting in different ways, which creates the potential for specific targeting of treatments.
No-one said it was simple. If it was, you wouldn’t need a degree.
The curcumin research by members of our Chemoprevention and Biomarkers Research Group continues. Bit by bit, molecule by molecule, scientists at Leicester are discovering what goes on inside cells - healthy and cancerous - when different chemicals are introduced. Only through this slow, painstaking process of biochemical research can doctors learn about what treatments will work best for which patients.