A team at the Weizmann Institute report that they destroyed malignant tumors in mice by using a new, two-step system to deliver allicin straight to the tumor cells.
Allicin is the substance that gives garlic its distinctive aroma and flavour. It is also potent and has been shown to kill not only cancer cells, but also the cells of disease-causing microbes, and even healthy human body cells. A researcher in the UK is currently using it to fight the hospital superbug MRSA.
Allicin is also highly unstable and breaks down quickly once ingested. This rapid breakdown and undiscriminating toxicity presented twin hurdles to creating an allicin-based therapy.
Writing in the December issue of Molecular Cancer Therapeutics (2003 2: 1295-1301), Dr Aharon Rabinkov and his team discuss an ingenious delivery method that works with the pinpoint accuracy of a smart bomb.
The method parallels the way allicin is synthesized in nature. Not present in whole, unbroken cloves of garlic, allicin is the product of a biochemical reaction between two substances stored apart, the enzyme alliinase and a normally inert chemical called alliin. When the clove is crushed, the membranes separating compartments are ruptured and rapid allicin production follows.
The scientists proposed that if doses of allicin could be repeatedly generated in this way at the site of the tumor, the highest concentration of the toxic molecules would be available for killing cancer cells.
To zero in on the targeted tumor, scientists first injected an antibody, chemically bound to allinase, that is 'programmed' to recognize the tumor's characteristic receptor. In the bloodstream, the antibody seeks out these cells and lodges itself and its passenger enzyme on the tumor cells. The scientists then inject the second component, alliin, at intervals.
When it encounters the alliinase, the resulting reaction turns the normally inert alliin molecules into lethal allicin molecules, which penetrate and kill the tumor cells. Due to the precise delivery system, neighbouring, healthy cells remain intact.
The researchers write that they succeeded in blocking the growth of gastric tumors in mice using this method. The tumor-inhibiting effects were seen up to the end of the experimental period, long after the internally produced allicin was spent.
This method could work for most types of cancer, as long as a specific antibody can be customized to recognize receptors unique to the cancer cells, add the researchers. The technique could prove invaluable for preventing metastasis following surgery.
"Even though doctors cannot detect where metastatic cells have migrated and lodged themselves, the antibody-alliinase-alliin combination should chase them down and destroy them anywhere in the body," said team member Professor David Mirelman.