CYANIDE has been conscripted into the war against cancer. The idea is to
target the deadly poison at cancer cells without harming the patient.
Laboratory results presented at the BA have demonstrated the strategy is on
course. 鈥淲e鈥檙e hoping to begin animal trials in a year鈥檚 time,鈥� says Mahendra
Deonarain, head of the team at Imperial College, London, that is developing the
treatment for Antisoma, a London-based biotechnology company.
His plan is to make sure that the cyanide is only produced in tumour tissue.
An antibody that binds only to cancer cells will be joined to an enzyme from the
cassava plant that makes cyanide. This double protein unit鈥攅ffectively a
hook plus a miniature poison factory鈥攃ould be infused into a patient鈥檚
blood.
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Once the antibody hooks onto tumour tissue, tiny amounts of cyanide
manufactured by the cassava enzyme will diffuse into the cancer cells and kill
them. Any traces of poison leaking away from the site will be rapidly detoxified
in the liver, says Deonarain.
The therapy will exploit well-known plant biochemistry. Cassava, apricots and
almonds repel chewing insects by making their own supplies of cyanide. Nibbling
triggers production of the enzyme linamarase, which converts a harmless plant
sugar called linamarin into the poison.
In the first step of Deonarain鈥檚 two-stage treatment, patients would receive
the double protein. In step two, patients will be given linamarin. 鈥淚t washes
through the whole body, but would only be converted to cyanide by the cancer
cells,鈥� says Deonarain.
Though the first treatment will be aimed at colorectal tumours, any type
could be targeted, given suitable antibodies.