Killer that may be a life-saver

Press, 13 April 1982, Page 21

Killer that may be a life-saver

By

ROBERT JACKSON,

author of

30 books on scientific and military subjects.

It could have been something straight out of a James Bond movie. A Bulgarian exile. Georgii Markoff, waiting for a bus in a crowded London street, suddenly felt a stabbing pain in his leg.

A few hours later he was dead, victim of a platinum pellet fired into his leg from a modified umbrella wielded by an unknown assassin.

The pellet contained ricin, one of the deadliest poisons known to man. But today, four years after it killed Georgii Markoff, ricin is turning from a life-taker into a life-saver.

H the latest experiments are successful, it could be the key to a new cancer treatment which would bring renewed hope to thousands of sufferers.

It is certainly an unlikely substance to do anyone any

good. This ■ white powder, derived from pressed castor oil bran, is so deadly that the British Army, after experimenting with it for a time as a possible toxic agent, abandoned it altogether. As little as one-thousandth of a gramme is all it takes to kill a man. But at a recent conference in Hamburg, scientists — mainly from West Germany, tne United States, and Israel — reported that they had succeeded in injecting ricin molecules into cancer cells in laboratory mice, hoping to use the deadly poison as a cancerkilling agent. Medical experts admit that

up to now all forms of cancer treatment — including radiation — have suffered from one major drawback. No matter what anti-cancer agent is used, it destroys not only the cancer cells, but also healthy cells that surround them. But the injection of ricin molecules seems to overcome this obstacle. The groundwork for the new method was actuallv laid as long as 20 years ago. when scientists began research into lectins — plant proteins ■ that ■ induce red blood cells to cluster together. Ricin is a member of the lectin group.

Lectins have other startling properties. They persuade sugar molecules to attach themselves to the surfaces of certain cells, forming a kind of protective barrier, and somehow appear to be able to tell the difference between one kind of cell and another. They also help to stimulate the production of lymphocytes. which are present everywhere in the blood stream and which form the

body’s built-in defence mechanism against cancer-pro-voxing agents. Key research in this field is being carried out by Professor Nathan Sharon and a team of scientists at the Weizmann Institute in Rechovot. Israel. Much of their research has dealt with bone marrowtransplants. where- rejection problems have frequentlybeen experienced because of the action of lymphocytes.

Professor Sharon's team claims to be well on the way to overcoming this by extracting the lymphocytes from the marrow before a transplant takes place. Scientists have also discovered that lectins produced bywheat and soya beans provoke a powerful reaction when introduced to cancer cells. These cells cling together rapidly after receiving only a tiny dose and gradually die. whereas healthy cells require a veryhigh dose to act in a similar manner. The hope is that scientists may soon be able to introduce members of this highly

toxic sub-group of lectins — to which ricin belongs — into cancer cells in human beings. Already they know that one single molecule of ricin is sufficient to block all protein production inside a cell and kill it rapidly. Inevitably, there are massive problems which have to be solved. Lectins attack a cell by "homing in" on sugar molecules attached to the cell's membrane., and specific types of sugar molecule will allow the lectins to pass through them into the cell's interior, like a door opening. Unless the killers can somehow be "aimed” accurately, they might wander off-course

and attack the wrong targets. The scientists now think they may have found a possible solution. A ricin molecule is composed of two distinct parts — the detective, that “sniffs out” the sugar molecule and acts on it, and the killer, which then slips through.

Since the detective is not too fussy about the kind of sugar molecule it attacks, researchers think that the answer is to remove it altogether and replace it with a much more accurate agent.

It will require some tricky genetic engineering, but it is not impossible. Ironically. the deadly poison that has taken thousands of lives could one day become the vital key to a wav to save millions. — Features International.