The Computer Cell

A living cell is so tiny that it usually can be seen only with the aid of a microscope; yet within this basic unit of life exists an extraordinarily intricate chemical plant. In the cell's nucleus alone, scientists have identified more than 100 distinct chemical reactions that occur as the cell takes in food, grows and reproduces itself. Five years ago, Edward J. Davison, a computer specialist at the University of Toronto, began to translate these complex processes into a series of equations that were in effect a mathematical model of the nucleus of a cell. Now, having finally completed his model, Davison has used it to program a computer to duplicate some of the key processes that take place in the living cell, including its transformation into a cancerlike state.

Davison's computer cell not only "grows" when it is "fed" the right diet of chemicals, but acts up when it is mistreated. In a year of testing, for instance, Davison found that when he subjected his hypothetical cell to disturbances --the mathematical equivalent of a dose of cosmic rays, say, or a virus--it usually died. Sometimes, however, the disturbances affected the chemical reactions involved in the synthesis of messenger RNA (ribonucleic acid), which carries instructions from DNA, the master molecule of heredity, to the cell's protein-producing machinery. Under these conditions, the cell began to grow wildly, used up energy at an enormous rate and displayed all the earmarks of cancer.

Davison's mathematical mutant tends to support what many molecular biologists already suspect: that malignancy is apparently linked to aberrations in the RNA. The nature of the deadly change in RNA remains a puzzle--in part because scientists find the study of chemical reactions on the cellular level so enormously difficult and timeconsuming. But if suspect reactions could first be tested in a computer, using a mathematical substitute for the cell, molecular biologists could perhaps achieve in a few seconds what normally might take them months in the laboratory. Thus Davison's computerized cell may some day provide them with a powerful new tool in their quest to understand and control cancer.

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