Now, a biocomputer to find and kill cancer cells

Washington, Sep 4 - Scientists have developed a new DNA-based logic circuit which they say can identify and kill cancer cells without harming the healthy ones.

The researchers, who developed the cell-level diagnostic

system, said it could be used for drug screening or perhaps

for disease treatment, killing tumors while leaving healthy

cells alone.

The circuit, they said, works like any other logic

circuit: It analyses multiple inputs and makes a decision.

In this case, the circuit really consists of genes that

can detect up to five cancer-specific molecules and their

concentrations. When all five of those characteristics are

present, the circuit makes a positive determination, and then

it triggers cell death, they reported in the journal Science.

The biocomputer combines the factors using logic

operations such as AND and NOT, and only generates the

required outcome, namely cell death, when the entire

calculation with all the factors results in a logical TRUE

value, lead researcher Yaakov Benenson, of Federal Institute

of Technology in Zurich, said in a statement.

The researchers, including a team from the Massachusetts

Institute of Technology in the US, tested the biocomputer with

HeLa cells, a prolific type of cervical cancer cell.

They studied the cells' microRNA, which regulates gene

expression by destroying messenger RNA, the substance that

brings the DNA blueprint to the rest of the cell. They

eventually pinpointed one microRNA combo that was unique to

HeLa cells.

Once they had the right combination, the researchers

designed a synthetic gene which codes for a protein that

promotes apoptosis, or programmed cell death. The special gene

would turn on in the presence of miRNA levels that match the

HeLa profile.

If the miRNA levels were too high or too low, the gene would not switch on, and the cell would not be killed. Healthy cells, which would also lack the HeLa profile, would be similarly left alone, the researchers said.

The next step, they said, would be to test this system in

a living animal, but this will be difficult. Current methods

use viruses or chemicals to bring foreign DNA inside cells,

but these make permanent changes, which could have their own

complications.

So the method is still far from being usable for cancer

treatment, they said, but added that it is an important step

toward building a single-cell-level diagnostic method.