"Suicide gene" injection shrinks cancer growth

Injectable “suicide gene” therapy may be a highly effective way of preventing colon cancer from spreading (metastasising), finds research in Gut. Human colon cancer carries a high risk of death because it is often not found in the early stages and readily spreads to the liver, but also the lungs and throughout the abdominal cavity (peritoneum).

And the suicide gene treatment seems to be just as effective when injected beneath the skin as it is when introduced directly into the tumour site, the research shows.

In “suicide gene” therapy a normally harmless compound is converted into a lethal drug which will then attack malignant cancer cells. Because it is specifically targeted, the treatment avoids all the toxic side effects associated with conventional chemotherapy as it kills off healthy cells.

Tumour cells carrying the genetic component of the gut bacterium Escherichia coli were injected beneath the skin or directly into the liver tumours of rats with experimentally induced, aggressive colon cancer which had spread to the liver and beyond. The rats were then treated with an antifungal drug, 5-fluorocytosine. The E coli gene codes for an enzyme cytosine deaminase, which transforms 5-fluorocytosine into one of the widely used chemotherapy drugs 5-fluoracil or 5-FU.

Injecting the tumour cells carrying the bacterial genetic material beneath the skin or straight into the liver tumour both reduced tumour size and prevented the spread of cancerous cells to other sites. Within 30 days the tumours had shrunk by an average 70 per cent compared with a group of rats, which had not been given the injectable therapy.

The authors conclude that suicide gene therapy triggers the immune system into producing a systemic response to the genetically modified tumour cells, so affecting tumours at other sites far from the original tumour. And they suggest that it is a powerful approach to preventing the development and spread of metastatic colon cancer.