Silicon Valley, April. 22 (PTI): In a finding that could help develop an effective anti-cancer drug, researchers have revealed that human lung cancer tumours grew less than half as fast in mice that were injected with moderate doses of tetrahydrocannabinol (THC), an active compound in marijuana. The marijuana compound slows the growth of lung tumours and reduce the spread of cancer in these mice, the findings, presented at the American Association for Cancer Research meeting in Los Angeles, said.

The researchers at the Harvard Cancer Centre in Boston, Massachusetts, led by Ramesh Ganju, hope drugs mimicking the apparent anti-cancer effects of THC could one day help treat patients, reported NewScientist.

According to Ganju, THC inhibits cancer growth by blocking the formation of blood vessels within tumours. Previous tests on human lung cancer cells in a dish suggested that THC blocked the signalling of a substance known as epidermal growth factor (EGF). Under normal circumstances, EGF may promote blood vessel development.

The researchers deposited human lung cancer cells under the skin of a dozen mice and allowed the tumours to grow in the animals for about two weeks. They then began giving half of these mice daily injections of about 250 micrograms of synthetic THC right next to the tumours for three weeks.

Tumours in the control mice averaged about 0.6 grams in weight by the end of the five-week trial. By comparison, those in the mice that received THC weighed just 0.25 grams, 60 per cent less.