HIV's machinery adapted to help attack cancer cells
Scientists have adapted a protein made by the HIV virus so that it can import a 'death signal' protein into cancer cells, increasing the effectiveness of cancer therapy in animal models.
Mice with cancer who were treated with the proteins before radiotherapy survived for much longer than mice treated with radiotherapy alone.
Cancer cells are able to grow and divide because they have lost the ability to react to internal signals telling them to commit suicide. A long-held goal for cancer therapy is to switch this suicide mechanism back on.
"HIV knows how to insert itself into many different types of cells," said senior author William Hawkins, assistant professor of surgery and a member of the Siteman Cancer Centre at the School of Medicine and Barnes-Jewish Hospital.
During its life-cycle, the HIV virus produces a number of different proteins. One, called 'TAT', transports biologically active compounds into cells. The team took advantage of this to use TAT to feed a protein called Bim into cancer cells.
Bim is a so-called 'pro-apoptotic' protein, which is involved in transmitting the suicide signals that tells a cell to shut down and die.
"TAT is small, but it can move massive molecules. You could almost hook TAT up to a train, and TAT would drag it inside a cell. So we've taken advantage of this ability," said Professor Hawkins.
During the study, 80 per cent of mice receiving the TAT-Bim therapy survived to 40 days, compared to just 20 per cent of the untreated mice.
"Now that we've proven we can do this, we've started creating a battery of proteins that can push cancer cells to die," said senior researcher, Professor Hawkins.
"Unlike most healthy cells, cancer cells grow very fast. So they are always on the verge of running out of natural ingredients like sugars, and mistakes are accumulating in their DNA.
"This results in signals telling cancer cells to die, but the cells don't quite have the permission they need to do it. Proteins like TAT-Bim can tip the balance in favour of death." The study is published in the the Annals of Surgical Oncology.