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HIV drug Protease Inhibitors tackles cancer cells
Tumour growth blocked by anti-HIV agent.
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Nature.com 31 August 2007
Mary Muers
A type of drug commonly used to treat HIV can slow the growth of cancer cells, researchers have found. The discovery raises hopes that drugs developed to fight one killer disease could help tackle another.
The HIV drug nelfinavir is now going through its first trial in patients with a range of cancers, in light of the new evidence. Cancer scientists think that by 'repositioning' drugs already approved as HIV therapies, they could help to save lives by reducing the 15-year wait and estimated US$1 billion for getting a cancer drug from lab to clinic.
Phillip Dennis and his co-workers at the US National Cancer Institute in Bethesda, Maryland, began testing HIV drugs on cancer cells after noticing that the toxic effects the virus has on cells are similar to the changes seen in cancerous cells. The quest for new ways to treat cancer has previously led to painkillers and morning-sickness treatments being enlisted to fight the disease.
Double dipping
Dennis's team tried adding six approved HIV drugs to a wide variety of cancer cell types grown in the lab. Three of the drugs significantly slowed the growth
of the tumour cells and increased cell death, the researchers report in the journal Clinical Cancer Research1. The most effective of the three, nelfinavir, which impedes the activity of protein-degrading enzymes in the cell, also blocked tumour growth in mice injected with cancer cells.
"The concept of screening all drugs for anti-cancer properties has potential."
Phillip Dennis
US National Cancer Institute
The effect is not particularly surprising, says Ian Hampson from the University of Manchester, UK, who has previously found that a different HIV drug, lopinavir, has potential for stopping cervical cancer. "Cancers have many parallels to viral infection," he says.
Hampson suggests that viruses such as HIV defend themselves against the immune system by switching on the host cell's garbage disposal unit - called the proteasome - so that protective immune proteins are destroyed before they can fight the virus. Cancer-causing mutations can also activate the proteasome, so drugs that block protein breakdown, such as nelfinavir, could theoretically halt both diseases.
Nelfinavir is now in preliminary clinical trials, which should reveal the dose that can be tolerated by patients with cancer, and how it affects solid tumours in the body.
The idea of moving drugs between branches of medicine is gaining ground - HIV drugs are being tested against the SARS virus, and the anti-malarial drug chloroquine is being explored as a potential cancer therapy. Dennis says that "the concept of screening all drugs for anti-cancer properties has potential", and he hopes that a plan to test every drug approved by the US Food and Drug Administration on tumour cells will go ahead.
References
1. Gills, J. et al. Clin. Cancer Res. 13, 5183-5194 (2007)
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