Fighting cancer with precious metals
Platinum is more precious than gold, and not just in money terms. The metal is a killer of cancer cells, but as Dr Celine Marmion at the Royal College of Surgeons in Ireland observed, so far only three platinum-based drugs have been approved for worldwide clinical use.
Platinum, she explained, is effective because it latches onto the backbone of DNA, and that stops it replicating. Tumour growth is brought to a halt, but unfortunately, platinum does not discriminate between cancer and normal cells, so treatment has to be carefully focused on the tumour itself. The trade off, said Dr Marmion, involves killing the cancer while leaving enough normal cells for recovery.
One of Dr Marmion’s objectives is to make delivery of platinum drugs more selective. Already, she said, it’s known that different platinum compounds are more selective than others, and that cancer cells can develop resistance. “There is some sort of self-defence mechanism at work,” she said. There is also another serious barrier in that platinum likes to bind to sulphurcontaining biomolecules thus making them unavailable to bind to the DNA of cancer cells. The cell has no shortage of these, so most of the platinum gets mopped up before it ever reaches through to the DNA. “It is believed”, said Dr Marmion, “that only about 1% of a platinum drug actually reaches its intended target, and that means higher doses are required which can lead to serious side effects”.
With SFI funding, Dr Marmion has been looking for ways to get around these problems. One of her approaches has been to find out if platinum compounds could be attached to something else that targets cancer cells.
“We think we have found that hook,” she said. Her group have developed a new class of platinum-based compounds that have been shown to be very effective at killing cancer cells but are much less toxic towards normal cells. These are currently being tested on a whole range of cancer cells”.
Novel technology developed by the group through two SFI-Research Frontier Programme awards, has produced an innovative class of multi-functional platinum (Pt) drug candidates as anti-cancer therapies. A research paper has been published in the flagship journal Chemical Communications. The technology is now the subject of a PCT Application and a pharmaceutical company has expressed a keen interest in this technology.
