Scientists have developed an innovative method to target cancer cells, by administering a rare metal that is largely native to meteorites.
Iridium, a heavy metal found in small quantities in meteorites, is even less present on Earth, the majority being close to the Earth's core.
Its detection in higher concentration (than average) in the ground serves as an indicator of meteorite impact, which also provided important evidence for the theory on the asteroid which would have caused the extinction of the dinosaurs.
It is a metal that also has the ability to resist corrosion at high temperatures. Its use for x-rays and to treat cancer with brachytherapy is known, but the latter method involves irradiation of the area where the tumor is growing, which can lead to other risks and side effects.
Scientists from the group of Dr. Peter Sadler at the University of Warwick in England, have developed an iridium complex to kill cancer cells without radioactivity.
When exposed to light, certain molecules, such as this iridium complex, produce oxidizing agents to which cancer cells are more sensitive than healthy cells.
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If they could reach the nucleus of tumor cells and be illuminated by an optical fiber, healthy cells could be spared the disadvantages of treatment.
The iridium complex cannot reach the desired location by itself, but the group has found a solution:albumin, a protein particularly attracted to cancer cells, is able to enter their nucleus while carrying it the molecules of the complex.
"It's fascinating to see how albumin can deliver our photosensitizer in a nucleus-specific way says Dr. Cinzia Imberti, co-author of the study paper.
There are two advantages to administering Sadler's group iridium complex combined with albumin:the complex prefers to target the nucleus rather than other organelles, and it is highly luminescent, the latter characteristic allowing scientists to observe in real time the destruction of cancer cells.
So far, the experiments have been performed in vitro and must first be tested on animals, but the chances of success of the treatment on humans are high.
One of the factors that can limit the use of iridium is none other than its rarity in the earth's crust. Fortunately, the amount needed for treatment is very small, and if there isn't enough left, mining asteroid impact sites remains a solution.
