Targeted killing of cancer stem cells

Published in The Hindu on August 14, 2009

Cancer treatment has got a shot in the arm. Scientists have been able to successfully demonstrate a chemical molecule that targets only cancer stem cells. The directed targeting makes cancer stem cells less effectively in seeding tumour when injected into mice. It also slowed down the growth of tumour in the mice.

The work was done on cultured breast cancer cells. Breast cancer affects a large number of women in many developed and developing countries. In the U.S., the incidence of breast cancer this year has been over 1.9 lakh and the number of deaths has been over 40,000.

This is the first time that a chemical compound that directly targets the cancer stem cells has been discovered. The study was published online in the journal Cell and was carried out by a team led by Piyush Gupta of the Massachusetts Institute of Technology (MIT).

What made it possible was the development of a high-throughput screening method that looked for chemical compounds that destroyed cancer stem cells. It was then a routine process of zeroing the most effective chemical compound.

Of the 16,000 natural and commercial chemical compounds that were screened, the team was able to narrow down to 32 effective chemicals. Finally, Salinomycin was found to be the most effective one.

Salinomycin was able to bring about more than 100-fold reduction in the cancer stem cell compared with a commonly used chemotherapeutic agent — paclitaxel. When injected in to mice, the cancer stem cells that were treated with Salinomycin had reduced ability to seed tumour in the animals and the growth of tumour was also slowed down.

More work has to be done to find out if Salinomycin can bring about similar results in cancers of other organs. Also, the exact mechanism by which the chemical targets the cancer stem cells is not known.

The work is at a very primitive stage. More studies and clinical trials have to be carried out before the drug, if at all, become available for therapy.