Old drug may help fight cancer better

A drug used for decades to treat leukaemia may have other uses in the fight against cancer, researchers, including one of Indian-origin, have found.

Previously, doctors used 6-Thioguanine, or 6-TG, as a chemotherapy treatment to kill cancer cells in patients with leukaemia. In recent years, many doctors have shelved 6-TG in exchange for newer drugs that are more effective.

Now, Jeffrey Bryan, from the University of Missouri College of Veterinary Medicine and his colleagues found that 6-TG can not only kill cancer cells, but also works to change how certain cancer cells function, weakening those cells so they can be killed by other drugs.

Every cell in the body has certain genetic characteristics called epigenetic markers that give cells instructions on how to act, when to multiply and when to die.

Cancer cells often have epigenetic markers that cause genes to be either turned off or out of control. This causes those cells to grow rapidly, become difficult to kill and ultimately damage the body.

When testing the drug on cells from dogs with cancer, researchers, including Senthil Kumar, from the MU College of Veterinary Medicine, found that 6-TG can affect these epigenetic markers in cancer cells through a chemical process called demethylation.

This process works to turn off damaging epigenetic markers and turn on markers that make the cells act in a healthy manner.

Bryan said this discovery could lead to future cancer treatments using multiple drugs to fight the disease from different sides.

“While 6-TG is no longer one of the more powerful cancer-killing drugs doctors have at their disposal, we found that it could still be useful to fight cancer in conjunction with other drugs,” said Bryan, who also is the director of the Comparative Oncology and Epigenetics Laboratory at MU.

“If we can use 6-TG to turn off dangerous markers in cancer cells so that those cells become easier to kill, we then can use more powerful cancer-killing drugs to eliminate the cells for good,” said Bryan.

Bryan said this research could potentially open doors for future research on other old cancer drugs that are no longer used by doctors.

By re-examining other potential uses for these old drugs, Bryan said more effective treatments could be found. He also said that doing this research on dogs with cancer could translate well to human diseases.

“Epigenetic markers work similarly in dogs and humans, so we expect to see similar results with these drugs in humans as we do in dogs,” Bryan said.

The study was published in the journal BMC Veterinary Research.

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