Synthetic plant hormones kill cancer cells by halting DNA repair

In In The News by Barbara Jacoby

By: Honor Whiteman


With more than 1.6 million new cancer cases diagnosed in the US alone last year, the race is on to uncover new treatments for the disease. Now, a new study suggests two synthetic plant hormones could offer just that.

The team found that, when combined with another cancer drug, the agents MEB55 and ST362 disrupted DNA repair in prostate cancer cells, causing them to self-destruct.

Senior investigator Ronit Yarden, assistant professor in the Department of Human Science at Georgetown University Medical Center in Washington, DC, and colleagues publish their findings in the journal Oncotarget.

MEB55 and ST362 are synthetic versions of strigolactones – hormones produced in the roots of plants that regulate their growth.

The agents were synthesized by researchers from the Agricultural Research Association (ARO), Israel, and the University of Turin, Italy, who also collaborated on the study.

Over the past 7 years, the team has conducted numerous studies showing that synthetic versions of strigolactones can halt growth in prostate, colon, lung and breast cancer cells. But until now, the mechanisms underlying this process have been unclear.

For their study, Yarden and colleagues tested and analyzed the effects of MEB55 and ST362 in conditionally reprogrammed prostate cancer cells, which are cells that do not stop growing.

The researchers tested each agent separately in combination with poly ADP ribose polymerase (PARP) inhibitors – cancer drugs that halt DNA repair in cancer cells by blocking the PARP enzyme.

Both MEB55 and ST362 killed the prostate cancer cells when combined with PARP inhibitors.

The researchers found that each synthetic plant hormone stopped the DNA repair process of cancer cells that occurs before cell division but after the cells have copied DNA. The PARP inhibitors halted a second DNA repair process, according to the team, which caused the cancer cells to die.

“Mistakes in copying DNA are especially prevalent in cancer cells, so without any way to repair their DNA, these cells self-destruct,” explains Yarden.

While it is very early days to be hailing the synthetic plant hormones as a possible cure for cancer, the team says they will soon be testing the agents on animal models with various forms of the disease.

Commenting on their overall findings, Yarden says:

“MEB55 and ST362 appear to be very promising agents. Our study suggests that when used with anti-cancer drugs called PARP inhibitors, the combination is effective and does not harm normal cells.”

Last week, Medical News Today reported on a study that suggests a natural extract from the leaves of the neem tree may be effective against pancreatic cancer.