Could antidepressants hold key to beating cancer?

When carrying out research, scientists have to deal with the universal tenet of solving puzzling relationships. The difference between causation and correlation is a hugely important part of the scientific process, and cracking the riddle of why something happens the way it does is ultimately what leads to a breakthrough study.

Mental health researchers have stumbled upon one such intriguing quirk in data that is only now starting to become understandable. Those who studied the long-term health of patients taking antidepressants have noticed that over the years, such individuals tend to have a lower risk of cancer. It is a slight effect, but one that has consistently reared its head across many studies, over many decades. This phenomena was well known, but until now, nobody knew exactly why it happened.

This discovery may bring hope for many countries, including China, where heavy investment into oncology has been hastened by its rising cancer rates. One study by McKinsey estimates that China's large population means around 55 people die of cancer every 10 minutes in the country. Any new developments in the fight against cancer are therefore welcome.

Published in the American Association for Cancer Research journal, a new study reveals that the antidepressant drug sertraline aids the inhibition of cancer cell growth. Sertraline, also known commercially in the United States as Zoloft, is a drug widely used to combat anxiety and depression, as well as obsessive compulsive disorder. It is also widely used in the United Kingdom, with around 17 percent of the entire adult population prescribed antidepressants, including sertraline, last year.

New research indicates that sertraline acts on a metabolic pathway, which under conditions arising from cancer, spurs on the growth of tumors. This inhibition effect has been demonstrated on cell cultures as well as animal studies, meaning that although far from being an established treatment for cancer, initial results at an experimental stage are promising.

The key to sertraline's effect is through a cancer cell's appetite for the amino acids serine and glycine. Certain types of cancer such as brain tumors, breast cancer and lung cancer, which is one of the biggest killers in China, all produce serine and glycine, which then stimulate the growth of even more cancer cells.

Professor Kim De Keersmaecker from the Laboratory for Disease Mechanisms in Cancer, who led the study, said in a statement: "This mechanism is an interesting target because cancer cells are so dependent on it. Healthy cells use this mechanism to a lesser extent and also to take up serine and glycine from food. This is not sufficient for cancer cells however, meaning that they start producing more. If we can halt this production, we will be able to fight the cancer without affecting healthy cells." Currently, treatments such as chemotherapy come with devastating side effects, which can severely impact a patient's quality of life.

In the study, sertraline demonstrated the ability to inhibit production of serine and glycine, meaning that cancer cell growth decreased. Models carried out with mice also showed strongly-reduced cancer growth. The exciting prospect is that sertraline is already an established drug, and knowledge of its side-effects seem to be widely accepted as being on the milder end of the scale for antidepressants.

With the battle to save lives from cancer through clinical trials of new drugs often taking decades, it is the years and months that matter to those living with the disease. Using existing treatments and repurposing their therapeutic use may just help save valuable time.

Barry He is a London-based columnist for China Daily.