Key Points

Researchers from the University of California, Los Angeles (UCLA) found that selective serotonin reuptake inhibitors (SSRIs), best known for the role they play in the brain, can significantly enhance the ability of T cells to fight cancer.

In the study, published in the journal Cell, the researchers tested SSRIs in mouse and human tumour models representing melanoma, breast, prostate, colon, and bladder cancer.

They found that SSRI treatment reduced average tumour size by over 50 per cent and made the cancer-fighting T cells more effective at killing cancer cells.

"It turns out SSRIs don't just make our brains happier; they also make our T cells happier -- even while they're fighting tumours," said Dr. Lili Yang, senior author and a member of the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA.

"These drugs have been widely and safely used to treat depression for decades, so repurposing them for cancer would be a lot easier than developing an entirely new therapy," Yang added.

Yang and her team first began investigating serotonin's role in fighting cancer after noticing that immune cells isolated from tumours had higher levels of serotonin-regulating molecules.

At first, they focused on MAO-A -- an enzyme that breaks down serotonin and other neurotransmitters, including norepinephrine and dopamine.

However, because MAOIs have safety concerns, including serious side effects and interactions with certain foods and medications, the team turned its attention to a different serotonin-regulating molecule: SERT.

"Unlike MAO-A, which breaks down multiple neurotransmitters, SERT has one job -- to transport serotonin," explained Dr. Bo Li, a research scientist in the Yang lab.

"SERT made for an especially attractive target because the drugs that act on it -- SSRIs -- are widely used with minimal side effects," Li added.

Notably, combining SSRIs with existing cancer therapies also improved treatment outcomes.

The combination significantly reduced tumor size in all treated mice and even achieved complete remission in some cases, the researchers said.

To confirm these findings, the team will investigate whether real-world cancer patients taking SSRIs have better outcomes.

- IANS