A widely prescribed antidepressant may hold promise in the fight against cancer, according to a new study by researchers at the University of California, Los Angeles (UCLA). The research, published in the journal Cell, suggests that selective serotonin reuptake inhibitors (SSRIs), commonly used to treat depression, could reduce tumour size and enhance the immune system&rsquo;s ability to target cancer.
The UCLA team discovered that SSRIs can significantly improve the function of cancer-fighting T cells. In laboratory tests involving both human and mouse tumour models&mdash;including melanoma, breast, prostate, colon, and bladder cancers&mdash;SSRI treatment cut tumour size by more than 50% and boosted the effectiveness of T cells.
"These drugs have been used safely for decades, so repurposing them for cancer treatment could accelerate the path to clinical application," said Dr. Lili Yang, lead researcher and member of UCLA&rsquo;s Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research.
The team&rsquo;s interest was sparked by elevated levels of serotonin-related molecules found in immune cells within tumours. Initially, they focused on the enzyme MAO-A, which breaks down serotonin. However, due to its side effects and dietary restrictions, the researchers shifted focus to another serotonin-related target: the serotonin transporter (SERT).
&ldquo;SERT is responsible solely for transporting serotonin, making it a safer and more targeted option,&rdquo; said Dr. Bo Li, a scientist in Yang&rsquo;s lab. Since SSRIs act directly on SERT, they offered a promising therapeutic route.
Importantly, the study found that combining SSRIs with existing cancer treatments led to better outcomes, with some mice even achieving complete tumour remission.
Researchers now plan to investigate whether cancer patients already taking SSRIs experience improved clinical outcomes, potentially opening a new front in cancer therapy.

SSRIs can significantly improve the function of cancer-fighting T cells

UCLA study finds SSRIs may shrink tumours and enhance T cell response in multiple cancer types

Antidepressant Shows Promise in Cancer Treatment

UCLA study finds SSRIs may shrink tumours and enhance T cell response in multiple cancer types

May 22, 2025 | 22:23 IST