"It turns out SSRIs don't just make our brains happier; they also make our T cells happier- even while they're fighting tumors. 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," said senior author of the study, Dr. Lili Yang, member of the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA, in a press release.
In the current study, researchers investigated the use of SSRIs in mouse and human tumor models of melanoma, breast, prostate, colon, and bladder cancer. Treatment with SSRIs reduced tumor size by more than 50% on average and increased the efficacy of killer-T cells at killing cancer cells.
The researchers also explored the effects of combining SSRIs with existing cancer therapies. In particular, they combined an SSRI and an anti-PD-1 antibody- an immune checkpoint blockade- to treat mouse models of melanoma and colon cancer. The combination significantly reduced tumor size in all mice treated and led to remission in some cases.
"Immune checkpoint blockades are effective in fewer than 25% of patients. If a safe, widely available drug like an SSRI could make these therapies more effective, it would be hugely impactful." said study co-author, James Elsten-Brown, a graduate student in the Yang lab, in a press release.
The findings suggest that SSRIs are promising candidates for cancer immunotherapy, wrote the researchers in their study.
Given that 20% of cancer patients take antidepressants, with most taking SSRIs, Yang noted that a 'unique opportunity' exists to expore how the drugs may improve cancer outcomes. To this end, the researchers now intend to design a clinical trial to compare treatment outcomes between cancer patients who take SSRIs and those who do not.
Sources: Science Daily, Cell