Research Study Suggests SSRIs May Suppress Tumor Growth

A new research study suggests that SSRIs may significantly enhance the ability of T cells to fight cancer, suppressing tumor growth across a range of cancer types in mouse and human tumor models.

One out of eight adults in the U.S. takes an antidepressant, “and SSRIs are the most commonly prescribed.” These drugs “increase levels of serotonin…by blocking the activity of a protein called serotonin transporter, or SERT.” Serotonin is a “critical player in processes that occur throughout the body, including digestion, metabolism, and immune activity.”

The research team noticed that “immune cells isolated from tumors 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.” Treating mice with melanoma and colon cancer using MAO inhibitors, or MAOIs, “helped T cells attack tumors more effectively.” MAOIs have safety concerns, including serious side effects, so the researchers then targeted SERT.

When the researchers then tested SSRIs, they found that treatment “reduced average tumor size by over 50% and made the cancer-fighting T cells, known as killer T cells, more effective at killing cancer cells.”

The team also combined SSRIs with existing cancer therapies and found the combination of an SSRI and “anti-PD-1 antibody…significantly reduced tumor size in all treated mice and even achieved complete remission in some cases.”