Abstract
Epidemiological studies have demonstrated that the use of antidepressants is associated with a decreased risk of colorectal cancer (CRC); however, the mechanisms behind this association are yet unknown. Adrenergic system contributes to the stress-related tumor progression, with norepinephrine (NE) mainly secreted from adrenergic nerve fibers. Norepinephrine serotonin reuptake inhibitors are successfully used antidepressants. This study demonstrates that a widely used antidepressant venlafaxine (VEN) antagonizes NE-promoted colon cancer in vivo and in vitro. Bioinformatic analysis suggested that NE transporter (NET, SLC6A2), a target of VEN, was closely associated with the prognosis of clinical patients with CRC. In addition, the knockdown of NET antagonized the effect of NE. The NET-protein phosphatase 2 scaffold subunit alpha/phosphorylated Akt/vascular endothelial growth factor pathway partially mediates the antagonizing effect of VEN on NE's actions in colon cancer cells. These were also confirmed by in vivo experiments. Our findings revealed for the first time that, in addition to its primary function as a transporter, NET also promotes NE-enhanced colon cancer cell proliferation, tumor angiogenesis, and tumor growth. This provides direct experimental and mechanistic evidence for the use of antidepressant VEN in the treatment of CRC and a therapeutic potential for repurposing existing drugs as an anti-cancer approach to improve the prognosis of patients with CRC.