Abstract Gamma-aminobutyric acid (GABA) receptors are ligand-gated ion channels that are essential for neurotransmitter function and neuronal cell homeostasis. Activation of these channels triggers the opening of a chloride-sensitive pore, which causes a hyperpolarization via an influx of chloride ions into the cell. The presence of these channels was recently implicated in several cancers, and the neurotransmitter GABA has been cited as a tumor suppressor. We propose that commercially available pharmacological treatments that manipulate GABA receptor function could be repurposed to target cancer. We have identified functional GABA receptors in a spectrum of colon cancer cell lines and examined the effects of the channels on invasion of the metastatic cell line SW620. Electrophysiological techniques were used to confirm that these channels have functional expression. Treatment with propofol, an agonist which slows the channel closing time, and GABA led to a decrease in invasive potential. Conversely, treatment with the antagonist gabazine, which allosterically blocks GABA from binding in the channel, facilitated invasion by preventing chloride influx. Curiously, treating the cells with bicuculline, which blocks GABA's inhibitory action, led to a decrease in invasion. In some situations bicuculline can also act as a GABA agonist by causing spontaneous gating of homomeric β3 channels. The expression of the β3 subunit was also confirmed through immunocytochemistry. In addition to colon cancer cell lines, β3 expression was detected at higher quantities in colon cancer patient samples compared to matched controls. To further understand how GABA signaling is implicated in cancer, we have looked at the association of GABA with the EGF signaling pathway, which is commonly dysregulated in cancer. The EGF pathway has also been linked with a loss of the glucagon receptor in liver cancer, suggesting that a common pathway may exist between GABA and glutamate that can be exploited for treatment. Altogether, our data suggest that ligand-gated GABA channels inhibit the metastatic potential of cancer cells and can be targeted to treat colon cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 927. doi:1538-7445.AM2012-927