Discovery and characterization of [3H]8-OH-DPAT binding to HeLaS3 cells

Some G protein-coupled receptors (GPCRs) have functional links to cancer biology, yet the manifestation of GPCRs in tumor types is little studied to date. Using a battery of radioligand binding assays, we sought to characterize GPCR recognition binding sites on HeLaS3 tumor cells. High levels of binding of the selective serotonin 5-HT1A receptor agonist [3H]8-OH-DPAT were observed in these cells. Saturation and homologous competition experiments indicated that [3H]8-OH-DPAT bound different populations of high- and low-affinity sites. In competition experiments, several serotonergic compounds displaced [3H]8-OH-DPAT binding with low potency from its high-affinity binding sites, suggesting that low-affinity binding is the predominant mode of binding. A variety of drugs targeting different classes of receptors did not affect [3H]8-OH-DPAT binding. These observations may help elucidate the pathophysiological and functional relevance of 5-HT receptors in tumor cells and link GPCRs and tumorigenic mechanisms to pharmacological and chemotherapeutic paradigms.