Anticancer activity study of A3 adenosine receptor agonists

Aims: A3 adenosine receptor (A3AR) signalling activation seems to mediate anticancer effect, and it has been targeted for drug development. The identification of potent and selective A3AR agonists could be crucial for cancer drug development. Materials and methods: In the present study was determined the in vitro activity of known 1–3 and newly 4–6 synthesized compounds with high A3AR affinity and selectivity (Ki in the low nanomolar range) in binding studies. Effect of known and novel A3AR agonists on human prostate cancer (PC3), hepatocellular carcinoma (Hep G2), and epithelial colorectal carcinoma (Caco-2) cells were analysed by cytotoxicity assay, dose and time dependent inhibitor assay, migration, apoptosis, autophagy and reactive oxygen species (ROS) assays. Key findings: Results show that the anticancer effect is not due to A3AR activation alone. In fact, the more active and selective agonist versus A3AR, compound 1, results inactive on cancer cells such as compounds 2–4. Moreover, results show that the novel compound 5, at micromolar concentration range (IC50 = 28.0 μM), inhibits the growth of PC3, Hep G2, and Caco-2 cells and their migration in time- and dose- dependent manner. The mechanism involved in cell death is attributable to apoptosis. At the same time compound 5 promotes autophagy, which induce apoptosis producing autophagic cell death. Further investigation revealed that compound 5 elevates the level of ROS in all cancer cells tested, suggesting the involvement of ROS in cell death. Significance: These results show that the new compound 5 exerts inhibitory effect on cancer cells through differential effect and may serve as a potential anticancer agent.