Alpha-2c Adrenoceptor promotes the malignant phenotype of human colon cancer cells

Abstract

Introduction: Cancer remains one of the leading causes of death worldwide, with colorectal cancer (CRC) being the third most common type. Accumulating evidence shows that stress plays a pivotal role in the malignant phenotype of CRC, by promoting hallmarks of CRC including cellular proliferation, migration, invasion, and angiogenesis. During stressful situations, the sympathetic nervous system is activated, causing an elevation in levels of catecholamines including epinephrine which elicits its effects mainly by activating adrenoceptors. Stimulation of adrenoceptors induces malignancy of CRC. In the presence of blockers for both and 1-ARs, epinephrine continued to promote a malignant phenotype. This indicates that receptors other than and 1-ARs, namely 2-ARs, are involved. In our CRC cell line model, the expression of 2A-AR and 2B-AR is extremely negligible. Interestingly, the role of 2c-AR in CRC malignancy remains obscure. Here, we proposed that activation of 2c-AR potentiates the malignant phenotype of human CRC cells. Methods and Results: Treatment of human colon cancer cell line, SW480, with increasing concentrations of 2-AR specific agonist (UK 14,304; 1, 10 or 100 nM) for different time points (24, 48, or 72 hours) did not cause a significant change in proliferation. However, using monolayer scratch assay, a significant increase in migration was observed after treatment with UK 14,304 (100 nM). This was further supported by a transwell migration assay where UK 14,304 increased cell migration. Pretreatment with a specific 2c-AR antagonist (JP 1302; 100 nM) abolished the UK 14,304-induced cell migration. This increase in migratory capacity was concomitant with increased Rho activation evident by translocation of Rho from the cytoplasm to the cell membrane as well as via a Rhotekin-binding activation assay. The induced Rho activation could be mediated by increased oxidative stress since treatment with UK 14,304 increased NADPH oxidase activity and ROS production. Because ROS is known to induce migration