Growth inhibition of human hepatocellular carcinoma cells by overexpression of G‐protein‐coupled receptor kinase 2

Abstract

Hepatocellular carcinoma (HCC) is one of the deadliest forms of human liver cancer and does not respond well to conventional therapies. Novel effective treatments are urgently in need. G-protein-coupled kinase 2 (GRK2) is unique serine/threonine kinase that involves in many signaling pathways and regulates various essential cellular processes. Altered levels of GRK2 have been linked with several human diseases including cancer. In this study, we investigated a novel approach for HCC treatment by inducing overexpression of GRK2 in human HCC cells. We found that overexpression of GRK2 through recombinant adenovirus transduction inhibits the growth of human HCC cells. BrdU incorporation assay showed that the growth inhibition caused by elevated GRK2 level was due to reduced cell proliferation but not apoptosis. To examine the anti-proliferative function of increased GRK2 level, we performed cell cycle analysis using propidium iodide staining. We found that the proliferation suppression was associated with G2/M phase cell cycle arrest by the wild-type GRK2 but not its kinase-dead K220R mutant. Furthermore, increased levels of wild-type GRK2 induced upregulation of phosphor-Ser15 p53 and cyclin B1 in a dose-dependent manner. Our data indicate that the anti-proliferative function of elevated GRK2 is associated with delayed cell cycle progression and is GRK2 kinase activity-dependent. Enforced expression of GRK2 in human HCC by molecular delivery may offer a potential therapeutic approach for the treatment of human liver cancer.

GRK2: multiple roles beyond G protein-coupled receptor desensitization

“…However, whether the kinase activity of GRK2 is required for this effect on the cell cycle has yet to be determined. Overexpression of GRK2 has been recently reported to attenuate hepatocellular carcinoma cell (HCC) proliferation through inducing G2/M phase cell cycle arrest [71]. This growth arrest is accompanied by increased levels of p53 phosphorylation and cyclin B and was shown to be GRK2 kinase activity dependent.…”

Inhibition of G-protein-coupled Receptor Kinase 2 (GRK2) Triggers the Growth-promoting Mitogen-activated Protein Kinase (MAPK) Pathway

“…Because growth-regulatory pathways are essential for cardiomyocyte survival (16,17), we considered the impact of GRK2 inhibition on cell growth and proliferation. However, the role of GRK2 in cell growth and proliferation is not clear, because in addition to the above mentioned growth-promoting activity, GRK2 can also exert growth inhibition leading to suppressed growth and proliferation of tumor cells (18,19).…”

GRK2 Targeted Knock-down Results in Spontaneous Hypertension, and Altered Vascular GPCR Signaling

“…GRK2 plays an inhibitory role in cell cycle progression and GRK2 overexpression reduces smooth muscle, thyroid cancer, and hepato-carcinoma cell growth and that GRK2 and ␤-arrestin2 regulate cell migration (37)(38)(39)(40)(41)(42). The proliferation and migration of VSMCs derived from older shGRK2 mice is significantly increased in response to Ang II stimulation via an ERK1/2-and Akt-dependent mechanism.…”