Cortistatin production by HepG2 human hepatocellular carcinoma cell line and distribution of somatostatin receptors

Background/Aims Recently, trials of octreotide have shown a significant survival benefit in the treatment of advanced hepatocellular carcinoma but new data are controversial. We, therefore, examined the production of somatostatin and cortistatin, the expression and distribution of somatostatin receptors (sst) in HepG2 human hepatocellular carcinoma cells, and the possible antiproliferative effect of octreotide on these cells. Methods Radioimmunoassay and RT-PCR studies were performed for the detection of somatostatin and cortistatin. RT-PCR, radioligand binding and immunocytochemistry assays were employed for the detection of the ssts. Growth and viability of cells were measured by the tetrazolium salt assay. Results HepG2 cells were found to express sst2, sst3 and sst5 receptors. Immunocytochemistry revealed a mainly intracellular distribution of all ssts with unique patterns for each of them. Membrane binding sites for somatostatin were mainly of the sst3 (39±8%) and sst5 (59±5%) types, while only minor sst2 binding could be detected (5±12%). Octreotide was found to inhibit the proliferation of HepG2 cells (IC50 1.25×10−9 M) via protein tyrosine phosphatases. HepG2 cells produced cortistatin while somatostatin expression was not detected. Conclusions In conclusion, HepG2 cells express cortistatin, which regulates somatostatin receptors. Cell proliferation was reduced by octreotide via a protein tyrosine phosphatase dependent mechanism.