Cytostatic effect of octreotide on human cholangiocarcinoma cell proliferation via a G_0/G_1 cycle block

To observe the expression of somatostatin receptor(SSTR) in four cholangiocarcinoma cell lines(RBE, NEC, QBC 939 , SSP 25), and to investigate the inhibitory effects of somatostatin analog octreotide (OCT) on the proliferation of them, Type 2 and 3 SSTR mRNA in cholangiocarcinoma cell lines were detected by reverse transcriptase polymerase chain reaction technique (RT PCR).The effects of various doses (10?1?0.1?0.01 and 0.001mg/L) of OCT on the proliferation of above cholangiocarcinoma cell lines were evaluated by MTT assays with serum free medium as control. The cell cycle and apoptosis of the cells with and without OCT treatment were analyzed in flow cytometry with propidium iodide (PI) staining and FITC conjugated Annexin V PI double staining. Not only SSTR 3 but also SSTR 2 mRNA were be detected in all cholangiocarcinoma cell lines. OCT (10, 1 and 0.1mg/L) significantly inhibited the proliferation of four cholangiocarcinoma cell lines in vitro (P values were all less than 0.05 when compared with control). After 48h of exposure to 1mg/L OCT, flow cytometric analysis demonstrated increased cell number of G 0/G 1 phase accompanied with decreased cell number of G 2/M and S phase (P values were all less than 0.01 when compared with control), while apotosis was not seen in all samples. The results proved that OCT inhibited proliferation of cholangiocarcinoma cells, this effect seems mainly due to cytostatic effect rather than promoting the way of apoptosis. Thereby, OCT may posess the perspectives in the adjuvant therapy for SSTR positive biliary tract malignancies.