Cholangiocarcinoma cells express somatostatin receptor subtype 2 and respond to octreotide treatment.
OBJECTIVE
We investigated the in vitro and in vivo inhibitory effects of a somatostatin analogue (octreotide, OCT) on cholangiocarcinoma cell lines.


METHODS
The reverse transcriptase-polymerase chain reaction (RT-PCR) was employed to detect the gene expression of five somatostatin receptor (SSTR) subtypes in four cholangiocarcinoma cell lines (RBE, NEC, QBC939, and SSP-25). The antiproliferative effects of OCT on these cell lines were determined by means of an MTT assay in vitro, as well as in a nude mouse tumor heterograft model in vivo. Apoptosis and cell cycles in the cholangiocarcinoma cell lines after OCT administration were evaluated by flow cytometry; and the effects of OCT on the expression of cyclin E, cyclin-dependent kinase 2 (CDK2), and p27kipl were evaluated by Western blots.


RESULTS
Only SSTR2 mRNA was detected in these four cholangiocarcinoma cell lines. OCT significantly inhibited the proliferation of the four cholangiocarcinoma cell lines in vitro ( P < 0.05 vs control), and the weights of the QBC939 xenografts in the OCT-treated group were lower than those in the control group, but there was no significant difference between them. After 48-h exposure to 10(3) ng/ml OCT, flow cytometric analysis demonstrated an increased number of cells in G0/G1 phase associated with a decreased number of cells in G2/M and S phases ( P < 0.01 vs control). Apoptosis was not observed in any samples. The expression of p27kipl was promoted by OCT administration, while that of cyclin E and that of CDK2 were inhibited.


CONCLUSIONS
The results proved that OCT inhibits the proliferation of cholangiocarcinoma cells through G0/G1 cell cycle arrest rather than through the process of apoptosis. These effects are partially mediated by enhancing the expression of p27kipl, and decreasing the amounts of cyclin E-CDK2 complex.
Zhao
Bo
B
Department of General Surgery, People's Hospital, Peking University, XiZhiMenNan Street 11#, Beijing 100044, China.
Zhao
Hua
H
Zhao
Na
N
Zhu
Xue-Guang
XG
D000818:Animals; D018931:Antineoplastic Agents, Hormonal / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use*; D017209:Apoptosis; D001650:Bile Duct Neoplasms / Q000188:drug therapy*; D001653:Bile Ducts, Intrahepatic; D026481:Blotting, Far-Western; D042846:CDC2-CDC28 Kinases; D018797:Cell Cycle Proteins / Q000378:metabolism; D018281:Cholangiocarcinoma / Q000188:drug therapy*; D019927:Cyclin E / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005260:Female; D005434:Flow Cytometry; D016193:G1 Phase; D016147:Genes, Tumor Suppressor / Q000502:physiology; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D008819:Mice, Nude; D008938:Mitosis / Q000187:drug effects; D015282:Octreotide / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D017481:Receptors, Somatostatin / Q000187:drug effects / Q000378:metabolism*; D016192:Resting Phase, Cell Cycle / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016196:S Phase / Q000187:drug effects; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins / Q000378:metabolism
D018931:Antineoplastic Agents, Hormonal; C493961:Cdkn1b protein, mouse; D018797:Cell Cycle Proteins; D019927:Cyclin E; D017481:Receptors, Somatostatin; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; C495893:Cdk2 protein, mouse; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D015282:Octreotide