[Effect of HBV X gene transfection on octreotide-inhibited growth of hepatocellular carcinoma cell line HepG2].
OBJECTIVE
In vitro and in vivo experiments have shown that octreotide, a kind of somatostatin analogue, could inhibit hepatocellular carcinoma (HCC) growth. However, its clinical efficacy is unsatisfactoryû the reason is unclear. This study was to investigate if some characters of HCC cells transfected with hepatitis B virus (HBV) x gene have altered their response to octreotide, and explore the possible mechanisms.


METHODS
The proliferation of HCC cell lines HepG2 and HepG2x (with HBV x gene transfection) was measured by (3)H-thymidine incorporation into DNA. Immunocytochemistry was used to detect the expression of proliferating cell nuclear antigen (PCNA) in tumor cells. Annexin-V and TUNEL in situ assays were used to detect apoptotic cells. The expressions of extracellular signal-regulated kinase (ERK-1/ERK-2) and somatostatin receptors (SSTR-2, SSTR-3, SSTR-5) were measured with Western blot.


RESULTS
At the concentration of 1 x 10(-5) - 1 x 10(-9) mol/L, octreotide significantly inhibited (3)H-TdR incorporation into HepG2 cells in a dose-dependent manner (r=-0.917, P < 0.01) and PCNA expression, and greatly enhanced the apoptosis of HepG2 cells either in Annexin V positive rate [control vs. octrotide=(1.18+/-0.13)% vs. (14.20+/-2.57)%, P < 0.05] or TUNEL apoptotic index [control vs. octrotide=(3.6+/-0.9)% vs. (18.8+/-3.3)%, P < 0.05]. However, no such response happened in HepG2x cells when treated with octrotide or octrotide plus lamivudine. The expressions of SSTR-2 and SSTR-5 were significantly lower in HepG2x cells than in HepG2 cells (P < 0.01); the expressions of ERK-1 and ERK-2 were significantly higher in HepG2x cells than in HepG2 cells (P < 0.05). Octreotide didn't inhibit ERKs expression in HepG2x cells.


CONCLUSIONS
The down-regulated expression of SSTR-2 and SSTR-5, due to HBV x gene transfection, result in decreased growth inhibitory effects of octreotide on HepG2x cells.
Xie
Yi
Y
Division of Peptides Related with Human Diseases, MOE Key Laboratory of Biotherapy of Human Diseases, West China Hospital, Sichuan University, Chengdu, Sichuan, P. R. China.
Tang
Cheng-Wei
CW
Wang
Chun-Hui
CH
D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D006528:Carcinoma, Hepatocellular / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D006801:Humans; D019259:Lamivudine / Q000494:pharmacology; D008113:Liver Neoplasms / Q000378:metabolism / Q000473:pathology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D015282:Octreotide / Q000008:administration & dosage / Q000494:pharmacology*; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D017481:Receptors, Somatostatin / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics*; D014162:Transfection; D054334:Viral Regulatory and Accessory Proteins
D018931:Antineoplastic Agents, Hormonal; D018809:Proliferating Cell Nuclear Antigen; D017481:Receptors, Somatostatin; D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein; D019259:Lamivudine; C094573:somatostatin receptor 5; C093733:somatostatin receptor 2; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D015282:Octreotide