Elucidation of susceptible factors to endoplasmic reticulum stress-mediated anticancer activity in human hepatocellular carcinoma.
The initiation of endoplasmic reticulum (ER) stress has been suggested to play potential roles in hepatocarcinogenesis. However, many obstacles remain as to whether ER stress plays a role in carcinogenesis or tumoricide. This study sought to identify the signals that can serve as anticancer effectors in cells in response to ER stress. Tunicamycin (an N-glycosylation inhibitor) inhibited cell proliferation with IC(50) values of 0.19 and 0.62 microg/ml in hepatoma (Hep) 3B and HepG2 cells, respectively. It induced G1 arrest of the cell cycle in both cell lines. The anticancer mechanism of tunicamycin was investigated in Hep3B cells. Tunicamycin induced a rapid decline of cyclin D1 and cyclin A expression and an early increase of glucose-related protein (GRP) 78 and growth arrest and DNA damage-inducible transcription factor (GADD) 153 levels. Cyclin A was the most sensitive regulator to tunicamycin-triggered degradation mechanism. The association of p27(Kip1) with cyclin D1/cyclin-dependent kinase (Cdk) 4 was also increased by tunicamycin. The inhibition of GADD153 expression by transfection of GADD153 antisense did not modify tunicamycin-induced G1 arrest and cyclin/Cdk expressions. The knockdown of GRP78 expression by the siRNA transfection technique moderately increased tunicamycin-induced apoptosis but not the antiproliferative effect by sulforhodamine B assay. We suggest that tunicamycin induces G1 arrest through down-regulation of cyclins and Cdks, in which cyclin A is more susceptible to ER stress-triggered degradation mechanism in Hep3B cells. The increased association of p27(Kip1) with cyclin D1/Cdk4 may also contribute to tunicamycin-induced cell-cycle arrest. GADD153 and GRP78 play a minor role in tunicamycin-mediated antiproliferative effect, although GRP78 moderately inhibits apoptosis in Hep3B cells. These data provide evidence that cell-cycle regulators are susceptible factors in hepatocellular carcinoma (HCC) responsive to ER stress.
Chiang
Po-Cheng
PC
School of Pharmacy, National Taiwan University, Taipei, Taiwan.
Hsu
Jui-Ling
JL
Yeh
Ting-Chun
TC
Pan
Shiow-Lin
SL
Guh
Jih-Hwa
JH
D000970:Antineoplastic Agents / Q000494:pharmacology*; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000473:pathology; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D019938:Cyclin D1 / Q000502:physiology; D051358:Cyclin-Dependent Kinase 4 / Q000502:physiology; D050760:Cyclin-Dependent Kinase Inhibitor p27; D004721:Endoplasmic Reticulum / Q000187:drug effects* / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins / Q000502:physiology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000502:physiology; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000473:pathology; D018832:Molecular Chaperones / Q000502:physiology; D051742:Transcription Factor CHOP / Q000502:physiology; D014415:Tunicamycin / Q000494:pharmacology*
D000970:Antineoplastic Agents; C436291:CDKN1B protein, human; C497249:DDIT3 protein, human; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D047908:Intracellular Signaling Peptides and Proteins; D018832:Molecular Chaperones; D014415:Tunicamycin; D019938:Cyclin D1; D051742:Transcription Factor CHOP; D050760:Cyclin-Dependent Kinase Inhibitor p27; C495900:CDK4 protein, human; D051358:Cyclin-Dependent Kinase 4