Opposing action of estrogen receptors alpha and beta on tumor necrosis factor-alpha gene expression and caspase-8-mediated apoptotic effects in HA22T cells.
Hepatocellular carcinoma (HCC), the major manifestation of primary liver cancer, is one of the most frequent and malignant cancers worldwide, especially in Taiwan. Estrogen receptors (ERs) have been reported to play either a proliferation- or apoptosis-enhancing role in the differentiation of cancers, including HCC. In a previous experiment, we showed that transient overexpressed estrogen receptor-alpha induced early stage HCC cell line Hep 3B cell apoptosis by increasing the hTNF-alpha gene expression in a ligand-independent manner. To further clarify if the apoptotic effect occurs in poorly differentiated HCC cell line, HA22T, and elucidate the roles of ERs and TNF-alpha, DNA fragmentation and caspase activity were measured in late stage HCC cell line, HA22T, by measuring the expression of hER-alpha and hER-beta using a Tetracycline-inducible system (Tet-on). Increased DNA fragmentation and caspase-3 activity were found in hERbeta-overexpressed HA22T cells treated with estrogen (10(-8) M) but not in hERalpha-overexpressed HA22T cells. Using RT-PCR/PCR and western blotting in HA22T cells, overexpressed hER-beta was also found to increase the expression of hTNF-alpha mRNA and induce hTNF-alpha-dependent luciferase activity in a ligand-dependent manner. Additionally, LPS treatment and hER-beta overexpression both enhance caspase-8 activities, whereas neither hER-beta nor E2 treatment affected caspase-9 activities. In addition, the overexpressed hER-beta plus E2 enhanced DNA fragmentation and caspase-8 activities were only partially reduced by anti-hTNF-alpha (0.1 ng/ml), which was possibly due to the involvement of P53 and TGF-beta. Taken together, our data indicates that overexpressed hER-beta but not hER-alpha may induce caspase-8-mediated apoptosis by increasing the hTNF-alpha gene expression in a ligand-dependent manner in poorly differentiated HA22T cells.
Huang
Erh-Jung
EJ
Center of General Education, Central Taiwan University of Science & Technology, Taichung, 406, Taiwan.
Wu
Cheng-Chung
CC
Lee
Shin-Da
SD
Chen
Juen-Hau
JH
Liu
Jer-Yuh
JY
Ko
Jiunn-Liang
JL
Lin
James A
JA
Lu
Min-Chi
MC
Chen
Li-Mien
LM
Huang
Chih-Yang
CY
Kuo
Wei-Wen
WW
D017209:Apoptosis; D006528:Carcinoma, Hepatocellular / Q000473:pathology*; D053181:Caspase 8 / Q000502:physiology*; D045744:Cell Line, Tumor; D053938:DNA Fragmentation; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000502:physiology*; D047629:Estrogen Receptor beta / Q000235:genetics / Q000502:physiology*; D005786:Gene Expression Regulation; D006801:Humans; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics
D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D014409:Tumor Necrosis Factor-alpha; D053181:Caspase 8