Doxorubicin-induced apoptosis and chemosensitivity in hepatoma cell lines.
OBJECTIVE
Doxorubicin (DOX) is a commonly used anticancer drug which causes DNA damage and kills cancer cells mainly by apoptosis. However, the process leading to killing of cancer cells and the molecular basis of resistance to DOX are not well understood. To evaluate the role of p53 and the cellular effects of DOX on hepatoma cell lines, we examined three hepatoma cell lines with different p53 status--Huh-7 (mutated p53), HepG2 (wild-type p53) and Hep3B (deleted p53).


METHODS
The chemosensitivity of the three hepatoma cell lines was assessed using the MTT assay, and cell cycle distribution was evaluated by flow cytometry. Western blotting and immunostaining were employed to examine the protein alterations in response to DOX treatment, and a DNA fragmentation assay was performed to detect apoptosis.


RESULTS
Of the three cell lines, HepG2 was found to be most resistant to DOX, followed by Hep3B, and Huh-7 was most sensitive to DOX treatment. HepG2 showed G1 arrest 24 h after drug administration and upregulation of p53 protein level in a time-dependent manner. In Hep3B cells (deleted p53), G2/M phase arrest was observed soon after drug administration, accompanied by induced apoptosis that was p53-independent. In Huh-7 cells (mutated p53), which were most sensitive to DOX, there was neither G1 nor G2 arrest, and the level of p53 mutated protein was downregulated after DOX treatment. MDM2 and p27 proteins were downregulated in all cell lines independently of p53 status. p21 was upregulated following p53 activation at low doses of DOX in HepG2 cells, but at higher doses, p21 was downregulated in Huh-7 and HepG2 cells.


CONCLUSIONS
DOX confers different chemosensitivity on different hepatoma cell lines with different p53 status. The contrasting relationships between chemosensitivity and p53 status and expression suggest that DOX-induced apoptosis and cell death involve pathways that are independent of p53.
Lee
Terence Kin-Wah
TK
Department of Pathology and Center for the Study of Liver Disease, University of Hong Kong, China.
Lau
Tracy Ching-Man
TC
Ng
Irene Oi-Lin
IO
D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000473:pathology*; D002453:Cell Cycle / Q000187:drug effects; D018797:Cell Cycle Proteins / Q000096:biosynthesis; D004249:DNA Damage / Q000502:physiology; D053938:DNA Fragmentation / Q000187:drug effects; D004317:Doxorubicin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D006801:Humans; D007150:Immunohistochemistry; D013778:Tetrazolium Salts; D013844:Thiazoles; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000235:genetics* / Q000378:metabolism
D000903:Antibiotics, Antineoplastic; D018797:Cell Cycle Proteins; D013778:Tetrazolium Salts; D013844:Thiazoles; D016159:Tumor Suppressor Protein p53; D004317:Doxorubicin; C022616:thiazolyl blue