Thymosin-alpha 1, but not interferon-alpha, specifically inhibits anchorage-independent growth of hepatitis B viral transfected HepG2 cells.
BACKGROUND
Thymosin-alpha 1 is a biological response modifier that has been used clinically, alone and in combination with interferon-alpha for the treatment of chronic hepatitis B viral infection. Both immunomodulatory and immediate intracellular mechanisms have been postulated to explain the effect of these two agents on HBV-infected hepatocytes.


METHODS
In this study, hepatitis B transfected HepG2 hepatoblastoma cells (HepG2-Nu2), derived from 2.2.15 cells, were used as an in vitro model to determine the efficacy of thymosin-alpha 1 and interferon-alpha, individually and combined, as proliferation inhibitors of HBV-infected cells. For comparison, parental HepG2 cells and an SV40-transfected HepG2 cell line (HepG2P9T2) were also evaluated.


RESULTS
In a clonogenic soft agar assay, thymosin-alpha 1 inhibited the anchorage-independent growth of the HepG2-Nu2 cells by 40% compared with untreated controls, but did not inhibit parental HepG2 or HepG2P9T2 clonal growth. The response was dose dependent over concentrations spanning three log units. In comparison, 10000 units/ml of interferon-alpha inhibited parental HepG2, HepG2-N4Z and HepG2P9T2 by 33%, 41% and 87%, respectively. The combination of thymosin-alpha 1 and interferon-alpha consistently inhibited HepG2-Nu2 clonal growth more effectively than either treatment alone, reaching maximum inhibition levels of 51%.


CONCLUSIONS
Thymosin-alpha 1 specifically inhibits the tumorigenic growth of HBV-transfected HepG2 cells in contrast to the general inhibition displayed by interferon-alpha. This panel of cell lines may be an important resource for dissecting the mechanism by which thymosin, alone or in combination with other drugs, influences HBV-infected hepatocytes and/or HBV-associated carcinoma.
Moshier
J A
JA
Department of Internal Medicine, Wayne State University School of Medicine, Detroit, Michigan, USA.
Mutchnick
M G
MG
Dosescu
J
J
Holtz
T K
TK
Akkary
S
S
Mahakala
K
K
Merline
J R
JR
Naylor
P H
PH
D000276:Adjuvants, Immunologic / Q000008:administration & dosage / Q000494:pharmacology*; D000998:Antiviral Agents / Q000008:administration & dosage / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D002472:Cell Transformation, Viral; D004279:DNA, Viral / Q000096:biosynthesis / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004359:Drug Therapy, Combination; D004797:Enzyme-Linked Immunosorbent Assay; D006515:Hepatitis B virus / Q000187:drug effects* / Q000235:genetics; D018197:Hepatoblastoma / Q000188:drug therapy* / Q000821:virology; D006801:Humans; D016898:Interferon-alpha / Q000008:administration & dosage / Q000494:pharmacology*; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000821:virology; D000077596:Thymalfasin; D013947:Thymosin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D014162:Transfection; D014407:Tumor Cells, Cultured; D014779:Virus Replication / Q000187:drug effects
D000276:Adjuvants, Immunologic; D000998:Antiviral Agents; D004279:DNA, Viral; D016898:Interferon-alpha; D013947:Thymosin; D000077596:Thymalfasin