Induction of Bcl-2 expression by hepatitis B virus pre-S2 mutant large surface protein resistance to 5-fluorouracil treatment in Huh-7 cells.
BACKGROUND
Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide with poor prognosis due to resistance to conventional chemotherapy and limited efficacy of radiotherapy. Our previous studies have indicated that expression of Hepatitis B virus pre-S2 large mutant surface antigen (HBV pre-S2Δ) is associated with a significant risk of developing HCC. However, the relationship between HBV pre-S2Δ protein and the resistance of chemotherapeutic drug treatment is still unclear.


RESULTS
Here, we show that the expression of HBV pre-S2Δ mutant surface protein in Huh-7 cell significantly promoted cell growth and colony formation. Furthermore, HBV pre-S2Δ protein increased both mRNA (2.7±0.5-fold vs. vehicle, p=0.05) and protein (3.2±0.3-fold vs. vehicle, p=0.01) levels of Bcl-2 in Huh-7 cells. HBV pre-S2Δ protein also enhances Bcl-2 family, Bcl-xL and Mcl-1, expression in Huh-7 cells. Meanwhile, induction of NF-κB p65, ERK, and Akt phosphorylation, and GRP78 expression, an unfolded protein response chaperone, were observed in HBV pre-S2Δ and HBV pre-S-expressing cells. Induction of Bcl-2 expression by HBV pre-S2Δ protein resulted in resistance to 5-fluorouracil treatment in colony formation, caspase-3 assay, and cell apoptosis, and can enhance cell death by co-incubation with Bcl-2 inhibitor. Similarly, transgenic mice showed higher expression of Bcl-2 in liver tissue expressing HBV pre-S2Δ large surface protein in vivo.


CONCLUSIONS
Our result demonstrates that HBV pre-S2Δ increased Bcl-2 expression which plays an important role in resistance to 5-fluorouracil-caused cell death. Therefore, these data provide an important chemotherapeutic strategy in HBV pre-S2Δ-associated tumor.
Department of Biotechnology, Chia Nan University of Pharmacy and Science, Tainan, Taiwan. hung86@mail.chna.edu.tw
Jui-Hsiang
JH
Hung
Yen-Ni
YN
Teng
Lily Hui-Ching
LH
Wang
Ih-Jen
IJ
Su
Clay C C
CC
Wang
Wenya
W
Huang
Kuan-Han
KH
Lee
Kuan-Ying
KY
Lu
Lyu-Han
LH
Wang
D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D001483:Base Sequence; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D017931:DNA Primers; D019008:Drug Resistance, Neoplasm; D000091342:Endoplasmic Reticulum Chaperone BiP; D005472:Fluorouracil / Q000494:pharmacology*; D006514:Hepatitis B Surface Antigens / Q000235:genetics / Q000378:metabolism*; D007150:Immunohistochemistry; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation; D016328:NF-kappa B / Q000378:metabolism; D010766:Phosphorylation; D016133:Polymerase Chain Reaction; D011494:Protein Kinases / Q000378:metabolism; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*
D000964:Antimetabolites, Antineoplastic; D017931:DNA Primers; D000091342:Endoplasmic Reticulum Chaperone BiP; D006514:Hepatitis B Surface Antigens; C000717248:Hspa5 protein, mouse; D016328:NF-kappa B; D011498:Protein Precursors; D019253:Proto-Oncogene Proteins c-bcl-2; C050807:presurface protein 2, hepatitis B surface antigen; D011494:Protein Kinases; D053148:Caspase 3; D005472:Fluorouracil