Overexpression of regucalcin suppresses cell proliferation in cloned rat hepatoma H4‐II‐E cells: Involvement of intracellular signaling factors and cell cycle‐related genes
- 16 June 2005
- journal article
- research article
- Published by Wiley in Journal of Cellular Biochemistry
- Vol. 95 (6), 1169-1177
- https://doi.org/10.1002/jcb.20490
Abstract
The role of regucalcin, which is a regulatory protein in intracellular signaling pathway, in the regulation of cell proliferation was investigated by using the cloned rat hepatoma H4-II-E cells overexpressing regucalcin. The hepatoma cells (wild type) and stable regucalcin/pCXN2 transfectants were cultured for 72 h in a medium containing 10% fetal bovine serum (FBS) to obtain subconfluent monolayters. The proliferation of cells was significantly suppressed in transfectants cultured for 24–72 h. The proliferation of wild-type cells was significantly inhibited when the cells were cultured for 72 h in a medium containing an inhibitor of transcriptional activity or protein synthesis. Such an effect was not seen in transfectants. The presence of various inhibitors of protein kinase including PD 98059 (10−7 or 10−6 M), dibucaine (10−6 M), wortmannin (10−8 or 10−6 M), or genistein (10−5 M) caused a significant inhibition of the proliferation of wild-type cells. These inhibitory effects were not seen in transfectants. Staurosporine (10−8 − 10−7 M) significantly inhibited the proliferation of wild-type cells and transfectants. Also, the effect of vanadate (10−5 M), an inhibitor of protein tyrosine phosphatase, or Bay K 8644 (10−6 M), an agonist of calcium entry into cells, in inhibiting the proliferation of wild-type cells was not observed in transfectants. Moreover, the proliferation of wild-type cells was significantly inhibited in the presence of roscovitine (10−7 or 10−6 M) or sulforaphane (10−7 M), which induces cell-cycle arrest. Such effect was not seen in transfectants. The inhibitory effect of sodium butyrate (8.3 × 10−4 M) on proliferation of wild-type cells was also induced in transfectants. Gene expression in hepatoma cells cultured for 72 h with 10% FBS was determined by using reverse transcription-polymerase chain reaction (RT-PCR). The expression of p21 mRNA was significantly enhanced in transfectants, while cdc2a and chk2 mRNA expression were not significantly changed. Insulin-like growth factor-I (IGF-I) mRNA expression was significantly suppressed in transfectants. This study demonstrates that overexpression of regucalcin has a suppressive effect on cell proliferation that is partly mediated through various intracellular signaling-related factors, and that the effect may be partly involved in the change in p21 or IGF-I mRNA expression. The finding further supports that regucalcin plays an important role as a suppressor in the enhancement of cell proliferation.Keywords
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