Effects of signal regulatory proteinalpha1 on proliferation of hepatocellular carcinoma: a preliminary study.
BACKGROUND
Signal regulatory protein alpha1 (Sirpalpha1) is a negative regulatory factor, and inhibits receptor tyrosine kinase-dependent cell proliferating signal. This study was undertaken to observe the effect of signal regulatory proteinalpha1 (Sirpalpha1)on gankyrin,cyclin D1,CDK4 and Fas expression in Sk-hep1 mouse hepatoma carcinoma cell line.


METHODS
BOSC 23 packed cells were respectively transfected by means of recombinated retrovirus including pLXSN, pLXSN- Sirpalpha1 and pLXSN- Sirpalpha1P4Y2 with lipofectin, and various plasmid virus media(viral titer 2.1X10(6) CFU/ml) were collected and infected respectively in 80% confluent Sk-hep1 cells. Transfected Sk-hep1 cells were selectively screened with G418 (1200 mug/ml), and Sk-hep1 cell lines transfected with various plasmids were obtained. The protein expressions of gankyrin, cyclin D1, CDK4 and Fas in various Sk-hep1 lines were determined by Western blotting. Various Sk-hep1 lines were recovered to culture with 10% fetal bovine serum at 12 hours and 24 hours after starving culture with free serum for 72 hours, and cells were collected to determine the percentage of S phase cells of proliferating cycle by flow cytometry.


RESULTS
Sirpalpha1 transfection remarkably downregulated gankyrin and cyclin D1 expression. Sirpalpha1P4Y2 downregulation of gankyrin expression was greater than that of Sirpalpha1 (P<0.05), but no significant effect of Sirpalpha1 and Sirpalpha1P4Y2 on CDK4 and Fas protein expression was observed in transfected Sk-hep1 lines (P>0.05). The percentage of S phase cells significantly decreased in Sk-hep1 cells transfected with Sirpalpha1 and Sirpalpha1P4Y2 plasmids (vs pLXSN Sk-hep1, P<0.05). The percentage of S phase cells in various Sk-hep1 cells increased when recovering to culture with 10% fetal bovine serum at 12 hours, but the percentage of S phase cells in Sk-hep1 cells transfected with Sirpalpha1 was the lowest (vs pLXSN and Sirpalpha1P4Y2 Sk-hep1, P<0.05). The percentage of S phase cells in transfected pLSXN Sk-hep1 cells was the largest (vs Sirpalpha1 and Sirpalpha1P4Y2 Sk-hep1, P<0.05). There was no significant difference between the transfected Sirpalpha1 Sk-hep1 cells and Sirpalpha1P4Y2 Sk-hep1 cells (P>0.05).


CONCLUSIONS
Sirpalpha1 decreases gankyrin and cyclin D1 expression, and inhibits proliferation of liver carcinoma cells. It may be one of the forms for an Sirpalpha1 negative regulation of carcinogenesis and development of hepatocellular carcinoma.
Qin
Jian-Min
JM
International Cooperative Laboratory on Signal Transduction, Eastern Hepatobiliary Surgery Institute, Second Military Medical University, Shanghai 200438, China. jianminqin@yahoo.com
Yan
He-Xin
HX
Wan
Xing-Wang
XW
Liu
Shu-Qin
SQ
Zeng
Jin-Zhang
JZ
Cao
Hui-Fang
HF
Wu
Meng-Chao
MC
Wang
Hong-Yang
HY
D000704:Analysis of Variance; D000818:Animals; D015153:Blotting, Western; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D019938:Cyclin D1 / Q000378:metabolism*; D005260:Female; D022781:Hepatocytes / Q000502:physiology*; D008297:Male; D051379:Mice; D048052:Mitogen-Activated Protein Kinase 3 / Q000494:pharmacology*; D015513:Oncogene Proteins / Q000032:analysis / Q000378:metabolism; D011336:Probability; D046988:Proteasome Endopeptidase Complex; D011518:Proto-Oncogene Proteins; D014162:Transfection
D015513:Oncogene Proteins; C403591:PSMD10 protein, human; D011518:Proto-Oncogene Proteins; D019938:Cyclin D1; D048052:Mitogen-Activated Protein Kinase 3; D046988:Proteasome Endopeptidase Complex