Hepatic natural killer cells exclusively kill splenic/blood natural killer-resistant tumor cells by the perforin/granzyme pathway.
Hepatic natural killer (NK) cells are located in the liver sinusoids adherent to the endothelium. Human and rat hepatic NK cells induce cytolysis in tumor cells that are resistant to splenic or blood NK cells. To investigate the mechanism of cell death, we examined the capacity of isolated, pure (90%) rat hepatic NK cells to kill the splenic/blood NK-resistant mastocytoma cell line P815. Cell death was observed and quantified by fluorescence and transmission electron microscopy, DNA fragmentation, and (51)Cr release. RNA and protein expression were determined by real time reverse transcription-polymerase chain reaction and Western blotting. Compared with splenic NK cells, hepatic NK cells expressed higher levels of perforin and granzyme B and readily induced apoptosis in P815 cells. Although P815 cells succumbed to recombinant Fas ligand (FasL) or isolated perforin/granzyme B, hepatic NK cells used only the granule pathway to kill this target. In addition, hepatic NK cells and sinusoidal endothelial cells strongly expressed the granzyme B inhibitor, protease inhibitor 9 (PI-9)/serine PI-6 (SPI-6), and P815 cells and hepatocytes were negative. Transfection of target cells with this inhibitor resulted in complete resistance to hepatic NK cell-induced apoptosis. In conclusion, hepatic NK cells kill splenic/blood NK-resistant/FasL-sensitive tumor cells exclusively by the perforin/granzyme pathway. Serine protease inhibitor PI-9/SPI-6 expression in liver sinusoidal endothelial cells may protect the liver microenvironment from this highly active perforin/granzyme pathway used to kill metastasizing cancer cells.
Vermijlen
David
D
Laboratory for Cell Biology and Histology, Vrije Universiteit Brussel, Brussels, Belgium. dvermijl@cyto.vub.ac.be
Luo
Dianzhong
D
Froelich
Christopher J
CJ
Medema
Jan Paul
JP
Kummer
Jean Alain
JA
Willems
Erik
E
Braet
Filip
F
Wisse
Eddie
E
D000818:Animals; D017209:Apoptosis / Q000276:immunology*; D053222:Fas Ligand Protein; D053804:Granzymes; D006801:Humans; D007694:Killer Cells, Natural / Q000276:immunology*; D008099:Liver / Q000166:cytology / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000276:immunology* / Q000494:pharmacology; D051379:Mice; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D051381:Rats; D011916:Rats, Inbred F344; D017208:Rats, Wistar; D011994:Recombinant Proteins / Q000494:pharmacology; D012697:Serine Endopeptidases / Q000235:genetics / Q000276:immunology* / Q000494:pharmacology; D015843:Serpins / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology*; D013154:Spleen / Q000166:cytology / Q000276:immunology; D014407:Tumor Cells, Cultured
C505661:FASLG protein, human; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; C505662:Faslg protein, rat; D008562:Membrane Glycoproteins; D052899:Pore Forming Cytotoxic Proteins; D011994:Recombinant Proteins; C102316:SERPINB9 protein, human; D015843:Serpins; D054353:Perforin; C509213:GZMB protein, human; D053804:Granzymes; C509214:Gzmb protein, mouse; C509215:Gzmb protein, rat; D012697:Serine Endopeptidases