title: Selective role of mevalonate pathway in regulating perforin but not FasL and TNFalpha release in human Natural Killer cells.
abstract: We have analyzed the effects of fluvastatin, an inhibitor of the enzyme 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase involved in mevalonate synthesis, on human NK cell-mediated anti-tumor cytolysis. Fluvastatin inhibited the activation of the small guanosin triphosphate binding protein (GTP) RhoA and the consequent actin redistribution induced by ligation of LFA1 involved in NK-tumor target cell adhesion. Also, fluvastatin reduced ganglioside M1 rafts formation triggered through the engagement of NK cell activating receptors as FcγRIIIA (CD16), NKG2D and DNAM1. Cytolysis of tumor targets was inhibited up to 90% when NK cells were cultured with fluvastatin by affecting i) receptor-mediated increase of the intracellular free calcium concentration, ii) activation of akt1/PKB and iii) perforin and granzyme release. Fluvastatin displayed a stronger inhibiting effect on NKG2D, DNAM1, 2B4, NKp30, NKp44 and NKp46 than on CD16-mediated NK cell triggering. This was in line with the impairment of surface expression of all these receptors but not of CD16. Remarkably, fluvastatin did not affect the expression of the inhibiting receptors CD94, KIR2D and LAIR1. FasL release elicited by either NK-tumor cell interaction or CD16 or NKG2D engagement, as well as FasL-mediated killing, were not sensitive to fluvastatin. Moreover, TNFα secretion triggered in NK cells upon incubation with tumor target cells or engagement of NKG2D receptor was not impaired in fluvastatin-treated NK cells. Likewise, antibody dependent cellular cytotoxicity (ADCC) triggered through FcγRIIIA engagement with the humanized monoclonal antibody rituximab or trastuzumab was only marginally affected in fluvastatin-treated NK cells. Altogether these findings suggest that interference with mevalonate synthesis impairs activation and assembly of cytoskeleton, degranulation and cytotoxic effect of perforins and granzyme but not FasL- and TNFα-mediated cytotoxicity.
authors.affiliation: Molecular Oncology and Angiogenesis Unit, IRCCS AOU San Martino - IST National Institute for Cancer Research, Genoa, Italy. alessandro.poggi@istge.it
authors.forename: Alessandro
authors.initials: A
authors.lastname: Poggi
authors.forename: Silvia
authors.initials: S
authors.lastname: Boero
authors.forename: Alessandra
authors.initials: A
authors.lastname: Musso
authors.forename: Maria Raffaella
authors.initials: MR
authors.lastname: Zocchi
mesh_terms: D000199:Actins / Q000378:metabolism; D000911:Antibodies, Monoclonal / Q000276:immunology; D000920:Antibody-Dependent Cell Cytotoxicity / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D045744:Cell Line, Tumor; D004789:Enzyme Activation / Q000187:drug effects; D053222:Fas Ligand Protein / Q000378:metabolism*; D005229:Fatty Acids, Monounsaturated / Q000494:pharmacology*; D000077340:Fluvastatin; D005677:G(M1) Ganglioside / Q000378:metabolism; D053804:Granzymes / Q000378:metabolism; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D007694:Killer Cells, Natural / Q000166:cytology / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism*; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism; D008798:Mevalonic Acid / Q000378:metabolism*; D054353:Perforin / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D017452:Receptors, IgG / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
chemical_list: D000199:Actins; D000911:Antibodies, Monoclonal; C496124:FCGR3A protein, human; D053222:Fas Ligand Protein; D005229:Fatty Acids, Monounsaturated; D007211:Indoles; D016169:Lymphocyte Function-Associated Antigen-1; D017452:Receptors, IgG; D014409:Tumor Necrosis Factor-alpha; D054353:Perforin; D005677:G(M1) Ganglioside; D000077340:Fluvastatin; D051057:Proto-Oncogene Proteins c-akt; D053804:Granzymes; D020742:rhoA GTP-Binding Protein; D008798:Mevalonic Acid; D002118:Calcium