title: FAP-1-mediated activation of NF-kappaB induces resistance of head and neck cancer to Fas-induced apoptosis.
abstract: Molecular mechanisms responsible for tumor resistance to apoptosis often involve the Fas/FasL pathway. While squamous cell carcinomas of the head and neck (SCCHN) express both Fas and FasL, their resistance to self-induced apoptosis or apoptosis mediated by Fas agonistic antibody (CH-11Ab) was independent of the level of Fas surface expression or the presence of soluble Fas in supernatants of primary or metastatic SCCHN cell lines. By in vitro immunoselection, using PCI-15A cell line treated with successive cycles of CH-11 Ab, Fas-resistant sublines with the parental genotype were selected. Such sublines failed to cleave caspase-8 upon Fas engagement and were resistant to CH-11 Ab, although they remained sensitive to VP-16 or staurosporin. In the presence of cycloheximide, the selected SCCHN sublines become susceptible to CH-11 Ab, and showed cleavage of caspase-8, suggesting that apoptosis resistance was mediated by an inhibitory protein(s) acting upstream of caspase-8. Overexpression of Fas-associated phosphatase 1 (FAP-1), but not cellular FLICE-inhibitory protein (cFLIP) in SCCHN sublines was documented by Western blots and RT-PCR analyses. The FAP-1+ selected sublines also downregulated cell surface Fas. A high phosphorylation level of IkappaB kappa, NFkappaB activation and upregulation of Bcl-2 expression were observed in the FAP-1+ sublines. Treatment with the phosphatase inhibitor, orthovanadate, or silencing of FAP-1 with siRNA abolished their resistance to apoptosis, suggesting that FAP-1 phosphatase activity could be responsible for NF-kappaB activation and resistance of SCCHN cells to Fas-mediated apoptosis.
authors.affiliation: University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: Eva
authors.initials: E
authors.lastname: Wieckowski
authors.forename: Yoshinari
authors.initials: Y
authors.lastname: Atarashi
authors.forename: Joanna
authors.initials: J
authors.lastname: Stanson
authors.forename: Taka-Aki
authors.initials: TA
authors.lastname: Sato
authors.forename: Theresa L
authors.initials: TL
authors.lastname: Whiteside
mesh_terms: D000906:Antibodies / Q000494:pharmacology; D017209:Apoptosis; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000378:metabolism; D002294:Carcinoma, Squamous Cell / Q000378:metabolism / Q000473:pathology*; D045744:Cell Line, Tumor; D002470:Cell Survival; D003514:Cyclohexylamines / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology; D006258:Head and Neck Neoplasms / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism*; D054645:Protein Phosphatase 1; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D054595:Protein Tyrosine Phosphatase, Non-Receptor Type 13; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction; D019311:Staurosporine / Q000494:pharmacology; D015854:Up-Regulation; D014638:Vanadates / Q000494:pharmacology; D019014:fas Receptor / Q000276:immunology / Q000378:metabolism*
chemical_list: D000906:Antibodies; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C481004:CH-11 anti-fas antibody, human; D003514:Cyclohexylamines; D016328:NF-kappa B; D011500:Protein Synthesis Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D019014:fas Receptor; D014638:Vanadates; D005047:Etoposide; D054645:Protein Phosphatase 1; C516742:PTPN13 protein, human; D054595:Protein Tyrosine Phosphatase, Non-Receptor Type 13; D017027:Protein Tyrosine Phosphatases; D019311:Staurosporine