title: Frequent nuclear localization of ICAD and cytoplasmic co-expression of caspase-8 and caspase-3 in human lymphomas.
abstract: Lymphoma cells often display in vitro resistance to FAS-induced apoptosis, in which caspases act as crucial cell death effectors. Following FAS stimulation, caspase-8 activates caspase-3, which in turn activates the caspase-activated DNAse (CAD) by proteolysis of its inhibitor (ICAD). To investigate the mechanism of FAS resistance, the expression of caspase-8 was analysed by immunohistochemistry, together with that of the substrates caspase-3 and ICAD, in 52 representative samples from non Hodgkin's lymphoma (NHL), 12 from Hodgkin's disease (HD), and eight benign lymphoid tissues. In benign tissues, caspase-8 was co-expressed with caspase-3 in the cytoplasm in germinal centre (GC) cells and was co-expressed with ICAD in the nuclei of the mantle and marginal zone cells. ICAD expression was weak or absent in GC cells. Cytoplasmic staining for both caspase-8 and caspase-3 was present in 11/12 cases of diffuse large cell B-NHL. Caspase-8 positivity was nuclear and cytoplasmic in 9/9 follicular NHLs, in 5/5 mantle cell NHLs and in 6/6 marginal zone NHLs. Five out of six peripheral T-cell NHLs expressed cytoplasmic caspase-8. Ten out of the 12 HD cases lacked significant cytoplasmic staining for caspase-3 and caspase-8 in the majority of Reed-Sternberg cells. All lymphoma cases exhibited predominant nuclear ICAD positivity. Subcellular fractionation analysis of three lymphoma samples and normal mantle zone cells confirmed that ICAD and caspase-8 were at least partly localized in the nucleus. These results show that the profile of caspase-8 expression is correlated with histological lymphoma subtypes; that caspase-8 is co-expressed with caspase-3 in GC cells and their neoplastic counterparts; that ICAD has an immunohistochemical nuclear localization in vivo; and that caspase-8 and ICAD can be co-expressed in the nuclei of mantle zone and marginal zone cells; their unexpected nuclear localization allows a reappraisal of the biochemical cascade of caspase activation.
authors.affiliation: Department of Pathology, Institut Paoli-Calmettes, Marseille, France. xemil@marseille.fnclcc.fr
authors.forename: L
authors.initials: L
authors.lastname: Xerri
authors.forename: F
authors.initials: F
authors.lastname: Palmerini
authors.forename: E
authors.initials: E
authors.lastname: Devilard
authors.forename: T
authors.initials: T
authors.lastname: Defrance
authors.forename: R
authors.initials: R
authors.lastname: Bouabdallah
authors.forename: J
authors.initials: J
authors.lastname: Hassoun
authors.forename: F
authors.initials: F
authors.lastname: Birg
mesh_terms: D051017:Apoptosis Regulatory Proteins; D001402:B-Lymphocytes / Q000201:enzymology; D015153:Blotting, Western; D016022:Case-Control Studies; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D002467:Cell Nucleus / Q000201:enzymology*; D003593:Cytoplasm / Q000201:enzymology*; D003851:Deoxyribonucleases / Q000037:antagonists & inhibitors*; D018858:Germinal Center / Q000201:enzymology; D006689:Hodgkin Disease / Q000378:metabolism; D006801:Humans; D008228:Lymphoma, Non-Hodgkin / Q000145:classification / Q000378:metabolism* / Q000473:pathology; D009363:Neoplasm Proteins / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D016539:Reed-Sternberg Cells / Q000201:enzymology
chemical_list: D051017:Apoptosis Regulatory Proteins; D009363:Neoplasm Proteins; D011506:Proteins; C109664:caspase-activated DNase inhibitor; D003851:Deoxyribonucleases; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases