Expression and function of CD95 (FAS/APO‐1) in leukaemia‐lymphoma tumour lines

Abstract

Summary. Cross-linkage of the CD95 (FAS/APO-1) antigen is responsible for the induction of programmed cell death or apoptosis in a variety of normal and malignant cells of the haemopoietic system. In order to evaluate predominant expression of the CD95 gene in a cell lineage-specific manner, we have determined the CD95 expression patterns in cell lines of myeloid, T-, pre-B-or B-cell origin as well as those established from Hodgkin's disease (HD). Our results reveal constitutive transcriptional activation of the CD95 gene in all cell lines derived from the lymphoid and myeloid lineages. Despite the ubiquitous expression of CD95 transcripts in haemopoietic cells, the corresponding protein was undetectable in 2/5 cell lines derived from Burkitt lymphomas and 6/16 leukaemia cell lines of the megakaryocytic or monocytic lineage. In an effort to identify apoptosis-resistant cell lines resulting from mutations in the death-signalling domain of CD95 or from defects in the apoptotic pathway or in survival programmes, we applied a CD95-mediated apoptosis assay. However, 21/38 CD95-expressing cell lines were sensitive upon induction with an anti-CD95 antibody whereas the remaining cell lines (predominantly of myeloid derivation) were resistant to antibody-induced cell death. Resistance to CD95-mediated apoptosis was not due to mutations within the CD95 open reading frame as confirmed by a combined reverse transcription PCR sequencing method. Five myeloid out of 13 tumour lines with the apoptosis-resistance phenotype analysed showed programmed cell death, when protein synthesis was blocked by treatment with cycloheximide prior to CD95-mediated induction. These data suggest an active cellular mechanism for the maintenance of an apoptosis-resistant phenotype. Elucidating the steps in such an active process of resistance to apoptosis might be expected to provide new approaches for therapeutic intervention in certain tumours.

Caspase-3 activation in systemic anaplastic large-cell lymphoma

“…Proteolytic activation of caspase-3 may result from either extrinsic apoptotic signals, such as CD95L (FasL), after binding to specific receptors (CD95, Fas), or intrinsic apoptotic signals from mitochondria, such as expression of BCL-2 family members that can lead to activation of caspase-9 and release of cytochrome c. 22 Previous in vitro studies have shown that the CD95/CD95L pathway is active in ALCL cells. 32,33 Furthermore, overexpression of BCL-2 family proteins 13,34 may also contribute to caspase-3-mediated cell death in ALK-positive ALCL.…”

Differential Expression of BCL-2 Family Proteins in ALK-Positive and ALK-Negative Anaplastic Large Cell Lymphoma of T/Null-Cell Lineage

“…Previous in vitro studies using cell lines derived from systemic ALCL cases have provided evidence that t(2;5)-positive ALCL cells express CD95 and undergo CD95-induced apoptosis. 45 Clusterin, recently reported to be specifically expressed in ALCL cell lines and tumors, also may be involved. 46 Clusterin (also known as sulfated glycoprotein 2, human apolipoprotein A-I, J) is a highly conserved glycoprotein, which among its other functions, promotes cell death.…”

Clonal variability in CD95 expression is the major determinant in Fas-mediated, but not chemotherapy-mediated apoptosis in the RPMI 8226 multiple myeloma cell line

“…25,26,37 Shima and colleagues 38 examined the relationship between CD95 expression and sensitivity to death receptor-mediated apoptosis in several multiple myeloma cell lines and patient specimens. This report demonstrated that CD95 expression correlates to some degree with sensitivity to CD95 death signaling, however, this trend was not consistent over all the cell lines investigated.…”