benzyloxycarbonylvalyl-alanyl-aspartyl-fluoromethyl-ketone and fludarabine

B-cell chronic lymphocytic leukemia (B-CLL) is an accumulating disease of slowly proliferating cells. CD10 is not normally expressed on the surface of B-CLL cells. The aim of this study was to ascertain whether B-CLL cells, induced into apoptosis, expressed surface CD10, since a correlation between apoptosis and CD10 expression has been demonstrated.. Peripheral blood cells from 31 untreated B-CLL patients were induced into apoptosis by etoposide, fludarabine or Ga(mu)-Ab treatment and tested for CD10 expression by flow cytometry. Normal CD5+ B cells were also induced into apoptosis and tested for CD10 expression.. CD10 positive cells were absent in B-CLL cell suspensions, but were detected following in vitro culture, and their appearance paralleled that of apoptotic cells. Treatment with etoposide, fludarabine or Ga(mu)-Ab enhanced both apoptosis and CD10 expression. Inhibition of apoptosis by VAD-fmk or Ga(delta)-Ab prevented CD10 expression. Cell separation tests following induction of apoptosis demonstrated that CD10+ cells were apoptotic. CD10+ cells were observed in the peripheral blood of two patients within a few hours following fludarabine infusion. In another patient, who failed to respond, no CD10+ cells were seen. Expression of CD10 was observed also in normal CD5+ B cells when these were induced into apoptosis.. This study demonstrates that B-CLL cells, as well as normal CD5+ B cells, become CD10+ following apoptosis induction in vitro. Some of the data obtained also suggest a use for CD10 to monitor apoptosis of B-CLL in a clinical setting.

Topics: ADP-ribosyl Cyclase; ADP-ribosyl Cyclase 1; Amino Acid Chloromethyl Ketones; Antibodies; Antibodies, Monoclonal; Antigens, CD; Apoptosis; B-Lymphocytes; Cell Line, Tumor; Etoposide; Gene Expression Regulation, Neoplastic; Humans; Immunoglobulin A; Immunoglobulin D; Immunoglobulin M; Leukemia, Lymphocytic, Chronic, B-Cell; Membrane Glycoproteins; Neprilysin; Palatine Tonsil; Vidarabine

Caspases are known to be involved in the apoptotic killing of chronic lymphocytic leukaemia (CLL) cells by fludarabine. However, it is unclear whether these enzymes are required for the induction of such killing, or whether they simply determine the mode of cell death. To address this question, we examined the effect of the broad-spectrum caspase inhibitor Z-VAD.fmk on six different manifestations of nucleoside cytotoxicity. Our results indicate that while caspase activity is required for nucleoside-induced poly(ADP-ribose) polymerase (PARP) cleavage and DNA fragmentation, other manifestations of cell death (mitochondrial depolarization, exposure of phosphatidyl serine, cell membrane disruption and cell shrinkage) are caspase independent. By showing that caspases influence the mode, but not the extent, of nucleoside cytotoxicity, our results exclude defects in these enzymes as a mechanism of nucleoside resistance in CLL.

Topics: Amino Acid Chloromethyl Ketones; Antineoplastic Agents; Apoptosis; Caspase Inhibitors; Caspases; Cell Membrane; Cell Size; Cells, Cultured; Enzyme Inhibitors; Humans; Leukemia, Lymphocytic, Chronic, B-Cell; Vidarabine