Expression of CD10 by B-chronic lymphocytic leukemia cells undergoing apoptosis in vivo and in vitro

Background and Objectives. 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. Design and Methods. Peripheral blood cells from 31 untreated B-CLL patients were induced into apoptosis by etoposide, fludarabine of Gamu-Ab treatment and tested for CD10 expression by flow cytometry. Normal CD5(+) B cells were also induced into apoptosis and tested for CD10 expression. Results. 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 Gamu-Ab enhanced bot apoptosis and CD10 expression. Inhibition of apoptosis by VAD-fmk or Gadelta-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. Interpretation and Conclusions. 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.