Comparative flow cytometric evaluation of bcl-2 oncoprotein in CD5+ and CD5- B-cell lymphoid chronic leukemias.
OBJECTIVE
Levels of intracellular bcl-2 oncoprotein have been found to be increased in leukemic cells of CD5+ B-chronic lymphocytic leukemia (CLL) patients. However, it is not clear whether bcl-2 overexpression is a peculiar feature of CD5+ B-CLL. Based on this background we carried out a quantitative flow cytometric evaluation of intracellular bcl-2 levels on leukemic cells of CD5+ and CD5- B-CLL.


METHODS
We assessed in flow cytometry levels of bcl-2 protein using a quantitative indirect immunofluorescence assay (QIFI kit) on samples from 46 previously untreated CD5+ B-CLL patients. Results were compared with those obtained on either normal peripheral blood B-lymphocytes or leukemic cells from 7 CD5- B-CLL patients intentionally selected for statistical comparison.


RESULTS
A relatively homogeneous amount of bcl-2 protein which did not reflect either clinical-biological features at the time of diagnosis nor in vivo response to therapy was found. Results expressed as antibody binding capacity (ABC) accounted for a mean value of 12.2 +/- 1.5 x 10(3) molecules/cell (range, 6.4-13 x 10(3) molecules/cell). Levels of bcl-2 detected on CD5+ B-CLL leukemic cells were significantly lower than those of B peripheral blood lymphocytes from healthy donors (p = 0.0001). The same applied when comparing CD5+ and CD5- B-CLL patients (bcl-2 ABC, 8.07 +/- 0.26 x 10(3) molecules/cell vs. 12.2 +/- 1.5 x 10(9) molecules/cell; p = 0.0001).


CONCLUSIONS
According to the role of bcl-2 in preventing apoptosis, our results indicate that differences in the pattern of expression of such an oncoprotein, might, at least in part, explain the more aggressive clinical course of CD5- B-CLL forms.
Molica
S
S
Divisione Ematologia, Azienda Ospedaliera, Pugliese-Ciaccio, Catanzaro, Italy.
Mannella
A
A
Crispino
G
G
Dattilo
A
A
Levato
D
D
D000368:Aged; D001402:B-Lymphocytes / Q000737:chemistry*; D018956:CD5 Antigens / Q000032:analysis*; D002469:Cell Separation; D005260:Female; D005434:Flow Cytometry; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis*; D011933:Reagent Kits, Diagnostic
D018956:CD5 Antigens; D019253:Proto-Oncogene Proteins c-bcl-2; D011933:Reagent Kits, Diagnostic