CD39 activity correlates with stage and inhibits platelet reactivity in chronic lymphocytic leukemia.
BACKGROUND
Chronic lymphocytic leukemia (CLL) is characterized by accumulation of mature appearing lymphocytes and is rarely complicated by thrombosis. One possible explanation for the paucity of thrombotic events in these patients may be the presence of the ecto-nucleotidase CD39/NTDPase-1 on the surface of the malignant cells in CLL. CD39 is the major promoter of platelet inhibition in vivo via its metabolism of ADP to AMP. We hypothesize that if CD39 is observed on CLL cells, then patients with CLL may be relatively protected against platelet aggregation and recruitment and that CD39 may have other effects on CLL, including modulation of the disease, via its metabolism of ATP.


METHODS
Normal and malignant lymphocytes were isolated from whole blood from patients with CLL and healthy volunteers. Enzyme activity was measured via radio-TLC assay and expression via FACS. Semi-quantitative RT-PCR for CD39 splice variants and platelet function tests were performed on several samples.


RESULTS
Functional assays demonstrated that ADPase and ATPase activities were much higher in CLL cells than in total lymphocytes from the normal population on a per cell basis (p-value < 0.00001). CD39 activity was elevated in stage 0-2 CLL compared to stage 3-4 (p < 0.01). FACS of lymphocytes demonstrated CD39 expression on > 90% of normal and malignant B-lymphocytes and approximately 8% of normal T-lymphocytes. RT-PCR showed increased full length CD39 and splice variant 1.5, but decreased variant 1.3 in CLL cells. Platelet function tests showed inhibition of platelet activation and recruitment to ADP by CLL cells.


CONCLUSIONS
CD39 is expressed and active on CLL cells. Enzyme activity is higher in earlier stages of CLL and decreased enzyme activity may be associated with worsening disease. These results suggest that CD39 may play a role in the pathogenesis of malignancy and protect CLL patients from thrombotic events.
Pulte
Dianne
D
Research Service, Veterans Affairs New York Harbor Healthcare System, New York, NY 10010, USA. dpulte1@yahoo.com
Olson
Kim E
KE
Broekman
M Johan
MJ
Islam
Naziba
N
Ballard
Harold S
HS
Furman
Richard R
RR
Olson
Ashley E
AE
Marcus
Aaron J
AJ
D000244:Adenosine Diphosphate / Q000494:pharmacology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism*; D001081:Apyrase / Q000235:genetics / Q000378:metabolism*; D001402:B-Lymphocytes / Q000378:metabolism / Q000473:pathology; D002855:Chromatography, Thin Layer; D005260:Female; D005434:Flow Cytometry; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000235:genetics / Q000503:physiopathology*; D016131:Lymphocyte Subsets / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D015539:Platelet Activation / Q000187:drug effects / Q000502:physiology*; D010974:Platelet Aggregation / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013601:T-Lymphocytes / Q000378:metabolism / Q000473:pathology
D015703:Antigens, CD; D000244:Adenosine Diphosphate; D001081:Apyrase; C067869:CD39 antigen