The biological characteristics of CD34+ CD2+ adult acute promyelocytic leukemia and the CD34 CD2 hypergranular (M3) and microgranular (M3v) phenotypes.
OBJECTIVE
Acute promyelocytic leukemia (APL) is characterized by leukemic cells blocked at the promyelocytic stage of granulocytic differentiation. To date, it is still not clear whether CD34 expression identifies a subset of APL patients with peculiar characteristics. We, therefore, conducted a detailed analysis of CD34 expression at diagnosis in 136 adults with de novo APL.


METHODS
We investigated 136 newly diagnosed APL patients from four Italian Institutions. All 136 cases were tested for CD34 and CD2 expression: 124 (91%) cases were classified as hypergranular (M3) and 12 (9%) as the hyporgranular M3 variant (M3v). The parameters considered were white blood cell (WBC) and platelet counts, hemoglobin levels, percentage of peripheral blood leukemic promyelocytes (PBLP), CD15, CD56 and HLA-DR expression, and the PML/RARalpha isoform, to assess their relationship with CD34 and CD2 expression.


RESULTS
CD34 expression was associated with the M3v subtype and higher proportion of HLA-DR+ and CD2+ cases. Moreover, compared with CD34- APL patients, CD34+ APL patients had a significantly higher percentage of PBLP at presentation, were more frequently female and had a higher proportion of bcr3 expression. Among the 136 APL cases, 24 (17.6%) and 80 (58.8%) were identified as CD34+CD2+ and CD34-CD2-, respectively. The two groups showed statistically significant differences in terms of M3vfrequency, WBC and platelet counts, percentage of PBLP, and bcr3 expression. Moreover, the CD34+CD2+ group showed a higher proportion of CD34+ and bcr3 isoforms compared to the M3v cases. There were no differences between the two groups in terms of complete remission, overall survival and disease-free survival.


CONCLUSIONS
Our findings suggest that immunophenotypic analysis can distinguish a subset of APL patients with different biological characteristics.
Albano
Francesco
F
Department of Hematology, University of Bari, Italy.
Mestice
Anna
A
Pannunzio
Alessandra
A
Lanza
Francesco
F
Martino
Bruno
B
Pastore
Domenico
D
Ferrara
Felicetto
F
Carluccio
Paola
P
Nobile
Francesco
F
Castoldi
Gianluigi
G
Liso
Vincenzo
V
Specchia
Giorgina
G
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018952:Antigens, CD34 / Q000096:biosynthesis* / Q000235:genetics; D018801:CD2 Antigens / Q000096:biosynthesis / Q000235:genetics*; D005260:Female; D014644:Genetic Variation / Q000235:genetics; D006801:Humans; D015473:Leukemia, Promyelocytic, Acute / Q000235:genetics* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010641:Phenotype
D018952:Antigens, CD34; D018801:CD2 Antigens