A. Falanga et al., CANCER PROCOAGULANT IN THE HUMAN PROMYELOCYTIC CELL-LINE NB4 AND ITS MODULATION BY ALL-TRANS-RETINOIC ACID, Leukemia, 8(1), 1994, pp. 156-159
Acute promyelocytic leukemia (APL) cells express different types of pr
ocoagulant activity (PCA), including tissue factor (TF), and cancer pr
ocoagulant (CP). The aim of this study was to investigate whether the
NB4 cell line, the first ever isolated human APL line, with the typica
l t(15;17) chromosomal balance translocation, possess CP as well as th
e cells freshly isolated from APL patients. Secondly, since the NB4 li
ne is maturation inducible by all-trans-retinoic acid (ATRA), we wante
d to verify whether CP, if present, was affected by ATRA treatment. Th
e NB4 cells were able to shorten the recalcification assay of normal h
uman plasma (total PCA). To distinguish CP in the assay for clotting a
ctivity, two criteria were used, the independence from factor VII to t
rigger blood coagulation and the sensitivity to cysteine proteinase in
hibitors. Forty-seven per cent of total PCA of cell extracts was found
to be FVII-independent PCA. A similar proportion of FVII-independent
activity (42%) was detected in the cell serum-free supernatants. The a
ctivity was significantly decreased by cysteine proteinase inhibitors,
including HgCl2 lodoacetic acid and Z-Ala-AlaCHN(2). Additionally CP
was directly identified and quantified by an immunocapture enzyme assa
y. The mean +/- SD concentration of CP detected by this assay in the N
B4 cells, before any treatment, was 1.89 +/- 0.5 mu g/mg protein. Trea
tment of NB4 cells with 10(-6) M ATRA for 5 days significantly decreas
ed the expression of CP, which became virtually undetectable by the cl
otting assay, and was 64% less than the untreated control by the immun
ocapture enzyme assay. This study provides the first evidence that the
human promyelocytic cell line NB4 possess CP. The expression of this
procoagulant is modulated by ATRA.