Cb. Zang et al., Enhanced migration of the acute promyelocytic leukemia cell line NB4 underin vitro conditions during short-term all-trans-retinoic acid treatment, J CANC RES, 126(1), 2000, pp. 33-40
All-trans-retinoic acid (RA) is a potent differentiating agent that is very
effective in the treatment of patients with acute promyelocytic leukemia (
APL). Since clinical response can be accompanied by extramedullary manifest
ations, we have investigated the influence of RA on cell adhesion to and mi
gration through reconstituted basement membranes (Matrigel) in the APL cell
line NB4. No apparent cellular differentiation was observed during a 24-h
incubation with 1 mu M RA, as indicated by the nitroblue tetrazolium reduct
ion test. However, exposure to RA significantly enhanced NB4 cell adhesion
to Matrigel and consecutive migration through Matrigel barriers in a dose-d
ependent manner. Several integrin molecules potentially involved in this pr
ocess, i.e., CD29, CD18, CD11a, CD11b and CD11c, were therefore studied by
fluorescence-activated cell sorting analysis. The expression of the beta su
bunit of the beta 2 integrins (CD 18), but not that of beta 1 integrins (CD
29), was increased during 24-h RA treatment. Among the PZ integrins, the ex
pression of LFA-1 (CD11a) and of Mac-1 (CD11b), but not of p150,95 (CD11c),
was induced by RA. When monoclonal antibodies that specifically block the
interaction of these integrins with their ligands were used, we observed th
at CD29 is only involved in adhesion and CD11b only in migration, whereas C
D11a participates in both processes. NB4 cells constitutively secreted the
matrix metalloproteinases MMP-9 and MMP-2, which are known to promote cellu
lar invasion processes by degradation of the extracellular matrix. RA treat
ment had no influence on the quantity of secreted MMP-9 or MMP-2 in these c
ells as determined by zymography. Addition of Batimastat (BB-94), a synthet
ic inhibitor of matrix metalloproteinases, blocked RA-induced cell migratio
n without affecting cellular adhesion to Matrigel. These findings indicate
that adhesion molecules as well as matrix metalloproteinases are involved i
n RA-stimulated migration of NB4 cells through Matrigel, possibly providing
some explanation of tissue infiltration by leukemic cells as observed duri
ng treatment of APL patients with RA.