V. Pijuan-thompson et al., Retinoic acid alters the mechanism of attachment of malignant astrocytoma and neuroblastoma cells to thrombospondin-1, EXP CELL RE, 249(1), 1999, pp. 86-101
Based on the hypothesis that the attachment of neuroectodermal cells to thr
ombospondin-1 (TSP-1) may affect tumor spread and play a role in the anti-t
umor effects of retinoic acid, we investigated the expression of TSP-1 in t
hese cells in situ and the effect of retinoic acid on the morphology of TSP
-1-adherent neuroblastoma (SK-N-SH) and malignant astrocytoma (U-251MG) cel
ls in vitro. TSP-1-adherent SK-N-SH cells demonstrated process outgrowth, w
ith further neuronal differentiation after retinoic acid treatment, consist
ent with the in situ studies showing that TSP-1 expression occurs in a diff
erentiation-specific manner in neuroblastic tumors, TSP-1-adherent U-251MG;
cells failed to spread; however, after retinoic acid treatment the cells d
emonstrated broad lamellipodia containing radial actin fibers and organizat
ion of integrins alpha 3 beta 1 and alpha 5 beta 1 in clusters in lamellipo
dia and filopodia, The attachment of both SK-N-SH and U-251MG cells to TSP-
1 was found to be mediated by heparan sulfate proteoglycans, integrins, and
the CLESH-1 adhesion domain first identified in CD36, Heparin and hepariti
nase treatment inhibited TSP-1 attachment. Integrins alpha 3 beta 1 and alp
ha 5 beta 1 mediated TSP-1 attachment of SK-N-SH cells, and integrins alpha
3 beta 1, alpha 5 beta 1, and alpha v beta 3 mediated TSP-1 attachment of
U-251MG: cells. Attachment was dependent on the RGD sequence which is locat
ed in the carboxy-terminus of TSP-1, Treatment with a pharmacologic dosage
of retinoic acid altered the TSP-1 cell adhesion mechanism in both cell lin
es in that neither heparin nor micromolar concentrations of the RGD peptide
inhibited attachment; after treatment, attachment was inhibited by the CSV
TCG peptide located in the type I repeat domain of TSP-1 and a recombinant
adhesion domain (CLESH-1) from CD36. Expression of CD36 was found in the re
tinoic acid-treated U-251MG; cells. These data indicate that neuroectoderma
lly derived cells utilize several mechanisms to attach to TSP-1, and these
are differentially modulated by treatment with retinoic acid. These data al
so suggest that the CSVTCG sequence of TSP-1 modulates or directs cytoskele
tal organization in neuroblastoma and astrocytoma cells. (C) 1999 Academic
Press.