Bidirectional morphological changes induced by dexamethasone in Morris hepatoma cell lines McA-RH7777 and McA-RH8994: independence of fibronectin and its receptor.
Two Morris hepatoma-derived cell lines, McA-RH7777 (7777) and McA-RH8994 (8994), exhibit different alterations in morphology upon exposure to glucocorticoid. After treatment with synthetic glucocorticoid dexamethasone (DEX), 7777 cells show increased adhesiveness and more flattened shape, while DEX-treated 8994 cells show decreased adhesiveness to substratum and exhibit a marked increase of round and detached cells. Since fibronectin has been thought to play an important role in cell adhesiveness to substratum in hepatoma cell culture, we have also compared the effects of DEX on the biosynthesis of fibronectin (FN) and the functional level of FN receptor in 7777 and 8994 cells. Northern blot analysis and immunofluorescent studies showed that 7777 cells have a high basal expression level of FN synthesis and that DEX treatment induces FN expression two- to threefold with establishment of an extensive fibrillar FN network around the cells. On the other hand, 8994 cells were shown to express little FN and no apparent FN was localized on nonstimulated 8994 cells. However, DEX-treatment drastically increased FN expression in 8994 cells to the level of more than that of DEX-treated 7777 cells and induced a detectable level of cell-associated FN around DEX-treated 8994 cells, which appears to be contradictory to the decreased adhesiveness to the substratum in DEX-treated 8994 cells. Cell attachment assays using FN-coated plates demonstrated that DEX does not exhibit significant effects on the attachment of either 7777 or 8994 cells to FN-coated dishes. Our results suggest that decrease of adhesiveness to the substratum and increase of round detached cells in DEX-treated 8994 cells are independent of changes in the FN expression and the function of FN receptor.
Fukuda
K
K
Department of Biochemistry, University of Vermont College of Medicine, Burlington 05405.
Xie
R L
RL
Chiu
J F
JF
D000818:Animals; D015152:Blotting, Northern; D002448:Cell Adhesion; D002454:Cell Differentiation / Q000187:drug effects; D003907:Dexamethasone / Q000494:pharmacology; D005109:Extracellular Matrix / Q000502:physiology; D005353:Fibronectins / Q000235:genetics / Q000502:physiology*; D015870:Gene Expression; D066298:In Vitro Techniques; D008114:Liver Neoplasms, Experimental / Q000473:pathology*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017469:Receptors, Fibronectin; D011971:Receptors, Immunologic / Q000502:physiology*; D014407:Tumor Cells, Cultured
D005353:Fibronectins; D012333:RNA, Messenger; D017469:Receptors, Fibronectin; D011971:Receptors, Immunologic; D003907:Dexamethasone