Role of RhoA activation in the growth and morphology of a murine prostate tumor cell line.
Prostate cancer cells derived from transgenic mice with adenocarcinoma of the prostate (TRAMP cells) were treated with the HMG-CoA reductase inhibitor, lovastatin. This caused inactivation of the small GTPase RhoA, actin stress fiber disassembly, cell rounding, growth arrest in the G1 phase of the cell cycle, cell detachment and apoptosis. Addition of geranylgeraniol (GGOL) in the presence of lovastatin, to stimulate protein geranylgeranylation, prevented lovastatin's effects. That is, RhoA was activated, actin stress fibers were assembled, the cells assumed a flat morphology and cell growth resumed. The following observations support an essential role for RhoA in TRAMP cell growth: (1) TRAMP cells expressing dominant-negative RhoA (T19N) mutant protein displayed few actin stress fibers and grew at a slower rate than controls (35 h doubling time for cells expressing RhoA (T19N) vs 20 h for untransfected cells); (2) TRAMP cells expressing constitutively active RhoA (Q63L) mutant protein displayed a contractile phenotype and grew faster than controls (13 h doubling time). Interestingly, addition of farnesol (FOL) with lovastatin, to stimulate protein farnesylation, prevented lovastatin-induced cell rounding, cell detachment and apoptosis, and stimulated cell spreading to a spindle shaped morphology. However, RhoA remained inactive and growth arrest persisted. The morphological effects of FOL addition were prevented in TRAMP cells expressing dominant-negative H-Ras (T17N) mutant protein. Thus, it appears that H-Ras is capable of inducing cell spreading, but incapable of supporting cell proliferation, in the absence of geranylgeranylated proteins like RhoA.
Ghosh
P M
PM
Department of Pathology, University of Texas Health Science Center, San Antonio 78284, USA.
Ghosh-Choudhury
N
N
Moyer
M L
ML
Mott
G E
GE
Thomas
C A
CA
Foster
B A
BA
Greenberg
N M
NM
Kreisberg
J I
JI
D008841:Actin Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D000230:Adenocarcinoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D019883:Alkyl and Aryl Transferases / Q000235:genetics / Q000502:physiology*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D002448:Cell Adhesion; D002455:Cell Division / Q000187:drug effects; D048429:Cell Size; D004224:Diterpenes / Q000494:pharmacology; D004347:Drug Interactions; D004789:Enzyme Activation; D005204:Farnesol / Q000494:pharmacology; D016193:G1 Phase; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011905:Genes, ras; D006160:Guanosine Triphosphate / Q000502:physiology; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology*; D008148:Lovastatin / Q000494:pharmacology*; D008297:Male; D008798:Mevalonic Acid / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D011106:Polyisoprenyl Phosphates / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D017368:Protein Prenylation / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D012717:Sesquiterpenes; D014407:Tumor Cells, Cultured / Q000187:drug effects; D020744:rac GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein
D000970:Antineoplastic Agents; D004224:Diterpenes; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D011106:Polyisoprenyl Phosphates; D012717:Sesquiterpenes; D005204:Farnesol; C004808:farnesyl pyrophosphate; D006160:Guanosine Triphosphate; D008148:Lovastatin; C017338:geranylgeraniol; D019883:Alkyl and Aryl Transferases; C068462:rhoA p21 geranylgeranyltransferase; D019204:GTP-Binding Proteins; D016283:Proto-Oncogene Proteins p21(ras); D020744:rac GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein; C002963:geranylgeranyl pyrophosphate; D008798:Mevalonic Acid