AP-1-mediated invasion requires increased expression of the hyaluronan receptor CD44.
Fibroblasts transformed by Fos oncogenes display increased expression of a number of genes implicated in tumor cell invasion and metastasis. In contrast to normal 208F rat fibroblasts, Fos-transformed 208F fibroblasts are growth factor independent for invasion. We demonstrate that invasion of v-Fos- or epidermal growth factor (EGF)-transformed cells requires AP-1 activity. v-Fos-transformed cell invasion is inhibited by c-jun antisense oligonucleotides and by expression of a c-jun dominant negative mutant, TAM-67. EGF-induced invasion is inhibited by both c-fos and c-jun antisense oligonucleotides. CD44s, the standard form of a transmembrane receptor for hyaluronan, is implicated in tumor cell invasion and metastasis. We demonstrate that increased expression of CD44 in Fos- and EGF-transformed cells is dependent upon AP-1. CD44 antisense oligonucleotides reduce expression of CD44 in v-Fos- or EGF-transformed cells and inhibit invasion but not migration. Expression of a fusion protein between human CD44s and Aequorea victoria green fluorescent protein (GFP) in 208F cells complements the inhibition of invasion by the rat-specific CD44 antisense oligonucleotide. We further show that both v-Fos and EGF transformations result in a concentration of endogenous CD44 or exogenous CD44-GFP at the ends of pseudopodial cell extensions. These results support the hypothesis that one role of AP-1 in transformation is to activate a multigenic invasion program.
Lamb
R F
RF
CRC Beatson Laboratories, Beatson Institute for Cancer Research, Bearsden, Glasgow, Scotland.
Hennigan
R F
RF
Turnbull
K
K
Katsanakis
K D
KD
MacKenzie
E D
ED
Birnie
G D
GD
Ozanne
B W
BW
D000818:Animals; D002461:Cell Line, Transformed; D002471:Cell Transformation, Neoplastic; D004815:Epidermal Growth Factor / Q000502:physiology; D005347:Fibroblasts; D005786:Gene Expression Regulation / Q000502:physiology*; D049452:Green Fluorescent Proteins; D006801:Humans; D018960:Hyaluronan Receptors / Q000032:analysis / Q000235:genetics*; D008164:Luminescent Proteins / Q000235:genetics; D009361:Neoplasm Invasiveness / Q000235:genetics*; D016376:Oligonucleotides, Antisense; D016761:Oncogene Proteins v-fos / Q000502:physiology; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics; D051381:Rats; D011993:Recombinant Fusion Proteins; D018808:Transcription Factor AP-1 / Q000502:physiology*
D018960:Hyaluronan Receptors; D008164:Luminescent Proteins; D016376:Oligonucleotides, Antisense; D016761:Oncogene Proteins v-fos; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D011993:Recombinant Fusion Proteins; D018808:Transcription Factor AP-1; D049452:Green Fluorescent Proteins; D004815:Epidermal Growth Factor