Antisense-fos RNA causes partial reversion of the transformed phenotypes induced by the c-Ha-ras oncogene.

Abstract

Several lines of evidence have suggested that c-fos may act downstream from c-Ha-ras in a growth-regulatory signal transduction pathway. We used antisense RNA to inhibit c-fos gene expression and investigated the effects of diminished c-fos expression on the phenotypes induced by the EJ c-Ha-ras oncogene in NIH 3T3 cells.Immunofluorescent staining demonstrated that the antisense RNA caused a marked reduction in the amount of c-fos protein expressed following serum stimulation. EJ cells containing antisense-fos RNA continued to overexpress ras and remained capable of proliferating in vitro. However, the antisense-fos RNA caused a partial reversion of the major transformed phenotypes of EJ cells, including a restoration of both densitydependent growth arrest and the ability to be rendered quiescent by serum deprivation, a reversion to a flat morphology, inhibition of anchorage-independent growth, and inhibition of tumorigenicity in nude mice. Our results indicate that inhibition of c-fos expression, to a level still supporting in vitro proliferation, prevents the transforming effects of the ras oncogene; they thus provide additional evidence for the participation of c-fos in ras-regulated signal transduction pathways.

Testing the in vivo role of protein kinase C and c-fos in neurite outgrowth by microinjection of antibodies into PC12 cells.

“…Increased AP-1 DNA-binding activity has been found in nuclear extracts of ras-infected PC12 cells, suggesting a possible involvement of fos and jun in the action of ras (Sassone-Corsi et al, 1989;Wu et al, 1989). That fos is an effector downstream of ras is supported also by studies in other cell types, NIH 3T3 and rat 208F fibroblast cells, which show that microinjection of the transforming ras protein causes a rapid induction of c-fos (Stacey et al, 1987;Riabowol et al, 1988a) and that the expression of antisense-c-fos mRNA reverses the transforming effects of the ras oncogene (Ledwith et al, 1990). Thus, induction of c-fos may constitute an essential part of the signal for differentiation by NGF and bFGF in PC12 cells.…”

Ral GTPases Contribute to Regulation of Cyclin D1 through Activation of NF-κB

“…To begin to define the role of Ral activation in growth control, we examined the consequences of Ral expression on gene regulatory responses that are downstream of Ras activation and required for oncogenic Ras-induced transformation. The activation of SRE-dependent gene expression, induction of cyclin D1 protein expression, and activation of NF-B transcription factors have all been defined as critical events mediating Ras transformation (15,29,49) and are convergence points for multiple Ras-dependent signals (18,41,43,64).…”

Transcription factors control invasion: AP-1 the first among equals

“…Experiments that inhibit AP-1 activity in these model systems suggest a critical role for AP-1 in oncogenic transformation. Antisense c-fos is able to revert transformation by upstream oncogenes such as c-H-ras and v-sis (Mercola et al, 1987;Ledwith et al, 1990). Dominant-negative constructs of c-fos and c-jun revert the transformed phenotype induced by activated Ras (Lloyd et al, 1991;Okuno et al, 1991) and inhibit the invasiveness and tumorigenesis of keratinocytes (Dong et al, 1997).…”