FRA1 is a determinant for the difference in RAS-induced transformation between human and rat fibroblasts

doi:10.1073/pnas.0601222103

FRA1 is a determinant for the difference in RAS-induced transformation between human and rat fibroblasts

*Laboratory of Molecular Oncology, Osaka Bioscience Institute, Saito Bioincubator, Room 204, 7-7-15 Saito Asagi, Ibaraki, Osaka 567-0085, Japan;
^‡Department of Developmental Neurobiology, St. Jude Childrens’s Research Hospital, 322 North Lauderdale Street, Memphis, TN 38138;
^§Department of Oncogene Research, Research Institute for Microbial Diseases, and
^¶Department of Cell Biology, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan; and
^†Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan

Communicated by Hidesaburo Hanafusa, Osaka Bioscience Institute, Osaka, Japan, February 14, 2006 (received for review February 6, 2006)

Abstract

Human diploid fibroblasts (HDF) immortalized by hTERT and simian virus 40 (SV40) early region (ER) exhibit a limited degree of transformation upon the expression of activated H-RAS (H-RAS V12) compared with rat embryonic fibroblasts (REF) immortalized by SV40 ER. Here, we identified FRA1 as a determinant for this difference in RAS-induced transformation. FRA1 was not induced by H-RAS V12 in the immortalized HDF, in contrast to its marked accumulation in the immortalized REF. Ectopic expression of FRA1 significantly enhanced anchorage-independent growth of various HDF expressing hTERT, SV40 ER, and H-RAS V12. More importantly, FRA1 could induce anchorage-independent growth as well as nude mice tumor formation of the immortalized HDF in the absence of H-RAS V12. The results of an in vitro kinase assay clearly showed that the RAS-induced extracellular signal-regulated kinase (ERK) activation, which is responsible for FRA1 induction, was markedly attenuated in the HDF compared with that in the REF, despite no obvious differences in the phosphorylation status of ERK between the species. Our results strongly suggest that HDF negatively regulate the mitogen-activated protein kinase kinase (MEK)/ERK pathway more efficiently than REF, and consequently express less malignant phenotypes in response to H-RAS V12.

Footnotes

^‖To whom correspondence should be addressed. E-mail: takagi{at}obi.or.jp
Author contributions: K.K., T.S., C.O., H.H., and T.A. designed research; K.K., K. Shibutani, and H.M. performed research; K. Sasai, S.I., H.M., and E.M. contributed new reagents/analytic tools; K.K., K. Sasai, and H.M. analyzed data; and K.K. and T.A. wrote the paper.
Conflict of interest statement: No conflicts declared.
Abbreviations:

Abbreviations:

SV40,

simian virus 40;

ER,

early region;

REF,

rat embryonic fibroblast;

MEF,

mouse embryonic fibroblast;

HA,

hemagglutinin;

HDF,

human diploid fibroblast;

ERK,

extracellular signal-regulated kinase;

MEK,

mitogen-activated protein kinase kinase.