FRA1 is a determinant for the difference in RAS-induced transformation between human and rat fibroblasts.
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.
Laboratory of Molecular Oncology, Osaka Bioscience Institute, Saito Bioincubator, Room 204, 7-7-15 Saito Asagi, Ibaraki, Osaka 567-0085, Japan.
Kyoko
K
Kakumoto
Ken
K
Sasai
Taiko
T
Sukezane
Chitose
C
Oneyama
Satoshi
S
Ishimaru
Kana
K
Shibutani
Hiroto
H
Mizushima
Eisuke
E
Mekada
Hidesaburo
H
Hanafusa
Tsuyoshi
T
Akagi
D000818:Animals; D015153:Blotting, Western; D002471:Cell Transformation, Neoplastic; D011905:Genes, ras; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D016760:Proto-Oncogene Proteins c-fos / Q000502:physiology*; D051381:Rats; D000099169:Fos-Related Antigen 1
D020928:Mitogen-Activated Protein Kinases; D016760:Proto-Oncogene Proteins c-fos; D000099169:Fos-Related Antigen 1