Defining the critical gene expression changes associated with expression and suppression of the tumorigenic and metastatic phenotype in Ha-ras-transformed cloned rat embryo fibroblast cells.
Carcinogenesis requires a complex series of genetic changes often involving multiple oncogenes and the inactivation of multiple tumor-suppressor genes. We presently examined the effect of the Krev-1 tumor-suppressor gene on the tumorigenic and metastatic potential of Ha-ras-transformed cloned rat embryo fibroblast (CREF) cells. Ha-ras-transformed CREF cells are morphologically transformed and anchorage independent; produce reduced levels of nm23-H1 (a putative metastasis-suppressor gene product) and TIMP-1 (tissue inhibitor of metalloproteinase 1) transcripts and mRNA compared with CREF cells; produce increased levels of cripto, 94-kDa gelatinase/type IV collagenase (94-kDa GEL), osteopontin (OPN) and transin/stromelysin transcripts and mRNA compared with CREF cells; and are tumorigenic and metastatic in both nude mice and syngeneic rats. Ha-ras-transformed CREF cells coexpressing the Krev-1 gene display a reversion in cellular phenotype and gene expression to that of untransformed CREF cells. However, Ha-ras/Krev-1-coexpressing CREF cells retain, albeit with extended latency periods, both tumorigenic and metastatic potential that is not related directly to the final level of Ha-ras or Krev-1 mRNA or the Ha-ras p21 transforming protein. Development of metastatic potential is, however, directly correlated with a reduction in nm23-H1 and TIMP-1 transcription and mRNA levels and an enhanced expression of cripto, 94-kDa GEL, osteopontin and transin. In contrast, expression of additional tumor-suppressor genes, such as the RB gene and p53, or genes associated with tumorigenesis in other model systems, such as major excreted glycoprotein (MEP), 72-kDa gelatinase/type IV collagenase (72-kDa GEL), fibronectin (FIB), tenascin and intracellular adhesion molecule 1 (ICAM-1) is not altered in a consistent manner during in vitro transformation suppression or escape from tumorigenic and metastatic suppression. These results indicate that Krev-1 suppression of the Ha-ras-transformed/oncogenic phenotype is associated with a distinct program of gene expression changes manifested by altered rates of transcription and steady-state mRNA levels of specific oncogenic-suppressing and oncogenic-inducing genes. These data support a model of Ha-ras-induced metastasis in CREF cells that involves a direct modulation in the expression/suppression of specific combinations of oncogenic-suppressor genes and metastasis-promoting genes that are regulated coordinately in the process of tumor progression.
Su
Z Z
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Department of Urology, Columbia University, College of Physicians and Surgeons, New York, New York 10032.
Austin
V N
VN
Zimmer
S G
SG
Fisher
P B
PB
D000818:Animals; D001483:Base Sequence; D002461:Cell Line, Transformed; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D002999:Clone Cells; D004622:Embryo, Mammalian; D005347:Fibroblasts; D015972:Gene Expression Regulation, Neoplastic; D016147:Genes, Tumor Suppressor; D011905:Genes, ras; D051379:Mice; D008969:Molecular Sequence Data; D009362:Neoplasm Metastasis; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
D012333:RNA, Messenger