RT Journal Article
SR Electronic
T1 A Link between <em>ras</em> and Metastatic Behavior of Tumor Cells: <em>ras</em> Induces CD44 Promoter Activity and Leads to Low-Level Expression of Metastasis-specific Variants of CD44 in CREF Cells
JF Cancer Research
JO Cancer Res
FD American Association for Cancer Research
SP 1516
OP 1521
VO 53
IS 7
A1 Hofmann, Martin
A1 Rudy, Wolfgang
A1 Günthert, Ursula
A1 Zimmer, Stephen G.
A1 Zawadzki, Volker
A1 Zöller, Margot
A1 Lichtner, Rosemarie B.
A1 Herrlich, Peter
A1 Ponta, Helmut
YR 1993
UL http://cancerres.aacrjournals.org/content/53/7/1516.abstract
AB The activated oncogene c-Ha-ras induces expression of the surface glycoprotein CD44 in cloned rat embryonic fibroblasts (CREF). Induction is transcriptional as shown by transient cotransfections of c-Ha-ras expression constructs and CD44 promoter reporter gene constructs and depends on the presence of an AP-1 binding site at position −110. Increased transcript levels for the standard isoform of CD44 (CD44s) are accompanied by the appearance of alternatively spliced RNAs and the synthesis of variants of CD44 (CD44v). These CD44v molecules differ from the standard type by the addition of sequences in the extracellular portion of the molecules. The occurrence of CD44v molecules in CREF cells upon induction of the CD44 promoter is probably due to leakiness of the splice control in these cells since stable transfection with c-Ha-ras does not alter the CD44v/total CD44 ratio. Upon ras overexpression, however, using an inducible mouse mammary tumor virus-ras construct, a transient increase of CD44v/total CD44 ratio of 3–4 has been determined suggesting that a burst of ras expression, in the genetic background of CREF cells, influences both promoter activity and splice control or accuracy. The expression of CD44v proteins is responsible for the metastatic potential in a variety of tumors (U. Günthert et al., Cell, 65: 13–24, 1991). Also in CREF cells expression of CD44v correlates with metastatic behavior. ras-transfected CREF cells are not only fully transformed but also give rise to metastatic spread as measured in the spontaneous metastasis assay. The adenoviral oncogene EIA counteracts ras-induced promoter function and, consequently, inhibits metastatic behavior without extinguishing transformation. ©1993 American Association for Cancer Research.