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Investigation of the cooperative effects of transforming growth factor α and c‐ myc overexpression in rat liver epithelial cells
Author(s) -
Presnell Sharon Collins,
Thompson Melissa T.,
Strom Stephen C.
Publication year - 1995
Publication title -
molecular carcinogenesis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.254
H-Index - 97
eISSN - 1098-2744
pISSN - 0899-1987
DOI - 10.1002/mc.2940130406
Subject(s) - biology , tgf alpha , transforming growth factor , transfection , hepatocyte , transforming growth factor beta , microbiology and biotechnology , growth factor , cancer research , alpha (finance) , cell culture , transforming growth factor, beta 3 , cell growth , hepatocyte growth factor , epidermal growth factor , in vitro , biochemistry , genetics , receptor , medicine , construct validity , nursing , patient satisfaction
Overexpression of both transforming growth factor (TGF)‐α and c‐ myc is consistently reported in hepatic tumors. We transfected rat liver epithelial cells (RLECs) with expression vectors for TGF‐α, c‐ myc , or both and analyzed the morphology, biological properties, and tumorigenicity of clones that overexpressed these genes. The transfectants were morphologically indistinguishable from the parental RLECs, but the overexpression of TGF‐α resulted in changes in growth properties and an enhanced response to the mitogenic effects of hepatocyte growth factor. The concomitant overexpression of c‐ myc decreased growth factor requirements of the TGF‐α/c‐ myc clones compared with RLEC and TGF‐α clones. The TGF‐α and TGF‐α/c‐ myc clones were tumorigenic in nude mice at frequencies of 27% and 53%, respectively, indicating that the genes cooperate in malignant transformation. However, the untransformed nature and low tumorigenicity of the transfectants suggest that transformation depends on other cellular events in addition to the overexpression of TGF‐α or c‐ myc . Characterization of tumor cell lines showed that in contrast to the transfectants, the tumor clones were morphologically transformed, capable of autonomous growth and anchorage‐independent growth, and aggressively tumorigenic with a frequency of 100%. Clearly, the tumor cells differed from the transfectants and had undergone biological or genetic alterations (or both) as a consequence of the overexpression of TGF‐α or c‐ myc . Our data suggest that the overexpression of TGF‐α leads to enhanced responsiveness to hepatocyte growth factor, whereas the concomitant overexpression of c‐ myc confers growth‐factor independence, providing a potential explanation of the mechanisms by which the overexpression of these genes results in transformation. © 1995 Wiley‐Liss, Inc.