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Contextual effects of transforming growth factor beta on the tumorigenicity of human colon carcinoma cells

S C Ye1, J M Foster, W Li

  • 1Department of Biochemistry and Molecular Biology, Medical College of Ohio at Toledo, 43614-2595, USA.

Cancer Research
|September 24, 1999
PubMed

Insights

Transforming growth factor-beta (TGF-beta) signaling has paradoxical effects on colon carcinoma. Modulating TGF-beta receptors or ligands can either suppress or promote tumor growth depending on the specific genetic context.

Area of Science:

  • Oncology
  • Molecular Biology
  • Cell Biology

Background:

  • Transforming growth factor-betas (TGF-betas) are known for their negative autocrine growth functions in epithelial cells, including colon carcinoma.
  • Both type I (RI) and type II (RII) TGF-beta receptors are crucial for TGF-beta-mediated growth regulation.
  • Previous studies on TGF-beta modulation in cancer have yielded contradictory results regarding tumorigenicity, suggesting context-dependent effects.

Purpose of the Study:

  • To investigate the context-dependent effects of modulating the TGF-beta system on colon carcinoma cell growth.
  • To determine how alterations in TGF-beta receptor II (RII) expression or TGF-beta1 ligand levels impact in vitro and in vivo tumorigenicity.
  • To elucidate the paradoxical tumor-promoting and -suppressing roles of TGF-beta signaling in colon cancer.

Main Methods:

  • Utilized two independent isogenic human colon carcinoma cell line models (CBS and FET).
  • Generated stable cell lines with tetracycline-repressible expression vectors for RII, a truncated RII lacking kinase activity (deltaRII), or TGF-beta1.
  • Assessed TGF-beta sensitivity, in vitro growth, and in vivo tumorigenicity in athymic mice.

Main Results:

  • Overexpression of RII increased TGF-beta sensitivity and reduced tumorigenicity in CBS4 cells.
  • Expression of truncated RII (deltaRII) or TGF-beta1 (beta1S) increased TGF-beta insensitivity and enhanced tumorigenicity in both CBS4 and FET6 models.
  • FET6-deltaRII and FET-beta1S cells formed rapidly growing tumors, while wild-type FET6 cells were nontumorigenic.

Conclusions:

  • TGF-beta signaling exhibits paradoxical tumor-suppressing and tumor-promoting effects in colon carcinoma.
  • The impact of TGF-beta modulation on malignancy is highly contextual, depending on the specific genetic alterations and cellular environment.
  • These findings highlight the complex role of TGF-beta in colon cancer progression and suggest therapeutic strategies must consider context-specific signaling.

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