Mitogenic conversion of transforming growth factor-β1 effect by oncogenic Ha-Ras-induced activation of the mitogen-activated protein kinase signaling pathway in human prostate cancer

Bum Joon Park, Jae I. Park, Do S. Byun, Jae Hoon Park, Sung-Gil Chi

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96 Citations (Scopus)

Abstract

Elevated expression of transforming growth factor (TGF)-β1 has been implicated in prostate tumorigenesis despite its growth-inhibitory effect on normal epithelial and carcinoma cells of the prostate. In this study, we identified that G1-to-S transition of the cell cycle is stimulated by TGF- β1 in the prostate cancer cell line TSU-Pr1. No mutation of signal mediators, including Smads, and induction of PAI-1 transcription indicated that the TGF-β1 signaling cascade is functionally intact in this cell line. Whereas pharmacological inhibitors of various mitogenic signaling pathways showed no effects, blockade of the mitogen-activated protein kinase (MAPK) pathway by the MAPK kinase 1 inhibitor PD98059 restored the growth inhibitory role of TGF-β1 in TSU-Pr1, which carries an oncogenic mutation in Ha-Ras (V12). Moreover, expression of antisense Ha-Ras or dominant negative Raf-1 abrogated the mitogenic effect of TGF-β1 in TSU-Pr1, and the TGF-β1 inhibition of DU145 was switched to stimulation by V12Ha-Ras transfection. Whereas the negative growth regulation by TGF-β1 was completely inhibited by dominant negative Smad2, Smad3, or Smad4, its mitogenic effect was not affected, suggesting that this action is Smad-independent. Interestingly, whereas the TGF-β1-mediated up-regulation of p15(INK4B) and p21(WAF1) transcription was abolished in TSU-Pr1 and V12Ha-Ras-transfected DU145, inhibition of the Ras/MAPK pathway restored the TGF-β1 induction of these genes. Taken together, our data suggest that prostate carcinomas with the Ras/MAPK pathway activation might have a selective growth advantage by autocrine TGF-β1 production.

Original languageEnglish
Pages (from-to)3031-3038
Number of pages8
JournalCancer Research
Volume60
Issue number11
Publication statusPublished - 2000 Jun 1
Externally publishedYes

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ASJC Scopus subject areas

  • Cancer Research
  • Oncology

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