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SKI and MEL1 cooperate to inhibit transforming growth factor-beta signal in gastric cancer cells

Mami Takahata1, Yasumichi Inoue2, Hitoshi Tsuda3

  • 1Division of Biochemistry, the Cancer Institute of the Japanese Foundation for Cancer Research (JFCR), 3-10-6 Ariake, Koto-ku, Tokyo 135-8550; Department of Molecular Pathology, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033.

The Journal of Biological Chemistry
|December 4, 2008
PubMed

Insights

Chromosomal co-amplification of SKI and MEL1 in gastric cancer impairs TGF-beta signaling. Restoring this pathway through gene knockdown inhibits tumor growth, revealing new therapeutic targets.

Area of Science:

  • Oncology
  • Molecular Biology
  • Cancer Genetics

Background:

  • Chromosomal amplifications are common in solid tumors, often correlating with poor patient outcomes.
  • Co-amplification of oncogenic factors within the same amplicon suggests cooperative roles in cancer, but their functional interactions are not fully understood.
  • Transforming growth factor (TGF)-beta signaling is crucial for normal epithelial cell functions, and its dysregulation is implicated in numerous cancers.

Purpose of the Study:

  • To investigate the functional correlation between co-amplified genes in gastric cancer.
  • To elucidate the mechanism by which co-amplified transcriptional co-repressors of TGF-beta signaling impact cancer progression.
  • To identify potential therapeutic targets for gastric cancer treatment.

Main Methods:

  • Analysis of chromosomal co-amplification in MKN28 gastric cancer cells.
  • Gene knockdown of SKI and MEL1 (MDS1/EVI1-like gene 1).
  • Assessment of TGF-beta signaling pathway restoration and tumor growth in vivo.
  • Investigation of protein interactions between MEL1 and SKI.

Main Results:

  • Aberrant expression of SKI and MEL1 was linked to chromosomal co-amplification at 1p36.32 in MKN28 gastric cancer cells.
  • Synergistic knockdown of SKI and MEL1 restored TGF-beta responsiveness and reduced tumor growth in vivo.
  • MEL1 was found to interact with SKI, stabilizing the inactive Smad3-SKI complex and inhibiting TGF-beta target gene expression.

Conclusions:

  • Distinct transcriptional co-repressors (SKI and MEL1) can be co-amplified and functionally cooperate in gastric cancer.
  • This co-amplification mechanism contributes to the inhibition of TGF-beta signaling, promoting tumor growth.
  • The SKI-MEL1 interaction and its role in TGF-beta pathway inhibition present novel molecular targets for gastric cancer therapy.

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