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Cyclin D2-cyclin-dependent kinase 4/6 is required for efficient proliferation and tumorigenesis following Apc loss

Alicia M Cole1, Kevin Myant, Karen R Reed

  • 1Beatson Institute of Cancer Research, Glasgow, United Kingdom; School of Biosciences, Cardiff, United Kingdom.

Cancer Research
|August 26, 2010
PubMed

Insights

Apc gene inactivation triggers colorectal cancer (CRC) by activating Wnt signaling. Cyclin D2, not cyclin D1, drives proliferation after Apc loss, offering a potential therapeutic target for CRC prevention.

Area of Science:

  • Oncology
  • Molecular Biology
  • Gastroenterology

Background:

  • Apc gene inactivation is a critical early step in sporadic colorectal cancer (CRC) development.
  • Loss of Apc leads to constitutive Wnt signaling activation, promoting transcription of target genes like c-Myc.
  • While cyclin D1 is necessary for adenoma formation, its delayed upregulation post-Apc loss suggests involvement of other D-type cyclins in intestinal proliferation.

Purpose of the Study:

  • To investigate the expression and functional significance of cyclin D2 in the intestinal epithelium following Apc loss.
  • To determine if cyclin D2 plays a role in the immediate proliferative response to acute Apc loss.
  • To evaluate cyclin D2 as a potential therapeutic target for colorectal cancer.

Main Methods:

  • Investigated cyclin D2 expression in the intestinal epithelium after Apc loss.
  • Assessed the impact of cyclin D2 deficiency on enterocyte proliferation and crypt size in Apc-deficient models.
  • Evaluated the effect of cyclin D2 on tumor growth and development in Apc(Min/+) mice.
  • Examined the impact of CDK4/6 inhibition on normal and adenomatous cells from Apc(Min/+) mice.

Main Results:

  • Cyclin D2 is upregulated immediately following Apc loss, coinciding with increased cyclin-dependent kinase 4 (CDK4) and hyperphosphorylated Rb levels.
  • Cyclin D2 deficiency reduced enterocyte proliferation and crypt size in Apc-deficient intestines.
  • Cyclin D2 deficiency significantly inhibited tumor growth and development in Apc(Min/+) mice.
  • CDK4/6 inhibition suppressed proliferation of adenomatous cells but not normal enterocytes in Apc(Min/+) mice.

Conclusions:

  • Cyclin D-CDK4/6 complexes are essential for the proliferation of cells with deregulated Wnt signaling.
  • Targeting the cyclin D-CDK4/6 complex represents a promising chemopreventative strategy for colorectal cancer.
  • Cyclin D2 is a key mediator of proliferation following Apc loss in the intestinal epithelium.

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