Oncogenic K-ras promotes early carcinogenesis in the mouse proximal colon

Shelly R. Calcagno, Shuhua Li, Migdalisel Colon, Pamela A. Kreinest, E Aubrey Thompson, Alan P Fields, Nicole R Murray

Research output: Contribution to journalArticle

43 Citations (Scopus)

Abstract

Oncogenic K-ras mutations are frequently observed in colon cancers and contribute to transformed growth. Oncogenic K-ras is detected in aberrant crypt foci (ACF), precancerous colonic lesions, demonstrating that acquisition of a K-ras mutation is an early event in colon carcinogenesis. Here, we investigate the role of oncogenic K-ras in neoplastic initiation and progression. Transgenic mice in which an oncogenic K-rasG12D allele is activated in the colonic epithelium by sporadic recombination (K-rasLA2 mice) develop spontaneous ACF that are morphologically indistinguishable from those induced by the colon carcinogen azoxymethane (AOM). Similar neoplastic changes involving the entire colon are induced in transgenic mice constitutively expressing K-ras G12D throughout the colon (LSL-K-rasG12D/Villin-Cre mice). However, the biochemistry and fate of K-ras-induced lesions differ depending upon their location within the colon in these mice. In the proximal colon, K-rasG12D induces increased expression of procarcinogenic protein kinase CβII (PKCβII), activation of the MEK/ERK signaling axis and increased epithelial cell proliferation. In contrast, in the distal colon, K-ras inhibits expression of procarcinogenic PKCβII and induces apoptosis. Treatment of K-rasLA2 mice with AOM leads to neoplastic progression of small ACF to large, dysplastic microadenomas in the proximal, but not the distal colon. Thus, oncogenic K-ras functions differently in the proximal and distal colon of mice, inducing ACF capable of neoplastic progression in the proximal colon, and ACF with little or no potential for progression in the distal colon. Our data indicate that acquisition of a K-ras mutation is an initiating neoplastic event in proximal colon cancer development in mice.

Original languageEnglish (US)
Pages (from-to)2462-2470
Number of pages9
JournalInternational Journal of Cancer
Volume122
Issue number11
DOIs
StatePublished - Jun 1 2008

Fingerprint

Colon
Carcinogenesis
Aberrant Crypt Foci
Azoxymethane
Colonic Neoplasms
Protein Kinases
Mutation
Transgenic Mice
Mitogen-Activated Protein Kinase Kinases
Carcinogens
Biochemistry
Genetic Recombination
Epithelium
Epithelial Cells
Alleles
Cell Proliferation
Apoptosis
Growth

Keywords

  • ACF
  • Carcinogenesis
  • Colon
  • Dysplasia
  • K-ras
  • PKCβII
  • Progression

ASJC Scopus subject areas

  • Cancer Research
  • Oncology

Cite this

Oncogenic K-ras promotes early carcinogenesis in the mouse proximal colon. / Calcagno, Shelly R.; Li, Shuhua; Colon, Migdalisel; Kreinest, Pamela A.; Thompson, E Aubrey; Fields, Alan P; Murray, Nicole R.

In: International Journal of Cancer, Vol. 122, No. 11, 01.06.2008, p. 2462-2470.

Research output: Contribution to journalArticle

Calcagno, Shelly R. ; Li, Shuhua ; Colon, Migdalisel ; Kreinest, Pamela A. ; Thompson, E Aubrey ; Fields, Alan P ; Murray, Nicole R. / Oncogenic K-ras promotes early carcinogenesis in the mouse proximal colon. In: International Journal of Cancer. 2008 ; Vol. 122, No. 11. pp. 2462-2470.
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AB - Oncogenic K-ras mutations are frequently observed in colon cancers and contribute to transformed growth. Oncogenic K-ras is detected in aberrant crypt foci (ACF), precancerous colonic lesions, demonstrating that acquisition of a K-ras mutation is an early event in colon carcinogenesis. Here, we investigate the role of oncogenic K-ras in neoplastic initiation and progression. Transgenic mice in which an oncogenic K-rasG12D allele is activated in the colonic epithelium by sporadic recombination (K-rasLA2 mice) develop spontaneous ACF that are morphologically indistinguishable from those induced by the colon carcinogen azoxymethane (AOM). Similar neoplastic changes involving the entire colon are induced in transgenic mice constitutively expressing K-ras G12D throughout the colon (LSL-K-rasG12D/Villin-Cre mice). However, the biochemistry and fate of K-ras-induced lesions differ depending upon their location within the colon in these mice. In the proximal colon, K-rasG12D induces increased expression of procarcinogenic protein kinase CβII (PKCβII), activation of the MEK/ERK signaling axis and increased epithelial cell proliferation. In contrast, in the distal colon, K-ras inhibits expression of procarcinogenic PKCβII and induces apoptosis. Treatment of K-rasLA2 mice with AOM leads to neoplastic progression of small ACF to large, dysplastic microadenomas in the proximal, but not the distal colon. Thus, oncogenic K-ras functions differently in the proximal and distal colon of mice, inducing ACF capable of neoplastic progression in the proximal colon, and ACF with little or no potential for progression in the distal colon. Our data indicate that acquisition of a K-ras mutation is an initiating neoplastic event in proximal colon cancer development in mice.

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