A large number of human cancers display genetic alterations that aberrantly activate the G1-control kinases, cyclin D-associated Cdk4 and Cdk6, suggesting critical roles for these proteins in oncogenic transformation. Escape from senescence is requisite for transformation. Senescence induced by Ras activation or continuous in vitro proliferation is accompanied by increased expression of p16ink4a and ARF. p16ink4a inhibits Cdk4 and Cdk6, leading to enhance growth-inhibitory action of Rb. ARF stabilizes p53, resulting in induction of another Cdk inhibitor, p21Cip1/Waf1. These senescence-associated pathways are critical for tumor suppression. Cdk4-null mouse embryonic fibroblasts (MEF) proliferate normally, but are resistant to oncogenic transformation upon Ras activation with p53 inhibition or Ink4a/ARF disruption. Senescence without ARF-p53 function accounts for this lack of transformation potential. Furthermore, Cdk4-null mice display reduced susceptibility to carcinogen- or radiation-induced tumorigenesis. Thus, Cdk4 disruption may effectively render cells insensitive to transformation, by inducing senescence under conditions that normally immortalize cells. The long-term goal is to establish the basis for therapeutic intervention of oncogenic transformation. This proposal will evaluate the hypothesis that aberrant activation of cyclin D/Cdk4 and cyclin D/Cdk6 is required for a cell to overcome the senescence-dependent tumor suppressive mechanism, leading to immortalization and tumorigenesis.
The specific aims are: (1) Determine how Cdk4 disruption leads MEF to senescence under inhibition of the ARF-p53 pathway, by investigating senescence/immortalization-associated proteins in Cdk4-null MEF; (2) Determine whether Cdk4 is required for Ras-induced carcinogenesis of the mammary epithelium in mice, by examining MMTV-Ras transgenic mice with mammary-specific Cdk4 disruption; (3) Determine how Cdk4 and Cdk6 interact in immortalization, transformation and oncogenesis, by examining Cdk6-null MEF and mice. These studies are expected to clarify essential roles of the cyclin D-dependent kinases during oncogenesis. This program takes innovative approaches that should lead us to better understanding of the oncogenic interplay of Cdk4 and Cdk6 with the senescence-dependent tumor suppressive pathways, using unique mouse and cell models.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA100204-02
Application #
6724949
Study Section
Special Emphasis Panel (ZRG1-CAMP (01))
Program Officer
Blair, Donald G
Project Start
2003-04-01
Project End
2007-03-31
Budget Start
2004-04-01
Budget End
2005-03-31
Support Year
2
Fiscal Year
2004
Total Cost
$312,130
Indirect Cost
Name
University of Illinois at Chicago
Department
Biochemistry
Type
Schools of Medicine
DUNS #
098987217
City
Chicago
State
IL
Country
United States
Zip Code
60612
Gillam, M P; Nimbalkar, D; Sun, L et al. (2015) MEN1 tumorigenesis in the pituitary and pancreatic islet requires Cdk4 but not Cdk2. Oncogene 34:932-8
Ray, Dipankar; Terao, Yasuhisa; Christov, Konstantin et al. (2011) Cdk2-null mice are resistant to ErbB-2-induced mammary tumorigenesis. Neoplasia 13:439-44
Adon, Arsene M; Zeng, Xiangbin; Harrison, Mary K et al. (2010) Cdk2 and Cdk4 regulate the centrosome cycle and are critical mediators of centrosome amplification in p53-null cells. Mol Cell Biol 30:694-710
Kiyokawa, Hiroaki; Ray, Dipankar (2008) In vivo roles of CDC25 phosphatases: biological insight into the anti-cancer therapeutic targets. Anticancer Agents Med Chem 8:832-6
Shehu, Aurora; Mao, Jifang; Gibori, Gil B et al. (2008) Prolactin receptor-associated protein/17beta-hydroxysteroid dehydrogenase type 7 gene (Hsd17b7) plays a crucial role in embryonic development and fetal survival. Mol Endocrinol 22:2268-77
Ray, Dipankar; Kiyokawa, Hiroaki (2008) CDC25A phosphatase: a rate-limiting oncogene that determines genomic stability. Cancer Res 68:1251-3
Osmundson, Evan C; Ray, Dipankar; Moore, Finola E et al. (2008) The HECT E3 ligase Smurf2 is required for Mad2-dependent spindle assembly checkpoint. J Cell Biol 183:267-77
Ray, Dipankar; Terao, Yasuhisa; Fuhrken, Peter G et al. (2007) Deregulated CDC25A expression promotes mammary tumorigenesis with genomic instability. Cancer Res 67:984-91
Ray, Dipankar; Kiyokawa, Hiroaki (2007) CDC25A levels determine the balance of proliferation and checkpoint response. Cell Cycle 6:3039-42
Ray, Dipankar; Terao, Yasuhisa; Nimbalkar, Dipali et al. (2007) Hemizygous disruption of Cdc25A inhibits cellular transformation and mammary tumorigenesis in mice. Cancer Res 67:6605-11

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