In vivo, tumor aggressiveness correlates with increased resistance to apoptosis. Additionally, anti-neoplastic therapies, including gamma-radiation and chemotherapeutic drugs, eliminate malignant cells by the induction of apoptosis. Therefore, it is to the advantage of tumor cells to overexpress cellular genes which protect against this process. bcl-2, an important modulator of apoptosis, is negatively regulated at the transcriptional and post-transcriptional level by tumor suppressor p53 and positively by activated Ras. In contrast, Bcl-2 is able to overcome p53-dependent apoptosis, perhaps by cooperating with myc to subcellularly localize p53 to the cytoplasm. Overexpression of bcl-2 is transforming when accompanied by either c-myc or activated ras. In colorectal and prostate cancers, greater than 90 percent of metastatic tumors overexpress the Bcl-2 protein, supporting a role for Bcl-2 in oncogenesis. Another tumor suppressor, WT1, has been demonstrated to modulate the bcl-2 promoter and to inhibit p53-mediated apoptosis. Preliminary data presented in this research proposal demonstrates that activated ras and three Ras-responsive transcription factors (AP-1, C/EBPbeta, and EGR-1) lead to the transactivation of the bcl-2 promoter, and that at least one of these transcription factors, C/EBPbeta, directly interacts with the promoter. Furthermore, tumor suppressors p53 and WT1 were able to inhibit positive transactivation of the bcl-2 reporter. Importantly, a high affinity bindking site for WT1 was identified in the bcl-2 promoter. The primary goals of this research proposal are to determine the functional consequence of oncogenic Ras and tumor suppressors, WT1 and p53, on bcl-2 expression and the significance of this dysregulation on oncogenic transformation.
Aim 1 will employ transient transfections, using bcl-2 reporters, to confirm the location of the AP-1, C/EBPbeta and EGR-1 responsive sites and to determine the importance of these sites for p53-dependent repression. M1p53 135 cells, which contain a temperature-sensitive p53 mutant, and cells isolated from p53-deficient mice will be employed to determine whether gamma-radiation and interleukin-6, physiological inducers of AP-1, Egr-1, and C/EBPbeta, protect cells against apoptosis by inducing Bcl-2 expression.
Aim 2 will determine whether oncogenic Ras elevates endogenous bcl-2 gene expression and to determine the importance of C/EBP and p53 on bcl-2 expression and on cellular transformation.
Aim 3 will determine whether the WT1 binding site(s) is required for p53-mediated repression of the bcl-2 promoter and to determine the functional consequence of WT1 expression on endogenous bcl-2 expression in vivo. Primary sporadic Wilms' tumors will be analyzed for elevated bcl-2 expression, and a WT1 mouse xenograft model will be characterized to determine whether the anti-apoptotic activity of Bcl-2 is critical for sustained growth of Wilms' tumor. These studies have important implications not only toward understanding the functional consequence of oncogenic Ras and tumor suppressors on bcl-2 modulation, but may provide important therapeutic insight as to how to eradicate solid tumors display overexpressed Bcl-2.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA072771-03
Application #
2856439
Study Section
Pathology B Study Section (PTHB)
Program Officer
Spalholz, Barbara A
Project Start
1997-01-01
Project End
2001-12-31
Budget Start
1999-01-01
Budget End
1999-12-31
Support Year
3
Fiscal Year
1999
Total Cost
Indirect Cost
Name
University of North Carolina Chapel Hill
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
078861598
City
Chapel Hill
State
NC
Country
United States
Zip Code
27599
Mayo, Marty W; Madrid, Lee V; Westerheide, Sandy D et al. (2002) PTEN blocks tumor necrosis factor-induced NF-kappa B-dependent transcription by inhibiting the transactivation potential of the p65 subunit. J Biol Chem 277:11116-25
Poligone, B; Baldwin, A S (2001) Positive and negative regulation of NF-kappaB by COX-2: roles of different prostaglandins. J Biol Chem 276:38658-64
Holmes-McNary, M Q; Baldwin Jr, A S; Zeisel, S H (2001) Opposing regulation of choline deficiency-induced apoptosis by p53 and nuclear factor kappaB. J Biol Chem 276:41197-204
Cusack Jr, J C; Liu, R; Houston, M et al. (2001) Enhanced chemosensitivity to CPT-11 with proteasome inhibitor PS-341: implications for systemic nuclear factor-kappaB inhibition. Cancer Res 61:3535-40
Madrid, L V; Mayo, M W; Reuther, J Y et al. (2001) Akt stimulates the transactivation potential of the RelA/p65 Subunit of NF-kappa B through utilization of the Ikappa B kinase and activation of the mitogen-activated protein kinase p38. J Biol Chem 276:18934-40
Keifer, J A; Guttridge, D C; Ashburner, B P et al. (2001) Inhibition of NF-kappa B activity by thalidomide through suppression of IkappaB kinase activity. J Biol Chem 276:22382-7
Cogswell, P C; Guttridge, D C; Funkhouser, W K et al. (2000) Selective activation of NF-kappa B subunits in human breast cancer: potential roles for NF-kappa B2/p52 and for Bcl-3. Oncogene 19:1123-31
Holmes-McNary, M; Baldwin Jr, A S (2000) Chemopreventive properties of trans-resveratrol are associated with inhibition of activation of the IkappaB kinase. Cancer Res 60:3477-83
Guttridge, D C; Mayo, M W; Madrid, L V et al. (2000) NF-kappaB-induced loss of MyoD messenger RNA: possible role in muscle decay and cachexia. Science 289:2363-6
Madrid, L V; Wang, C Y; Guttridge, D C et al. (2000) Akt suppresses apoptosis by stimulating the transactivation potential of the RelA/p65 subunit of NF-kappaB. Mol Cell Biol 20:1626-38

Showing the most recent 10 out of 20 publications