The objective of this R29 proposal is to understand what role inactivation of the p16 tumor suppressor gene plays in the multi-stage development of oral cancers, with an emphasis on premalignant lesions. The studies described herein address the hypothesis that a subset of the genetic changes commonly present in end-stage oral squamous cell carcinomas (SCC) will have already occurred in premalignant (leukoplakia, erythroplakia and proliferative verrucous leukoplakia) lesions. The p16 gene has previously been shown to be inactivated through a variety of mechanisms in 80 percent of SCC of the head and neck. In contrast, a critical evaluation of the role of p16 inactivation in premalignant oral lesions has yet to be explored. Therefore, we will focus our studies on this critical cell cycle regulatory gene in premalignant cells. The experimental approach involves a combination of genetic and biochemical methodologies. Studies in Specific Aim 1 are designed to determine the incidence and mechanism of p16 inactivation (including deletions, insertions, single nucleotide substitutions, and gene hypermethylation events) in premalignant oral lesions. Secondary to our evaluation of premalignant lesions, SCC will be screened for p16 mutations in an effort to identify a larger number of missense mutations for subsequent studies in Specific Aims 2 and 3. Once identified, premalignant and malignant oral lesions exhibiting p16 mutations will be assessed at the level p16 transcription and translation for altered p16 expression compared to patient-matched normal tissues (Specific Aim 2). These expression studies will be performed as a means of determining a precise level of p16 deregulation. In addition, specific P16 mutant proteins will be evaluated in Specific Aim 3 for their degree of biologic activity compared to the wild-type P16 protein. Mutant P16 proteins will be constructed by site-directed mutagenesis and evaluated for their ability to bind to CDK4 and inhibit CDK4 kinase activity in vitro. The in vivo functional activity of specific mutant P16 proteins will also be evaluated indirectly by determining the levels of phosphorylated and unphosphorylated RB proteins in samples derived from individual premalignant and malignant oral lesions. Overall, it is anticipated that the results from these studies will not only broaden our understanding of the molecular mechanisms of oral cancer development, but may also aid in the identification of specific causative agents, intermediate endpoint biomarkers, and the development of successful intervention strategies which target premalignant disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of Dental & Craniofacial Research (NIDCR)
Type
Research Project (R01)
Project #
5R01DE011943-03
Application #
6176072
Study Section
Oral Biology and Medicine Subcommittee 1 (OBM)
Program Officer
Sandberg, Ann
Project Start
1998-06-01
Project End
2003-05-31
Budget Start
2000-06-01
Budget End
2001-05-31
Support Year
3
Fiscal Year
2000
Total Cost
$162,009
Indirect Cost
Name
Ohio State University
Department
Public Health & Prev Medicine
Type
Schools of Public Health
DUNS #
098987217
City
Columbus
State
OH
Country
United States
Zip Code
43210
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Kresty, Laura A; Mallery, Susan R; Knobloch, Thomas J et al. (2008) Frequent alterations of p16INK4a and p14ARF in oral proliferative verrucous leukoplakia. Cancer Epidemiol Biomarkers Prev 17:3179-87
Li, Junan; Warner, Blake; Casto, Bruce C et al. (2008) Tumor suppressor p16(INK4A)/Cdkn2a alterations in 7, 12-dimethylbenz(a)anthracene (DMBA)-induced hamster cheek pouch tumors. Mol Carcinog 47:733-8
Mahajan, Anjali; Guo, Yi; Yuan, Chunhua et al. (2007) Dissection of protein-protein interaction and CDK4 inhibition in the oncogenic versus tumor suppressing functions of gankyrin and P16. J Mol Biol 373:990-1005
Pasche, Boris; Knobloch, Thomas J; Bian, Yansong et al. (2005) Somatic acquisition and signaling of TGFBR1*6A in cancer. JAMA 294:1634-46
Li, Junan; Qin, Dongyan; Knobloch, Thomas J et al. (2003) Expression and characterization of Syrian golden hamster p16, a homologue of human tumor suppressor p16 INK4A. Biochem Biophys Res Commun 304:241-7
Casto, Bruce C; Kresty, Laura A; Kraly, Carrie L et al. (2002) Chemoprevention of oral cancer by black raspberries. Anticancer Res 22:4005-15
Lang, J C; Borchers, J; Danahey, D et al. (2002) Mutational status of overexpressed p16 in head and neck cancer: evidence for germline mutation of p16/p14ARF. Int J Oncol 21:401-8
Kresty, Laura A; Mallery, Susan R; Knobloch, Thomas J et al. (2002) Alterations of p16(INK4a) and p14(ARF) in patients with severe oral epithelial dysplasia. Cancer Res 62:5295-300
Poi, M J; Yen, T; Li, J et al. (2001) Somatic INK4a-ARF locus mutations: a significant mechanism of gene inactivation in squamous cell carcinomas of the head and neck. Mol Carcinog 30:26-36

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