Mutation in the p53 tumor suppressor gene is a common event in human cancer. In the majority of human carcinomas with p53 mutations the mutant protein is over-expressed suggesting the existence of a selective advantage to maintain expression. The long-term goal of our research is to understand how p53 mutations lead to oncogenesis. The short-term objective is to test the following hypothesis: Expression of p53 mutants in human cells deregulates pathways controlled by the NF-kB2, a property critically important for chemosensitivity and tumor progression. The above-mentioned hypothesis is based on the following observations: Compared to vector transfected cells, H1299 p53-null human lung carcinoma cells expressing mutant p53 showed chemo-resistance when treated with common chemotherapeutic agents;however, cells expressing transactivation deficient mutants lose this function significantly, suggesting that transactivation by mutant p53 is crucial for chemo-resistance. A number of lung and breast cancer cell line with mutant p53 show chemo-resistance that is dependent on the level of p53 as the chemo-resistance decreases when the p53 level is lowered. p53 mutants induced expression of a number of genes involved in cell growth, survival, invasion, metastasis and angiogenesis. NF-kB2 was among this group. Introduction of short interfering RNA specific for NF-:B2 made these cells lose chemo-resistance. A preliminary screen of human lung cancer specimens shows co-existing p53 mutation and over-expression of NF-kB2 suggesting that, in the clinic, there is a subset of patients with p53 mutation and NF-kB2 over-expression. Our data also indicate that mutant p53 expression enhances cell adhesion, motility, tumorigenicity and metastatic phenotype. The following are the specific aims: 1. (a) To determine whether mutant p53 over-expression leads to higher levels of NF-kB2 in lung cancer. (b) To determine whether NF-kB2 is involved in reducing chemosensitivity in cancer cells expressing mutant p53. 2. To determine whether NF-:B2 enhances motility of cells expressing mutant p53. 3. To determine the mechanism of NF-kB2 up-regulation by mutant p53. 4. To identify factors interacting specifically with GOF p53 mutants utilizing mass spectrometric analysis. The proposed research will investigate the relationship between p53 mutants commonly found in cancer and the NF-:B2 pathway. In future, tumors with p53 mutations can be targeted at NF-:B2, mutant p53 and many of their potential target genes. Chemoresistance and Motility: Role of Mutant p53 and NF-:B2 in Cancer.
This application is based on a novel observation that tumor-derived p53 mutants up-regulate NF-kB2 expression in cell culture. Preliminary examination of human tumors also indicates that lung tumors with p53 mutation have a higher NF-:B2 level. We also find that mutant p53 expression induces higher motility and chemo-resistance in cells expressing them. We propose to determine the molecular mechanism of this up- regulation and find out how that is related to chemo-resistance and higher motility of cells expressing mutant p53. Results obtained from this study should lead to identification of a subset of lung tumors co- expressing NFkB2 and mutant p53 that could be targeted by inhibitors of NF-kB pathway to prevent tumor progression.
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