Lung cancer is the leading cause of cancer mortality in the world. Although exposure to carcinogens is considered to be the main cause, genetic variation may contribute to lung cancer risk. Murine double minute 2, MDM2, is a key regulator of p53 activity and recently a polymorphism in the promoter region of the MDM2 gene was characterized. This single nucleotide polymorphism, SNP309, was shown to influence MDM2 transcription, MDM2 protein levels and p53 activity. The aim of this study was to investigate whether this functionally important SNP is associated with risk of nonsmall cell lung cancer. The study consisted of 341 nonsmall cell lung cancer cases and 412 healthy controls of Norwegian origin. Our results indicate that the G/G genotype of SNP309 is associated with lung cancer risk with an odds ratio of 1.62 (95% CI: 1.06-2.50). Interestingly, the strongest effect of the polymorphism was seen among women. Females homozygous for SNP309 G/G had associated odds ratio 4.06 (1.29-12.8). We also explored the MDM2 SNP309 in relation to TP53 gene mutations and age at nonsmall cell lung cancer diagnosis. Our results indicate that the G/G genotype of SNP309 is associated with higher age at diagnosis in individuals with TP53 mutations (p 5 0.037).

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We extended our development of the means to measure point mutations at the DNA level to the problem of detecting TP53 gene variants in the area around tumors where mutant fractions are expected to be as low as one mutant per 1000 wild-type (WT) sequences. We met this criterion by using the following methods. The TP53 exon 8 sequence was amplified from genomic DNA samples under conditions of high polymerase fidelity using a fluorescein-labeled primer. This mixture of WT and mutant sequences was converted to heteroduplexes of mutant and WT sequences by melting and re-annealing. The mixture was resolved by capillary gel electrophoresis under appropriate constant denaturing conditions. Using laser-induced fluorescence, we found that fractions as low as 1/1000 could be detected without any prior enrichment for mutant sequences, and that the melting properties of the amplified DNA will leave "fingerprints" in the electropherogram that can be used to identify the specific mutation. This method is fast and robust and should be applicable to clinical analyses in which rapid scanning for any mutation in an exonic sequence is important.

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Over the past few decades, advances in genetics and molecular biology have revolutionized our understanding of cancer initiation and progression. Molecular progression models outlining genetic events have been developed for many solid tumors, including colon cancer. Previous reports in the literature have shown a relationship between different KRAS mutations and prognosis and response to medical treatment in colon cancer patients. Furthermore, the presence of a mutated KRAS has been correlated with different clinicopathological variables including age and gender of patients and tumor location. To our knowledge, few institutions screen for KRAS mutations on regular basis in colon cancer patients despite such evidence that knowledge of KRAS exon 1 status is informative. Here, we report on a mutation analysis method adapted to a 96-capillary electrophoresis instrument that allows identification of all 12 oncogenic mutations in KRAS exon 1 under denaturing conditions. To determine the optimal parameters, a series of DNA constructs generated by site-directed mutagenesis was analyzed and the migration times of all mutant peaks were measured. A classification tree was then made based on the differences in migration time between the mutants and an internal standard. A randomized series of 500 samples constructed with mutagenesis as well as 60 blind samples from sporadic colon carcinomas was analyzed to test the method. No wild-type samples were scored as mutants and all mutants were correctly identified. Post polymerase chain reaction (PCR) analysis time of 96 samples was performed within 40 min.