Analysis of K-RAS and P53 mutations in sputum samples

Mutations in the P53 tumor suppressor gene and the K-RAS oncogene have frequently been found in sputum and bronchoalveolar lavage (BAL) samples of lung cancer patients, and also in samples from patients prior to presenting clinical symptoms of lung cancer, suggesting they may provide useful biomarkers for early lung cancer diagnosis. However, the detection of these mutations has been complicated by the fact that they often occur in only a small fraction of epithelial cells among sputum cells, and, in the case of the P53 gene, inactivating mutations may occur at many codons. This chapter describes methods to identify P53 and K-RAS mutations present in low fractions of epithelial cells among the excess of other cell types in sputum samples from lung cancer patients.