CLONAL ORIGIN OF MULTIPLE LUNG CANCERS - K-RAS AND P53 MUTATIONS DETERMINED BY NONRADIOISOTOPIC SINGLE-STRAND CONFORMATION POLYMORPHISM ANALYSIS

Disease stage is the most important factor in determining prognosis an d treatment of lung cancer. Staging of lung cancer is complicated by p resentation of multiple pulmonary malignant lesions with a similar his tology. It is a dilemma to decide if these lesions are synchronous pri maries arising from different malignant clones or metastases from a si ngle clone. Lung cancer is associated with multiple genetic abnormalit ies including mutations of K-ras and p53, which are believed to occur prior to onset of metastasis. To determine the clonal origin of multip le pulmonary malginant nodules, we analyzed point mutations of K-ras a nd p53 by microdissection, polymerase chain reactions (PCR), nonradioi sotopic single-strand conformation polymorphism (SSCP) analysis, and D NA sequencing. Each pulmonary lesion was microdissected from paraffin slides. Genomic DNA was amplified by two sequential PCRs followed by e lectrophoresis in a minigel and silver staining. Deoxyribonucleic acid sequencing was performed if necessary to confirm a mutation found upo n SSCP analysis. Applying this molecular approach, we were able to dif ferentiate the clonal origins of multiple malignant nodules of the lun g as exemplified by the two cases presented.