Chromosomal amplifications detected by FISH markers to predict the neoplastic potential of cells in fine needle biopsies of abnormal nodules identified by spiral CT

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Introduction: Spiral computed tomography (CT) screening is a highly sensitive method for detecting early lung cancers. Spiral CT combined with fine needle biopsy (FNA) increases the diagnostic rate however a portion of the cases are undetermined due to non-specific pathological diagnosis thus requiring multiple scans in six months intervals. Amplification of genes associated with growth promotion and the reduction of genes associated with growth inhibition have been demonstrated in various human cancers. Previous studies using comparative genomic hybridization (CGH) revealed frequent amplification of DNA for chromosomes 1q, 3q, 5p and/or 8q in non-small cell lung carcinomas. Database analysis of 84 non-small cell carcinomas demonstrated that 95% of the tumors could potentially be detected based on the amplification of one or more chromosomal markers in the tumor samples (Table 1). Methods: We selected BAC probes from each of these four chromosome regions and tested their use as molecular markers for cancer diagnosis in FNA specimens. Nuclei were isolated from formalin fixed and paraffin embedded biopsy samples of patients with or without cancer. The slides were hybridized with fluorescently labeled probes specific for the respective chromosomal regions and analyzed using fluorescent microscopy. Hybridization signals were analyzed in 200 nuclei per sample. Samples having 4 signals or less per nuclei were considered normal while samples with 5 or more signals per nuclei were considered as potentially neoplastic in nature. Results: Preliminary data from 10 normal control samples showed that 100% of nuclei contained 4 or less than 4 signals per nuclei. In contrast, analyses of 8 biopsy samples so far have detected amplification of at least two or more markers in 7 cases. A total of 40 FNA samples will be tested blindly using probes from all four chromosomes and the results will be compared with the pathological diagnoses and the clinical outcome of the patients to determine the potential of using FISH-markers to enhance the diagnosis of Spiral CT identified small lung nodules.

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