Quantitative fluorescence in situ hybridization in lung cancer as a diagnostic marker

Abstract

The diagnosis of lung cancer is quite often hampered by the existence of various cell types within samples such as biopsies or pleural effusions. We have established a new marker for image cytometry of interphase tumor cells of the lung by using the most recurrent and early cytogenetic event in lung cancer, the loss of the short arm of chromosome 3. The method is based on the detection of the imbalance between the long and the short arms of chromosome 3 by performing two-color fluorescence in situ hybridization on both arms. Fourteen tumors were analyzed after short-term culture and compared with the corresponding cytogenetic data obtained from metaphase analysis. Results on interphase nuclei and control experiments on metaphases were the same, with imbalance ratios ranging from 1.0 to 2.0 (mean value 1.6, median 1.5). To assess the clinical significance of this approach, three pleural effusions were analyzed. Data showed that normal cells within the sample could have been distinguished from the tumor cells based on different imbalance values between the long and the short arms. Thus, our method allows refined detection of lung tumor cells within samples containing heterogeneous cell populations.

Figure 1.

Metaphases from lung cancer samples. Images were taken with double filter (FITC-Rhodamine) and a 100× objective. A: Metaphase obtained from an SCLC (case SCLC10). B: Metaphase obtained from NSCLC (case NSCLC1). C: Metaphase obtained from an effusion (EFF1). D: Metaphase obtained from SCLC108 showing an isochromosome i(3q).

Figure 2.

Scatter plot of the distribution of integrated fluorescence for the long arm (3q) and short arm (3p) paintings, quantified on approximately 500 nuclei of one single population and one pleural effusion containing three subpopulations. Integrated fluorescence is given in arbitrary units (a.u.) on both axes (x axis = 3q and y axis = 3p). A: Case SCLC 6 with Ii = 1.7. B: Same case, Region 1 (normal cells) Ii = 1, region 2 (tumor cells) Ii = 1.5, and region 3 (artifacts) Ii = 0.8.