DNA Content Analysis of Barrett's Esophagus by Flow Cytometry

Abstract

The purpose of this study was to investigate the correlation of flow cytometric (FCM) DNA content and cell cycle characteristics of Barrett's Esophagus (BE) with age and sex of the patients, length, histologic type and dysplasia of BE. Forty-one patients affected by histologically confirmed BE had multiple biopsies taken from the metaplastic epithelium and one biopsy taken from the gastric fundus, as control. The samples were either stored at -80° C or immediately measured. Nuclei suspensions were obtained, stained with DAPI, measured with a high resolution flow cytometer (ICP22A, Ortho Instruments) and analyzed for the evaluation of the relative DNA content and the S- and G2+M phases of the cell cycle. DNA histograms having two distinct G0/G1 peaks were classified as DNA aneuploid. The degree of DNA aneuploidy (DNA Index, DI), defined as the ratio of abnormal to normal DNA content, was obtained from the mixture of each BE sample with its control sample and trout erytrocytes.

We found six patients with DNA aneuploid populations (14.6 %), whose DNA Index values were 1.05 (in two), 1.8 (in one), and 2.0 (in three cases). DNA ploidy did not correlate with age and sex of the patients, length, histologic type, and dysplasia of BE. Among the 13 patients with dysplasia (6 indefinite, 4 low grade and 2 high grade with intramucous adenonocarcinoma) only two (one indefinite and one low grade) showed DNA aneuploidy (15.4 %). In addition, we found that the S-phase and the G2+M-phase fractions in BE samples were both significantly higher than those of the controls (respectively, p = 0.01 and p = 0.0008).

We suggest that near-diploidy and tetraploidy in BE are indicative of an early genomic instability which may lead to a more abnormal DNA content. This expected DNA ploidy evolution would be in agreement with a recent model obtained from the analysis of a large number of preneoplastic and neoplastic lesions of the colon-rectum (1).