Interglandular cytogenetic heterogeneity detected by comparative genomic hybridization in pancreatic cancer

Abstract

The aim of this study is to explore the mechanisms of intratumoral cytogenetic heterogeneity (ICH) in pancreatic cancer. Using comparative genomic hybridization (CGH) analysis, we investigated interglandular variation in 20 primary invasive ductal adenocarcinomas of the pancreas. Three or four adjacent neoplastic glands were individually microdissected from a tumor specimen. Extracted DNA from each gland was amplified by degenerate oligonucleotide primed-PCR, followed by CGH. In addition, DNA index (DI) was measured by laser scanning cytometry in each case. CGH profiles displayed a wide variety of differences between glands within the same tumor in all cases, i.e., interglandular cytogenetic heterogeneity was distinct in pancreatic cancers. In this study, genetic changes detected in all regions of a tumor were classified as "region-independent" alterations, whereas changes seen in at least one, but not all regions were designated as "region-dependent" alterations, which resulted in ICH. The degree of ICH, which was manifested as the ratio of these two types of alterations, correlated closely with DI (Spearman rho = 0.842; P = 0.0002). Therefore, DI might be a surrogate marker for ICH. These results suggest that with tumor progression, ICH and DNA aneuploidy result from the successive appearance of region-dependent alterations attributable to chromosomal instability in tumor cells. Our data support a concept of individual cell heterogeneity in pancreatic cancer.