Analysis of subclonal expansion of colorectal carcinomas by flow cytometry.

DNA heterogeneity of colorectal carcinomas has been investigated by flow cytometry, most studies have focused on the clinical usefulness of DNA ploidy analysis. Since cancers consist of predominant subclones with proliferative advantage due to clonal expansion, we attempted to analyse the clonal expansion of colorectal carcinomas within a tumour by measuring DNA ploidy. The DNA ploidy and heterogeneity of multiple fresh samples obtained from 164 colorectal adenocarcinomas were analysed by flow cytometry. Each tumour was divided into an average of six specimens, which were analysed separately. For 146 of the tumours (89%) at least one DNA aneuploid population was found within the cancer tissue examined. DNA multiploidy was detected in 26 cases (17.8%) among the cancers with aneuploidy. Based on the DNA index (DI), hypertriploid aneuploidy (1.7<DI<1.8) was found most frequently in the aneuploid colorectal cancers examined. DNA ploidy heterogeneity was seen in 75 (51.4%) of the DNA aneuploid tumours. There were only 3 cases with more than three subclones including a diploid line. The present results indicate that colorectal carcinomas consist of a few dominant subclones and have a DNA content (hypertriploid aneuploid) that confers a proliferative advantage.