Analysis of subclonal expansion of colorectal carcinomas by flow cytometry

DNA heterogeneity of colorectal carcinomas Introduction has been investigat ed 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 t he clonal expansion of colorectal carcinomas within a tumour by measuring D NA ploidy. The DNA ploidy and heterogeneity of multiple fresh samples obtai ned from 164 colorectal adenocarcinomas were analysed by flow cytometry. Ea ch tumour was divided into an average of six specimens, which were analysed separately. For 146 of the tumours (89%) at least one DNA aneuploid popula tion was found within the cancer tissue examined. DNA multiploidy was detec ted 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 frequentl y in the aneuploid colorectal cancers examined. DNA ploidy heterogeneity wa s 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 result s indicate that colorectal carcinomas consist of a few dominant subclones a nd have a DNA content (hypertriploid aneuploid) that confers a proliferativ e advantage.