Drosophila salivary gland imaginal ring tumor single cell DNA copy number variation (CNV)
Variation and heterogeneity in ploidy are general features of human cancers. This variation can be an increase of the number of chromosome set (polyploidy), an increase or decrease of a small numbers of chromosomes (aneuploidy), or regional ploidy changes and copy number variations (CNVs). Increased aneuploidy and CNVs are associated with tumor progression, malignant transformation, and metastasis. Using a Drosophila solid-tumor model where oncogenic Notch drives tumorigenesis in a transition-zone microenvironment in the salivary gland imaginal ring, we find that the tumor-initiating cells normally undergo endoreplication to become polyploid. Upregulation of Notch signaling, however, induces these polyploid transition-zone cells to re-enter mitosis and undergo tumorigenesis. To determine the extent of genome instability in NICD tumors, we applied the single-cell DNA CNV (scCNV) profiling technique, which allowed us to examine genomic CNV events at 2-Mb resolution at the single-cell level.