Image Cytofluorometry for the Quantification of Ploidy and Endoplasmic Reticulum Stress in Cancer Cells

One of the mechanisms of cancer-associated genomic instability involves a transient phase of polyploidization, in most cases tetraploidization, followed by asymmetric divisions and chromosome loss. Increases in ploidy are consistently accompanied by the activation of an endoplasmic reticulum (ER) stress response, resulting in the translocation of calreticulin to the outer surface of the plasma membrane where it stimulates anticancer immune responses. Conversely, immunoselection leads to a coordinated reduction in ploidy, ER stress, and calreticulin exposure. To simultaneously investigate the ER stress and ploidy, we developed an image cytofluorometric method that allows to measure DNA content, ER stress-associated phosphorylation of eIF2α, and calreticulin exposure at the cell surface. Here, we specify this methodology, which is useful for investigating the correlation between ploidy and ER stress at the single cell level.