Fig 6. Cytotoxicity tests performed in 2D monolayer culture.

A) Cell proliferation/cell number, B) programmed cell death (apoptosis), and C) number of dead cells were assessed by conventional assays, combined with high-content microscopy (Operetta). Cells were treated with the five most effective betulin derivatives, including paclitaxel control for 72h. Proliferation was measured as the total number of nuclei (= cells), apoptosis as ratio of caspase-3 positive versus all cells, and cell death as ethidium homodimer-2 positive nuclei versus all cells.