Figure 3: High-resolution cell-based structure-activity profiling.

(a) Hierarchical clustering of cytological profiles of a group of 16 closely related derivatives of podophyllotoxin reveals highly similar patterns of activity on a set of markers as well as pronounced individual differences. Full cytological profiles were used for clustering (left). Cytological profiles showing a reduced set of 20 core markers are displayed for easier visualization of affected processes and a vertical grey bar was used to separate between regulatory (i.e. NFkB, p53, and caspase 9 activation) and other cellular markers. Colors indicate positive (yellow) or negative (blue) deviation from the mean of untreated control cells (value = 1). The dendrogram depicts distances between individual cytological profiles based on Pearson correlation. (b) Comparison of cell cycle profiles (bar plots) and cytological profiles (heat map) of two chlorinated derivatives distinguished only by the position of chlorine in the phenyl ring. Cell cycle profiles indicate percentages of cells in each phase of the cell cycle: Low = damaged or apoptotic cells (low DNA content); 2N = cells in G0/G1 phase; 2N_4N = cells in S phase; High = cells M phase and higher ploidy. (c) Comparison of cytological profiles (upper bar plots) and cell cycle profiles (lower bar plots) of three brominated derivatives distinguished only by the position of bromine in the phenyl ring. Most pronounced differences of the three compounds (i.e., 10, 11, 12) in the cytological profiles are represented in the colored bar plot. Dashed line indicates control treatment levels (i.e., 1). Cell cycle profiles indicate percentages of cells in each phase of the cell cycle: Low = damaged or apoptotic cells (low DNA content); 2N = cells in G0/G1 phase; 2N_4N = cells in S phase; High = cells in M phase and higher ploidy. Chemical structures show podophyllotoxin and a scaffold of the derivatives of podophyllotoxin that were used in this study.