Fig. 1

Gene targeting validation in SKBR3 cells and response of knockin derivative cells to lapatinib treatment. A Targeted Sanger sequencing of E545K locus (left) and H1047R locus (right) on both genomic DNA (top) and cDNA (bottom) shows correct targeting in two clones for each mutation (arrows). B Drug response to lapatinib after 72 h shows that overexpression of PIK3CA mutations (top panel) makes cells less sensitive to lapatinib treatment regardless of which mutation is introduced. Site-specific genome editing reveals that while the E545K mutation does not confer reduced sensitivity to lapatinib treatment (middle panel) whereas the H1047R mutation does (bottom panel). Error bars represent standard deviation of triplicate assays. C GR50 calculations for SK-BR-3 parental, control, and mutant clones shows that overexpression clones and H1047R mutant knockin clones have significantly higher GR50 values than parental and control cells, but that E545K knockin mutant clones do not. Error bars represent standard deviation of triplicate measurements. * denotes significant difference from control or parental cells by t-test (p < 0.05)