AR-42 blocks the invasion of C2 cells. C2 cells were pretreated with 1μM AR-42 or 17-AAG for 8 hours and then transferred onto cell-culture inserts coated with Matrigel for another 20 hours. Cells that had invaded and migrated into the lower chambers were collected and enumerated using the CyQUANT assay. To account for drug-induced loss of cell viability, equivalent numbers of C2 cells were treated identically in standard culture wells and the proportion of cells surviving at the end of treatment served as the control for each group (*P < .05). These experiments were performed in triplicate and repeated 3 times.