G2/M arrest and cell death in MCF-7 and MDA231 treated with PJ-34. The effect of PJ-34 on the cell cycle was examined with flow cytometry. PJ-34 (10 μM) was applied to both types of cells, 24 hours after seeding. Controls: Untreated MCF-7 48 hours after seeding and untreated MDA231 cells 72 hours after seeding. At the indicated time, cells were collected, permeabilized (75% ethanol in DDW), and stained with propidium iodide (PI). The effects of PJ-34 on cell eradication and the kinetics of S-phase entry and G2/M transition were evaluated by the percentages of cells at these phases. G2/M arrest accompanied by cell death was detected in both cell types after 6 hours of incubation with PJ-34. Similar results for both cell types were obtained in three different experiments.