Figure 4.

Cell cycle study of A549 cells treated with lapatinib. A. Lapatinib significantly alters cell cycle phases (G1 arrest and DNA synthesis reduction) analyzed by flow cytometry after propidium iodide staining (**: P < 0.01; ***: P < 0.001); B. Western blot showing the effect of lapatinib on the expression of the cell cycle regulators cyclins A, B1 and D1. In treated cells, the lower levels of cyclins A and B1, regulators of S and G2/M stages, respectively, corroborated the results described by cytometry. Levels of cyclin D1, a regulator of the G1 phase, were very low and remained unchanged upon treatment.