PP2A regulates eEF2 phosphorylation in an additional cell line model of acquired lapatinib resistance. (A) Effect of lapatinib on growth of HCC1954-par and HCC1954-L cells. (B) Immunoblot analysis of total and phosphorylated eEF2(Thr56) in HCC1954-par and HCC1954-L cells following 24 hr lapatinib treatment. (C) Activity of PP2A in HCC1954-par and HCC1954-L cells, untreated and treated with 5 nM OA for 24 hr. (D) Immunoblot examining the effect of okadaic acid (OA) alone and in combination with lapatinib on levels of total and phosphorylated eEF2(Thr56) and AKT(Ser473). (E) Effect of 5 nM OA on growth of SKBR3-par and SKBR3-L cells. (F) Effect of OA alone and in combination with lapatinib on the growth of HCC1954-par cells and (G) HCC1954-L cells. *denotes p ≤ 0.05, **denotes p ≤ 0.01. Error bars represent the mean ± SD (n = 3).