PEITC Targets EGFR to Suppress Ovarian Cancer Figure 3. PEITC induces apoptosis in ovarian cancer cells. SKOV-3, OVCAR-3, TOV-21G, cells were treated with varying concentrations of PEITC for 24 hours. Flowcytometry and western blotting were used to determine apoptosis. (A) SKOV-3, (B) OVCAR-3 and (C) TOV-21G cells treated with varying concentrations of PEITC. doi:10.1371/journal.pone.0043577.g003 weight in the treatment group was reduced by almost 70% as compared with control groups (Fig. 1A). Tumor Growth Inhibition by PEITC was Associated with Blockade of EGFR-AKT Pathway EGFR-AKT pathway is constitutively activated in majority of ovarian tumors. Over-expression of EGFR or its mutations are reported in approximately 70% of ovarian tumors. Since we observed suppression of ovarian tumors by oral administration of PEITC, we hypothesized that growth inhibitory effects of PEITC in ovarian tumors in vivo were through inhibition of EGFR-AKT. To test our hypothesis, phosphorylation levels of EGFR and AKT were examined in tumor lysates by western blotting. As shown in Figure 1B, phosphorylation of EGFR at Tyr-1068 and AKT at Ser-473 were drastically suppressed by PEITC treatment. Next, we looked for apoptosis in the tumors from PEITC treated mice. As expected, we observed cleaved products of caspase-3 and PARP in the tumors from PEITC treated mice indicating that PEITC induces apoptosis in ovarian tumors in vivo (Figure 1B). These observations indicate that tumor growth suppression by PEITC was associated with the inhibition of EGFR-AKT pathway and induction of apoptosis. PEITC Inhibits the Proliferation of Ovarian Cancer Cells To determine the mechanism of PEITC, three different ovarian cancer cells were used. SKOV-3, OVCAR-3 and TOV-21G cells were exposed to varying concentrations of PEITC for 24 h. We observed that PEITC treatment reduced the proliferation of ovarian cancer cells in a concentration dependent manner (Figure 2 A–C). The IC50 of PEITC was approximately 15 mM in SKOV-3 cells (Figure 2A). In OVCAR-3 and TOV-21G cells, IC50 was observed to be approximately 20 mM and 5 mM respectively (Figure 2 B–C). PLOS ONE | www.plosone.org 5 August 2012 | Volume 7 | Issue 8 | e43577