Emodin sensitizes human pancreatic cancer cells to EGFR inhibitor through suppressing Stat3 signaling pathway

Background: Excessive expression of EGFR is closely related to tumor formation, transfer and deterioration, which has attracted much attention. EGFR overexpression may be detected in up to 90% of pancreatic tumors. However, drug resistance of EGFR inhibitors targeting treatment severely limits its clinical application. Methods: In this study, Western blotting was used to detect the expression of p-Stat3, EGFR, Bcl-2, cleaved-caspase3 and Bax. Cell apoptosis was evaluated via flow cytometry. The colon assay and MTT assay were applied for detecting the cell proliferation in vitro. The xenograft mouse model was used to examine the cell proliferation in vivo. Results: Emodin remarkably enhanced the anti-cancer effect of EGFR inhibitor on pancreatic cancer cells. In addition, emodin promoted afatinib-induced apoptosis by inhibiting the Stat3 signaling pathway. Meanwhile, siRNAs against Stat3 significantly increased the apoptosis of pancreatic cancer cells. EGFR inhibitor promoted phosphorylation of Stat3 in pancreatic cancer cells. Interestingly, emodin combined with EGFR inhibitor inhibited the proliferation of pancreatic cancer cells in vitro. The tumor xenograft mice model was further confirmed that emodin possessed a synergy anticancer effect with afatinib on pancreatic cancer cells by regulating the Stat3 expression. Conclusion: These results indicate that the combination of emodin with EGFR inhibitor is an effective therapeutic strategy to sensitize human pancreatic cancer.