Regorafenib (Stivarga) pharmacologically targets epithelial-mesenchymal transition in colorectal cancer

Abstract

Epithelial-to-mesenchymal transition (EMT) is well-known to evoke cancer invasion/metastasis, leading to a high frequency of mortality in patients with metastatic colorectal cancer (mCRC). Protein tyrosine phosphatase (PTPase)-targeted therapy has been identified as a novel cancer therapeutic. Previously, we proved that sorafenib with anti-EMT potency prevents TGF-β1-induced EMT/invasion by directly activating SH2-domain-containing phosphatase 1 (SHP-1)-dependent p-STAT3^Tyr705 suppression in hepatocellular carcinoma. Regorafenib has a closely related chemical structure as sorafenib and is approved for the pharmacotherapy of mCRC. Herein, we evaluate whether regorafenib activates PTPase SHP-1 in the same way as sorafenib to abolish EMT-related invasion/metastasis in CRC. Notably, regorafenib exerted potent anti-EMT activity to curb TGF-β1-induced EMT/invasion in vitro as well inhibited lung metastatic outgrowth of SW480 mesenchymal cells in vivo. Mechanistically, regorafenib-enhanced SHP-1 activity significantly impeded TGF-β1-induced EMT/invasion via low p-STAT3^Tyr705 level as proved by a SHP-1 inhibitor or siRNA-mediated SHP-1 depletion. Conversely, overexpression of SHP-1 further enhanced the inhibitory effects of regorafenib on TGF-β1-induced p-STAT3^Tyr705 and EMT/invasion. Regorafenib directly activates SHP-1 by potently relieving the autoinhibited N-SH2 domain of SHP-1 to inhibit TGF-β1-induced p-STAT3^Tyr705 and EMT/invasion. Importantly, the clinical evidence indicated that SHP-1 was positively correlated with E-cadherin and that significantly determined the overall survival of CRC patients. This result further confirms our in vitro data that SHP-1 is a negative regulatory PTPase in EMT regulation and serves as a pharmacological target for mCRC therapy. Collectively, activating PTPase SHP-1 by regorafenib focusing on its anti-EMT activity might be a useful pharmacotherapy for mCRC.