Small Molecules Target the Interaction between Tissue Transglutaminase and Fibronectin

Abstract

Tissue transglutaminase (TG2) is a multi-functional protein, with enzymatic, GTP-ase and scaffold properties. TG2 interacts with fibronectin (FN) through its N-terminus domain, stabilizing integrin complexes, which regulate cell adhesion to the matrix. Through this mechanism, TG2 participates in key steps involved in metastasis in ovarian and other cancers. High throughput screening identified several small molecule inhibitors (SMIs) for the TG2/FN complex. Rational medicinal chemistry optimization of the hit compound (TG53) led to second generation analogues (MT1–6). ELISA demonstrated that these analogues blocked TG2/FN interaction and bio-layer interferometry (BLI) showed that the SMIs bound to TG2. The compounds also potently inhibited cancer cell adhesion to FN and decreased outside-in signaling mediated through the focal adhesion kinase (FAK). Blockade of TG2/FN interaction by the small molecules caused membrane ruffling, delaying the formation of stable focal contacts and mature adhesions points and disrupted organization of the actin cytoskeleton. In an in vivo model measuring intraperitoneal (ip) dissemination, MT4 and MT6 inhibited the adhesion of ovarian cancer (OC) cells to the peritoneum. Pre-treatment with MT4 also sensitized OC cells to paclitaxel. The data support continued optimization of the new class of SMIs that block the TG2/FN complex at the interface between cancer cells and the tumor niche.