Antibody-Mediated Blockade for Galectin-3 Binding Protein in Tumor Secretome Abrogates PDAC Metastasis

Abstract Background One of the major challenges in pancreatic ductal adenocarcinoma (PDAC) management is a local or distant metastasis and limited targeted therapeutics to prevent the process. We aimed to identify a druggable target by screening abnormally secreted protein from PDAC and explore its therapeutic intervention. Methods A LC-MS/MS-based proteomics was carried out for TIF (Tumor Interstitial Fluids) obtained from patient derived xenograft (PDX) models of PDAC. To develop a blocking antibody for selected target protein, antibody phage-display technology was used. Results The proteomic screening of PDAC secretome identified Galectin-3 binding protein (Gal-3BP hereafter) as a top candidate. The Gal-3BP is highly expressed and secreted in PDAC tumors and primary cells. Subsequent functional tests by stable knockdown revealed the Gal-3BP is required for PDAC cell proliferation, migration and invasion. In addition, the depletion of Gal-3BP significantly abrogated in vivo tumor formation and metastasis of pancreatic cancer cells. Mechanistically, we found Gal-3BP enhances the galectin-3 mediated EGFR signaling, leading to the activation of cMyc and its target genes related to EMT. To examine the clinical usability of these findings, we screened a Gal-3BP-immunized chicken antibody library using phage display technique. The two isolated blocking antibody clones against Gal-3BP profoundly inhibited the metastasis of PDAC cells in vivo. Conclusions Altogether, our data demonstrates the Gal-3BP is an important therapeutic target in PDAC and proposed its blockade by antibody as a novel, therapeutic option for the inhibition of PDAC metastasis.