A humanized, immunoglobulin (Ig) G2 monoclonal antibody against the secreted form of human clusterin (sCLU) expressed by tumor cells, with potential antineoplastic and anti-metastatic activities. Upon administration, anti-sCLU monoclonal antibody AB-16B5 specifically binds to tumor-associated sCLU and inhibits its activity. This inhibits both the sCLU-mediated signal transduction pathways and epithelial-to-mesenchymal transition (EMT), which leads to the inhibition of tumor cell migration and invasion. In addition, AB-16B5 enhances chemo-sensitivity. sCLU, a heterodimeric disulfide-linked glycoprotein overexpressed by various types of cancer cells, contributes to proliferation and survival of cancer cells, and stimulates tumor cell EMT.