A Chimeric Signal Peptide-Galectin-3 Conjugate Induces Glycosylation-Dependent Cancer Cell-Specific Apoptosis

Purpose: Exploitation of altered glycosylation in cancer is a major goal for the design of new cancer therapy. Here designed a novel chimeric signal peptide-Galectin-3 conjugate (sGal-3) and investigated its ability to induce cancer-specific cell death by targeting aberrantly N-glycosylated cell surface receptors in cancer cells. Experimental Design: sGal-3 was genetically engineered from Gal-3 by extending its N-terminus with a non-cleavable signal peptide from tissue plasminogen activator (tPA). sGal-3 killing ability was tested on normal and tumor cells in vitro and its anti-tumor activity evaluated in subcutaneous lung cancer and orthotopic malignant glioma models. The mechanism of killing was investigated through assays detecting sGal-3 interaction with specific glycans at the surface of tumor cells and the elicited downstream pro-apoptotic signaling. Results: We found sGal-3 preferentially binds to b1 integrin on the surface of tumor cells due to aberrant N-glycosylation resulting from cancer-associated upregulation of several glycosyltransferases. This interaction inducespotent cancer-specific death by triggering an oncoglycan-b1/calpain/caspase-9 pro-apoptotic signaling cascade. sGal-3 could reduce the growth of subcutaneous lung cancers and malignant gliomas in brain, leading to increased animal survival. Conclusions: We demonstrate that sGal-3 kills aberrantly glycosylated tumor cells and antagonizes tumor growth through a novel integrin b1-dependent cell-extrinsic apoptotic pathway. These findings provide proof of concept that aberrant N-oncoglycans represent valid cancer targets and support further translation of the chimeric sGal-3 peptide conjugate for cancer therapy.