Antibodies that bind to primitive human growth factor NME7-AB block interaction with MUC1* growth factor receptor to inhibit cancer growth and metastasis

Purpose: Develop therapeutic antibodies that block the tumorigenic action of MUC1* ligands and bacterial mimics thereof. Methods: Ligand fishing using the MUC1*ecd-45 peptide as bait identified NME1 and NME7-AB as ligands of MUC1*. Dimeric NME1 and monomeric NME7-AB, which has two MUC1* binding domains, dimerize MUC1* extracellular domain (ecd) and activate MAP kinase growth pathway. IF microscopy showed NME7-AB is secreted by all Day 3 cells of a human blastocyst, then only by cells of the Inner Cell Mass by Day 5. NME7-AB is then replaced by adult form, NME1, which only binds MUC1* when a dimer. At higher concentration, NME1 switches from dimer to hexamer, which doesn't bind MUC1* but instead triggers differentiation. NME7 is cytoplasmic until cleavage removes an N-terminal DM10 fragment, which allows secretion, then ‘NME7-AB'. Alternative splice variant NME7-X1 is transcribed without the DM10 domain, so is always secreted and active. Cancer cells that have acquired resistance to cancer drugs, increase expression of MUC1*, NME7-AB and NME7-X1. We mapped the MUC1* interaction site on NME7-AB and generated antibodies that block the interaction. We discovered a subset of antibiotic-resistant bacteria that make NME7-AB mimics that function like human NME7-AB. We developed monoclonal antibodies that specifically bind to these bacterial mimics. Results: Growing cancer cells with recombinant NME7-AB as the only growth factor, enabled anchorage independent cell growth, induced upregulation of metastasis markers and formed tumors as well as metastasis from injection of as few as 10,000 cells within 10-20 days. 50-times as many parent cells did not. A novel antibody, prevented NME7-AB from inducing upregulation of metastatic markers, and prevented anchorage independent growth. In animals, NME7-AB monoclonal antibodies reversed total metastasis in a few days. They also inhibited metastasis of established sub-cu tumors. Similarly, bacterial mimics of NME7-AB induced upregulation of metastatic markers and, in animals, accelerated tumor growth and their metastasis. We developed monoclonals antibodies that bind to the interaction region on bacterial mimics. Conclusions: MUC1 has long been an elusive target for cancer therapeutics. However, there has been little focus on its onco-embryonic ligand NME7-AB. NME7-AB is turned off early in embryogenesis but is turned on again in all MUC1-positive cancers. Levels of NME7 determine growth rate and metastatic potential of human cancers. Demonstration of NME7-AB antibodies inhibiting cancer and metastasis in animals xenografted with human cancers supports the further clinical development of NME7-AB targeted therapeutics. Discovery of a molecular link between specific bacteria and acceleration of human cancers may be an important area for future research.