GPNMB and breast cancer: Specifically, OLR1 has been recognized as a cell migration stimulator in breast cancer cells, and potentially up‐regulated by oncogene TBC1D3 through activation of TNFa/NF‐KB pathway.25 Non‐metastatic glycoprotein melanoma protein B (GPNMB), also known as osteoactivin (OA) is expressed in verified tumours and represents an emerging target for drug development.