EGF and plasma cell myeloma: We next determined whether pro-EGF was present in other recombinant proteins produced by R&D Systems using this cell line; immunoblot analyses of human noggin (#6057-NG-025) and BMP6 (#507-BP-020/CF) were negative for pro-EGF (not shown), demonstrating that pro-EGF is not a common impurity in recombinant proteins expressed in the murine myeloma cell line.