Using co-immunoprecipitation combined with LC-MS/MS, our research group identified six potential tumor-derived IgG whole molecule-interacting proteins, including myosin, heavy chain 9, complement component 4A, complement component 4B, acyl-CoA synthetase long-chain family member 3, ribosomal protein L19 and dermcidin, for obtaining clues to study IgG biological functions. This evidence concerns the gene C4B and neoplasm.